A transimpedance amplifier comprises a transconductance amplifier having a nonlinear resistive feedback element. The feedback element includes a pair of resistors and a pair of diodes, one of which conducts (depending upon the voltage polarity) only when the voltage across the diode exceeds the diode on-voltage. This includes additional resistance in the feedback element thereby changing the amplifier gain. The largest value of the resistive feedback element is substantially equal to or less than the output resistance of the transconductance amplifier. The feedback element is both symmetrical and nonlinear. A shunt amplifier is driven by circuit which produces a control signal that varies with a signal current. Increasing signal current increases the DC current shunted from the amplifier input thus decreasing pulse edge distortion and increasing dynamic range. A capacitor AC couples the current input to the amplifier.

1. Field of the Invention
The present invention relates to signal amplifiers and more particularly to such amplifiers which produce an output voltage signal proportional to an input current signal and which are generally known as transimpedance amplifiers.
2. Description of the Related Art
Prior art transimpedance amplifiers are typically implemented by providing a feedback resistor across the input and output of a voltage amplifier. The current signal applied to the amplifier input is thus passed substantially through the feedback resistor because of the high input impedance of the voltage amplifier. A voltage proportional to the input current thus appears on the amplifier output.
One such prior art transimpedance amplifier shown in FIG. 5 of U.S. Pat. No. 4,540,952 issued to Williams for a nonintegrating receiver.
A typical use for transimpedance amplifiers is in optical transmission systems. An optical source, such as a laser or light emitting diode, is used to transmit information by modulating the intensity of the light source. An electrooptic device such as a PIN diode or avalanche photodiode receives the optical signal and converts the same to a current which is applied to the input of the transimpedance amplifier. The amplifier thus produces a voltage proportional to the diode current. In optical transmission systems the information transmitted is usually digital and generally is in the form of a pulse train.
Optical transmission systems are typically designed to provide an electrical output signal which has a predetermined amplitude. In the prior art, an automatic gain control (AGC) is used in conjunction with the transimpedance amplifier described above in order to produce an output voltage which comprises a pulse train switched in accordance with the optical source and having a substantially constant amplitude when the input signal is larger than a preselected threshold. Increasing the gain for low signal inputs thus increases the dynamic range of the amplifier.
One such AGC circuit is described in U.S. Pat. No. 4,415,803 to Muoi for an optical receiver with improved dynamic range. Such an AGC circuit effectively varies the gain of the transimpedance amplifier in order to maintain the output signal at the desired amplitude for signals above the threshold. In transimpedance amplifiers which are implemented with voltage amplifiers, varying the value of the feedback resistance varies the amplifier bandwidth. The closed-loop -3db bandwidth for such an amplifier is approximately equal to A.sub.v /(2.pi.R.sub.f C.sub.t), where A.sub.v is the amplifier gain, R.sub.f is the value of the feedback resistance and C.sub.t is the total input capacitance of the diode, the amplifier and any other parasitic capacitance. The bandwidth of the amplifier thus varies with the value of the feedback resistance as in several embodiments disclosed in the Williams patent.
Should the bandwidth fall too low, undesirable filtering of the signal occurs. On the other hand, if the bandwidth becomes too high, overshoot, ringing, and, in extreme cases, amplifier oscillation occurs, thus producing at the very least, an increase in the error rate of information passed. Furthermore, increased bandwidth also increases noise and therefore the error rate. It would thus be desirable to provide a transimpedance amplifier having a variable gain and a constant bandwidth.
In another prior art device for increasing the dynamic range of an amplifier, a FET is used as a resistive shunt to reduce the value of the current applied to the input terminal of the amplifier in order to increase dynamic range. In such a circuit, one side of the FET is connected to the amplifier input, the other side is connected to a bias voltage and the gate is connected to the output of an AGC circuit which produces a control signal which varies in response to the amplifier output. For high input signal levels, more amplifier input current is shunted thereby increasing the dynamic range of the amplifier. In order to be effective, such a FET must typically have a resistance of 10 ohms or less. Such a FET is typically one to several thousand microns wide. This takes up a tremendous amount of space on a chip and also adds a large amount of unwanted capacitance which lowers the bandwidth and degrades the noise performance.


A method performed by a first Station (STA) for any one out of: transmitting Narrow Band (NB) signals to, and receiving NB signals from, second STAs in a Wireless Local Area Network (WLAN) is provided. The STA performs one or more out of: Transmitting (1001) the NB signals to the second STAs, and receiving (1002) the NB signals from the second STAs. The NB signal symbol boundaries are aligned in time with symbol boundaries of a Wide Band (WB) signal transmitted by any one out of the first STA and another STA. The NB signals start with a preamble comprising an NB-Short Training Field (STF) followed by a NB-Long Training Field (LTF). The NB LTF and NB STF are designed to avoid interference between the NB signals and WB signals.

In a typical wireless communication network, wireless devices, also known as wireless communication devices, mobile stations, stations (STA) and/or User Equipments (UE), communicate via a Local Area Network such as a Wi-Fi network or a Radio Access Network (RAN) to one or more core networks (CN). The RAN covers a geographical area which is divided into service areas or cell areas, which may also be referred to as a beam or a beam group, with each service area or cell area being served by a radio network node such as a radio access node e.g., a Wi-Fi access point or a radio base station (RBS), which in some networks may also be denoted, for example, a NodeB, eNodeB (eNB), or gNB as denoted in 5G. A service area or cell area is a geographical area where radio coverage is provided by the radio network node. The radio network node communicates over an air interface operating on radio frequencies with the wireless device within range of the radio network node.
Specifications for the Evolved Packet System (EPS), also called a Fourth Generation (4G) network, have been completed within the 3rd Generation Partnership Project (3GPP) and this work continues in the coming 3GPP releases, for example to specify a Fifth Generation (5G) network also referred to as 5G New Radio (NR). The EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as the Long Term Evolution (LTE) radio access network, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E-UTRAN/LTE is a variant of a 3GPP radio access network wherein the radio network nodes are directly connected to the EPC core network rather than to RNCs used in 3G networks. In general, in E-UTRAN/LTE the functions of a 3G RNC are distributed between the radio network nodes, e.g. eNodeBs in LTE, and the core network. As such, the RAN of an EPS has an essentially "flat" architecture comprising radio network nodes connected directly to one or more core networks, i.e. they are not connected to RNCs. To compensate for that, the E-UTRAN specification defines a direct interface between the radio network nodes, this interface being denoted the X2 interface.
Multi-antenna techniques can significantly increase the data rates and reliability of a wireless communication system. The performance is in particular improved if both the transmitter and the receiver are equipped with multiple antennas, which results in a Multiple-Input Multiple-Output (MIMO) communication channel. Such systems and/or related techniques are commonly referred to as MIMO.
In addition to faster peak Internet connection speeds, 5G planning aims at higher capacity than current 4G, allowing higher number of mobile broadband users per area unit, and allowing consumption of higher or unlimited data quantities in gigabyte per month and user. This would make it feasible for a large portion of the population to stream high-definition media many hours per day with their mobile devices, when out of reach of Wi-Fi hotspots. 5G research and development also aims at improved support of machine to machine communication, also known as the Internet of things, aiming at lower cost, lower battery consumption and lower latency than 4G equipment.
Some communication technologies have a Physical layer (PHY) in which the beginning of a transmission burst (or packet) constitutes a training, or synchronization, signal. In Institute of Electrical and Electronics Engineers (IEEE) 802.11 for WLAN, referred to as 802.11, this sequence is divided into two parts; a Short Training Field (STF), and a Long Training Field (LTF). The main purpose of the STF is Automatic Gain Control (AGC), signal detection, and coarse time- and frequency synchronization. The main purpose of the LTF is fine time- and frequency synchronization, and channel estimation. It is of great importance that the STF and LTF are carefully designed since poor design may lead to performance bottlenecks. In the OFDM based 802.11 technologies, for example the IEEE 802.11 a, g, n, ac, and ax, the STF and LTF can conveniently be defined in the frequency (or subcarrier) domain.
FIG. 1 depicts a Resource Unit (RU) allocation in the 20 MHz band for IEEE 802.11ax, referred to as 802.11ax herein.
Preamble Design in Legacy 802.11
The preamble design in legacy OFDM 802.11 can be found in Next Generation Wireless LANs—IEEE 802.11n and 802.11ac, Eldad Perahia and Robert Stacey. Legacy 802.11 OFDM uses 64 subcarriers. Assume the STF and LTF OFDM symbols as STFlegacy and LTFlegacy, the symbols are repeated with Cyclic Prefix CP as in FIG. 2 and FIG. 3. In these figures, GI2 has the length such as duration of 2 GI. GI means Guard Interval and in this framework is equivalent to the CP of the OFDM symbol. FIG. 2 depicts an IEEE 802.11 (legacy) STF field. The left and right are, with the numerology of legacy, equivalent. FIG. 3 depicts an IEEE 802.11 (legacy) LTF field.
Preamble Design in IEEE 802.11ax
In 802.11ax, there is additional HE-STF and HE-LTF defined in IEEE P802.11 ax™ The main purpose of the HE-STF is AGC in MIMO situations, and the main purpose of HE-LTF is for MIMO channel estimation. The details on these fields can be found in Sections 188.8.131.52 and 184.108.40.206 in IEEE P802.11ax™/D1.1—Draft Standard for Information technology—Telecommunications and Information exchange between systems Local and metropolitan area networks—Specific requirements. An overview of the packet structure for 802.11ax High Efficiency (HE) packets is shown in FIG. 4 depicting an IEEE 802.11ax signal.
Note that the HE-STF and HE-LTF are defined with the 256-Fast Fourier Transform (FFT). The length THE-STF-FIELD may have different length per:                THE-STF-FIELD=4 μs when the transmission is a HE SU Physical layer Protocol Data Unit (PPDU), HE extended range Single User (SU) PPDU, or HE Multi User (MU) PPDU.        THE-STF-FIELD=8 μs when the transmission is a HE trigger-based PPDU.
Similarly, the length THE-LTF-FIED may have different values. First, if there are several spatial streams, we have that
            T              HE                          -                        LTF                          -                        FIELD              =                  N        LTF                          T                  HE                                -                              LTF                                -                              SYM                      ,                      where                                              N        LTF              =          {                                                                  N                STS                            ,                                                if                                                                                N                    STS                                                  =                1                            ,              2              ,              4              ,              6              ,              8                                                                                N                  STS                                +                1                            ,                                                if                                                                                N                    STS                                                  =                3                            ,              5              ,              7
Here, NSTS denotes the number of space-time streams. Furthermore, we have that the guard interval for the data TGI,Data can take three different values, TGI1,Data, TGI2,Data, TGI3,Data, depending on the configuration. The value of the duration of the HE-LTF, THE-LTF-SYM, can also have different durations according to the expressions below.
            T              HE                          -                        LTF                          -                        SYM              =                  T        GI            +              T                  HE                                -                              LTF                      ,                      where                                              T        GI              =          {                                                                                0.8                                                                                µs                                                                                if                                                                                T                                          GI                      ,                      Data                                                                      =                                  T                                                            GI                                                                                1                                        ,                    Data                                                                                1.6                                                                                µs                                                                                if                                                                                T                                          GI                      ,                      Data                                                                      =                                  T                                                            GI                                                                                2                                        ,                    Data                                                                                3.2                                                                                µs                                                                                if                                                                                T                                          GI                      ,                      Data                                                                      =                                  T                                                            GI                                                                                3                                        ,                    Data                                                                                ,                                                                and                                                                                T                              HE                                                  -                                                LTF                                              =                      {                                                                                T                                              HE                                                                          -                                                                        LTF                                                                          -                                                                        1                                                X                                                              =                                          3.2                                                                                µs                                                                                T                                              HE                                                                          -                                                                        LTF                                                                          -                                                                        2                                                X                                                              =                                          6.4                                                                                µs                                                                                T                                              HE                                                                          -                                                                        LTF                                                                          -                                                                        4                                                X                                                              =                                          12.8                                                                                µs

