text:
|Publication number
|Publication type
|Publication date
|Jun 28, 1974
|Filing date
|Jul 3, 1972
|Priority date
|Jul 3, 1972
|Also published as
|Publication number
|Ehrlich S
|Original Assignee
|Raytheon Co
|Export Citation
|BiBTeX, EndNote, RefMan
|Referenced by (37), Classifications (17)
|External Links: USPTO, USPTO Assignment, Espacenet
nited States Patent [191 I Ehrlich June 28, 1974 SUPER-DIRECTIVE SYSTEM [75] Inventor: Stanley L. Ehrlich, Middletown, RI. [73] Assignee: Raytheon Company, Lexington,
22 Filed: July 3, '1972 [21] Appl. No.: 268,416
[52] U.S. Cl. 343/100 SA, 340/6 R, 340/16 R,
' 343/7 A [51] Int. Cl G0ls 3/74, H04b 7/04 [58] Field of Search..... 340/6 R, 16 R; 343/100 SA,
[56] References Cited UNlTED STATES PATENTS 3,124,801 3/1964 Callahan, .lr 343/100 SA 3,356,989 12/1967 Autrey 340/6 R 3,449,71 l 6/1969 Ricketts, Jr. et a1 340/6 R 3,560,985 2/1971 Lyon 343/100 SA 3,71 1,820 1/1973 Starkey 340/6 R 3,725,855 4/1973 Murphree et a1. 340/6 R Primary Exar ninerRichard.A. Farley Assistant ExaminerG. E. Montone D. Pannone; David M. Warren [57] ABSTRACT A system of radiating elements arranged for forming one or more beams of radiation having radiation patterns such as a monopole, dipole, quadrupole, other multipoles or combination thereof. The individual radiating elements of the array are interconnected by circuitry providing for the summing and differencing of signals provided by adjacent radiating elements in response to incident radiation. In one embodiment the signal of one radiating element is delayed relative to the signal of an adjacent radiating element. The differencing of the signals provides for the deep nulls found in radiation patterns such as the dipole and quadrupole radiation patterns, while the delay between signals of adjacent radiating elements is adjusted for varying the shape of the directivity pattern. The system provides for varying the direction and shape of beams of the radiation pattern to provide for the detection, classification and/or tracking of a distant source of radiation as well as for illuminating a distant object. The system is responsive to the intensity of radiation received along one or more beams of the radiation pattern, and in response thereto, varies the delay between the signals of adjacent radiating elements and also provides for the selective coupling of specific radiating'elements of the system.
1 Claim, 19 Drawing Figures f 24 54 FORM SELECT] 66 7c ANGLE ANGLE U 1 ll TRACKER I Ei E' E L Y L l j 35 5s 1 50 DISPLAY j I 74 I TI I ,1 48 I BEAM -R BEAM RANGE I SWITCHER CIRCUITS AMHJHERS I FORMER 6O CORRELATOR 68 I T RANGE I 64 76 I c sstsct 'g 26 1 POWER BEAM AMPLIFIERS 78 i FORMER 'SQ'A TIMING I 7? 1 J l 40 28 '42 LC I 1 PMENTBJUNN IsII .SHEEYEUFB A IiI GLE WC ARITH R' t l TRACKER I A DELAY I I l UNIT I L J? L L L iLL ELIL L E Q JQEM fl TO CORRELATOR DELAY 1* /02 P76 5 /06 L l SHIFT REGISTER I sIGNAL I W I I l I I I I I I I //0 I V W W W i DIGITAL SELECTOR (FIG 4) D --I PATEMTEDJIIIMB I974 3.821.. M0
SHEEI I [If 8 \AZ \Aj' \J MULTIPLEXING CIRCUITRY I I 26 I 73Z l AMPLIFIER AMPLIFIER AMPLIFIER I A L A I I L A LA L A I l BAND PASS U4 BAND PASS BAND PASS I I FILTER FILTER FILTER I A A M i 1 M0) I l SELECT DELAY I i I INVERTER I s L0 k I SELECT I DELAY I ,40 L5 C1 L8 L0 I l A WAVEFRONT /44A /46A /445 M55 /52 I, /76 /53 /54 //5/ K? i lNVERTER /0 /50 I suMMER DELAY A PATENTED 1 3. 821. 740
SHEEY 6 0F 8 i I /82 I194 9 SEARCH SEARCH MEMORY SELECTOR PATTERN v MEMORY 62 PROGRAMMER PROGRAMMER TO BEAM TO BEAM SWITCHER FORMERS 64(FIG. I) SW TCH DETECTOR SWITCH 32 AND 40 j A FROM II A (FIG. I) /90 CORRELATOR /94 50 5 TRACK (FIG. I) TRACK 98 SP SELECTOR PATTERN 70(F|G I) 66 PROGRAMMER PREDICTCIJR W PROGRAMMER I /86 200 i F/G /5 54 I E+w E+ w 5 1/3 s (|/3)cos6 ARRAY MULT'PLEX'NG RECEIVER LOGIC --B- OIsPLAY I CIRCuITRY I n I L M M A M SIGNAL RANGE T I GENERATOR NG GATING 1 SUPER-DIRECTIVE SYSTEM BACKGROUND OF THE INVENTION This invention relates to super-directive arrays and more particularly to a system including such an array wherein signals from adjacent elements of the array are delayed with respect to each other by preselectable amounts of delay.
Dipole and quadrupole radiators have been well known for many years in the fields of electromagnetic and acoustic radiators. These radiation patterns are obtained at all frequencies for which the interelement spacing and the size of an element are substantially smaller than a wavelength of the radiation transmitted or received by the radiator or array of radiators. For example,- in the case of the electromagnetic dipole radiator, the two active regions of the radiator, namely, the positively and negatively charged termini of the radiating element are spaced apart, preferably less than onequarter wavelength. In the case of theacoustic dipole radiator, a pair of monopole or omnidirectional radiating elements are placed close together, preferably less than one-quarter wavelength spacing, and the effect of a positive and negative pulsation is provided by subtracting the signal received by one of the elements from that of the other element. A directional sonar system employing omnidirectional and dipole radiation patterns is disclosed in U.S. Pat. No. 3,176,262 which issued to S. L. Ehrlich et al. on Mar. 30, 1965. Since the invention to be described hereinafter is particularly useful for acoustic radiators, the ensuing description will be directed towards acoustic systems while it is understood that these teachings are also applicable to electromagnetic systems. 7
It is evident that an array of closely spaced radiating elements is essential for the directional transmission and reception of acoustic energies at very low frequencies since a typical phased array antenna in which the radiating aperture is many wavelengths long would be prohibitively large in many applications utilizing frequencies as low as, for example, 10 hertz. However, even with higher frequencies, an array of closely spaced radiating elements may be useful since the directivity pattern of such an array is substantially invariant with the frequency of radiation for all radiations having a wavelength substantially larger than the overall dimensions of the array. At still higher frequencies where the wavelength becomes smaller than the array, the array may still be useful for specific applications such as where a multiple lobed beam pattern is desired, however, such a system tends to be of very narrow band width. It is also apparent that an array of closely spaced radiating elements is inherently useful in situations requiring small size and expense.
A problem arises in that such an array produces beam widths which are excessively wide for the standard techniques utilized in sonar tracking, for example, the tracking of an object submerged in the ocean. In addition, due to the subtraction of signals of adjacent elements as compared with the summation of such signals in the standard phased array antenna, the sensitivity of such an array, namely, the amplitude of the resultant signal produced by the array in response to an incident amplitude of sound pressure, is significantly reduced thereby increasing the unwanted efiects of noise.
SUMMARY OF THE INVENTION In accordance with the invention there is provided a system incorporating an array of radiating elements which overcome the aforementioned problems in the prior art to permit the use of such an array for communicating information by acoustic signals. In one embodiment providing for a polypole radiation pattern, the invention comprises a plurality of radiating elements each of which provides signals in response to incident acoustic energy, the radiating elements being intercoupled via delay lines and circuitry for combining the signals to permit the summing of such signals, the differencing of such signals and the scaling of such signals. In another embodiment utilizing three radiating elements, a simplification is presented which permits the use of a single delay line by connecting the radiating elements via summing resistors having values which provide for a scaling of the signal voltage of one radiating element relative to the signal voltage of the other radiating element; this provides, in the case of small phase angles, (less than approximately 20), the equivalent of three delay lines. There is also disclosed a multiple element array including a switching circuit for selectively coupling groups of three radiating elements whereby a beam of acoustic radiation can be directed in any one ofa plurality of directions by appropriately selecting the group of three elements. In addition there is disclosed the use of an angle tracking circuit interconnected with the switching circuit and the delay lines for operating the switching circuit and the delay lines to rotate a beam of radiation by means of the switching circuit and to alter the shape of the array directivity pattern by varying the amount of delay provided by each of the delay lines. The combination of signals from the radiating elements provides for polypole radiation patterns described mathematically by a power series and polymode radiation patterns described mathematically by a Fourier series. Means are also disclosed for digitizing the signal as by means of a sampling circuit which provides voltage states corresponding to logical ls for the positive portions of the sinusoidal waveform of the acoustic wave and logical Us for the negative portions of the wave. A digital delay line in the form of a shift register with multiple outputs is utilized in the digital embodiment as a variable delay line.
