An exchange system comprising a plurality of redundant clock supply modules for receiving respective clock signals to maintain synchronization. Each redundant clock supply module includes a phase locked loop coupled to receive a network synchronizing reference signal, for generating a most significant clock of the exchange system synchronized to the network synchronizing reference signal; a clock generator for counting the most significant clock to generate a plurality of system clocks including a least significant clock and a first frame pulse; and a redundancy synchronizer for synchronizing the first frame pulse and a second frame pulse from a counterpart redundancy module to generate a redundancy synchronization signal for establishing synchronization between redundancy modules from the most significant clock to the least significant clock.

1. Technical Field
The present invention relates to a clock generating circuit for an exchange system, and more particularly, relates to such a clock generating circuit and method for an exchange system capable of maintaining the constant timing in a range from a most significant clock to a least significant clock and redundancy synchronization.
2. Background Art
Generally, an exchange system improve reliability by using redundancy modules in a parallel fashion to insure that a particular task is carried through completion even when one of the modules becomes impaired. Such a redundant system is tolerant of faults as disclosed, for example, in U.S. Pat. No. 5,117,442 for Methods And Circuits For Synchronizing Signals In A Modular Redunaant Fault Tolerant Computer System issued to Hall, U.S. Pat. No. 5,377,205 for Fault Tolerant Clock With Synchronized Reset issued to Shi, U.S. Pat. No. 5,377,206 for Multiple-Channel Fault-Tolerant Clock System issued to Smith, and U.S. Pat. No. 5,537,655 for Synchronized Fault Tolerant Reset issued to Truong.
In such an exchange system employing redundancy modules, it is desirable that redundancy modules perform operations in synchronization with respect to other parallel modules. Conventional redundancy synchronization system which seeks to establish such synchronization typically requires synchronization of respective system clocks of high and low frequency bands between redundancy modules. While there are other clock synchronization systems known in the art as disclosed, for example, in U.S. Pat. No. 5,459,764 for Clock Synchronization System issued to Ohgami et al., it is my observation that none is available to synchronize clocks generated from redundancy modules with a constant timing in the range from a most significant clock to a least significant clock.

Redundancy clock supply module for exchange system


Provided is a printed circuit board consisting of laminated substrates each with a fiberglass cloth contained in its resin and with a wiring arranged onto at least one of its surfaces, wherein, in at least one of substrates provided with a wiring for transmitting a higher speed signal than that transmitted by wirings arranged onto the other substrates, a fiberglass cloth having a different property from that of the other substrates is contained.

In recent years, with the increase in data processing speed of calculating equipment such as a computer, decrease in the dielectric constant of a printed circuit board is demanded.
A printed substrate used for a usual printed circuit board is fabricated by impregnating a base material such as a fiberglass cloth or a paper with resin material. Accordingly, in decreasing the dielectric constant of a printed circuit board, effective is decrease in the dielectric constant of a fiberglass cloth or of a resin.
Further, in recent years, with the increase in scale of an LSI (Large Scale Integration), degradation in reliability of a connection between a BGA (Ball Grid Array) package and a printed circuit board owing to the difference between their thermal expansion coefficients has become a problem. For the purpose of improving such connection reliability, demanded is decrease in the thermal expansion coefficient of a printed circuit board.
As a method of fabricating a printed circuit board by the use of a low dielectric constant resin, it is considered, for example, to use the low dielectric constant resin only for a layer for transmitting a high speed signal and use a usual resin for the other layers. The cost of such a printed circuit board using a low dielectric constant resin only for a layer for transmitting a high speed signal and using a resin with a usual dielectric constant for the other layers is lower than that of a printed circuit board with all layers made of the low dielectric constant resin.
However, in the case of such a printed circuit board using a low dielectric constant resin only for a layer for transmitting a high speed signal and a usual resin for the other layers, the use of different resins in the fabrication process lowers the productivity.
As a fiberglass cloth with a lower dielectric constant and a lower thermal expansion coefficient compared to that made of E-glass, which is a usual 10 fiberglass cloth, for example, there are fiberglass cloths made of D-glass, S-glass and the like. However, the use of these fiberglass cloths has a problem in that the cost of substrate material becomes high. Additionally, D-glass has a problem with drill processability such as wear of a drill and hole positioning accuracy in drilling.
Patent Document 1 (Japanese Laid-open Patent Application No. 2000-234239) discloses, as a substrate for a printed circuit board with low dielectric constant, low cost and excellent drill processability, a substrate using a fiberglass cloth in which either of its warp and weft is made from E-glass and the other from D-glass. Through such combining of different types of glass yarn, the fiberglass cloth of Patent Document 1 can be given a different property from the original one. Further, by fabricating a printed circuit board with the fiberglass cloth of Patent Document 1, decrease in dielectric constant and that in thermal expansion coefficient become possible.
However, even in the case of using a fiberglass cloth consisting of different types of glass yarn such as in Patent Document 1, there is no change in the fact that a high cost material with a low dielectric constant or a low thermal expansion coefficient is used as the warp or the weft. Accordingly, the fiberglass cloth of Patent Document 1 has a problem in that it costs higher than a usual fiberglass cloth.
Further, the printed circuit board according to Patent Document 1 has a structure consisting of laminated fiberglass cloths each containing low dielectric constant glass yarn with poor drill processability. Accordingly, the fiberglass cloth of Patent Document 1 has also a problem with wear of a drill and hole positioning accuracy in drilling, if compared with a usual fiberglass cloth.
The objective of the present invention is to provide a printed circuit board which enables transmission of a high speed signal, with low cost and with no degradation in processability.

Printed circuit board consisting of laminated substrates and electronic device comprising the same


A distance-measuring apparatus is arranged to project light toward an object at a distance to be measured, receive reflected light from the object, and detect the distance to the measured object through arithmetic operation and integration. In the distance-measuring apparatus, an integrating capacitor discharge/charge to a maximum when a time necessary for a first integration is longer a minimum. In the detection of the distance to the object, when the time necessary for the first integration is longer than the minimum time, a first integration and a second integration by the integrating capacitor are carried out repeatedly.