STA and method in a wireless local area network


This invention relates to a method and apparatus for transmitting a downlink signal from a communication station to one or more subscriber units to achieve a desired radiation level over a desired sector (e.g., everywhere), the communication station including an array of antenna elements and one or more signal processors programmed (in the case of programmable signal processors) to weight the downlink signal according to one of a sequence of complex valued weight vectors. The method includes sequentially repeating transmitting the downlink signal, each repetition with a different weight vector from the sequence until all weight vectors in the sequence have been transmitted with. The sequence is designed for achieving the desired radiation level during at least one of the repetitions. In this way, every user in the desired region is transmitted to in the time period.

Cellular wireless communications systems are known, wherein a geographical area is divided into cells, and each cell includes a base station (BS, BTS) for communicating with subscriber units (SUs) (also called remote terminals, mobile units, mobile stations, subscriber stations, or remote users) within the cell. In such a system, there is a need for broadcasting information from a base station to subscriber units within the cell, for example to page a particular subscriber unit in order to initiate a call to that SU, or to send control information to all subscriber units, for example on how to communicate with the base station, the control information including, for example, base station identification, timing, and synchronization data. Such paging and control information is broadcast on what are called common control channels. Because often there is no prior information regarding the location of the remote user(s) that need to receive the paging or control information, or because such information is intended for several users, it is preferable to transmit such signals omnidirectionally, or near omnidirectionally, where omnidirectional in general means that the radiated power pattern of the base station is independent of azimuth and elevation within the prescribed coverage area of the base station. This invention deals with methods and apparatuses for achieving such omnidirectional transmissions.
Some examples of a cellular system to which the present invention can be applied are analog systems using the AMPS standard, digital systems which use variants of the Personal Handy Phone System (PHS) protocol defined by the Association of Radio Industries and Businesses (ARIB) Preliminary Standard, RCR STD-28 (Version 2) December 1995, and digital systems that use the Global System for Mobile communications (GSM) protocol, including the original version, 1.8 GHz version called DCS-1800, and the North American 1.9 GHz personal communications system (PCS) version called PCS-1900, these three called "variants" of GSM herein. The PHS and GSM standards define two general sets of functional channels (also called logical channels): a control channel (CCH) set and a traffic channel (TCH) set. The TCH set includes bi-directional channels for transmitting user data between the subscriber units and a base station. The CCH set includes a broadcast control channel (BCCH), a paging channel (PCH), and several other control channels not of concern herein. The BCCH is a unidirectional downlink channel for broadcasting control information from the base station to the subscriber units that includes system and channel structure information, and the PCH is a one-way downlink channel that broadcasts information from the base station to a selected set of subscriber units, or to a wide area of multiple subscriber units (the paging area), and typically is used to alert a particular remote station of an incoming call. The present invention is applicable to all downlink broadcasts and transmissions. It is especially applicable for BCCH and PCH that are used by a base station to simultaneously transmit common information to more than one subscriber (i.e., to broadcast). It is also applicable to other situations where it is desired to transmit RF energy omnidirectionally or at least with no nulls anywhere in the intended region.
The use of antenna arrays for the radiation of radio frequency (RF) energy is well established in a variety of radio disciplines. For the purposes of transmitting in the downlink from a base station which includes an antenna array to a remote receiver (the subscriber unit), the signal intended for the SU can be provided as input to each of the radiating elements of the array, differing from element to element only by gain and phase factors, usually resulting, by design, in a directional radiation pattern focused at the subscriber unit. The benefits of this sort of transmission strategy include increased gain over that possible using a single radiating element and reduced interference to other co-channel users in the system as compared to transmission by means of a single radiating element. Using such an antenna array, spatial division multiple access (SDMA) techniques also are possible in which the same "conventional channel" (i.e., the same frequency channel in a frequency division multiple access (FDMA) system, timeslot in a time division multiple access (TDMA) system, code in a code division multiple access (CDMA) system, or timeslot and frequency in a TDMA/FDMA system) may be assigned to more than one subscriber unit.
Any downlink signals sent are received by a subscriber unit, and the received signal at such receiving subscriber unit is processed as is well known in the art.
When a signal is sent from a remote unit to a base station (i.e., communication is in the uplink), the base station typically (and not necessarily) is one that uses a receiving antenna array (usually, and not necessarily the same antenna array as for transmission). The base station signals received at each element of the receiving array are each weighted in amplitude and phase by a receive weight (also called spatial demultiplexing weight), this processing called spatial demultiplexing, all the receive weights determining a complex valued receive weight vector which is dependent on the receive spatial signature of the remote user transmitting to the base station. The receive spatial signature characterizes how the base station array receives signals from a particular subscriber unit in the absence of any interference. In the downlink (communications from the base station unit to a subscriber unit), transmission is achieved by weighting the signal to be transmitted by each array element in amplitude and phase by a set of respective transmit weights (also called spatial multiplexing weights), all the transmit weights for a particular user determining a complex valued transmit weight vector which also is dependent on what is called the "downlink spatial signature" or "transmit spatial signature" of the remote user which characterizes how the remote user receives signals from the base station absence of any interference. When transmitting to several remote users on the same conventional channel, the sum of weighted signals is transmitted by the antenna array. This invention is primarily concerned with downlink communications, although the techniques certainly are applicable also to uplink communications when the subscriber unit also uses an antenna array for transmitting and omnidirectional transmission from such a subscriber unit is desired.
In systems that use antenna arrays, the weighting of the signals either in the uplink from each antenna element in an array of antennas, or in the downlink to each antenna element is called spatial processing herein. Spatial processing is useful even when no more than one subscriber unit is assigned to any conventional channel. Thus, the term SDMA shall be used herein to include both the true spatial multiplexing case of having more than one user per conventional channel, and the use of spatial processing with only one user per conventional channel. The term channel shall refer to a communications link between a base station and a single remote user, so that the term SDMA covers both a single channel per conventional channel, and more than one channel per conventional channel. The multiple channels within a conventional channel are called spatial channels. For a description of SDMA systems, see for example, co-owned U.S. Pat. Nos. 5,515,378 (issued May 7, 1996) and 5,642,353 (issued Jun. 24, 1997) entitled SPATIAL DIVISION MULTIPLE ACCESS WIRELESS COMMUNICATION SYSTEMS, Roy, III, et al., inventors, both incorporated herein by reference; co-owned U.S. Pat. No. 5,592,490 (issued Jan. 7, 1997) entitled SPECTRALLY EFFICIENT HIGH CAPACITY WIRELESS COMMUNICATION SYSTEMS, Barratt, et al., inventors, incorporated herein by reference; co-owned U.S. patent application Ser. No. 08/735,520 (filed Oct. 10, 1996), entitled SPECTRALLY EFFICIENT HIGH CAPACITY WIRELESS COMMUNICATION SYSTEMS WITH SPATIO-TEMPORAL PROCESSING, Ottersten, et al., inventors, incorporated herein by reference; and co-owned U.S. patent application Ser. No. 08/729,390 (filed Oct. 11, 1996) entitled METHOD AND APPARATUS FOR DECISION DIRECTED DEMODULATION USING ANTENNA ARRAYS AND SPATIAL PROCESSING, Barratt, et al., inventors, incorporated herein by reference. Systems that use antenna arrays to improve the efficiency of communications and/or to provide SDMA sometimes are called smart antenna systems. The above patents and patent applications are collectively referred to herein as "Our Smart Antenna patents."