BRIEF DESCRIPTION OF THE DRAWINGS The aforementioned features and other advantages of the invention are explained in the following description and taken in connection with the accompanying drawings wherein:
FIG. 1 is a view, partially isometric and partially diagrammatic, of the radiating system in accordance with the invention;
FIG. 2 shows, by way of example, one form of directivity pattern obtainable with the array of radiating elements of FIG. 1;
FIG. 3 shows the underside of a boat in the ocean with a radiating array of the invention mounted thereon, the figure further showing a cardioid radiating pattern with the notch in the direction of the propeller for inhibiting propeller noise;
FIG. 4 shows a block diagram of a beam former of the system of FIG. 1 for received signals;
FIG. 5 shows a block diagram of a delay unit of the beam former of FIG. 4;
FIG. 6 shows a block diagram of an arithmetic unit of the beam former of FIG. 4;
FIG. 7 shows a block diagram of a beam former of FIG. 1 for transmitted signals;
FIG. 8 is a block diagram of an alternative embodiment of the beam former of FIG. 7;
FIG. 9 is a diagrammatic presentation of a generalized beam forming system for a multiple element array;
FIG. 10 is a block diagram, partially schematic, of a simplified embodiment of the beam former of FIG. 4;
FIG. 11 is a diagram of a portion of an array illuminated by a wave of radiant energy for use in a mathematical description of the beam formers of FIGS. 4 and FIGS. 12, 13 and 14 represent successive mathematical transformations utilized in developing the simplified beam forming system of FIG. 10;
FIG. 15 is a block diagram of an angle tracking unit of the system of FIG. I;
FIG. 16 is a schematic diagram of a polymode transducer and receiver of the invention;
FIG. 17 is a pictorial equation showing the combination of various receiving directivity patterns provided by the receiver of FIG. 16 to form a polymode directivity pattern; 1
FIG. 18 is a block diagram of a transmitting and receiving system incorporating the polymode array and receiver of FIG. 16; and
FIG. 19 .is a block diagram of an alternate embodiment of the receiver of FIG. 16.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, there is shown a system 20 comprising, in accordance with the invention, an array 22 of radiating elements which is coupled to a transceiver 24 via multiplexing circuitry 26. Each of the radiating elements takes the form of a transducer 28 suitable for converting electrical energy signals on wires 30 to sonic energy signals indicated by waves 32, and for converting from sonic energy to electrical energy.
The transducers 28 are of a well-known construction typically comprising an electrostrictive ceramic material such as barium titanate and are suitably mounted upon a base plate 34 to serve as monopole radiators. The surface 34 of each transducer 28 pulsates to provide a directivity pattern having axial symmetry. Six transducers 28 have been arranged, in this embodiment of the invention, in a circle about a seventh transducer 28 at the center of the array 22. As will be described hereinafter, this arrangement of the transducers 28 in the array 22 is particularly useful for providing a variety of radiation patterns as well as a capability for steering beams of radiation about a central axis 36 which is normal to the base plate 34.
The transceiver 24 comprises a beam former 38 for forming the receiving beam for radiation incident upon the array 22 and a beam former 40 for forming the transmitted beam of radiation. In the transceiver 24 a signal generator 42 provides a signal suitable for transmission via the array 22 to a distant object such as a boat 44, and is coupled to the array 22 via the beam former 40 and the multiplexing circuitry 26. Detection of a signal such as an echo from the boat 44, indicated by waves 46, is accomplished by processing the output of the beam former 38 on line 48 by conventional means. Accordingly, the transceiver 24 utilizes a correlator 50 which correlates the received signal on line 48 with a replica of the transmitted signal provided on line 52 from the signal generator 42. Such a correlator may employ recirculating delay lines which may be implemented digitally by shift registers as is disclosed in US. Pat. No. 3,594,718 which issued to Charles I. Black et al. on July 20,, 1971.
The transceiver 24 further comprises an angle tracker 54 which, in response to the correlator output on line 56, provides signals on lines 58 and 60 to the beam formers 38 and 40, as well as along line 62 to a beam switcher 64 for providing a desired shape to the directivity pattern of the array 22 and for switching the direction of a beam of radiation provided by the array 22. The beam switcher 64 comprises a well-known switching circuitry which may .be either electrical or mechanical, such as a stepping switch for coupling individual ones of the transducers 28 to the beam formers 38 and 40, the specific coupling arrangement being in accordance with the signal provided on line 62. This switching of the beam, analogous to sequential lobing in the radar art, enables the angle tracker 54 to obtain information on the direction of radiation, such as the waves 46, incident upon the array 22. Angle data provided by the angle tracker 54 on line 56 and range data provided by the correlator 50 on line 68 are presented on a display 70 which may be of conventional form such as a cathode ray tube or a graphical display. The signal generator 42, correlator 50, angle tracker 54, display 70 and the beam formers 38 and 40 are coordinated by timing signals from the timing unit 72. The timing signals applied to the beam formers 38 and 40 and the angle tracker 54 are clock pulses indicated by the symbol C.
The multiplexing circuitry 26 comprises in addition to the beam switcher 64, a transmit-receive circuit 74 and amplifiers 76 and 78 for amplifying respectively the received and transmitted signals. The transmitreceive circuit 74 is of conventional form and may comprise, for example, a diode circuit such as is frequently utilized in sonar applications.
Referring now to FIG. 2, there is seen a typical directivity patternachievable with a linear array of three radiating elements 80 which may be, for example, the transducers 28 of FIG. 1. In FIG. 2 the radiation pat tern is that of a quadrupole radiator modified such that one lobe is substantially larger than any other lobe. The particular spacings between the radiating'elements 80 and the signal delays to be applied between signals of these elements 80 for producing a specific radiation pattern will be disclosed hereinafter. Comparing the array 22 of FIG. 1 with the arrangement of radiating elements 80 of FIG. 2, it is apparent that any set of three transducers 28 arranged along a diameter of the array 22 correspond to the linear array of three radiating elements 80 of FIG. 2. Accordingly, the radiation pattern vof FIG. 2 can be obtained with any three transducers 28 arranged along a diameter of the array 22. F urthermore, by selectively switching in any such set of three transducers 28 by means of the beam switcher 64, the
- radiation pattern of FIG. 2 can be rotated about the acoustic contact with the water, the enclosure housing the array 22 of FIG. 1, not seen in FIG. 3. The multiplexing circuitry 26 and the transceiver 24 of the systern are not shown in FIG. 3 but are carried within the boat 82. The system 20 is seen providing a directivity pattern 88 having the general cardioid-type form with a notch 90 in the direction of the stern of the boat 82 so that noise caused 'by the movement of the ocean water 84 past the propeller shaft 92, the propeller 94 and the rudder 96 is greatly attenuated. It is noted that the directivity pattern 88 differs from that of the typical phased array antenna in that there are no reduced level side lobes in the direction of the propeller 94 but rather the notch 90 which can be accurately positioned to exclude the propeller noise. This feature permits the use of the invention in a relatively high noise environment even though the sensitivity of the array 22 of FIG. 1 is substantially decreased when the signal from the transducers 28 are combined in a manner, to be described hereinafter, wherein the signals of adjacent transducers 28 are subtracted from each other to produce cardioidtype or polypole-type radiation patterns.
Referring now to FIG. 4, there is seen a block diagram of the receiving beam former 38. The beam former 38 may utilize conventional analog delay lines for delaying the signals between adjacent radiating elements of the array 22 of FIG. 1 or, alternatively, may
.employdigital techniques in the form of shift registers ceived by the transducers 28 pass via the multiplexing .circuitry 26 to respective samplers 98. Each sampler is of conventional design and is driven by clock pulses received from the timing unit 72 of FIG. 2. Each sampler 98 preferably comprises a switch or gate driven by the clock pulses for obtaining samples of the incoming signal, and a comparator (not seen in the figures) which produces an output pulse on line 104 when the sample of the incoming signal is above a preset threshold. To simplify this explanation, it is assumed that the incoming acoustic signal is a sinusoid and, accordingly, the value of this threshold is selected so that for each positive' half cycle of the incoming sinusoidal signal, a succession of pulses having a logic state of 1 is provided along line 104, and that during each negative portion of the sinusoid there is an absence of the pulses on line 104 or, equivalently, the 0 logic state is present on line 104. The clock pulse frequency is greater than the frequency of the incoming signal by a factor of, for example, l,024 so thata total of 1,024 samples can be taken during each cycle of the incoming signal. The l,024 samples permit a lO-bit resolution of the phase of the incoming signal, namely, increments of approximately one-third degree.