1. Field of the Invention
The present invention relates to a distance-measuring apparatus for measuring the distance to an object and, more particularly, to an active distance-measuring apparatus suitably used in cameras and other equipment.
2. Related Background Art
The active distance-measuring apparatus used in the cameras etc. is arranged to project light from an infrared-emitting diode (hereinafter referred to as xe2x80x9cIREDxe2x80x9d) toward the measured object, to receive reflected light of the projected light by a position sensing device (hereinafter referred to as xe2x80x9cPSDxe2x80x9d), to process a signal from this PSD by a signal processing circuit and an arithmetic circuit to output distance information, and to determine the distance to the measured object by a CPU. Since the distance measurement with only one projection of light can cause an error, it is desirable that a plurality of light projection operations be carried out to gain a plurality of distance information pieces and that the plurality of distance information pieces be integrated in a fixed period by an integrating circuit to be averaged. The integral of distance information by the integrating circuit is carried out by applying a reference voltage to an integrating capacitor to store charge therein and discharging the capacitor according to the distance information from that state.
There is, however, a possibility that the distance-measuring apparatus described above fails to carry out accurate distance measurement. Namely, in cases wherein the discharge time of the integrating capacitor is changed depending upon the distance measurement conditions etc., discharge amounts vary depending upon the difference in the discharge time. Therefore, the capacitance of the integrating capacitor can be utilized fully as long as the discharge amount is large. However, if the discharge amount is small, the integral operation cannot be performed by fully utilizing the capacitance of the integrating capacitor, and the measurement accuracy will not be always sufficient.
Therefore, the present invention has been accomplished in view of this point and an object of the present invention is to provide a distance-measuring apparatus that can measure the distance with improved measurement accuracy.
A distance-measuring apparatus according to the present invention is a distance-measuring apparatus comprising: light projecting means for projecting pulses of light toward a measured object; light receiving means for receiving reflected light of the light projected toward the measured object, at a photoreceptive position on a position sensing device according to a distance to the measured object and outputting a signal according to the photoreceptive position; arithmetic means for carrying out an arithmetic operation based on the signal outputted from the light receiving means and outputting an output ratio signal according to the distance to the measured object; integrating means comprising an integrating capacitor, the integrating means carrying out a first integral in which the signal outputted from the arithmetic means is integrated by discharging/charging the integrating capacitor according to the signal outputted from the arithmetic means and thereafter carrying out a second integral by charging/discharging the integrating capacitor at a constant current, the integrating means comparing a voltage of the integrating capacitor with a reference voltage during the second integral and outputting a comparison result signal according to a result of the comparison; and detecting means for detecting the distance to the measured object, based on the signal outputted from the integrating means; wherein the integrating means is arranged in such a manner that a capacitance of the integrating capacitor is set so as to discharge/charge the integrating capacitor to the maximum when a time necessary for the first integral is minimum, and wherein the integrating means repeatedly carries out the first integral and the second integral of the integrating capacitor when the time necessary for the first integral is longer than the minimum time, in detection of the distance to the measured object.
Another distance-measuring apparatus according to the present invention is a distance-measuring apparatus comprising: light projecting means for projecting pulses of light toward a measured object; light receiving means for receiving reflected light of the light projected toward the measured object, at a photoreceptive position on a position sensing device according to a distance to the measured object and outputting a signal according to the photoreceptive position; arithmetic means for carrying out an arithmetic operation based on the signal outputted from the light receiving means and outputting an output ratio signal according to the distance to the measured object; integrating means comprising an integrating capacitor, the integrating means carrying out a first integral in which the signal outputted from the arithmetic mean s is integrated by discharging or charging the integrating capacitor according to the signal outputted from the arithmetic means and thereafter carrying out a second integral by charging/discharging the integrating capacitor at a constant current, the integrating means comparing a voltage of the integrating capacitor with a reference voltage during the second integral and outputting a comparison result signal according to a result of the comparison; and detecting means for detecting the di stance to the measured object, based on the signal outputted from the integrating means; wherein the integrating means comprises a plurality of integrating capacitors of different capacitances and wherein the integrating means carries out the first integral and the second integral while selecting one of the plurality of integrating capacitors so as to discharge/charge the integrating capacitor to the maximum in detection of the distance to the measured object.
Still another distance-measuring apparatus according to t he present invention is a distance-measuring apparatus comprising: light projecting means for projecting pulses of light toward a measured object; light receiving means for receiving reflected light of the light projected toward the measured object, at a photoreceptive position on a position sensing device according to a distance to the measured object and outputting a signal according to the photoreceptive position; arithmetic means for carrying out an arithmetic operation based on the signal outputted from the light receiving means and outputting an output ratio signal according to the distance to the measured object; integrating means comprising an integrating capacitor, the integrating means carrying out a first integral in which the signal outputted from the arithmetic means is integrated by discharging/charging the integrating capacitor according to the signal outputted from the arithmetic means and thereafter carrying out a second integral by charging or discharging the integrating capacitor at a constant current, the integrating means comparing a voltage of the integrating capacitor with a reference voltage during the second integral and outputting a comparison result signal according to a result of the comparison; and detecting means for detecting the distance to the measured object, based on the signal outputted from the integrating means; wherein the integrating means comprises a plurality of current sources of different output current values and wherein the integrating means carries out the first integral while selecting one of the current sources so as to discharge/charge the integrating capacitor to the maximum in detection of the distance to the measured object.
The present invention can maximize the utilization of the dischargeable or chargeable dynamic range of the integrating capacitor on the occasion of the first integral. Therefore, improvement can be made in the distance measurement accuracy.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

Distance-measuring apparatus comprising a plurality of integrating capacitors


Methods, systems, and software for improving the product quality of a production line having multiple production steps, at least some of which employ multiple individual tools, including producing product lots using different combinations of tools, setting a quality benchmark for the resulting product lots, identifying product lots that meet the quality benchmark, identifying the tools used to produce the identified quality product lots, and producing additional product lots using at least substantially the identified quality tools.

The present invention relates to production line processes, and more particularly to improving lot quality for product lots produced on a production line having a plurality of production steps, where at least some of the production steps utilize a plurality of individual tools.
A production line typically refers to a set of sequential manufacturing operations, where each step in the sequence brings the raw material submitted to the production line closer to the form of the desired manufactured product. The product of a given production line may be the final desired product, or the production line may produce an intermediate material that requires additional manufacturing steps, perhaps by traversing one or more additional production lines, in order to obtain the desired overall final product.
It is not unusual for a given production line to include multiple production steps, and some or all of these production steps may in turn employ multiple individual tools or workstations, where each tool is capable of carrying out the desired fabrication for that production step. In such cases each individual product lot may take very different routes through the production line overall, as each tool in a production step that includes multiple tools represents a branch in the flow of product.
While this kind of multiplicity may enhance overall throughput, it presents particular challenges when product lots begin exhibiting flaws or defects. The time and effort required to troubleshoot the entire production line and identify the particular tools and workstations that are generating the defects represents a substantial loss in valuable production time.

International Business Machines Corporation


Example embodiments relate to a mechanism for linking objects to obtain an executable file. In particular, example embodiments include a mechanism that determines a linker order for a plurality of objects included in a version of an executable file and a mechanism that generates a scatter loading file for the version of the executable file, the scatter loading file ordering the plurality of objects using the linker order. Example embodiments also include a mechanism that links the plurality of objects using the scatter loading file to create the version of the executable file.