Because broadcasting implies the simultaneous transmission of data over a common channel to a dispersed set of subscriber units, it is desirable to find methods for using the multiple element antenna array and associated transmitter hardware for broadcasting both common downlink channel information and traffic information intended for one or more particular users.
Desirable Characteristics
A successful strategy will have the following characteristics:                given no prior information on the likely location of remote receivers, a remote receiver at any azimuth receiving a signal at least once over a time period at approximately the same level as a user at any other location at any time during the time period. This is called "near omnidirectional" (NOR) broadcasting herein;        low variation in the transmit power of each element in the array so that good advantage is taken of all elements in the array and scaling issues that arise in practice are minimized;        significant pattern gain relative to that achievable with a single element of the array transmitting at comparable power to the individual transmission powers of the array elements in the time period; and        low total radiated energy so that all elements are being used efficiently.
The property "low relative radiated power" herein means low radiated power per antenna element over a time period relative to the power required to effect a comparable maximum radiation level (comparable in range, azimuth and elevation) using a single antenna element of the same gain (e.g., as measured in dBi) as the individual elements of the antenna array. Since the difference in radiated power may translate to different power amplifier requirements, and very high power amplifiers are relatively expensive, in some situations, even 1 dB may be a significant difference in radiated power. In more general cases, 3 dB will be considered a significant difference in radiated power.
Sectorized systems using antenna arrays are known in the art. In a sectorized system, rather than true omnidirectional broadcasting (360° of azimuth coverage) there is a need in the art for broadcasting efficiently in the intended coverage region (i.e., the sector) of the antenna array and associated electronics. Thus, in this document, the term "omnidirectional" will be taken in the following sense: 1) "omnidirectional" means approximately, nearly omnidirectional ("NOR"); 2) in an unsectorized cellular system, omnidirectional will mean NOR for 360° of azimuth coverage, and 3) in a sectorized system, omnidirectional will mean nearly omnidirectional in the intended sector width (e.g., 120° of azimuth coverage for 120° sectors).
The Prior Art
A common method for so broadcasting data is to use an omnidirectional antenna so that the RF carrier is transmitted more-or -less uniformly in all directions. This omnidirectional radiation pattern appears to be a reasonable choice for mobile cellular systems in which the subscriber units can be arbitrarily positioned within the cell area. In the case of a smart antenna system, one can achieve such an omnidirectional pattern either by using a separate single omnidirectional antenna (such as a vertical dipole) or one of the elements in the antenna array (assumed to have m elements). Unfortunately, this would require increasing the total transmitter power in that antenna element (or separate antenna) compared to the power levels used in ordinary TCH communications when all the antenna elements are operational, to achieve similar range for the traffic and control channels. The option of increasing power may not be allowed by regulation and, even if allowed, may not be a practical choice because, for example, power amplifier costs tend to increase rapidly with power.
The prior art method of transmitting from only a single array element would satisfy the desirable criteria of approximately constant gain as a function of azimuth and other quantities that describe the location of the remote receiver, and of low total radiated energy, but would not give low variation in the transmit power of each element in the array so that good advantage is taken of all elements in the array and scaling issues that arise in practice are minimized, and would not provide significant pattern gain relative to that achievable with a single element of the array transmitting at comparable power to the individual transmission powers of the array elements. In addition, transmitting from only one antenna would not enable simultaneous communications with several users on the same conventional channel.
Alternatively, the antenna array radiation pattern may be controlled through a combination of sending multiple beams and applying pre-processing to any signals prior to beamforming. U.S. Pat. No. 5,649,287, (issued Jul. 15, 1997), entitled ORTHOGONALIZING METHODS FOR ANTENNA PATTERN NULLFILLING, Forssen, et al., inventors, discloses a method for sending information in a cellular communication system comprising at least one base station with an antenna array and a plurality of mobile stations. The common information is pre-processed to create orthogonal signals. The orthogonal signals are then beamformed so that the orthogonal signals are delivered to the different beams in the array antenna. The orthogonal signals are transmitted and then received at one or more mobile stations. The signals are then processed at the mobile station to decipher the common information from the orthogonal signals. The orthogonalizing signals to be transmitted to the mobile stations are formed so as to prevent nulls from occurring in the antenna pattern.
The Forssen et al. method requires pre-processing (orthogonalizing) the control signal to form m orthogonal signals which are then fed to a beamformer. That is, any signal to be broadcast is first transformed to a set of uncorrelated signals, and then each of these signals is sent on a different beam. This requires extra hardware or processing steps. In addition, the particular embodiment described by Forssen et al. requires a high performance equalizer at the subscriber unit to resolve the orthogonalized signals from the other various lobes. It would be desirable to use a system in which any signal to be transmitted is weighted only in phase and amplitude without requiring an additional step (e.g., orthogonalization).
Thus there is a need in the art for methods for omnidirectional downlink transmitting that use the existing communications system apparatus including the existing antenna elements in an antenna array to achieve acceptable omnidirectional performance with low relative radiated power. There also is a need in the art for an apparatus that achieves this.

Downlink broadcasting by sequential transmissions from a communication station having an antenna array


In performing three-dimensional flow imaging using coded excitation and wall filtering, a coded sequence of broadband pulses (centered at a fundamental frequency) is transmitted multiple times to a particular transmit focal position. On receive, the receive signals acquired for each firing are compressed and bandpass filtered to isolate a compressed pulse centered at the fundamental frequency. The compressed and isolated signals are then wall filtered to extract the flow imaging data. This process is repeated for a multiplicity of transmit focal positions in each of a multiplicity of scanning planes to acquire a volume of flow imaging data. Volume rendered images are then produced which allow the user to view the data volume from any angle. In addition, the data volume may be reformatted to produce two-dimensional images of arbitrary cut planes through the data volume.