Referring now to the block diagram of FIG. 5, the
delay unit 102 comprises a shift register 106 and a digital selector 108 (also known as a decoder or multiplexer switch). The shift register 106 has a single terminal in which the input signal is applied, and a plurality of output terminals on lines 110, each of the lines 110 corresponding to one stage of the shift register 106. The shift register 106 is driven by clock pulses, indicated by the letter C in the figure, with the result that each pulse of the input signal appears after successive increments of delay at successive ones of the output terminals on lines 110, with each of these delay increments being equal to the interval between clock pulses. The digital selector 108 has multiple input terminals corresponding to each of the lines 110 and a single output terminal. A specific connection is made between one of the-input terminals and the output terminal in accordance with a binary number applied at terminal D and provided by the angle tracker 54 as seen in F IG. 4. Thus, the angle tracker 54 is able to select, via the digital selector 108, a specific output terminal of the shift register 106 so that the delay unit 102 provides a desired amount of delay between the input and output signals of the delay unit 102.
Referring now to the block diagram of FIG. 6, the arithmetic unit 100 comprises digital selectors 112 and 114, each of which is similar to and functions in a fashion analogous to the digital selector 108 of FIG. 5. The arithmetic unit 100 further comprises a scaling unit 116, an operational amplifier 118, a band-pass filter and a sampler 122 similar-to the sampler 98 of FIG. 4. The arithmetic unit 100 has two inputs, one providing a signal from the sampler 98 and the other providing a signal from the delay unit 102, and combines these two signals to provide a single output signal. The two input signals may be combined by summing the two together by taking their difference or by first scaling the signals to combine a fraction of one with the other. This is readily accomplished by summing resistors (not seen in the figures) applied to the input terminals of the operational amplifier 118; in this case; a multiplicity of such summing resistors of differing values are provided by the scaling unit 116, with the digital selectors 112' and 114 interconnecting each input signal with any desired summing resistor. The digital selectors 112 and 114 provide the inverse function of the digital selector 108, that is, each digital selector 112 and 114 has a single input and a multiplicity of outputs on lines 124 with a specific interconnection of one of the outputs to the input being provided in accordance with a binary number appearing at terminal A and provided by the angle tracker 54 as seen in FIG. 4. The two input signals to the arithmetic unit 100 are in binary digital format and, after being combined by the operational amplifier 118, are converted by the band-pass filter 120 to an analog signal on line 126. The pass band of the filter 120 is selected to pass the frequency of the acoustic radiation incident upon the array 22 of FIG. 1 while excluding the sampling frequencies introduced by the samplers 122. The analog signal on line 126 is then converted by the sampler 122 to a binary digital format to appear at the output terminal of the arithmetic unit 100.
Referring now to FIG. 7, there is shown a block diagram of the transmitting beam former 40 of FIG. 1. The beam former 40 accepts a signal in sampled format on line 128 from the signal generator 42 of FIG. 1 and converts this signal into analog signals suitable for being transmitted via the transducers 28. The beam former 40 comprises inverters 130, delay units 102 previously described with reference to the receiving beam former 38, a summer 132 and band-pass filters 134.
The beam former 40 may utilize analog signals and analog delay lines, however, the preferred embodiment of the invention, as shown in FIG. 7, utilizes digital delay units 102 with the aforementioned sampled or digital format of the signal on line 128. Each of the three transducers 28, namely, the left, the center and the right transducers 28, receive separate signals in order to radiate energy having a desired directivity pattern. The amplitude of the signals for each of the transducers 28 is controlled by amplifiers 136 and in accordance with a signal provided at terminal A from the angle tracker 54 of FIG. 1. To provide the signal for the left transducer 28, the digital format signal on line 128 is passed through the band-pass filter 134 having a pass band centered at the frequency of the acoustic signal radiated by the transducers 28; the pass band is sufficiently narrow to attenuate components of the sampling frequency so that only the baseband signal passes via the amplifier 136 and the multiplexing circuitry 26 to the transducer 28. To provide the signal for the right transducer 28, the digital format signal on line 128 is first applied to inverter 130, then delayed by delay unit 102, again inverted by a second inverter 130 and again delayed by a delay unit 102, and is finally filtered by a band-pass filter 134 to remove all of the sampling frequency components thereby converting it to the baseband signal suitable for radiation from the right transducer 28. Each of the inverters 130 is a digital inverter and converts a logic state of l to a logic state of and vice versa. The reason for using two inverters as Well as two delays will become apparent in a mathematical description of the operation to be provided hereinafter. Each of the delays 102 provides a suitable phase shift between the signals emanating from the right and left transducers 28 as is required for producing the desired directivity pattern. The ,center transducer 28 obtains its t signal via the summer 132 which sums together the delayed signal provided by a pair of delay units. 102 and the inverters 130. It is evident that the diagram of FIG. 7 can be simplified, as shown in FIG. 8, however, the diagram of FIG. 7 parallels that of FIG. 4 and thus shows an arrangement suitable for forming a polypole radiation pattern just as the diagram of FIG. 4 is suitable for receiving a polypole radiation pattern.
Referring now to FIG. 8 there is shown an alternative transmitting beam former 137 which may be substituted in place of the transmitting beam former 40. The beam former 137 is simpler than the beam former 40 in that the three delay units 102 of FIG. 7 have been replaced in FIG. 8 with two delay units 138 similar in operation to the delay units 102 but having different delays. In addition two selector switches 140 are provided to select either the signal on line 128 or the inverted form of-the signal and thereby provide a more general synthesis of directivity patterns.
Referring now to FIG. 9 there is shown a schematic diagram of the arithmetic units and delay units of a beam former 142 which is similar to the receiving beam former 38 of FIG. 1 except that the beam former 142 is shown in a generalized form which is suitable for any number of radiating elements such as the transducers 28. Arithmetic units 144, some of which are further identified by the letters A-C, are shown providing the differences between signals of neighboring transducers 28 while delay units 146 are shown providing the appropriate delays. In the beam former 38 of FIG. 4, the arithmetic units 100 are shown as being capable of forming either the sum or the difference of signals from neighboring transducers 28, however, in FIG. 9 the arithmetic units are presumed to be forming only the difference and this is adequate for demonstrating one form of higher order system in which any number of elements may be utilized for multiple radiation patterns. It is also noted that the delay units 146 in the first row of the diagram of FIG. 9 are of equal value as is indicated by thesymbol r similarly the values of the delays provided by the delay. units 146 in the second row of the diagram are of equal value as is indicated by the symbol T2, and that furthermore, there is one less delay in the second row than in the first row of the diagram. Similar comments apply to the third and subsequent rows of the diagram. Control lines 148 select the desired amount of delay, each control line 148 being energized from a suitable source similar to the angle tracker 54 of FIG. 1.
Referring now to FIG. 10 there is shown a simplified embodiment of a beam former 150 which may be used in lieu of the receiving beam former 38 of FIG. 1 in the situation wherein a polypole radiation pattern is to be received. The beam former 150 comprises four resistors 151-154, a delay unit 156 and summer 158. The appropriate values for the resistors and the value of delay of the delay unit 156 will be derived in terms of the values of delay utilized in the beam former 38 of FIG. 4 in the ensuing mathematical analysis.
The directivity patterns obtainable with a pair of radiating elements, such as the elements A and B seen diagrammatically in FIG. 11, may readily be expressed mathematically. A plane wave of radiation having an angular frequency w is impinging upon the array of the two elements A and B at an angle 0 to an axis of the array. Each radiating element is an omnidirectional hydrophone and has a sensitivity of K volts/microbar. If a pressure of 1 microbar is assumed, the voltages provided by each element in response to the impinging radiation is, in exponential notation,
ment spacing. The sum of these two voltages forms a monopole v given by the approximation being valid for small values of d/lt such that approximately. The. difference of these two voltages is I proportional to the pressure gradient and forms a dipole v given by I the approximation being valid similarly for small values of the argument 1r(d/ t)cos6. A cardioid response is obtained by combining the monopole and dipole patterns (ind/Mm, v,, wherein the factor (jn'd/A) is the same as that seen in the expression for v in Equation 4. The cardioid expression contains a term invariant with and a term dependent on 0. A quadrupole radiation pattern has a term dependent on cos 6 or cos20. The general representation of the voltage p-( 6) provided by the beam pattern of a polypole line array of (N 1) elements may be expressed as where 0 0 and 180 along the endfire directions of the line, and where the a are normalized such that Since reciprocity applies, the same expression may be utilized for a transmitting array.