Computer programs, which may be implemented in the form of software or firmware executable on a computing device, are susceptible to errors or faults that cause incorrect or unexpected results during execution. Such errors or faults are more commonly known as "bugs." In situations where a bug will affect performance, render a product unstable, or affect the usability of the product, the developer may find it advisable to release a software or firmware update to correct the problem. A developer may also release an update to add additional features or improve performance of the product. In general, the update includes a number of instructions used to transform the existing version stored on the user device to the updated version.
In a typical implementation, a developer transmits the software or firmware update package to the user over a wired or wireless network. For example, when the user device is a mobile phone, portable reading device, or other portable device, the user may receive the update over a cellular or other wireless network. Similarly, when the user device is a desktop or laptop computer, the user may receive the update over a wired network.
Regardless of the transmission medium used to transmit the update to the user, it is desirable to minimize the size of the update package. By making the update package as small as possible, the developer may reduce the amount of time required to transmit the update to the user and to install the update on the user's device, thereby resulting in an increase in the user's satisfaction. Similarly, minimizing the size of the update package reduces bandwidth usage, thereby reducing costs to both the user and the network provider. Existing solutions employ a number of techniques in an attempt to generate an update package of minimal size, but, ultimately, could be improved to further decrease download time, bandwidth usage, and installation time.

Object linking based on a determined linker order


The subject of the present invention is a pallet carrier for machine tools, said carrier being mounted on an NC work table and comprising profiled slideways as well as centering elements and hydraulic clamping members. For thorough cleaning and improved adjustment the invention provides pressure-fluid ducts within the pallet carrier coupled to quick-action connectors in the front of the pallet carrier and leading to spray nozzles which are disposed within the slide faces of the said slideways.

Pallet carriers of the above-specified type are known in various forms and are employed in program-controlled milling and drilling machines as well as machining centers so as to permit rapid and safe changing of the works loaded on pallets. One of the basic prerequisites for the repeated performance of identical machining operations to be carried out on the changed works is the automatic and high-precision positioning of the switched pallets on the pallet carrier and their firm mounting in the respective prescribed machining positions. With known pallet carriers there arises the problem that the pallets at the end of their transfer movement rest directly on the slideways and upon insertion of the centering bolts still have to perform some slight lateral adjusting movements in the transitional regions between static friction and sliding friction before the hydraulic clamping members become fully effective. This affects the precise positioning of the pallet on the pallet carrier.
Further, it has been found that the operability of full automatic machine tools is significantly reduced by deposits constituted of solid particles, fine chips and the like on the slide faces of the various slideways. When some object such as a pallet moves across these slide faces, said deposits will be urged into the frequently employed ductile slideway linings and will result in damage to the fine-finished slide faces.


A plastic container closure comprising a top panel, a skirt portion, an annular protruded portion that is formed inwardly from the inner surface of the top panel and on the inside of a portion near the root of the skirt maintaining a small gap therebetween, and a sealing liner that is fitted by press-molding on the inside of the top panel, wherein a substantially vertical portion is formed on said liner along the inner surface of the annular protruded portion, and sealing performance is maintained by the engagement between the outer edge of the mouth of the container and the substantially vertical portion. Since the sealing is accomplished over a surface having a predetermined width in the up-and-down direction, the sealing performance is not impaired even when the top panel is deformed by the pressure. Moreover, favorable sealing performance is maintained even against shock that is given to the container at the time of fitting the closure.

1. (Field of the Invention)
The present invention relates to a plastic container closure and to a method of producing the same. More specifically, the invention relates to a plastic container closure with liner featuring high sealing precision, excellent sealing performance to the mouth of the container and, particularly, excellent shock-resistant sealing performance and pressure-resistant sealing performance, and to a method of producing the same.
2. (Description of the Prior Art)
In recent years, metal container closures have been replaced by plastic container closures for hermetically sealing the mouths of plastic bottles and glass bottles owing to their merits of easy disposal and recycled use.
Some plastic container closures use, as the sealing material, the synthetic resin itself that is forming the inner surface of the top panel of the container closure. From the standpoint of obtaining hermetically sealing performance and, particularly, pressure-resistant sealing performance, however, it is desired to employ a liner or a packing that is excellent in softness and cushioning property.
Japanese Patent Publications Nos. 44627/1988, 48704/1988 and 8141/1994 are disclosing container closures provided with a liner, wherein provision is made of an inwardly extending annular liner-holding member on the inner surface of a skirt portion which is integrally continuous to the outer peripheral edge of the top panel, so that the liner will not escape from the closure shell.
Furthermore, Japanese Patent Publication No. 13349/1994 discloses a plastic container closure having a packing provided in the closure shell and further having a plurality of annular ribs formed on the top panel of the container closure.
According to the former-method of providing an annular liner-holding member on the inner surface of the skirt portion, however, a portion of the annular holding member of the container closure shell must be forcibly released at the time of molding the container closure shell and, hence, the annular liner-holding member must have a reduced thickness. In press-molding the liner, therefore, the annular holding member is deformed in an undulated manner at the time of bringing the outer sleeve of the molding tool and the annular holding member into engagement together, whereby the liner leaks outwardly or it becomes difficult to strictly control the size of the sealing portion on the outer periphery of the liner.
The container closure used for the contents that produce pressure loses pressure-resistant sealing performance due to its buckling deformation at the top panel portion. It is therefore desired to accomplish the sealing along the outer peripheral portion of the mouth of the bottle rather than at the top of the mouth of the bottle. The above-mentioned former container closure, however, does not permit to establish even such a sealing structure.
On the other hand, the latter container closure is satisfactory from the standpoint of accomplishing the sealing along the outer peripheral portion of the mouth of the bottle, but requires cumbersome operation for fitting the packing piece by piece into a number of container closures. Besides, the packing that is fitted may often escape, which is not still satisfactory from the viewpoint of operability.

Method of producing a plastic container closure


A microstrip plane antenna and a helical antenna are arranged substantially in line therewith. A base conductor of the microstrip plane antenna is electrically coupled with the helical antenna, thereby allowing stable communications with a orbiting communications satellite in the sky.