Conventional ultrasound scanners create two-dimensional gray-scale (B-mode) images which represent a thin slice through an area of anatomy. Flow information can also be extracted by detecting the Doppler shift between transmitted and returned ultrasound pulses. A conventional ultrasound system displays flow as either average Doppler power (power Doppler imaging) or average velocity (commonly referred to as color flow imaging). A flow image is conventionally displayed as an overlay on a B-mode image.
The transmitted pulses in power Doppler and color flow imaging are typically more narrowband than B-mode pulses in order to gain Doppler sensitivity. Operating on a packet of as many as 16 transmits, a high-pass wall filter rejects echoes from slower-moving tissue or vessel walls to reduce the signal dynamic range. The number of wall filter output samples per packet is given by (N-W+1), where N is packet size and W is wall filter length. Subsequently, the instantaneous Doppler power is computed as the magnitude squared of each wall filter quadrature output and the average of all outputs yields the average Doppler power. Alternatively, the average velocity is computed from the wall filter quadrature output based on the Doppler principle or time delay. The Kasai autocorrelation algorithm or a cross-correlation algorithm can be used to estimate the average flow velocity.
Although conventional color-flow imaging has very good flow sensitivity, the ability to see physical flow is limited by its limited dynamic range (which is partially dependent on the compression curve), limited resolution (due to narrowband pulses), limited frame rate (due to large packet sizes), and axialonly flow sensitivity (which is dictated by the reliance on the Doppler effect). In addition, conventional color-flow imaging suffers from artifacts such as aliasing, color blooming and bleeding.
If the ultrasound probe is swept over an area of body and the slices are stored in memory, a three-dimensional data volume can be acquired containing both the B-mode and flow information. The data volume can be used to project a three-dimensional view of the area of interest. The quality of three-dimensional projections of color flow and power Doppler data (either separately or combined with B-mode data) suffer for the aforementioned reasons, namely, reduced acoustic frame rate, Doppler sensitivity, reduced flow resolution, and "flash" artifacts. There is need for a method of performing three-dimensional flow imaging which is not afflicted with the drawbacks associated with Doppler flow imaging.
Conventional ultrasound images are formed from a combination of fundamental and harmonic signal components, the latter of which are generated in a nonlinear medium such as tissue or a blood stream containing contrast agents. In certain instances ultrasound images may be improved by suppressing the fundamental and emphasizing the harmonic signal components.
Contrast agents have been developed for medical ultrasound to aid in diagnosis of traditionally difficult-to-image vascular anatomy. The agents, which are typically microbubbles whose diameter is in the range of 1-10 micrometers, are injected into the blood stream. Since the backscatter signal of the microbubbles is much larger than that of blood cells, the microbubbles are used as markers to allow imaging of blood flow. One method to further isolate echoes from these agents is to use the (sub)harmonic components of the contrast echo, which is much larger than the harmonic components of the surrounding tissue without contrast agent. Flow imaging of (sub)harmonic signals has largely been performed by transmitting a narrowband signal at frequency .function..sub.0 and receiving at a band centered at frequency 2.function..sub.0 (second harmonic) or at frequency .function..sub.0 /2 (subharmonic) followed by conventional color flow processing. This approach has all the limitations of a conventional color flow system, namely, low resolution, low frame rate and flow sensitivity only in the axial direction.
In medical diagnostic ultrasound imaging, it is also desirable to optimize the signal-to-noise ratio (SNR). Additional SNR can be used to obtain increased penetration at a given imaging frequency or to improve resolution by facilitating ultrasonic imaging at a higher frequency. Coded excitation is a well-known radar technique used to increase signal-to-noise ratio in situations where the peak power of a transmitted signal cannot be increased but the average power can. This is often the situation in medical ultrasound imaging, where system design limitations dictate the peak amplitude of the signal driving the transducer. In this situation, longer signals can be used to deliver higher average power values, and temporal resolution is restored by correlating the return signal with a matched filter. Binary codes, or codes that can be easily represented digitally as a series of digits of +1, -1 or 0, are preferred. Binary codes are also preferred because they contain the most energy for a given peak amplitude and pulse duration.

Method and apparatus for three-dimensional flow imaging using coded excitation


An object of the present invention is to provide a wavelength converting device which generates a second harmonic by directly leading a laser beam emitted from a semiconductor laser to a waveguide. A waveguide is formed on a plate-shaped device substrate made of LiNbO.sub.3. The polarization of the waveguide is perpendicular to both the waveguide direction of the waveguide and a normal direction of the main surface of the device substrate. Further, the polarization of the waveguide is periodically inverted by the polarization inverting layers along the waveguide direction of the waveguide.

1. Field of the Invention
This invention relates to a wavelength converting device for generating a second harmonic of an incident laser beam and its manufacturing method.
2. Description of the Related Background Art
With regard to a wavelength converting device for generating a second harmonic of an incident laser beam, a device utilizing what is called QPM (quasi phase matching) is known.
In a nonlinear optical crystal used as a substrate of the device, an output of a polarization wave periodically repeats the maximum and minimum values every interference distance called a coherent length L.sub.c in association with its propagation. Thus, the QPM is a phase matching means for causing the phase of the polarization wave generated every coherent length L.sub.c to be alternately inverted and then added without mutually setting off so that an output of the second harmonic is increased.
A wavelength converting device utilizing the QPM includes a periodic polarization inverting structure where polarization inverting layers are periodically formed along the waveguide direction of a waveguide made of a ferroelectric.
To periodically invert the phase of the polarization wave, it is sufficient to invert the sign of a nonlinear coefficient. In the ferroelectric, inverting characteristics of domains are used. For instance, in case of lithium niobate (LiNbo.sub.3) crystal, a ferroelectric domain structure has an inverted domain where the polarization can invert at 180 degree in the direction of a c-axis. Particularly, a phenomenon is used such that a polarization inversion can easily occur on a +c surface due to various external factors such as impurities, distortion stress, heat, electric field, and the like.
In case of using the LiNbO.sub.3 crystal as a device substrate, for instance, as shown in FIG. 1, the c-axis direction of the crystal is set to the thickness direction of a device substrate 1 and a periodic inverting structure is formed on a +c surface 2 as a main surface. The periodic inverting structure is formed by the following method. For instance, at first, the direction of the spontaneous polarization of the device substrate 1 is aligned to the c-axis direction. After that, a periodic pattern of Ti (titanium) is formed on the +c surface 2 and is thermally processed for one hour at a temperature (about 1035.degree. C.) which is slightly lower than its Curie temperature and is suddenly cooled. The periodic inverting structure is consequently formed by a plurality of polarization inverting layers 3 formed every intervals. In the polarization inverting layer 3, the polarization is directed in the direction opposite to the original polarization of the device substrate 1. After that, a waveguide 4 is formed at a low temperature by a proton exchanging method so that a waveguide direction traverses the polarization inverting layers 3.
In a wavelength converting device 5 formed as mentioned above, the polarization of the polarization inverting laser 3 is parallel to the c-axis direction of the crystal and is directed in the thickness direction of the waveguide 4 as shown by arrows in FIG. 1.
In case of generating a second harmonic by using the wavelength converting device with the above structure and a semiconductor laser, a laser beam emitted from the semiconductor layer is emitted from a near-field in the TE mode. On the other hand, a waveguide mode waveguided in the waveguide of the wavelength converting device is a TM mode. Thus, when the laser beam in the TE mode merely passes into the wavelength converting device through a lens, the second harmonic can hardly excite in the waveguide. Since means for matching both of the modes to each other is necessary, the near-field of the semiconductor laser and the incident surface of the waveguide cannot directly be coupled to each other. Thus, as shown in FIG. 2, a collimator lens 7, a half-wave plate 8, and a coupling lens 9 are necessary, and they are sequentially arranged on the optical path between a semiconductor laser 6 and the wavelength converting device 5 from the laser 6 side. Therefore, the plane of the polarization is caused to be rotated so that the laser beam is allowed to enter the wavelength converting device 5.
To rotate the plane of the polarization of the laser beam by 90.degree., an apparatus for generating the second harmonic needs a number of elements to be assembled and it is difficult to make the apparatus at a lower price.

Wavelength converting device and its method for manufacturing


A system and a method of detecting a voiding event of a care-receiver uses a temperature sensor for measuring temperatures in real-time at a location adjacent a lower portion of the care-receiver's torso where the voiding event is to occur. The system and method then determines the voiding event based on the measured temperatures.

People with disabilities, impairments and/or special needs (collectively denoted as care-receivers hereinafter) often face serious personal care difficulties. For example, people with impaired mobility generally rely on wheelchairs for a significant amount of time each day, and consequently, face hygienic issues as they often have to urinate or void into a diaper or briefs or clothing when they are in wheelchairs. Sitting in urine-soaked briefs for prolonged period of time causes health issues such as urinary tract infections (UTI), various skin ailments, and the like. Many professionals and organizations provide a wide variety of suggestions for dealing with such issues. For example, Everyday Health (www.everydayhealth.com) provides articles regarding skin rashes and overactive bladder with advices to avoid developing skin rashes.
The occurrence of voiding events is generally unpredictable even if highly scheduled meals are provided to the care-receivers. Caregivers may help care-receivers with incontinence care by regularly changing their protective undergarments such as briefs and underwear. However, caregivers often do so under their own schedules rather than at the care-receivers' needs, at least partially because it is generally difficult to promptly determine when a change of soiled undergarments is required. Consequently, the care-receivers may have to spend significant amounts of time in soiled incontinence undergarments, thereby putting them at risk for UTIs and other diseases resulting increased medical care and cost, and in the worst cases, may result in severe UTI complications and death.
Voiding event detection using disposable sensor units integrated directly into disposable underwear is known. For example, the SIM™ sensor offered by Simavita Limited of North Sydney, Australia, is a single-use disposable device built into a disposable brief to measure, record, and wireless transmit voiding events to a server for creation of a profile to be used for a patient's care. However, such single-use sensors are cost-ineffective and are not environmentally friendly.
Voiding event detection using removable sensors that connect to the disposable undergarment is also known. For example, talli offered by Sensassure of Toronto, ON, Canada, is a sensor device in a form of a reusable strip attachable to the outside of a diaper or brief for detecting voiding events using a non-contact moisture-sensing method. However, such removable sensors have the risk of being soiled and present sanitation concerns due to their placement. Generally, such sensors have to be removed, cleaned, disinfected, and reattached each time when a brief is changed, thereby causing increased amounts of time required by caregivers during providing requisite care.