Considering the case of the three elements A, B and C in the array of FIG. 11 and, for convenience, setting the point of zero phase at the radiating element nearest the impinging wave, namely, element A, the output voltages are respectively units 146 are presumed for the purposes of this calculation to be analog delays (for ease of mathematicalrepresentation) with the delays and resultant phase shifts expressed in terms of the interelement spacing qd and rd where q and r are constants, typically fractions. Thus, letting T and r be delays equivalent to the incident wave propagating through distances qd and rd respectively, the voltage present on line 162 is given by the voltageon line 164 is given by and the voltage on line 160 is given by For small values of the arguments rr(d/)t)(q cost?) and w(d/)t)(r cost?) in the expression for the voltage on line 160, the peak amplitude of this voltage may be approximated by V 4K(1rd/)t) (q cos6)(r cos0) where (l/p) serves a normalization factor (Up qr q r 1) in Equation 14, and in which the bracketed term is recognized as a power series such as the polypole representation of Equation 5. It is also interesting to note that for small values of these arguments the voltages on the lines 162 and 164 are approximated by the sum of a monopole and a dipole radiation pattern, the monopole being provided by the factor q and the dipole being provided by the factor 0056.
The three constants pqr, p(q r) and p may be given any desired values for providing a desired directivity pattern to the three element array. In particular, a maximum directivity, in the sense of a maximum fraction of the overall radiant energy being found in the main lobe, is obtained in the three element case for the following values, namely,
The minus sign in front of q simply means that the delay units 146A- -B should provide a time advance or equivalently, the delay units l46A-B need be placed on the opposite input ports of the arithmetic units 144A-B respectively so that a delayed voltage from element A is combined with an undelayed voltage from the element B, and similarly, with respect to elements B and C.
The preceding mathematical development also applies to the beam former 38 of FIG. 4 in the case where the arithmetic units perform simply a subtraction operation as did the arithmetic unit 144 of FIG. 9. In such a case, the simplified beam former of FIG. 10
closely approximates the beam former 38 and may be substituted in its place as will now be seen.
Referring now to the signal flow diagrams of FIGS. 12, 13 and 14, the simplified configuration of the beam former 150 of FIG. is now derived. There are provided in FIGS. 12-14 delay units 166-170, and in each delay unit the exponential phase factor of the preceding mathematics is shown. The radiating elements are identified as in FIG. 9 by the letters A, B and C. Inverters 174A-C are provided in FIG. 12, and each applies a 180 phase shift to a sinusoidal signal waveform applied thereto from delay units respectively 166-168. These inverters 174A-C will be replaced by inverter 176 in FIGS. 13 and 14. Summers 178A-C in FIG. 12 combine the various signals by adding them together, the subtraction of FIG. 9 being accomplished by the use of the inverters l74A-C. In FIGS. 13 and 14, these summers 178A-C will be replaced by summer 180.
The beam former ofFIG. 12 is functionally equivalent to that portion of the generalized beam former of FIG. 9 comprising the first three radiating elements A-C and the delay units 146A-C described above with reference to FIG. 9; and the preceding mathematics applies also to FIG. 12. In FIG. 13 the delays presented to a signal from radiating element C by the delay units 167 and 168 have been combined into a single delay provided by the delay unit 169, and the delayed and inverted signals from radiating element B are now shown by an equivalent representation wherein inverter 176 replaces the inverters 174A and 174C. Since, in the FIG. 13 a single delay unit, namely, delay unit 169, provides all of the delay for the radiating element C, the summing together of the various signals can now be accomplished with a single summer, the summer 180.
The two delays provided by delay units 166 and 168 in FIG. 13 can be combined into the single delay of delay unit 170 of FIG. 14 in the following manner. In summing together the signals of the delay units 166 and 168, it is seen that the exponential delay terms add (since the two signals are otherwise equal and may be factored out) with the result (l where rr(r q)d/)t is small. The factor of 2 is provided for in the diagram of FIG. 14 by scaling the signals of the elements A and C by a factor of one-half.
FIG. 10 is readily seen to be equivalent to FIG. 14 since the resistors 151-154 provide for the scaling of one-half, these resistors being of equal value, and the inverter 176 as well as the amplifiers of the multiplexing circuitry 26 function as .voltage sources. With respect to the signal from element A, the signal splits between the resistors l52and 153 so that one-half goes to the summer 158 and one-half goes to the delay unit 156. Thus, at the output of the summer 158 there appears the following combination of delay factors above equation is seen to be the delay factor in the delay unit 170 of FIG. 14.
Referring now to the block diagram of FIG. 15, the angle tracker 54 comprises four programming units, re-
spectively, a search selector programmer 182, a search pattern programmer 184, a track selector programmer 186, and a track pattern programmer 188, a switch for selectively coupling the programming units 182 and 186 to a memory 192, and a switch 194 for selectively coupling the programming units 184 and 188 to a memory 196. The angle tracker 54 further comprises a detector 198 and a predictor 200 both of which are responsive to signals on line 56 from the correlator 50 of FIG. 1, the detector 198 actuating the switches 190 and 194, and the predictor adjusting the programs of the track selector programmer 186 and the track pattern programmer 188.
In operation, the detector 198 senses the magnitude of the correlator signal on line 56 to determine the presence of a distant source of sound such as the reflected waves 46 from the boat 44 in FIG. 1. The detector 198 has a preset threshold for determining that such a distant source of sound is or is not present. When no such source of sound is present, the switch 190 couples the search selector programmer 182 to the memory 192, and the switch 194 couples the search pattern programmer 184 to the memory 196. The memory 192 stores data with respect to specific ones of the transducers 28 of FIG. 1 which are to be coupled by the beam switcher 64 for orienting the radiation directivity pattern of the array 22 in a specific direction. The search selector programmer 182 provides a succession of directions, in response to the clock pulses at terminal C, for redirecting the directivity pattern of the array 22 for searching for a distant source of acoustic radiation. These directions are sent from the search selector programmer 182 via the switch 190 to the memory 192 which, in response thereto, provides signals along line 62 for operating the beam switcher 64 to couple the appropriate ones of the transducers 28. In a similar manner, the search pattern programmer 184 sequentially selects specific shapes for the directivity pattern during each orientation of the directivity pattern as provided by the beam switcher 64 to aid in the searching. Accordingly, the search pattern programmer 184 designates a specific shape via the switch 194 to the memory 196 which, in response thereto, commands the appropriate set of delays and scaling factors for the beam formers 38 and 40 of FIG. 1, these commands being transmitted in the form of digital signals on the lines 58 and 60.
When the detector 198 determines that a suitable source of acoustic radiation is present, it actuates the switches 190 and 194 to couple the track selector programmer 186 to the memory 192, and the track pattern programmer 188 to the memory 196. The track selector programmer 186 continually reorients the directivity pattern of the array 22 of FIG. 1 so that the source of acoustic radiation. is present on alternating sides of a null in the directivity pattern, this providing effectively a tracking error signal analogous to the tracking error signal developed by a monopulse feed in a radar antenna. Similarly, the track pattern programmer 188 commands the beam formers 38 and 40 via the switch 194 and the memory 196 to adjust the directivity pattern to provide a shape more amenable to tracking the source of radiation.
The predictor 200 monitors the angle coordinates of successive positions of the source of radiation and instructs the track selector programmer 186 to reorient the directivity pattern when the source-of radiation tends to move away from the null in the directivity pattern. When the source of radiation moves an angular distance smaller than an angular increment that can be provided by the beam switcher 64, the predictor 200 commands the track pattern programmer 188 to move the null of the-directivity pattern to accommodate the angular movement of the source of radiation rather than to command the track selector programmer 186 to update the orientation of the directivity pattern. The average angular orientation of the null in the directivity pattern corresponds to the angular coordinate of the source of radiatiomand this information is transmitted from the track selector programmer 186 along line 66 to the'display 70 of FIG. 1. To facilitate discrimination between targets of differing ranges from the array 22 of FIG. 1, the correlator 50 of FIG. 1 is provided with a range gate, not seen in the figures, which, in response to a signal from the timingunit 72, passes only those pulses on line 56 corresponding to a radiation source at the desired range, this range being selected by a manual control provided on line 201 in FIG. 1.