The concept of a portable telephone which uses a low or intermediate orbiting satellite as a communications satellite, has recently been proposed by various corporations. As the frequency bands for use in such communications, a frequency band of 1.6 GHz is assigned to communications from a ground portable telephone to a communications satellite, and a frequency band of 2.4 GHz is assigned to communications from the communications satellite to the ground portable telephone. The frequency band of 1.6 GHz is also assigned to a frequency band for use in bidirectional communications between ground stations and the communications satellite. A circularly polarized wave is commonly used in the communications in order to ensure the quality of a communications circuit.
An antenna has already been proposed as means for improving the quality of the communications circuit (as disclosed in Unexamined Japanese Patent Application No. Hei-7-183719). Specifically, a base conductor extends from a plane antenna in the direction opposite to an antenna element in order to improve the directivity of the antenna at a low elevation angle. FIG. 10 illustrates an example of a conventional antenna. In order to improve the directivity of the antenna at a low elevation angle, a microstrip plane antenna (MSA) 1 is comprised of a dielectric substrate 1c, a patched radiating element 1b provided on the dielectric substrate 1c, a ground conductor 1d attached to the bottom of the radiating element 1b, and a cylindrical ground conductor 1e downwardly extending from the base conductor 1d.
In a case where the conventional antenna receives an incoming circularly polarized wave from a satellite or sends the circularly polarized wave from a ground station to the satellite at a low elevation angle, the gain of the antenna and the axial ratio of the circularly polarized wave become too large, which in turn affects the quality of the communications circuit that is liable to variations in the positional relationship between the antenna of portable communications equipment and the antenna of the satellite. Thus, it has been difficult to maintain the sensitivity of communication of the antenna in every direction of the sky.
The present invention has been conceived in view of the aforementioned drawback in the art, and the object of which is to particularly improve the directivity and axial ratio of an antenna having a circularly polarized wave mode at a low elevation angle.
According to the present invention, the above-described object is accomplished by the structure disclosed in appended claims of the specification. More specifically, the present invention provides a composite antenna comprising:
a microstrip plane antenna (MSA) which possesses a circularly polarized wave mode and is made up of a conductive plate serving as a common base conductor, a dielectric layer provided on the conductor plate, and a patched radiating element provided parallel to the conductor plate with the dielectric layer between them; PA1 a linear radiating element which is helically wrapped in a substantially coaxial relationship with respect to the microstrip plane antenna and is provided below the conductor plate; and PA1 the upper ends of the helically coiled linear radiating element being electrically connected to the conductor plate, thereby forming a helical antenna. The helical antenna may be connected to the conductor plate by DC or capacitive coupling.
The directivity of a radiation pattern at a high elevation angle greatly depends on a plane portion of the patched radiating element of the MSA. In contrast, the directivity of the radiation pattern at a low elevation angle greatly depends on the helical antenna and the electric field developed between the periphery of the patched radiating element of the MSA and the base conductor.
If the base conductor of the MSA is downwardly extended as are the base conductor of the conventional antenna, the antenna has a high sensitivity with regard to a polarized wave in the axial direction of the antenna (i.e., a vertically polarized wave) but a low sensitivity with regard to a horizontally polarized wave.
According to the present invention, the sensitivity of the antenna with regard to the horizontally polarized wave is improved by electrically coupling the helical antenna to the conductor of the MSA in the way as previously described. The helical antenna contributes to improvements in the sensitivity of the antenna with regard to the horizontally polarized wave, due to horizontal components made of high frequency currents which flow through the helical antenna. The line width, length, the number of turns of the helical element, and the pitch with which the helical element is coiled, may be designed according to a satellite communications system as required.


A flexible protective support wrap or boot for supporting and protecting the lower leg of a horse, including the fetlock joint, is formed of a panel having a layer of flexible support material, an outer layer of closed loop fabric and an inner layer of woven fabric for contact with the horse's leg. Spaced apart pocket or cup portions are formed in the panel to engage the fetlock joint in overlying relationship to each other when the wrap is secured around the leg. A splint bone protection pad may be secured between and spaced from the side edges and provided with a ridge for locating the pad between the cannon bone and the front deep digital flexor tendon. The entire panel may include a layer of shock absorbing material in addition to the flexible support layer. Multiple spaced apart fastener straps with hook fastener pads are secured to the panel adjacent one side edge for engagement with the loop fabric layer to secure the wrap around the leg in snug fitting relationship.

Horses are particularly susceptible to injuries to the lower legs resulting from stress and shock forces incurred during hard running and from external blows due to the horse kicking itself or being kicked by other horses in close proximity, such as during races.
Accordingly, flexible, support boots or wraps have been developed to protect the lower leg area from external blows and to provide support for the tendons, bones and suspensory ligaments. Examples of prior art leg support wraps for horses are disclosed in U.S. Pat. No. 5,115,627 to Scott and 5,579,627 to Vogt.
However, in spite of the prior devices developed, such as disclosed in the Scott and Vogt patents, certain problems have gone unsolved with regard to providing support and protection for equine limbs, such as both the front and rear lower legs of a horse, particularly between the pastern and the knee and including the ligaments, tissues, tendons, the fetlock, fetlock joint and the splint bone. The fetlock joint, in particular, is susceptible to injury during hard running since stress on the joint structure tends to cause the joint to flex sufficiently to overstretch the joint tissues and such that the fetlock will impact the ground.
The construction of prior art support wraps does not provide adequate protection for the fetlock and the fetlock joint. For example, wraps which are provided with laterally extending straps or cradle slings for the fetlock are susceptible to being attached improperly when the wrap is applied to the leg, thus not adequately supporting the fetlock or the leg tendons and tissues. Moreover, the so-called fetlock cradle sling straps of the wraps disclosed in the Scott and Vogt patents do not adequately cover the fetlock and thus do not add additional protection to the fetlock to prevent injury from impact blows or contact with the ground, for example.
Prior art wraps have also been susceptible to rapid wear and deterioration of the cradle sling portions of wraps applied to the rear legs, since the fetlock joints of the rear legs, in particular are likely to make hard and scuffing contact with the ground.
Another problem with prior art support devices pertains to the difficulty with which the wrap or support is attached to the leg and properly positioned on the leg. If the wrap is not properly positioned on the leg, support for the suspensory ligaments, tendons and bone structure is inadequate and, if the wrap is improperly secured, it may become loose and fall off during use. If the wrap is applied too tightly it will be uncomfortable to the horse and may actually be the cause of injury.
Another longstanding problem in the art of protecting and supporting the lower legs of a horse pertains to the tendency for the horse to kick itself in the vicinity of the splint bone of the lower leg. This action typically occurs during turning movements of the horse while it is running and may result in breaking the bone in some instances.
Accordingly, further improvements in support wraps or boots for horses' legs have been sought and have been obtained with the present invention.