Incontinence care system and method therefor


A linking ligand compound includes three bidentate chemical moieties distributed about a central chemical moiety. Another linking ligand compound includes a bidentate linking ligand and a monodentate chemical moiety. Coordination polymers include a plurality of metal clusters linked together by residues of the linking ligand compounds.

1. Field of the Invention
In at least one aspect, the present invention relates to the synthesis of multidentate organic ligands, the use of these ligands is to form porous coordination polymers and their application as sorbents or catalyst components.
2. Background Art
Microporous materials are in high demand because of their ability to adsorb a wide variety of guest molecules. These sorption properties make microporous materials attractive for applications such as storage, separation or catalysis. Optimization of these applications requires a combination of high surface area, tunable functionality, and defined pore structure.
Among different classes of microporous materials, coordination polymers have demonstrated a high efficiency for the uptake of several gases and organic molecules. The periodicity of such systems and the ability to modulate the pore size and surface area through modification of either the organic linker or metal cluster have made coordination polymers extremely appealing for sorption and storage applications. A few benchmark coordination polymers which are developed for these purposes include MOF-5 and HKUST-1.
Although the prior art microporous materials work reasonably well, there are a number of unsolved concerns. For example, many materials have relatively low surface areas and pore volumes, with broad pore size distributions.
Against this prior art background, there is still a desire for novel multidentate ligands that are useful for constructing porous materials.

Strategies, linkers and coordination polymers for high-performance sorbents

The Regents of the University of Michigan


A speech recognition apparatus based on a deep-neural-network (DNN) sound model includes a memory and a processor. As the processor executes a program stored in the memory, the processor generates sound-model state sets corresponding to a plurality of pieces of set training speech data included in multi-set training speech data, generates a multi-set state cluster from the sound-model state sets, and sets the multi-set training speech data as an input node and the multi-set state cluster as output nodes so as to learn a DNN structured parameter.

1. Field of the Invention
The present invention relates to an apparatus and method for recognizing speech, and more particularly, to a speech recognition apparatus and method based on a deep-neural-network (DNN) sound model.
2. Discussion of Related Art
A context-dependent deep-neural-network (DNN)-hidden-Markov-Model (HMM) technique using a combination of a DNN and an HMM has been actively applied to sound models for speech recognition by replacing an existing CD-Gaussian-mixture-model-HMM (CD-GMM-HMM) (hereinafter referred to as 'GMM-HMM') technique.
A DNN-HMM technique according to the related art is performed as will be described below.
First, a state of an HMM corresponding to an output node or a target of a DNN structure is determined through a process of learning an HMM, and state-level alignment information of training speech data is extracted.
A process of learning a DNN may be a process of receiving information regarding the state of the HMM determined on the basis of a result of learning the HMM and the state-level alignment information of the training speech data, and obtaining characteristics of a shape which is most distinctive in terms of pattern recognition and model parameters.
In this case, the state-level alignment information may be obtained through a method capable of iterative learning after state-level realignment by including this information in the process of learning a DNN. However, in a DNN learning technique according to the related art, state-level alignment information is determined beforehand and thus an output node of a DNN structure cannot be changed.
Meanwhile, a state of an HMM for recognizing large-vocabulary speech is generally determined according to a decision tree-based method. However, it is inefficient to determine a state of large-size training speech data having different acoustic-statistical characteristics (e.g., a sound model for recognizing English speech of multiple native speakers who can speak, for example, Chinese, Korean, and English) using one decision tree.
A DNN-HMM structured sound model employing DNN structure-based machine learning has a very high discrimination performance and thus has recently been used in the field of pattern recognition including speech recognition by replacing an existing GMM-HMM-based sound model.
However, a DNN-HMM-based learning technique according to the related art is a method of learning a structure having characteristics and parameters that most appropriately discriminate predetermined states and thus is not applicable in the field of speech recognition application performed with respect to multiple native speakers having different acoustic-statistical characteristics.
In this regard, Korean laid-open patent publication No. 10-2006-0133610 entitled "Heart Sound Classification Method Using Hidden-Markov-Model" discloses a heart sound classification method of modeling an HMM using heart sound data and recognizing the modeled HMM.

Apparatus and method for recognizing speech based on a deep-neural-network (DNN) sound model

ELECTRONICS AND TELECOMMUNICATIONS RESEARCH INSTITUTE


A rubbing pedestal for cats includes a flat supporting base incorporating clamp blocks for releasably clamping an upwardly extending pedestal to the base. The pedestal is a flat rectangular member covered on both flat sides with a woven sisal material into which a cat may sink its claws. The opposite end of the pedestal from the base supports a platform which functions as an elevated perch for a cat. The base, pedestal and platform are releasably secured together by two pairs of clamp blocks.

This invention is related to copending application Ser. No. 07/350,294 now U.S. Pat. No. 4,996,946 owned by the inventor hereof.
1. Field of the Invention
This invention relates to comfort stations for house cats, and particularly to an article of furniture for the home where a house cat can stretch its nails and rest in comfort on an elevated platform.
2. Description of the Prior Art
It is well known that house cats seem to have the need to occasionally stretch their nails. Cats have been known to rip drapes and the upholstry on furniture to shreds in an attempt to satisfy this need. Cat owners who are aware of this need sometimes provide a post wrapped with a carpet material to provide the cat of the house with an alternative site where it can "stretch" its nails without damage to the drapes or upholstered furniture. Accordingly, it is an object of the present invention to provide an article of furniture specifically designed for use by a house cat to satisfy its need to "scratch" or "stretch" its nails.
The instinct to scratch or stretch its nails is not the only instinct possessed by a house cat. Another is the apparent need to rub its body on anything or anybody that is available. Cats will rub the sides of their bodies on furniture or on a person's pantlegs, or on a table leg or any other object that is available. It is not known why cats indulge in this rubbing ritual, but it is presumed that in some way it is akin to being stroked by a human hand. Cats have been observed to purr with contentment when engaged in this ritual in the same way that they purr with contentment when held in the arms and stroked. Accordingly, it is another object of the invention to provide a portable article of furniture that provides a relatively rough surface against which a house cat may rub its body to receive a self-administered massage by stroking its body against the rough surface.
Another object of the invention is the provision of a portable pedestal for a house cat that is designed to fit in with the decor of the room in which it is placed, be that a luxurious living room or a rustic family room.
Still another object of the invention is the provision of a portable pedestal for house cats that may be assembled and disassembled quickly and easily for shipping in a knocked-down condition or for storage.
A still further object of the invention is the provision of a novel clamping structure for retaining the upwardly extending rough-surfaced pedestal member securely yet easily removable from the base member.
Yet another object of the invention is the provision of a novel clamping structure that may be utilized to retain the rough-surfaced pedestal member detachably secured to the base and which may also be used to attach a perch member or platform on the end of the rough-surfaced pedestal member remote from the base so as to provide an elevated platform on which the cat may perch.
A still further object of the invention is the provision of a clamp block structure that may be utilized generally for clamping other objects.
The invention possesses other objects and features of advantage, some of which, with the foregoing, will be apparent from the following description and the drawings. It is to be understood however that the invention is not limited to the embodiment illustrated and described since it may be embodied in various forms within the scope of the appended claims.


A method for reducing an off-current of a field effect transistor in which two electrodes of the field effect transistor have fixed voltage values and the rest electrode has an alternating voltage value by an AC voltage pulse generator to form an off-stress near source and drain junctions in turn.