It is also apparent that while the preceding discussion has described the implementation of a directivity pattern formed by a linear array of three of the transducers 28 of FIG. 1,-it is apparent that four or more of the transducers 28 can be switched into the circuit to further tailor the directivity pattern to a desired shape so that it is possible to keep a null of the directivity pattern oriented towards the stern of the boat 82 to reduce the effects of propeller noise. It is also apparent that a cylindrical array of the transducer elements 28 can be provided by coupling all of the transducers 28, except for the central transducer 28, to the beam formers 38 and 40. Such an interconnection of the transducers 28 with the beam formers 38 and 40 can be accomplished, for example, by coupling together the pair of the transducers 28 labeled A and D, the pair of transducers labeled F'and E, and the pair of transducers labeled, E and C with these three pairs of transducers 28 being connected to the beam formers 38 and 40 in lieu of the previous connections of the transducers indicated earlier in FIG. 9 with reference to the transducers A, B and The description of the preferred embodiment of the invention, hereinbefore presented, provided for an implementation of the expression for a polypole radiation pattern as given by Equation 5. An analogous embodiment of the invention will now be presented with refer-. ence toFlGS. 16-18 for providing a polymode radiation pattern given by Equation 19 which is readily seen' to be of the same form as Equation 5 except that the summation is seen to be a Fourier series rather than a power series. For the three element array considered in 'FIG. 2, or the eight element array to be described in FIG. 16, the Fourier series of Equation 19 can readily be-converted by trigonometric identities to the power series of Equation 5. Accordingly, the terms polypole and polymode are seen to be convenient terms for describing the mathematical series representation of multiple mode types of radiation patterns.
Referring now to FIG. 16, there is seen a schematic diagram of an alternative embodiment of the invention showing an array 202 of radiating elements which are in the form of a cylindrical radiator having inner and outer concentric metallic electrodes located on the inner and outer surfaces of a ceramic cylinder 204. The outer electrode is identified by the numeral 206 while the inner electrode is segmented into eight segments, each of which are insulated from each other and are identified generally by the numeral 208 with specific segments being further identified by the letters A-H. In the most general form the array is of spherical or spheroidal shape; however, the preferred practical configuration is cylindrical when, for example, elevation angle are secondary to azimuthal angles.
The array 202 is shown coupled to a receiver 210 having eight preamplifiers which will be identified generally by the numeral 212 with individual ones of these preamplifiers 212 being further identified by the letters A-H which correspond respectively to the eight inner electrode segments 208 A-l-I. The inner electrode segments 208 are coupled to their respective preamplifiers 212 via wires 214. Each of the preamplifiers 212 are also identified in the figures by legends such as NNE meaning north-by-northeast and WSW means west-bysouthwest. A coordinate axis indicating the directions north, east, south and west is also seen overlaid upon the array 202.
The receiver 210 further comprises a first set of operational amplifiers 216 and a second set of operational amplifiers 218 with individual ones of these amplifiers being identified respectively by 216A-G and 218A-H. A filter 220 is provided at the output of the operational amplifier 216A and filters 222A-B are provided at the outputs of the operational amplifiers respectively 2l6F-G. Adjustable attenuators 223 are coupled to the outputs of the filters 220, 222A and 222B as well as to the outputs of the amplifiers 216B-E for sealing the respective signals, these attenuators being further identified by the letters A-G corresponding respectively to the amplifiers 216A-G. The operational amplifiers 216 are further identified by legends such as the legend M representing a monopole or an omnidirectional radiation pattern, NW/SE representing a dipole radiation pattern oriented with its axis running from northwest to southeast, 000 which identify a quadrupole radiation pattern having its reference axis at an angle of 0 (along the north-south axis) with respect to the array 202, and 045 which represents a quadrupole radiation pattern having its reference axis inclined at an angle of 45 with respect to the array 202. Each of the preamplifiers 212 is connected to all of the operational amplifiers 216, however, for purposes of simplifying the drawing, these interconnections are indicated by means of the numerals 1-8 identifying the output terminals of the preamplifiers 212 and the corresponding numerals l-8 at each of the eight input terminals to each of the seven operational amplifiers 216. As is well known, operational amplifiers are typically provided with a positive input and a negative input with summing resistors connecting with both the positive and the negative inputs to provide an algebraic combination in which a plurality of signals may be summed together and subtracted from a second plurality of signals which are summer together.
The filters 220 and 222A-B serve as equalizing networks to equalize the frequency response of the omnidirectional pattern and the frequency response of the quadrupole pattern with that of the dipole pattern. As is well known from the mathematics of dipole patterns in acoustic systems, the receiving frequency response of ceramic transducers for frequencies below resonance tends to rise at a rate of 6 dB/oct (decibles per octave) change in frequency. Accordingly, the omnidirectional pattern which has a fiat frequency response below resonance is passed through the filter 220 which may be, for example, a lead network,-introducing a phase shift of +90 and having a frequency response of +6 dB/oct. Since quadrupole radiating patterns have a frequency response for frequencies below the second order mode resonance frequency of the array 202, wherein the amplitude of signals provided by the amplifiers 216F and 216G rises at a rate of +1 2 dB/oct, each of the filters 222A-B which may be, for example, a lag network, provide a phase shift of 90 and a frequency responsivity of6 dB/oct. Thus the signals on each of the lines 224 are characterized by a frequency responsivity which varies at the rate of +6 dB/oct for all frequencies below the resonance region of the array 202. In the situation where a source of sound 226 transmits sound waves 228 towards the array 202, the sound waves 228 having become substantially-planar waves in the vicinity of the array 202, the array 202 is built with a diameter which is sufficiently smaller than the wavelength of the waves 228 so that the frequency of these waves is below the resonance region of the array 202.
Each of the lines 224 is connected to at least some of the operational amplifiers 218 but not necessarily all of these amplifiers. Here again, in order to simplify the drawings, the interconnections of individual ones of the lines 224 are indicated by legends affixed to each of the inputs of the respective operational amplifiers 2l8A-H. Thus, with respect to the operational amplifier 218A, the omnidirectional signal provided by the filter 220 is supplied to one input, the NE/SW dipole signal provided by the operational amplifier 216D is applied to a second input, and the quadrupole signal provided by the filter 222A is applied to the third input of the operational amplifier 218A. As is indicated by the plus signs adjacent each input of the operational amplifier 218A, each of these inputs are summed together to give a voltage V1 which is the voltage associated with one polymode directivity pattern for receiving the waves 228, as will now be described with reference to FIG. 17.
Referring now to FIG. 17, there is shown a schematic representation of the combination of an omnidirectional radiation pattern 230, a dipole radiation pattern 232 and a quadrupole radiation pattern 234 to give a polymode pattern 236 represented by the voltage V] of the operational amplifier 218A of FIG. 16. The omnidirectional pattern 230 is a graph of the voltage appearing at the output of the filter 220 of FIG. 16 as the source 226 is moved in a large circle around the array 202. Similarly, the dipole radiation pattern 232 and the quadrupole radiation pattern 234 represent the voltages provided by respectively the operational amplifier 216C and the filter 222A as the source of sound 226 is moved in a large circle around the array 202. The summation of these voltages by the operational amplifier 218A is represented in FIG. 17 by the pictorial equation having two plus signs and an equal sign. It is noted that the polymode pattern 236 has one main lobe in the north direction corresponding to the contributions of the northerly portions of the three radiation patterns 230, 232 and 234, each of which have a positive voltage in the northerly direction. On the east and west axis the negative portions of the lobes of the quadrupole radiation pattern 234 are portrayed as having equal and opposite amplitudes to the amplitude of the omnidirectional radiation pattern 230 at the east and west directions and therefore cancel each other so that zero amplitude appears at the east and west directions of the polymode pattern 236. Similar comments apply to the construction of the polymode pattern 236 and other directions. Mathematically this construction is indicated by the algebraic expressions beneath each of the radiation patterns 230, 232 and 234 in which the maximum amplitudes of these radiation patterns have all been set equal to one-third so that the peak amplitude of the polymode pattern 236 is equal to unity.
It is frequently desirable to scale the respective amplitudes of the respective radiation patterns 230, 232 and 234 to provide a maximum directivity for the polymode pattern 236 with the maximum directivity being understood to be a maximization of the ratio of energy received from the northerly direction of the radiation pattern 236 to the total isotropic incident energy received by all of the lobes of the pattern 236. This can be readily accomplished mathematically by integrating the energy received in each direction and forming the standard ratio for the directivity index, with the result that the maximum directivity is obtained for the scaling factors indicated in the attenuators 223A-G of FIG. 16. These scaling factors are, respectively, a value of 3 for the attenuator 223A a value of 4 for each of the attenuators 223B-E, and a value of 5 for each of the attenuators 223F-G. In FIG. 16, the arrow adjacent the scaling factor in each of the attenuators 223 indicates that the attenuation of these attenuators 223 may be varied to provide selective scaling of the monopole, dipole and quadrupole radiation patterns to produce a polymode pattern in which the positions of the nulls can be varied as well as for providing a selective tailoring of the shapes of the various lobes in the polymode radiation pattern.
Returning momentarily to FIG. 16, the operational amplifier 218B is seen to provide a polymode pattern having the same shape as the polymode pattern 236 of FIG. 17 but being oriented at an angle of 45 with respect to the coordinate system of the array 202. This results because of the summation of the monopole signal of the filter 220 with the signal of the operational amplifier 2168 and the quadrupole signal of the filter 222B, for which the dipole radiation pattern and the quadrupole radiation patterns have their main axis in the 45 or NW/SE direction. With respect to the voltage V3, provided by the operational amplifier 218C, a polymode radiation pattern perpendicular to that of the polymode pattern 236 of FIG. 17 is provided since here the quadrupole pattern provided by the filter 222A is subtracted from the sum of the monopole pattern of the filter 220 and the east-west dipole pattern of the operational amplifier 216E; this subtraction is indicated by the minus sign adjacent the third input of the operational amplifier 218C. Similar comments apply to the remaining .voltages V4-V8 wherein it is seen that a family of eight polymode radiation patterns are simultaneously produced by the receiver 210.