A fiberoptic assembly for optical spectroscopic analysis of a sample. In a preferred embodiment, the assembly is well-suited for use inside the working channel of an endoscope and comprises a tubular outer jacket and a tubular inner jacket, the inner jacket being coaxial with and positioned inside the outer jacket. The open front end of the inner jacket is spaced rearwardly a short distance relative to the open front end of the outer jacket. The outer jacket has an outer diameter of approximately 2.2 mm. The assembly also includes a plug made of fused silica. The plug has a front cylindrical portion of comparatively large cross-sectional diameter and a rear cylindrical portion of comparatively small cross-sectional diameter. The front portion is mounted within the outer jacket by a friction-fit and extends longitudinally from the open front end thereof to the open front end of the inner jacket. The rear portion of the plug is mounted within the inner jacket by a friction-fit and extends rearwardly from its open front end for a short distance. A narrow-band filter in the form of a dielectric-coating is formed on the rear end of the rear portion of the plug. The assembly also includes an illumination fiber centered within the inner jacket and spaced rearwardly a short distance from the narrow-band filter. The output end of the illumination filter is shaped to collimate light emergent therefrom. The assembly additionally comprises a plurality of light collection fibers, which fibers are disposed within the outer tubular jacket and are spaced about the outside of the inner tubular jacket.

The present invention relates generally to the field of optical spectroscopy and more particularly to the use of optical spectroscopy to observe, analyze and/or characterize biological materials.
The use of optical spectroscopy as a tool for the in vivo and/or in vitro analysis of biological tissues and materials has been studied extensively over approximately the last ten years. This work has demonstrated that optical spectroscopy can be used to provide useful information about both the chemical composition and the morphological structure of biological tissues and materials. Fluorescence spectroscopy and elastic scattering are two of the most common types of optical spectroscopy techniques used to study biological materials. In fluorescence spectroscopy, the photoexcitation of molecules present in a tissue being examined is used to cause the tissue to emit a fluorescence signal that is characteristic of a particular tissue state, e.g., normal vs. benign tumor vs. malignant tumor, etc. In the case of elastic scattering, the absorption and scattering effects that a sample tissue exhibits to illumination provide information that can be used to discern the structure and makeup of the sample. Both of the aforementioned techniques provide a good signal-to-noise ratio for short exposure times to the illuminating light.
An example of fluorescence spectroscopy is disclosed in U.S. Pat. No. 5,131,398, inventors Alfano et al., which issued Jul. 21, 1992, and which is incorporated herein by reference. More specifically, the aforementioned patent describes a method and apparatus for distinguishing cancerous tumors and tissue from benign tumors and tissue or normal tissue using native fluorescence. The tissue to be examined is excited with a beam of monochromatic light at 300 nm. The intensity of the native fluorescence emitted from the tissue is measured at 340 and 440 nm. The ratio of the two intensities is then calculated and used as a basis for determining if the tissue is cancerous as opposed to being benign or normal. The method and apparatus are based on the discovery that, when tissue is excited with monochromatic light at 300 nm, the native fluorescence spectrum over the region from about 320 nm to 600 nm is substantially different for cancerous tissue than for either benign or normal tissue.
Still another type of optical spectroscopy that has been used to study biological materials is Raman spectroscopy. Raman spectroscopy, which arises from inelastic scattering of molecules within a sample, results in the generation of a Raman spectrum, said Raman spectrum containing one or more spectrally narrow peaks. These peaks can be used to identify large biological molecules within the sample or, in some cases, to identify the composition of complex, multicomponent samples. Recently, the use of Raman spectroscopy in the study and diagnosis of diseased tissues has been shown.
For example, in U.S. Pat. No. 5,261,410, inventors Alfano et al., which issued Nov. 16, 1993, and which is incorporated herein by reference, there is disclosed a method for determining if a tissue is a malignant tumor tissue, a benign tumor tissue, or a normal or benign tissue using Raman spectroscopy. Said method is based on the discovery that, when irradiated with a beam of infrared, monochromatic light, malignant tumor tissue, benign tumor tissue, and normal or benign tissue produce distinguishable Raman spectra. For human breast tissue, some salient differences in the respective Raman spectra are the presence of four Raman bands at a Raman shift of about 1078, 1300, 1445 and 1651 cm.sup.-1 for normal or benign tissue, the presence of three Raman bands at a Raman shift of about 1240, 1445 and 1659 cm.sup.-1 for benign tumor tissue, and the presence of two Raman bands at a Raman shift of about 1445 and 1651 cm.sup.-1 for malignant tumor tissue. The aforementioned patent also teaches that, for human breast tissue, the ratio of intensities of the Raman bands at a Raman shift of about 1445 and 1659 cm.sup.-1 is about 1.25 for normal or benign tissue, about 0.93 for benign tumor tissue, and about 0.87 for malignant tumor tissue.
In addition to having applications of the type described above, Raman spectroscopy has also been suggested in recent reports to have the potential to be used in the study and diagnosis of the evolution of precancerous and cancerous lesions in human tissues in vivo.
The Raman scattering process is based on the inelastic scattering of light and typically generates an extremely weak signal, e.g., 10.sup.-6 -10.sup.-14 I.sub.0 where I.sub.0 is the illuminating laser light intensity. The Raman spectrum comprises two spectral components, the Stokes spectrum and the antiStokes spectrum. The Stokes spectrum is located at longer wavelengths than the illuminating laser line whereas the antiStokes spectrum is located at shorter wavelengths than the illuminating laser line. For the above reasons, it can be appreciated that it is essential for Raman spectroscopy that the illuminating laser light be monochromatic and spectrally clean in order for the weak Raman signal emitted by the sample to be observable. At present, Raman spectroscopy is typically performed using a near infrared laser source (e.g., diode laser) and cooled silicon CCD detectors. In general, this type of arrangement yields an acceptable S/N ratio with relatively short integration times.
For Raman spectroscopy to be performed in vivo inside a body, fiberoptics must be used. However, as the illuminating light travels through an optic fiber to a tissue located inside a body, it is common for other spectral components to be generated in the illuminating light due to Raman scattering, fluorescence or like phenomena taking place within the fiber medium. The result of these phenomena is that the light exiting the fiber is not as spectrally clean as necessary. This problem becomes more severe as the length of the fiber increases. As shown in FIG. 1, one way to address this problem is to position a spectrograph, spectrometer or filter array after the fiber. Unfortunately, however, the physical size of these types of filtering arrangements is large (e.g., a few centimeters or larger) and precludes the use of these types of arrangements in many in vivo applications where the fiber is inserted into a working channel of an endoscope, said working channel typically having a diameter about 3 mm.

Fiberoptic assembly useful in optical spectroscopy


A computational system is disclosed. The computational system includes a controller having a table including a plurality of sets of timing parameters. The plurality of sets of timing parameters are ordered based on a speed rate. The computational system also includes a device accessible to the controller. The controller communicates with the device in accordance with one set of timing parameters selected from the plurality of sets of timing parameters.