1. Field of the Invention
The present invention relates to field effect transistors and more particularly, to a method and system for reduction of OFF-current in field effect transistors.
2. Discussion of the Related Art
In general, field effect transistors are known to function where one of an electron or a hole plays a role of a carrier that contributes to electrical conduction. In addition, an oxide film is formed on a semiconductor layer and a metal layer is formed on the oxide film. Moreover, thin film transistors have been commonly used as switching elements in liquid crystal display (LCD) devices.
FIG. 1 is cross-sectional view of a field effect transistor according to the related art. In FIG. 1, the field effect transistor includes an active layer 2, an insulating layer 4, a gate electrode 8, a passivation layer 10, and source and drain electrodes 12 and 14. The active layer 2 is formed on a substrate 1, such as a glass or a wafer, and the insulating layer 4 is formed on the active layer 2. The gate electrode 8 is formed on the insulating layer 4, and the passivation layer 10 covers the gate electrode 8 and the insulating layer 4. The source and drain electrodes 12 and 14 contact the active layer 2 through the passivation layer 10 and the insulating layer 4. A source region "s" and a drain region "d" include impurity ions and are spaced apart from each other in the active layer 2. The impurity ions are not present within a channel region 3 located between the source region "s" and the drain region "d." The source electrode 12 is connected to the source region "s" and the drain electrode 14 is connected to the drain region "d." If a voltage is applied to the gate electrode 8 of the field effect transistor, carriers are driven into the channel region 3 and the source and drain electrodes 12 and 14 are in electrical communication with each other. A boundary between the source region "s" and the channel region 3 is commonly referred to as a source junction 2b, and a boundary between the drain region "d" and the channel region 3 is commonly referred to as a drain junction 2a.
Amorphous silicon or polycrystalline silicon may be used for the active layer 2. Amorphous silicon has been commonly used for flat panel display devices, such as liquid crystal display (LCD) devices, since it can be easily deposited over large areas under low temperatures of about 350° C. However, many localized defects occur since amorphous silicon has disordered atomic arrangement and weak Si—Si bonding. Alternatively, polycrystalline silicon has ordered atomic arrangement and electric mobility 100 times as fast as amorphous silicon. However, polycrystalline silicon demonstrates large amounts of leakage currents due to trap boundaries of crystal grains. Accordingly, the defects of both amorphous and polycrystalline silicon materials eventually increase an OFF-current of the field effect transistor, thereby the source and drain electrode 12 and 14 are frequently in electrical communication even when the field effect transistor is a desired OFF-state. The increase of the OFF-current of the field effect transistor decreases an ON-current of the field effect transistor, thereby deteriorating device reliability. The OFF-current condition is considered more serious in the field effect transistor that uses polycrystalline silicon.
Thus, many structural methods have been suggested to overcome the OFF-current problems. For example, a field effect transistor having a dual gate structure or a multi-gate structure has been suggested. In addition, an off-set region may be formed within a vicinity of the source and drain junctions, or a lightly-doped drain structure may be applied to the field effect transistor.
Alternatively, a method to reduce the OFF-current without changing the structure of the field effect transistor has been suggested. For example, the OFF-current can be reduced by generating an OFF-stress to each junction region using two AC (alternating current) voltage pulses to overcome the defects of the silicon active layer. The OFF-stress is generated in the junction regions by applying the AC (alternating current) voltage pulses respectively to the gate electrode and the drain electrode, respectively, as disclosed in U.S. Pat. No. 5,945,866, which is hereby incorporated by reference.
FIG. 2 is an equivalent circuit diagram of a pixel of a liquid crystal panel for a liquid crystal display (LCD) device according to the related art. In FIG. 2, the liquid crystal panel has a gate line 32 disposed along a first direction and a data line 34 disposed along a second direction. The gate line 32 transmits a scan signal voltage and the data line 34 transmits an image signal voltage. Crossings of the gate and data lines 32 and 34 define pixel regions, and the field effect transistor and the liquid crystal capacitor CLC are formed at each of the pixel regions. A thin film transistor is commonly used for the field effect transistor because of its light weight and small dimensions. A gate electrode G of the field effect transistor is connected to the gate line 32, and a drain electrode D is connected to the data line 34. A source electrode S is electrically connected to a pixel electrode (not shown), which is commonly used as one of electrodes for applying a voltage to liquid crystal material (not shown).
Although not shown, the liquid crystal capacitor CLC comprises the pixel electrode, a common electrode, and the liquid crystal material that is disposed between the pixel electrode and the common electrode, wherein a common line 37 is connected to the common electrode. Since the liquid crystal display device usually displays images on a frame-by-frame basis, a voltage that is applied to the liquid crystal capacitor CLC must be maintained until a voltage for a next frame is applied to the liquid crystal capacitor CLC. Accordingly, a storage capacitor CSt is provided to preserve the voltage until the next voltage for the next frame is applied. The storage capacitor CSt is electrically connected in parallel to the liquid crystal capacitor CLC, and may be a storage-on-common type (SOC) storage capacitor CSt that has an additional storage line 36. The storage capacitor CSt serves to stabilize gray level, reduce flicker and residual image, as well as to preserve the signal. Accordingly, the two different AC voltage pulses are applied to the gate electrode G and the drain electrode D of the field effect transistor to reduce the OFF-current.
FIG. 3A is a graph of voltages applied to each electrode of a field effect transistor for reducing an OFF-current in the field effect transistor according to the related art, and FIGS. 3B and 3C are schematic diagrams illustrating voltage values of each electrode of the field effect transistor when the voltages of FIG. 3A are applied according to the related art. In FIGS. 3A to 3C, if a negative voltage of −10V (volt) is applied to the gate electrode G to turn the field effect transistor ON, an electric current flows from the drain electrode D to the source electrode S. Accordingly, a negative voltage of −10V (volt) is subsequently applied to the drain electrode D and is conducted to the source electrode S. Then, the field effect transistor is turned OFF by application of a positive voltage of +30V (volt) to the gate electrode, and a voltage of 0V (volts) is applied to the drain electrode D. Accordingly, the gate electrode G has a voltage value of +30V, the drain electrode D has a voltage value of 0V, and the source electrode S has a voltage value of −10 V, as shown in FIG. 3B. Thus, a significant potential difference exists between the gate electrode G and the drain electrode D, and a significant potential difference exists between the gate electrode G and the source electrode S. Accordingly, an OFF-stress phenomenon occurs at regions near to the drain and source junction 2a and 2b (in FIG. 1). A greater OFF-stress effect is expected to occur at the source junction 2b (in FIG. 1), which is shown in FIG. 3B as an arrow, since the potential difference between the gate electrode G and the source electrode S is larger than the potential difference between the gate electrode G and the drain electrode D. If a negative voltage of −10 V is applied to the gate electrode G again to turn the field effect transistor ON, then the source electrode S is discharged to have a voltage of 0V. Subsequently, a positive voltage of +30 V is applied to the gate electrode G to turn the field effect transistor OFF and a negative voltage of −10 V is simultaneously applied to the drain electrode D. As a result, there are potential differences between the gate electrode G and the drain electrode D, and between the gate electrode G and the source electrode S, as shown in FIG. 3C. Since the potential difference between the gate electrode G and the drain electrode D is larger than the potential difference between the gate electrode G and the source electrode S, a greater OFF-stress effect occurs at the drain junction 2a (in FIG. 1) than the source junction 2b (in FIG. 1). Accordingly, the process reduces the defect of the silicon active layer by generating the OFF-stress at the drain and source junctions 2a and 2b (in FIG. 1). The process uses two AC voltage pulses for the gate electrode G and for one AC voltage pulse for the drain and source electrodes D and S. However, it is not easy to control the period of the AC voltage pulses accurately with proper timing.

This patent is subject to a terminal disclaimer.

Method and system for reduction of off-current in field effect transistors


Systems and methods for dynamic representation of a remote computing environment which can be implemented in the context of a virtual desktop infrastructure. A server hosting a computing environment may communicate system state to a remote client via a network. A representation of the computing environment may be generated by obtaining graphical data of a virtual computing environment, sub sampling the graphical data to determine a plurality of regions, determining a manner to prioritize the plurality of regions, and causing, based on the prioritization, an approximate representation of the graphical data to be transmitted to a second system.

In various contexts, managing the integrity of transmitted data is important. Organizations, for example, often utilize networks of computing devices that are interconnected to communicate with other devices and clients. Organizations may transmit and receive data across networks such as the Internet. The communications often use networks that connect with other networks, and often span multiple geographic regions. As the size and complexities of such networks grow, managing the integrity of transmitted data between devices can be increasingly difficult.
However, there are many challenges to accommodate increasing bandwidth requirements. In several contexts, such as remote computing environments, there may exists challenges in which large amounts of graphical data to a remote client and the remote client may have expectations to interact with the graphical elements in real-time or near real-time so as to mimic the remote computing environment being run locally on the remote client.

Dynamic representation of remote computing environment


A semiconductor memory device having transistors and capacitors on a semiconductor substrate with the lower electrodes and the contact holes for connection with the sources of the transistors formed on a self-alignment basis and a method of producing the same are disclosed. The transistor of the semiconductor memory device formed on the semiconductor substrate has a first insulating layer, a gate electrode, a source portion and a drain portion. The source and drain portions dispose in the vicinity of the gate electrode, on opposite sides of each other relative to the gate electrode, under the first insulating layer and in the semiconductor substrate. The capacitor of the semiconductor memory device has a lower electrode connecting with the source portion, a second insulating layer between the lower electrode and the upper surface of the gate electrode, a third insulating layer covering the source-side sidewall of the second insulating layer and that of the gate electrode, and a fourth insulating layer covering the drain-side of the upper surface and the source-side sidewall of the second insulating layer and that of the gate electrode. Displacement from the upper surface of the insulator on the gate electrode to the source portion is large and the slope is long enough so that the lower electrode of the capacitors formed on the slope may have a relatively large surface and the clearance between the gate electrode and the contact hole for connection with the lower electrode may be significantly reduced.