Referring now to FIG. 18, there is seen a system 238 comprising the array 202 and the receiver 210 of FIG. 16, here'shown coupled via multiplexing circuitry 240 similar to the multiplexing circuitry 26 of FIG. 1. A signal generator 242 similar to the signal generator 42 of FIG. 1 provides signals which are coupled via the multiplexing circuitry 240 to the array 202 for transmission therefrom as in an active sonar systempThe receiver 210 receives either echoes, which are reflected from an object such as the boat 44 of FIG. 1, or signals generated by a distant source of sound such as the source of sound 226 of FIG. l6. The direction of such a distant source of sound can readily be determined by means of logic circuitry 244 which performs the function of noting which of the voltages V 1-V8 has a maximum value. A display 246, such as a cathode ray tube display, is coupled to the logic circuitry 244 for displaying the direction of the distant source of sound. Additionally, a timing unit 248, similar to the timing unit 72 of FIG. 1, and a range gating unit 250 may be utilized in an active sonar mode for gating out all received signals except those corresponding to echoes emanating from a preselected range from the array 202. To implement this range gating, the timing unit 248 supplies timing signals to both the signal generator 242 and the range gating unit 250 so that a range gate can be set corresponding to a preselected time interval subsequent to the transmission of a signal generated by the signal generator 242. The range gating unit 250 is coupled to the receiver 210 at the gate terminals of the preamplifiers 212 (FIG. 16) to gate out all the polymode voltages of the receiver 210 except for such voltages falling within the designated range gate.
Referring now to FIG. 19 there is shown a block diagram of a receiver 250 which is similar to the receiver 210 of FIG. 16 in that it utilizes the eight preamplifiers 212, five of the operational amplifiers 216, namely, the operational amplifiers 216A, 216C, and 216E-G, and one of the operational amplifiers 218. Each of the preamplifiers 212 connect via the wires 214 to the array 202 as in FIG. 16. The receiver 250 differs from the receiver 210 in that the receiver 250 combines the output from a pair of dipole operational amplifiers, namely, the north-south and east-west dipole operational amplifiers 216C and 216E via a coordinate converter 252 to obtain a dipole, represented by a voltage on line 254, with an axis having any desired orientation with respect to the coordinate system of the array 202. The omnidirectional channel comprises the operational amplifier 216A and the filter 220 of FIG. 16 but no coordinate converter is utilized since the omnidirectional pattern is symmetric about the axis of the array 202. A quadrupole radiation pattern oriented in any direction about the axis of the array 202 is provided by the operational amplifiers 2l6F-G and the filters 222A-B of FIG. 16
summed together by the amplifier 2648. The multipliers 260A-D may operate in an analog or in a digital fashion. Thus, the multiplier 260A multiplies the northsouth dipole signal by cos0, and the multiplier 260B multiplies the east-west dipole signal by sin9 whereupon the two products are summed together to give a resultant dipole having the same amplitude as the north-south dipole but having a dipole axis inclined at an angle 0 relative to the axis of the array 202. Subscripts I and 2 are utilized with the angle 6 to indicate that the dipole pattern may be rotated at different amounts from the quadrupole pattern. Similar comments apply to the operation in the coordinate converter 256 except that here the multiplying factors are cos(20 and sin(26 since the expression for the quadrupole radiation pattern is in terms of cos(20), while that of the dipole is in terms of cost? where 6 is the angle relative to the coordinate system of the array 202.
With respect to the capability of rotating the dipole patterns relative to the quadrupole pattern, as seen with the embodiment of FIG. 19, it is noted that such a capability exists also in the embodiments of FIGS. 1 and 16 but to a limited extent. Thus, in FIG. 1 a rotation of 180 imparted by the beam switcher 64 rotates the dipole pattern 180 while rotating the quadrupole pattern 0, i 90 or 180 since each of these rotations are fully equivalent with the quadrupole pattern which is periodic with each rotation of I80". With respect to the embodiment of FIG. 16, a dipole pattern can be rotated with respect to a quadrupole radiation pattern by simply selecting the outputs from a different operational amplifier 216 such as the combination of the outputs of the operational amplifier 216C and 216F as is provided by the operational amplifier 218A or the combination of the outputs of the operational amplifiers 216E and 216F as is provided by the operational amplifier 218C.
To implement the coordinate conversion digitally, the multipliers 260A-D would comprise an analog-todigital converter, a digital multiplier, and a digital-toanalog converter (not seen in the drawings). The trigogain would be proportional to cos6 in the case of the multiplier 260A, and similarly for the other multipliers 260B-D. With respect to the trigonometric units 262A-B, in analog form they would comprise, for example, a non-linear diode-resistor circuit in which the output voltage approximates cos0, in response to input voltage of 0 with a second such circuit being provided to produce sin(), in response to 0 The omnidirectional channel also comprises an amplifier266 coupled to the output of the filter 220 and having a variable gain in accordance with a voltage applied at terminal G for varying the gain of the omnidirectional pattern relative to the gains of the dipole and quadrupole patterns. The relative gains for the three channels, namely, G G and G as well as the angles of rotation of the dipole, 0 and of the quadrupole 6 are provided by a beam former 268 in response to signals provided by a logic circuit 270. The logic circuit 270 is similar to the logic circuit 244 of FIG. 18 and is useful for tracking a source of sound such as the source 226 of FIG. 16. Thus, the logic circuit 270 in response to the polymode voltage, V, at the output of the operational amplifier 218 provides signals to the beam former 268 for rotating the polymode directivity pattern, and furthermore, for varying the shape of the directivity pattern by varying the gain G G and G The shape of the directivity pattern can also be varied by making 0 different from 0 this providing a flexibility not found in the receiver 210 of FIG. 16. The receiver 250 and the logic circuit 270 may be substituted in the system 238 of FIG. 18 in place of the receiver 210 and the logic circuit 244 to provide a tracking system with improved tracking capability.
It is also evident with respect to the receivers 210 and 250 of FIGS. 16 and 19 that an octopole radiation pattern could be formed by summing and differencing alternate outputs of the amplifiers 212. In this respect it is noted that alternate pairs of inputs to the operational amplifiers 2l6F-G are summed and differenced to provide the quadrupole radiation pattern, there being two such patterns spatially offset by 45. In the case of the octopole pattern, only one fixed pattern could be produced with the eight inner electrode segments 208, it being necessary to employ sixteen such segments for providing a second octopole radiation pattern, and similarly for providing a combination of these patterns to give a resultant octopole radiation pattern in any arbitrary direction. Via the same reasoning, it is also evident that if only four inner electrode segments 208 were employed in the array 202, then one fixed quadrupole radiation pattern could also be produced; however, there would be no facilities for altering the directional quality of such a pattern.
It is also apparent from a comparison of the array 202 of FIG. 16 and the array 22 of FIG. 1 that the two arrays may be combined into a single composite array (not seen in the figures) in which one or more transducers 28 of the array 22 are replaced with an array having the form of the array 202. In view of the fact that the diameter of the array 202 is substantially smaller than a wavelength, such a radiator may readily be substituted for a transducer 28. With respect to connecting this composite or hybrid array to the multiplexing circuitry 26 and the transceiver 24, the multiplexing circuitry 26 must be enlarged to accommodate a transmit-receive circuit for each of the wires 214 of FIG. 16 for each one of the arrays 202 utilized in the composite array. A plurality of the receivers 210 of FIG. 16 are utilized, one for each of the arrays 202 with the omnidirectional channel in each of these receivers being connected to the receiving beam former 38 of FIG. 1. This provides a composite receiving system having both features of the system 20 of FIG. 1 and features of the system 238 of FIG. 18, and may be referred to as a polypole, polymode receiving system; the composite array may similarly be referred to as a polypole-polymode array. Transmission of signals generated by the signal generator 42 of FIG! may still be accomplished in the polypole fashion by energizing each of the inner electrode segments 208 of an array 202 in parallel circuit from asingle output of the transmitting beam former 40 of FIG. 1.