Increasingly, consumers are demanding portable devices, such as personal digital assistants (PDA's), MP3 players, portable memory systems, advanced cell phone systems and cameras. Traditional non-volatile memory storage systems, such as floppy disks, hard drives, and optical drives are generally unsuitable for use in portable devices because they suffer from mechanical failures, excess weight, large size and high energy consumption. As a result, manufacturers of portable devices are turning to solid-state memory systems, such as flash memory and electrically erasable, programmable read-only memory (EEPROM). Similarly, other computational systems rely on solid-state memory devices and other specialized circuitry.
Each of these memory devices and other specialized circuitries operates and communicates in accordance with a particular set of timing parameters. A host device generates timed signals based on a clock signal and the set of timing parameters for communicating with the memory device or other circuitry. For example, memory devices utilize specific timing signals for data transfer, block erasing, and resetting. However, owing to the variability in semiconductor processing, devices having the same design are capable of operating at different rates.
Typically, a manufacturer of a device sets the timing parameters based on the lowest acceptable rate achieved by a set of devices. As such, many devices in any given set are capable of operating at rates faster than the rate specified by the manufacturer.
When connected to a system, controllers are provided with the manufacturer specified timing parameters and the devices are accessed in accordance with those timing parameters. For example, a controller may include a table having an entry that includes a device number and a set of timing parameters associated with a device represented by the device number. For large systems, the table is large, including 50 to 100 entries and occupying excess space within the controller. When accessing the device, the controller accesses the table, finds the device number entry and implements communications for access to the device using the timing parameters included in that entry.
In another method, the controller may include a single set of device timing parameters with which it accesses connected devices. In practice, such a set of timing parameters is the timing parameter set associated with the slowest device connected to the controller. As such, improved systems and methods for accessing and communicating with devices would be desirable.
The use of the same reference symbols in different drawings indicates similar or identical items.

Method and system for communicating with memory devices utilizing selected timing parameters from a timing table


A module for receiving a plurality of signals that are modulated with a common carrier, where each of the signals includes information that enables a determination of a distance from said receiver to a source that transmits the signal, and outputs to outside the module a digital representation of a downshifted replica of the received signals or, alternatively, outputs a stored and delayed version of the downshifted replica of the received signals together with information about the delay.