1. Field of the Invention
This invention relates to semiconductor memory devices such as DRAMs (dynamic random access memories), particularly those having memory cells formed of one transistor and one capacitor, and a method of producing the same.
2. Description of the Related Art
The semiconductor memory device has been demanded to have a larger scale capacity and high speed operation capability as information equipment is developed. In order to respond to this demand, high integration, high speed response and high reliability are required for the semiconductor memory device. Particularly the memory cell array for storing information data must be absolutely integrated at a very high density. However, in the conventional semiconductor memory device, particularly in DRAM having memory cells formed of a transistor and a capacitor, the contact holes through which information lines are connected to the sources or the drains of the transistors must be separated by a certain distance or above from the gate electrodes of the transistors in order not to be made in contact therewith, and thus the memory cells should have design margins in size allowing for this separation.
FIGS. 4 and 5 show the structure of conventional stacked capacitor cells used in a one-transistor/one-capacitor type DRAM. In a method of producing this structure, the gate electrodes, or word lines 12 of MOS transistors 11 which constitute memory cells, are covered by an interfacial isolation film 13, and a photoresist (not shown) is coated over the entire surface of the substrate. Then, the photoresist is patterned by photolithography so that contact holes 15 can be later bored in the interfacial isolation film at the locations corresponding to the sources 14a of the MOS transistors 11.
Then, the interfacial isolation film 13 and the gate insulating film thereunder are selectively etched with this patterned resist used as a mask, so that the contact holes 15 are bored in those films. Thereafter, lower electrodes 17, insulating films 21 and upper electrodes 22 of capacitors 16 which constitute memory cells are deposited sequentially. In addition, the upper electrodes 22 are covered by an interfacial isolation film 23, and contact holes 24 reaching the drains 14b of the MOS transistors 11 are bored in the interfacial isolation film 23. Then, bit lines 25 are formed on the interfacial isolation film covering the holes.
FIGS. 4 and 5 show a pair of memory cells formed in one active region, which are formed by two MOS transistors 11 sharing one drain and serving as access transistors for the corresponding capacitors respectively.
In the conventional structure mentioned above, however, since the contact holes 15 are formed by photolithography, it is difficult to precisely bore the contact holes because of unsufficient precision of mask alignment in exposure. Therefore, a considerably large design margin 26 is necessary between the word line 12 and the contact hole 15 For example, under 1 .mu.m level design rules, the design margin 26 is required 0.5 through 1.0 .mu.m. This large design margin becomes a great interference with the memory cell area reduction for high-density DRAMs.

Semiconductor memory device having memory cells formed of one transistor and one capacitor and a method of producing the same


A method and system for generating a user interface for controlling software components through a user control point device. The user interface system provides multiple software components that each can provide a user interface component. Each user interface component provides a user interface for the corresponding software component. A user control point component requests each software component to provide its user interface component. The user control point component then displays an indication of each software component. In response to the selection of a software component, the user control point component requests the user interface component for that software component to display its user interface through the control point device. When a user interacts with that user interface, the user interface component notifies the corresponding software component of the interaction.

The present invention relates generally to a computer system for generating user interfaces and, more particularly, to a system that generates a user interface for controlling distributed devices.
A large environment, such as a large building, a factory, or a large house, may have hundreds and thousands of devices that control various systems within the environment. These systems may include lighting systems, heating systems, elevators, and various electronic systems (e.g., monitors, cameras, and CD players). In such large environments, the controlling of the devices can be cumbersome. Each device may provide a control panel through which the device can be controlled. For example, a CD player may have a control panel on it for controlling the device to eject the CDs, to pause the CD, and so on. These devices may also provide an electronic interface through which the device can be controlled by a computer. A computer that is connected to the electronic interface may provide a user interface through which a user can control the device. These devices may be connected to a communications channel, such as a serial link, so that a central computer can control the devices. The connections to the communications channel may be direct when the device has an embedded interface to the communications channel or may be indirect by being connected to a computer system that is then connected to the communications channel. To control the devices from a central location, a user interface for each device needs to be developed for the computer at the central location. The development of the user interfaces for controlling these devices from a remote location can be expensive and time-consuming. Moreover, whenever new devices are added to the environment, new user interfaces also need to be developed so that the new devices can be controlled remotely.
In certain environments, such as a large house, it may be desirable to remotely control the devices from various locations rather than at a central location. In addition, it may be desirable to allow control of only certain devices from each location so that the user interface can be customized to the devices that can be controlled. For example, within a media room it may be desirable to control all the devices within that room and to control certain devices (e.g., lights) in adjacent rooms. The use of the same user interface, which is intended for controlling all the devices in an environment from a central location, would be cumbersome if used at multiple locations where it is only desired to control certain devices. For example, it would be cumbersome to have a user interface for controlling all devices within a large building, when only one type of device (e.g., a light switch) should logically be controlled from that location.
A method and system for generating a user interface for controlling software components through a user control point device is provided. The user interface system provides multiple software components that each can provide a user interface component. Each user interface component provides a user interface for the corresponding software component. A user control point component requests each software component to provide its user interface component. The user control point component then displays an indication of each software component. In response to the selection of a software component, the user control point component requests the user interface component for that software component to display its user interface through the control point device. When a user interacts with that user interface, the user interface component notifies the corresponding software component of the interaction. The user control point component may have an associated space (e.g., room within a house). The user control point component may identify each software component associated with that space and provide a user interface for the software components through their user interface components. In addition, a software component may provide a user interface component to more than one user control point component. In this way, multiple users can be controlling the software component simultaneously through different user control point devices. In one embodiment, the user interface component that is provided by a software component is customized to a combination of the user control point device and the particular software component that is requesting the user interface component.

Method and system for generating a user interface for distributed devices


A tape conveyor system for moving a carriage along a path having at least one vertical curve and at least one horizontal curve comprises a carriage track, a tape guide, and a carriage. A block on the tape is movably positioned between two elements on the carriage to effect movement of the carriage along the carriage track. The tape guide orients the tape width horizontally during each vertical curve and vertically during each horizontal curve. The carriage track has two opposing channels, and the carriage has wheels in each channel so that the carriage can move along both horizontal and vertical track portions in a stable manner. A container can be mounted to the carriage via a leveling mechanism which cooperates with cam guide surfaces on the carriage track to control the orientation of the container. Two cam followers are mounted on opposite ends of a leveler arm such that one of the cam followers can be actuated by contact with a cam guide surface to effect the rotation of the transport container with respect to the carriage as the carriage negotiates a vertical curve. A tape drive comprises two smooth rolls and a toothed cog wheel positioned between the rolls such that the tape passes around one roll, then the cog wheel and then the other roll, with the passage from the cog wheel to the second roll being substantially immediately to provide a reverse curvature of the tape.

Pneumatic conveyor systems are extensively utilized in drive-in banking facilities to transport money, checks and other documents in a tubular container which moves through a pneumatic tube extending between a customer's station at a location spaced from the bank building and a cashier's station within the bank building. The pneumatic tube can provide a path which includes numerous legs extending in various directions, both horizontal and vertical. This is particularly advantageous in providing great flexibility in locating either the customer's station or the cashier's station. The pneumatic conveyor systems have generally been satisfactory where the material being transported comprises only checks, deposit slips, paper currency, or other light weight paper documents. However, the transport of heavy articles, e.g., rolls of coins, in such pneumatic conveyor systems can present a problem in that, unless restraining material is included in the tubular container, the articles can move about within the tubular container and thus are free to crash against the forward end of the tubular container when the tubular container changes from a horizontal portion of the conveyor run to a vertical portion of the conveyor run. Such impacts can damage the tubular containers as well as interfere with the smooth movement of the tubular container through the pneumatic conveyor.
While mechanical conveyors, driven by chains, cables or drive tapes, can generally handle heavier loads than the pneumatic conveyor systems, in general they are still subject to the problems of load shifting, particularly upon the transition from a horizontal leg to a vertical leg of the conveyor run. Bavis, U.S. Pat. No. 4,957,188, describes one effort to provide a stabilized carrier for use in conveying food and beverage containers between a processing station in a drive-in restaurant and a customer at a delivery station located remotely from the restaurant. The conveyor has a pair of drive tapes which are horizontally spaced apart from each other and which are driven in unison by a common drive. The carrier basket is suspended from the pair of conveyor drive tapes by mounting blocks and is free to rotate relative to the horizontal axis through the mounting blocks. A stabilizing cam is provided on the carrier basket in engagement with a cam track so as to prevent rocking of the carrier basket. Thus, the carrier basket will remain vertically disposed as the drive tapes translate between the horizontal and vertical flights of the conveyor, provided that all of the flights of the conveyor are located in a single vertical plane. The drive tapes are flexible and can bend to negotiate curves by being guided in a channel or other guiding device. Thus, with the carrier basket being suspended from the horizontally spaced apart pair of drive tapes, the conveyor can readily negotiate the transitions from the vertical to the horizontal and from the horizontal to the vertical. However, the conveyor system is not adapted to provide a transition from one horizontal direction to another horizontal direction, thereby limiting the usefulness of the conveyor system to a planar path.
Bavis, U.S. Pat. No. 5,054,605, discloses a conveyor system utilizing either a single drive tape or a pair of drive tapes, with each tape being connected to a rigid carrier by two connectors spaced apart along the longitudinal length of the carrier, with at least one of the connectors comprising a pin in a slot in order to permit a limited movement of the adjacent portion of the tape with respect to the rigid carrier. This permits accommodation of the increase in longitudinal length of tape between the two attachment points when the carrier passes through a planar transition curve between a horizontal leg and a vertical leg due to the curvature of the tape.
Although U.S. Pat. No. 5,054,605 acknowledges that several prior conveyor systems were designed for conveying items which must remain vertically oriented throughout the conveying movements, such as liquid containers, food items, and the like, the apparatus disclosed in U.S. Pat. No. 5,054,605 is not capable of accomplishing that objective in any conveyor system which provides movement in any direction other than a single horizontal straight line or a single vertical straight line. Whether a pair of drive tapes or a single drive tape is employed, the carriage is positioned vertically with its first end up at the customer station and vertically with its first end down at the teller station, while being in a horizontal position for a portion of the distance between the two stations. Thus, any object placed in the carriage in a right-side-up position in one station would be upsidedown in the other station. Moreover, even though the patent acknowledges that the flexible drive tape is capable of assuming an almost unlimited variety of curves, bends and substantially straight sections, the only disclosed conveyor paths are planar paths and the disclosed apparatus is not suited for conveyor paths having transition curves in different planes.