A polypole or polymode or hybrid array may also be constructed in three dimensions, such as a four element array in which each of the radiating elements are located at the vertices of a tetrahedron. Such an array is readily implemented for polypole operation with radiating elements having a spherical radiating surface so as to radiate an omnidirectional pattern in three dimensions. In the case of the polymode operation, a radiating element must be segmented in three dimensions as by utilizing sectors of a sphere. The resultant radiating patterns of the tetrahedronal array are significantly more complex than those presented hereinbefore for the planar array, as may be understood by noting that the projections of the interelement spacing upon anaxis of the radiation pattern is dependent on the orientation of the axis relative to the tetrahedron configuration. In particular, there are six major axes each of which passes through the center of the tetrahedron and is parallel to an edge of the tetrahedron. It may also be desirable to place a radiating element at the center of the tetrahedron to provide greater flexibility in forming the radiation pattern in any desired direction. The same form of circuitry as has been disclosed hereinbefore, may be utilized for the tetrahedronal array, however, the beam forming circuitry and the logic control for the beam forming circuitry is extended to encompass all three dimensions in a manner which may be seen by extending the preceding mathematics to three dimensions.
It is understood that the above described embodiments of the invention are illustrative only and that modifications thereof will occur to those skilled in the art. Accordingly, it is desired that this invention is not to be limited to the embodiments disclosed herein but is to be limited only as defined by the appended claims.
What is claimed is:
1. A radiating system comprising:
a plurality of radiating elements;
a first means for combining the signals of a first set of radiating elements of said plurality of radiating elements, said first combining means including means for delaying the signal of a radiating element of said first set of radiating elements relative to the signal of another radiating element of said first set of radiating elements;
a second means for combining the signals of a second set of radiating elements of said plurality of radiating elements, said second combining means including means for delaying a signal of a radiating element of said second set of radiating elements relative to another radiating element of said second set of radiating elements, each of said delay means being a variable delay for delaying their corresponding signals a preselectable amount of delay;
a third means for combining signals, said third means including means for delaying a signal provided by said second means relative to a signal provided by said first means, said third means combining said delayed signal of said second means with said combined signal of said first combining means;
the radiating elements of said plurality of radiating elements being arranged in an array suitable for forming at least one beam of radiation, the directivity pattern of radiation of said array having a notch and being adjustablein accordance with the magnitude of the delays provided by said variable delay means;
means for selectively coupling energy from individual ones of said radiating elements to said first and said second combining means, said selector means moving said notch for detecting a source of radiant eny;
angle tracking means responsive to the energy of radiation received by said beam of said array, said angle tracking means being connected to each of said variable delay means and selecting the amount of delay to be provided by each of said variable delay means, said angle tracking means selecting and varying the directivity pattern of said beam of said angle tracking means comprises a memory for storing preselected values of delay for each of said variable delay means, and programming means for addressing said memory to select a set of delays to be provided by each of said variable delay means.
|Citing Patent
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|Rod-type multipole source for acoustic well logging
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|U.S. Classification
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|International Classification
|Cooperative Classification
|European Classification


text:
Introducing the THIN MINT COCKTAIL, inspired by THE BOSS!
Introducing the THIN MINT COCKTAIL, inspired by THE BOSS!
Brand New, Seven-Screen Cinema Coming to the Heart of Downtown Brooklyn to Celebrate the Best in Film, Food and Drink
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Trailblazing first-person POV action film will explode across Alamo screens nationwide starting with sneak previews for Alamo Victory Members 3/29 – and inspires exclusive, limited time "hardcore" food specials.
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Help decide the next Free Victory Screening in our March movie madness bracket!
For BvS, justice will indeed be served — and it will be very tasty, thanks to the superheroic efforts of Alamo Chef Brad Sorenson.

subset: commoncrawl


text:
As I sat on my couch tonight watching "America's Funniest Home Video's" while Rakes and Trot sat next to me and cackled like raving lunatics at the sight of a grown man getting hit in the marbles with a teeter totter, the following thought occurred to me.
I am a gigantic idiot.
Because if I'd have gone ahead with my initial plan of installing 24 hour video cameras when I built this house I'd have my own show on MTV, my star on the Walk of Fame in Hollywood, and these kids of mine would be making millions on their way to years of therapy.
Instead of JUST on their way to therapy.
Thursday, January 27, 2011
6 comments:
- Tex said...
Those two are NOT going to need therapy. They have more self esteem in their pinky than most kids do. They will need lots of insurance though...to pay for all the damage they'll 'accidently' be responsible for
- January 27, 2011 at 11:35 PM
- Ted D said...
OK. So the therapy is for me. Sue me.
- January 28, 2011 at 8:14 AM
- Rich in the Garage said...
And potentially costing you millions in a law suit.
- January 28, 2011 at 9:09 AM
- Ted D said...
That too.
- January 28, 2011 at 9:16 AM
- Stacy said...
Tex is right; those children will NOT need therapy. They are just little boys who will, sadly, one day grow up. They're just a little "active". :)
- January 28, 2011 at 10:06 AM
- Ted D said...
A little active?
- January 28, 2011 at 11:22 AM
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Rafael Nadal plans to take several weeks off after the Australian Open to recover from a nagging shoulder injury.
The world No 2 said the injury surfaced before the ATP World Tour Finals in November and that he was still "not 100 per cent". He decided only three days before the event to defend his title at the World Tennis Championships, a two-day exhibition tournament in Abu Dhabi.
"I had a problem before London with my shoulder and I had to stop for about 10 days before the [ATP] finals," said Nadal. "It felt better but again it resurfaced. In December, I did not have enough time to practice because of that." Nadal will play David Ferrer today in the Abu Dhabi semi-finals.
He is hopeful his shoulder will hold up as he attempts to win the tournament for the third year in a row and in Doha, where he plans to play at the Qatar Open next week. After that the 25-year-old Spaniard intends to compete in the Australian Open, which begins on 16 January, before taking February off to rest and practise.Reuse content


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Philosophy Lexicon of Arguments
|Fine-grained, logic, philosophy: statements can be be more or less detailed. E.g. the fine-grained statement (x)(y)(x = y > (N(x = x) > N(x = y))) could be displayed in a coarse-grained way as A > B. For the decision of problems the coarse-grained form is often inadequate. See also decidability, possible worlds, situation semantics, possible world semantics, hyperintensionality.
|Meta data
Books on Amazon
Fine-grained/Field: E.g. sets of possible worlds are coarser than possible belief objects: eg the axioms of set theory and the Banach-Tarski theorem (BTT, strongly counter-intuitive) are logically equivalent, i.e. valid in the same worlds - but the BTT is not believed by all the people who believe the axioms of set theory - sentence meaning/Lewis: is fine grained - belief/Lewis: what one believes, is coarse - punch line: so the conviction is always the same: with and without BTT!
FieldVsStalnaker: sets of possible worlds are too coarse to distinguish beliefs - e.g. set theory with and without Banach-Tarski theorem are the same.
Fie I
H. Field
Realism, Mathematics and Modality Oxford New York 1989
Fie II
H. Field
Truth and the Absence of Fact Oxford New York 2001
Fie III
H. Field
Science without numbers Princeton New Jersey 1980


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On the way up, though, you take your chances with the factory product, like everyone else. The first bass Bruce owned was called a Top 20, it was made in Japan and, on one memorable evening at the 100 Club, it nearly killed him.
'There was a surge of electricity, the strings burnt right into my hand and I got thrown across the stage, where I lay quivering until finally somebody kicked the plug out. They had to carry me into the dressing- room and I was completely rigid, so they laid me on top of the upright piano in there. And I seem to remember I was high for days after.'
Jack Bruce, who is 49, speaks with a quiet Scots voice and wears somewhat louder Versace shirts. Clapham will be his first London appearance for longer than he cares to remember. His new outfit is a trio, like the band that made him famous. They'll play some blues and some of Bruce's old material and probably go in for a fair bit of spooky improvisation in between. On bass and vocals: Jack Bruce. On drums: the distinguished session player Simon Phillips. On guitar: Blues Saraceno, a New Yorker so young that, by the time he was born, Cream had already split.
'I first took him on three years ago, when he was 17. Bernie Worrell was in the band and he complained, saying, 'I go on the road to get away from my kids.' When he auditioned, he was very rough but you could see the potential in the guy. He walked in with a purple mohawk and a plaid guitar, plugged into his Marshall, went krrung, and it blew up. So I said, OK, you're hired. He only had one knob on his guitar, just loud and quiet, and that impressed me too. I sent him off with a tape of songs to learn and he came back three days later with a bandage on his hand. But he had it down. He just lives for the guitar and it reminds me of myself when I was that age - bass and that was it.'
Like Saraceno, Bruce was 17 when he went for his first audition. Responding to an advertisement in Melody Maker, he slung his double-bass on a train and travelled from Glasgow to Coventry to audition for the Murray Campbell Big Band at the Mecca ballroom. 'They were doing Maynard Ferguson arrangements and Dizzy Gillespie big band transcriptions. The audition piece was 'One Bass Hit', with the Ray Brown bass solo actually transcribed. And I sight-read it, because I'd just come from college and I could do all that stuff, and I got the gig.'