This invention relates to global positioning, and more particularly to the issue of confidence that a user has in global positioning information that equipment may provide. In the context of this disclosure, global positioning encompasses the absolute geo-location as well are the relative location of one object relative to another object.
There are numerous electronic ways by which global positioning may be provided. Some are terrestrial, and some are based on satellites. A satellite system that currently is most commonly used is the Global Positioning System (GPS), and it is quite well known in the sense that many people have GPS receivers that assist them in determining their physical location. GPS uses a collection of satellites that are arranged to orbit the Earth so that at least four satellites are always within the reception range of a receiver, at any point on the globe. One of the signals that the satellites transmit is a signal at frequency L1, which is used as a carrier to modulate a data signal that is itself modulated with a Code Division Multiple Access (CDMA) code, commonly referred to as the C/A code. The CDMA code that is used by each satellite is unique to the satellite, but it is publicly known, which allows the receiver to discriminate, or detect, the individual signal of each of the satellites in the presence of signals from the other satellites and in the presence of noise. Actually, each satellite transmits at least one other signal, employing the same carrier frequency that is shifted 90 degrees. This second signal is modulated by another code, known as the P(Y) code. The P(Y) code is either the P, which is publicly known, or the encrypted Y code. Today, all satellites use the Y code and, consequently, the resulting transmitted signal that is encoded with the Y code cannot be used by anyone other than those who have the decryption algorithm and the key. Each satellite transmits yet another signal, on frequency L2, but the disclosure herein focuses on frequency L1 only. It should be understood that the principles disclosed herein apply to L1, L2, or any of the new frequencies that are planned for satellite navigation.
Because the invention that is disclosed herein is illustrated by way of an example that is based on the pervasive GPS system, the following gives an abbreviated review of the GPS signals and the processing that takes place in a conventional GPS receiver. It should be kept in mind that the deficiency in the GPS system that is mentioned later is found in all other non-encrypted systems, and that the applicability of the invention disclosed herein extends beyond the GPS system. It should be kept in mind, therefore, that terms referring to global positioning (without initial letters being capitalized) refers to the terms generically, and not necessarily solely to GPS.
A conventional GPS receiver, shown in FIG. 1, simultaneously receives a number of satellite signals on frequency L1, where the signal transmitted by satellite n can be expressed asStransmitted=A″D″(t)cos(2π(fL1)t+φ1)+B″D″(t)sin(2π(fL1)t+φ1)  (1)where D″(t) is the data signal, xC1An (t) is the C/A code signal assigned to satellite n, fL1 is the frequency of the carrier, and φ1 is the phase of the carrier relative to the beginning of the data and code signals.
A GPS receiver can engage in the processing of signals as if all of the possible satellites are present but, of course, some of the satellites are not within range of the GPS receiver's antenna so the processing results for those satellites are not viable. The following analysis follows the signal of only one satellite and, for sake of simplicity, superscript n is omitted from the equations, and the C/A subscript is shortened to C.
The transmitted signal is subjected to transit time delay to the receiver, τ, and the signal that is received by a receiver's antenna experiences a Doppler frequency shift, fD, due to the satellite's movement in its orbit and possible receiver motion. Also, the transmitter and the receiver do not have a common clock, which means that even when the transmitter and the receiver clocks are at identical frequency, there is, nevertheless, a phase difference between them. Thus, the received signal thus can be expressed asSreceived=AD(t−τ)xC(t−τ)cos(2π(fL1+fD)(t−τ)+φ1+BD(t−τ)xY(t−τ)sin(2π(fL1+fD)(t−τ)+φ1)  (2)or simplified toSreceived=AD(t−τ)xC(t−τ)cos(2π(fL1+fD)t+φ1−φ2)+BD(t−τ)xY(t−τ)sin(2π(fL1+fD)t)+φ1−φ2)  (3)
As shown in FIG. 1, the received signal is amplified in element 10, conventionally downshifted to a preselected intermediate frequency (IF) by multiplying the received signal in element 12 by signalsin(2π(fL1−fIF)t+φ3)  (4)and passing the resulting signal through low pass filter 15. The signal of equation (4) is generated from reference oscillator 20 by frequency synthesizer 22, where φ3 is the phase of the locally generated signal (relative to the beginning of the data and code signals at the transmitting satellite which, of course, is unknown). The result at the output of the low pass filter isSdownshifted=AD(t−τ)xC(t−τ)cos(2π(fIF+fD)t+φ1−φ2−φ3)+BD(t−τ)xY(t−τ)sin(2π(fIF+fD)t+φ1−φ2−φ3)  (5)or simplified toSdownshifted=AD(t−τ)xC(t−τ)cos(2π(fIF+fD)t+θ1)+BD(t−τ)xY(t−τ)sin(2π(fIF+fD)t+θ1).  (6)
It may be noted that the above-described use of downshifting by use of an IF modulator 12 and low pass filter 15 is illustrative, and that the A/D can be connected directly to amplifier 10 and controlled to generate a digital signal as if it were downshifted as shown in FIG. 1.
The output signal of low pass filter 15 is digitized in A/D converter 18 and applied to a combination of processor 100 and associated memory 110 where the remainder of the processing takes place.
The processing begins with a signal acquisition (software) module that includes a code generator element and a carrier generation module. The code generation module develops signalxC(t−{circumflex over (τ)}),  (7)where {circumflex over (τ)} is an estimate of τ, and the carrier generator module creates two signals that may be viewed as the phasorψ=cos(2π)(fIF+{circumflex over (f)}D)t+{circumflex over (θ)}1−i sin(2π)(fIF+{circumflex over (f)}D)t+{circumflex over (θ)}1),  (8)where {circumflex over (f)}D is an estimate of the Doppler frequency shift fD, and {circumflex over (θ)}1 is an estimate of the phase θ1. Multiplying the received (and downshifted) signal of equation (6) by the code signal of equation (7) and the phasor of equation (8) and then integrating the product over a preselected interval that is long enough to reliably detect a correlation peak (for example, more than one period of the C/A code) yields:∫FCΨ cos(2π(fIF+fD)t+θ1)]+∫FYΨ sin(2π(fIF+fD)t+θ1)]  (9)whereFC=AD(t−τ)xC(t−τ)xC(t−{circumflex over (τ)}) and FY=BD(t−τ)xY(t−τ)xC(t−{circumflex over (τ)})  (10)Equation (9) expands to
                                                                        S                I                            +                              S                Q                                      =                                          ∫                                                      F                    C                                                                          {                                                                                cos                                                                                (                                                                                2                                                                                π                                                                                (                                                                                f                                              IF                                                                                +                                                                                f                                                ^                                                                                D                                                                                )                                                                                t                                                                        +                                                                                θ                                        ^                                                                            1                                                                                )                                                                                cos                                                                                (                                                                                2                                                                                π                                                                                (                                                                                f                                              IF                                                                                +                                                                                f                                              D                                                                                )                                                                                t                                                                        +                                                                          θ                                      1                                                                                )                                                                                -                                                                                ⅈ                                                                                sin                                                                                (                                                                                2                                                                                π                                                                                (                                                                                f                                            IF                                                                                +                                                                                f                                              ^                                                                                D                                                                                )                                                                                t                                                                    +                                                                                θ                                      ^                                                                        1                                                                                )                                                                                cos                                                                                (                                                                                2                                                                                π                                                                                (                                                                                f                                            IF                                                                                +                                                                                f                                            D                                                                                )                                                                                t                                                                    +                                                                      θ                                    1                                                                                )                                                                                }                                                              +                              ∫                                                      F                    Y                                                                          {                                                                                cos                                                                                (                                                                                2                                                                                π                                                                                (                                                                                f                                              IF                                                                                +                                                                                f                                                ^                                                                                D                                                                                )                                                                                t                                                                        +                                                                                θ                                        ^                                                                            1                                                                                )                                                                                sin                                                                                (                                                                                2                                                                                π                                                                                (                                                                                f                                              IF                                                                                +                                                                                f                                              D                                                                                )                                                                                t                                                                        +                                                                          θ                                      1                                                                                )                                                                                -                                                                                ⅈ                                                                                sin                                                                                (                                                                                2                                                                                π                                                                                (                                                                                f                                            IF                                                                                +                                                                                f                                              ^                                                                                D                                                                                )                                                                                t                                                                    +                                                                                θ                                      ^                                                                        1                                                                                )                                                                                sin                                                                                (                                                                                2                                                                                π                                                                                (                                                                                f                                            IF                                                                                +                                                                                f                                            D                                                                                )                                                                                t                                                                    +                                                                      θ                                    1                                                                                )                                                                                }                                                                                or                                                                          to                                                                                (        11        )                                                      S            I                    +                      S            Q                          =                              ∫                                          F                C                                                          {                                                                                cos                                                                                (                                                                                2                                                                                π                                                                                (                                                                                2                                                                                f                                          IF                                                                                +                                                                              f                                        D                                                                            +                                                                                f                                          ^                                                                                D                                                                                )                                                                                t                                                            +                                                              θ                                1                                                            +                                                                                θ                                  ^                                                                1                                                                                )                                                                          +                                                                                cos                                                                                (                                                                                2                                                                                π                                                                                (                                                                                f                                        D                                                                            -                                                                                f                                          ^                                                                                D                                                                                )                                                                                t                                                            +                                                              θ                                1                                                            -                                                                                θ                                  ^                                                                1                                                                                )                                                                          -                                                                                ⅈ                                                                                sin                                                                                (                                                                                2                                                                                π                                                                                (                                                                                2                                                                                f                                            IF                                                                                +                                                                                f                                          D                                                                                +                                                                                f                                            ^                                                                                D                                                                                )                                                                                t                                                                +                                                                  θ                                  1                                                                +                                                                                θ                                    ^                                                                    1                                                                                )                                                                                +                                                                                ⅈ                                                                                sin                                                                                (                                                                                2                                                                                π                                                                                (                                                                                f                                        D                                                                            -                                                                                f                                          ^                                                                                D                                                                                )                                                                                t                                                            +                                                              θ                                1                                                            -                                                                                θ                                  ^                                                                1                                                                                )                                                                                }                                              +                      ∫                                          F                Y                                                                            {                                                                                sin                                                                                (                                                                                2                                                                                π                                                                                (                                                                                2                                                                                f                                            IF                                                                                +                                                                                f                                          D                                                                                +                                                                                f                                            ^                                                                                D                                                                                )                                                                                t                                                                +                                                                  θ                                  1                                                                +                                                                                θ                                    ^                                                                    1                                                                                )                                                                                +                                                                                sin                                                                                (                                                                                2                                                                                π                                                                                (                                                                                f                                          D                                                                                -                                                                                f                                            ^                                                                                D                                                                                )                                                                                t                                                                +                                                                  θ                                  1                                                                -                                                                                θ                                    ^                                                                    1                                                                                )                                                                                +                                                                                ⅈ                                                                                cos                                                                                (                                                                                2                                                                                π                                                                                (                                                                                2                                                                                f                                              IF                                                                                +                                                                                f                                            D                                                                                +                                                                                f                                              ^                                                                                D                                                                                )                                                                                t                                                                    +                                                                      θ                                    1                                                                    +                                                                                θ                                      ^                                                                        1                                                                                )                                                                                -                                                                                ⅈ                                                                                cos                                                                                (                                                                                2                                                                                π                                                                                (                                                                                f                                          D                                                                                -                                                                                f                                            ^                                                                                D                                                                                )                                                                                t                                                                +                                                                  θ                                  1                                                                -                                                                                θ                                    ^                                                                    1                                                                                )                                                                                }                                .                                                                        (        12        )
Since, as indicated above,FY=BD(t−τ)xY(t−τ)xC(t−{circumflex over (τ)}),  (13)and the C/A code is orthogonal to the Y code, the second integral of equation (12) yields zero. Also, the integration acts like a low pass filter that discards the high frequency signals of cos 2π(2fIF+fD+{circumflex over (f)}D)t and sin 2π(2fIF+fD+{circumflex over (f)}D)t, leaving
                                          S            I                    +                      ⅈ                                                                                S              Q                                      =                  ∫                                    F              C                                                                  {                                                                                +                                                      cos                                                                                (                                                                                2                                                                                π                                                                                (                                                                                f                                          D                                                                                -                                                                                f                                            ^                                                                                D                                                                                )                                                                                t                                                                +                                                                  θ                                  1                                                                -                                                                                θ                                    ^                                                                    1                                                                                )                                                                                +                                                                                ⅈ                                                                                sin                                                                                (                                                                                2                                                                                π                                                                                (                                                                                f                                        D                                                                            -                                                                                f                                          ^                                                                                D                                                                                )                                                                                t                                                            +                                                              θ                                1                                                            -                                                                                θ                                  ^                                                                1                                                                                )                                                                                }                            .                                                          (        14        )
It can be demonstrated that SI2+SQ2 equals
                                                                                S                  I                  2                                +                                  S                  Q                  2                                            =                                                                                (                                          ∫                                                                        F                          C                                                                                cos                                                                                (                                                                                2                                                                                π                                                                                (                                                                                f                                        D                                                                            -                                                                                f                                          ^                                                                                D                                                                                )                                                                                t                                                            +                                                              θ                                1                                                            -                                                                                θ                                  ^                                                                1                                                                                )                                                                                )                                    2                                +                                                                                (                                      ∫                                                                  F                        C                                                                                sin                                                                          (                                                                                2                                                                                π                                                                                (                                                                                f                                      D                                                                        -                                                                                f                                        ^                                                                            D                                                                                )                                                                                t                                                        +                                                          θ                              1                                                        -                                                                                θ                                ^                                                            1                                                                                )                                                                                )                                2                                                                                =                                                                                (                                          ∫                                                                        F                          C                                                                        cos                                                                                2                                                                          π                                                                                (                                                                                f                                D                                                            -                                                                                f                                  ^                                                                D                                                                                )                                                                                t                                                              )                                    2                                +                                                                                (                                      ∫                                                                  F                        C                                                                  sin                                                                                2                                                                    π                                                                          (                                                                                f                              D                                                        -                                                                                f                                ^                                                            D                                                                                )                                                                                t                                                        )                                2                                                                        (        15        )            which is independent of (θ1−{circumflex over (θ)}1). It can be also demonstrated that good estimates for τ, and fD are attained when code generation module is adjusted as to introduce a delay, {circumflex over (τ)}, and the carrier generator module is adjusted as to the introduced {circumflex over (f)}D so as to maximize SI2+SQ2.
For the more visually inclined reader, FIG. 2 shows a diagrammatic representation of the processing that takes place in the acquisition module.
The task of the acquisition module is to come up with a first-cut approximation of the delay and the Doppler frequency shift. A refinement of the approximations takes place in a tracking module, whose function is to both refine the estimates and track the changes in τ, fD and θ1 as conditions change, and whose diagrammatic representation is shown in FIG. 3.
The tracking module contains a phase lock loop comprising multiplier 31 that multiplies the Sdownshifted signal of equation (6) by the phasor of equation (8) provided by numerically controlled oscillator (carrier NCO) 32. The output of multiplier 31 is multiplied in multiplier 33 by the code signal obtained from code generator 38. The output of multiplier 33 is integrated in module 34 and applied to discriminator 35, which develops a carrier error signal (θ1−{circumflex over (θ)}1) that controls the frequency of the carrier NCO.
The output of multiplier 31 is also applied to multiplier 36, where it is multiplied by the code signal that is generated by element 38, but delayed by half of the duration of code C/A chip; i.e.,xC(t−{circumflex over (τ)}−TC/2),  (16)and to multiplier 37, where it is multiplied by the code signal that is generated by element 38, but advanced by half of the duration of code C/A chip; i.e.,xC(t−{circumflex over (τ)}−TC/2),  (16)
The outputs of multipliers 36 and 37 are integrated in elements 41 and 42, respectively, and applied to discriminator 39 which develops a delay error signal (τ−{circumflex over (τ)}) that is applied to code generator 38, controlling the frequency of the clock that generates the code.
While in both elements 32 and 38 the frequency of a clock is controlled by the respective discriminators, the result is that the generated carrier frequency phasor that is applied to multiplier 31 is in the formcos(2π(fIF+{circumflex over (f)}D)t+{circumflex over (θ)}1)−i sin(2π(fIF+{circumflex over (f)}D)t+{circumflex over (θ)}1)  (18)with the approximations {circumflex over (f)}D and {circumflex over (θ)}1 tracking closely the fD and θ1 of equation (6), and the generated codexC(t−{circumflex over (τ)})  (19)has a {circumflex over (τ)} that is a close estimate of τ.
The code and the carrier measurement are applied to subsequent modules (not shown) that decode the navigation message, determine satellite ephemeris, and compute the pseudo-range, and with corresponding pseudo-ranges obtained by processing other satellites, the physical location of the receiver is computed (through quadralateration) and displayed.
All of the above is conventional, and the reader is invited to peruse the book "Global Positioning System" by Misra and Enge, Ganga-Jamuna Press, 2006 for further details. In general, the GPS literature is enormous. It describes alternate implementation to the above, where, for example, the code and carrier removal processes described by equations (7), (8) and (9) are done in different order. It also describes implementations that use correlator spacings other than those chosen in equations (16) and (17). The literature is also replete with discriminator strategies that differ from the simple "early minus late" strategy described here.
In commercial applications the C/A code is publicly known and, consequently, GPS receivers are vulnerable to spoofing. A hostile party can generate a facsimile of one or more satellite signals that carry incorrect information, and a GPS receiver that accepts the bogus signals will compute an incorrect position and, in fact, may be caused to compute a position that the hostile party wishes to have the receiver compute. However, spoofing is not a problem for those who are able to use the Y code because this code is not publicly known, so a hostile party cannot create a signal that appears bona fide. This problem is not unique to GPS receivers, of course. It is endemic to all global positioning systems that rely on insecure signals.
The primary object of this disclosure is a method and a means for having confidence that a geographical position computation, or an assertion based on a geographical position, is bona fide.
Another object of this disclosure is a receiver that is adapted to provide a signal that can be authenticated as to source of the received signal, with the consequence of the authentication of the source being that geographical position of the receiver is also determined with certainty.