A three-dimensional array of memory elements is formed across multiple layers of planes positioned at different distances above a semiconductor substrate. The memory elements are each accessible by a word line in a plane and a local bit line. The three-dimensional array includes a two-dimensional array of pillar lines through the multiple layers of planes. The pillar lines are of a first type that act as local bit lines and a second type that provide access to the word lines by having respective memory elements preset to a permanently low resistance state for connecting second-type pillar lines for exclusive access to respective word lines. An array of metal lines on the substrate is switchably connected to the vertical bit lines to provide access to the local bit lines and the word lines.

The subject matter of this application is the structure, use and making of re-programmable non-volatile memory cell arrays, and, more specifically, to efficient access of word lines in three-dimensional arrays of memory storage elements formed on semiconductor substrates.
Uses of re-programmable non-volatile mass data storage systems utilizing flash memory are widespread for storing data of computer files, camera pictures, and data generated by and/or used by other types of hosts. A popular form of flash memory is a card that is removably connected to the host through a connector. There are many different flash memory cards that are commercially available, examples being those sold under trademarks CompactFlash (CF), the MultiMediaCard (MMC), Secure Digital (SD), miniSD, microSD, Memory Stick, Memory Stick Micro, xD-Picture Card, SmartMedia and TransFlash. These cards have unique mechanical plugs and/or electrical interfaces according to their specifications, and plug into mating receptacles provided as part of or connected with the host.
Another form of flash memory systems in widespread use is the flash drive, which is a hand held memory system in a small elongated package that has a Universal Serial Bus (USB) plug for connecting with a host by plugging it into the host's USB receptacle. SanDisk Corporation, assignee hereof, sells flash drives under its Cruzer, Ultra and Extreme Contour trademarks. In yet another form of flash memory systems, a large amount of memory is permanently installed within host systems, such as within a notebook computer in place of the usual disk drive mass data storage system. Each of these three forms of mass data storage systems generally includes the same type of flash memory arrays. They each also usually contain its own memory controller and drivers but there are also some memory only systems that are instead controlled at least in part by software executed by the host to which the memory is connected. The flash memory is typically formed on one or more integrated circuit chips and the controller on another circuit chip. But in some memory systems that include the controller, especially those embedded within a host, the memory, controller and drivers are often formed on a single integrated circuit chip.
There are two primary techniques by which data are communicated between the host and flash memory systems. In one of them, addresses of data files generated or received by the system are mapped into distinct ranges of a continuous logical address space established for the system. The extent of the address space is typically sufficient to cover the full range of addresses that the system is capable of handling. As one example, magnetic disk storage drives communicate with computers or other host systems through such a logical address space. The host system keeps track of the logical addresses assigned to its files by a file allocation table (FAT) and the memory system maintains a map of those logical addresses into physical memory addresses where the data are stored. Most memory cards and flash drives that are commercially available utilize this type of interface since it emulates that of magnetic disk drives with which hosts have commonly interfaced.
In the second of the two techniques, data files generated by an electronic system are uniquely identified and their data logically addressed by offsets within the file. Theses file identifiers are then directly mapped within the memory system into physical memory locations. Both types of host/memory system interfaces are described and contrasted elsewhere, such as in patent application publication no. US 2006/0184720 A1.
Flash memory systems typically utilize integrated circuits with arrays of memory cells that individually store an electrical charge that controls the threshold level of the memory cells according to the data being stored in them. Electrically conductive floating gates are most commonly provided as part of the memory cells to store the charge but dielectric charge trapping material is alternatively used. A NAND architecture is generally preferred for the memory cell arrays used for large capacity mass storage systems. Other architectures, such as NOR, are typically used instead for small capacity memories. Examples of NAND flash arrays and their operation as part of flash memory systems may be had by reference to U.S. Pat. Nos. 5,570,315, 5,774,397, 6,046,935, 6,373,746, 6,456,528, 6,522,580, 6,643,188, 6,771,536, 6,781,877 and 7,342,279.
The amount of integrated circuit area necessary for each bit of data stored in the memory cell array has been reduced significantly over the years, and the goal remains to reduce this further. The cost and size of the flash memory systems are therefore being reduced as a result. The use of the NAND array architecture contributes to this but other approaches have also been employed to reducing the size of memory cell arrays. One of these other approaches is to form, on a semiconductor substrate, multiple two-dimensional memory cell arrays, one on top of another in different planes, instead of the more typical single array. Examples of integrated circuits having multiple stacked NAND flash memory cell array planes are given in U.S. Pat. Nos. 7,023,739 and 7,177,191.
Another type of re-programmable non-volatile memory cell uses variable resistance memory elements that may be set to either conductive or non-conductive states (or, alternately, low or high resistance states, respectively), and some additionally to partially conductive states and remain in that state until subsequently re-set to the initial condition. The variable resistance elements are individually connected between two orthogonally extending conductors (typically bit and word lines) where they cross each other in a two-dimensional array. The state of such an element is typically changed by proper voltages being placed on the intersecting conductors. Since these voltages are necessarily also applied to a large number of other unselected resistive elements because they are connected along the same conductors as the states of selected elements being programmed or read, diodes are commonly connected in series with the variable resistive elements in order to reduce leakage currents that can flow through them. The desire to perform data reading and programming operations with a large number of memory cells in parallel results in reading or programming voltages being applied to a very large number of other memory cells. An example of an array of variable resistive memory elements and associated diodes is given in patent application publication no. US 2009/0001344 A1.
A three dimensional (3D) memory array is organized so that memory elements occupy multiple planes or multiple device levels, forming a structure in three dimensions (i.e., in the x, y and z directions, where the y direction is substantially perpendicular and the x and z directions are substantially parallel to the major surface of the substrate).
An issue with 3D memory array is the large number of word lines and bit lines that need to be deployed and more particularly, the requirement for a large number of word line drivers and bit line drivers that occupy space. Existing 3D memory has an array of bit line CMOS drivers formed on the substrate below the footprint of the stacked memory planes. That leaves no room for additional word line drivers, which must be located elsewhere on the substrate.
U.S. Published Application No. 2009/0122598 to Toda, et al ("Toda"), or U.S. Published Application No. 2010/0289084 to Yoon, et al ("Yoon") disclose extending the word lines outside the edge of the memory area and connect each via a zia to a CMOS transistor in the substrate. The CMOS transistor acts as a switch and word line driver. This has the disadvantage of increasing the die size of the memory. The more word lines in each plane and the more planes in the 3D memory, the more number of zias and word line drivers will be needed, which occupy additional die space.
U.S. Pat. No. 8,547,720 discloses a 3D memory where a portion of the vertical bit lines are used to access the word lines. Each word line is extended to an outside region beyond the memory elements to which it serves and a connector or contact is used to provide the electric conduction between the word line and a vertical bit line in the outside region. However, many of the processes in manufacturing the memory device have the structures in multiple memory layers formed in parallel and are often not amenable to replacing memory elements by metal connectors at different locations of each memory plane.
The need remains for a 3D memory having efficient and compact implementation of word line and bit line decoding.

Non-volatile 3D memory with cell-selectable word line decoding