Bruce says he then remained 'a jazz snob' until 1962, when he joined Alexis Korner's Blues Inc. 'Before that, I was down on anything with a back beat.' But then he started to listen to Delta blues and soon he was linked with the drummer Ginger Baker in the Graham Bond Organisation. 'We did something like 320 one- nighters in a year, which is why I tell people that I don't need much practice any more.' And in John Mayall's Bluesbreakers, he met Eric Clapton, 'who introduced me to even more esoteric strands of the blues'. By which time, he had traded his double-bass for an electric. 'I was hooked because it was loud: which is useful when you're playing with Ginger Baker, who plays hard. Suddenly I could be heard without sacrificing bits of my fingers.'
Cream only lasted three years (1966-69), but they sold 30 million records in that time. 'Funny to think that, at the time we formed, we hadn't started writing our own tunes and we were relying on Eric's knowledge of other people's stuff. In those days you would form a band and hit the road. I think now people might take a little more time - rehearse, maybe. Anyway, the songs gradually started to come. The first one I wrote was called 'NSU' about a sexually transmitted disease that Eric had. It's like an early punk song and I still play it sometimes.
'Our record label in America was Atlantic, and I must say they weren't too impressed by the music I wrote. I came up with 'Sunshine of Your Love' and 'White Room' and Ahmet Ertegun (Atlantic's president) would say, 'You can't do that, you can't have 5:4 time at the beginning of a pop song.' 'Sunshine of Your Love', he said, was psychedelic hogwash. But then it became the label's best-selling single at that point. I think there was a negative feeling about the bass player being the singer. I think they really wanted Eric to be the front-man of the band. But he couldn't really have done it at the time, it wouldn't have worked. I didn't want the job either, but it was like 'You be the singer', 'No, you be the singer', and I lost. At least I didn't have to have the curly hair, though. That was Eric's job.
'Thinking back on that band, it was really a jazz band, there was so much improvising by the time it evolved. We started off playing four- or five- minute tunes, but by the time we got to San Francisco in '67, it had started to stretch out. It became almost like an Ornette Coleman band, with Eric not knowing he was Ornette Coleman, Ginger and me not telling him. But there he was, doing these unaccompanied solos for 20 minutes, incredible stuff.'
Bruce says he sees Clapton 'now and again' and Baker, who was 53 on Wednesday, 'more frequently'. (When Baker played on Bruce's 1989 album, A Question of Time, it was the first time they had recorded together since Cream.) He got the urge to tour in a three-piece again last autumn, during Seville's 'Guitar Legends' festival, at which rock's aristocracy assembled for a jam session. Bruce performed 'Sunshine of Your Love' and played with Bob Dylan on a version of 'All Along the Watchtower'.
'It was great to get to know Dylan a little bit. I got the job of finding out what he wanted to play and communicating with him. Communication is not something he's famous for. He's one of my all-time heroes and I'm funny with that. I had been invited to meet him before, but actually bottled out, because I had a couple of bad experiences with heroes. I remember when Tony Williams introduced me to Charles Mingus at the Village Gate. Mingus is my all-time bloke. I did the terrible thing that people do to me sometimes: I said, rather gushingly, 'Thank you]]' And he said, very sternly, 'What for, boy?' '
The Jack Bruce Band has already toured Japan and Poland, appearing mostly at festivals. ('There's a certain crowd that will always come out for me, particularly in America: garage mechanics, mostly.') In September, they will go to Bill Laswell's studio in Brooklyn and begin recording an album. At all other times, Bruce will be in Suffolk, in the village he moved out to in 1970 when life in London started to swing a little too nauseatingly. 'I lived in Chalk Farm and it just got too much. Everybody knew where my house was and there were tons of people around every night, which I got fed up with. I've never regretted moving away. It probably saved my life.'
He says the neighbours resisted him at first, but no longer. 'I got phone-calls saying, 'We hear you're going to start a Roadhouse.' And I would say, 'No, I came here to live peacefully.' They thought I was going to tear the house apart and fill it with swimming pools. These days, though I hate to think so, you can be a musician and still be respectable. Charlie Watts came down not long ago. I took him into the pub. The village liked that.'
The Jack Bruce Band appears tonight at The Grand, Clapham (Box office: 071-738 9000)
'Jack Bruce: The Collection' is released by Castle Communications, catalogue number CCSCD 326
(Photograph omitted)
- More about:
- Bass Guitar Players
- Blues
- Clapham
- Cream


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text: Six sentenced in false billing scheme at former Massey Energy By Staff reports January 16, 2014 Story Share CHARLESTON, W.Va. -- Six people have been sentenced for their roles in a false billing scheme involving illegal invoices at the former Massey Energy.Donald Bryan Steele, 43, of Barboursville, was sentenced to 18 months in federal prison on Thursday, according to a news release issued by U.S. Attorney Booth Goodwin. Steele was a former owner of M&S Hydraulics, a major Massey supplier. Steele previously pleaded guilty to wire fraud and aiding and abetting in connection with the fraud scheme. Alpha Natural Resources purchased Massey Energy in 2011.When police approached Steele in February, he admitted to illegally providing cash and other items to former Massey sourcing agents, Joey R. Phalin, Edward Ellis Mullins and Nicholas R. Coleman in exchange for invoices for payment that M&S Hydraulics had not provided, according to the release.The three sourcing agents, who were responsible for ordering good and services for Massey, participated in the scheme to obtain goods for their own personal benefit, according to the release. The agents hid several illegal transactions by creating false invoices. Phalin, 36, of Crab Orchard, was sentenced to five years probation with the first ten months to be served on home confinement. Coleman, 29, of Lester, was sentenced to five years probation.Steele identified three other sourcing agents involved in scheme. Last week, Ricky R. Smith, 49, of Glen Daniels, was sentenced to one and a half years in federal prison. James Roger Long II, 34, of Beckley, was sentenced to one a half years in federal prison.Harold Wayne Brown II, a former Alpha underground maintenance chief, previously pleaded guilty to making false statements to federal authorities in connection to the fraud scheme. Brown, 41, of Madison, will be sentenced Jan. 21. Story Share Story Share Trending Now 1 Mingo man, woman charged with sex trafficking 2 2017 Gazette-Mail All-Kanawha Valley softball teams 3 Beckley man charged in online art scam, authorities say 4 Mitch Vingle: Examining WVU, Big 12 football schedules 5 Hurricane's Katie Adams named Kanawha Valley Softball Player of the Year Efforts underway to revive Theatre West Virginia Previous Story Pediatrician: Young children shouldn't drink the water Next Story


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Curtiss B-2 Condor
Photo Code:
WKP-Curtiss B-2 Condor
A colorfully painted Curtiss B-2 Condor bomber #1 (AC 29-36) in flight. Only 12 were built. The B-2 used Curtiss Conqueror engines and had a machine gunner in the rear of each nacelle. Circa 1931-1932. The aircraft are from the 11th Bombardment squadron.
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18 June 2013 @ 05:21 UTC
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Curtiss B-2 Condor
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✒I'm back in Boulder, Colorado, for the Conference on World Affairs which is, as I may have said before, basically a piss-up with speeches. The snow has almost disappeared from the Flatirons, the jagged stretch of the Rockies that looms over the town, and the sun shone from a deep navy sky almost all week.
Colorado is one of the states that has legalised marijuana for medicinal use (ie the treatment of more or less anything, such as "depression caused by not having any drugs to smoke"). The authorities here received 120 applications to dispense pot, in a city with just 30 pharmacies. Some of these tiny places try to pretend they are genuinely ministering to the sick, with names such as Med Shed. Others are more upfront, such as Weed World.
To buy pot you only need a card from your doctor saying you need to smoke it, and it's amazing how many students in this campus town have acquired the cards. But pot is still illegal under federal law, and the feds are trying to find all kinds of ways to close these operations down. The police code for drugs is a 4/20, so next Friday, April 20 in American notation, they are going to have a massive smoke-in on campus. Last year an estimated 11,000 students turned up. It will make an impressive cloud.
✒Everyone here is dazed by the election, and especially by the near-certain choice of Mitt Romney as the Republican nominee. One cartoon showed a puzzled voter looking at the list of Republican names, with "none of the above" along the bottom. "Well, he's the closest we could get." As one of the late-night comics said: "Republicans are not excited. It's like taking your sister to the prom."
Romney has famously changed all his policies since he was a liberal governor of Massachusetts. He is now running against his old self. Obama, a big disappointment to many people who voted him in, is – as the New York Times pointed out – basically running on the sole platform "I'm not Mitt Romney". So is Mitt Romney. The election will presumably be won by whoever least resembles Mitt Romney.
✒ Romney says weird, off-putting things at the same rate as George W Bush did. "I like to be able to fire people who provide services to me," he said. Talking to the unemployed he said, "I'm unemployed too" which might be technically true, though last year he made $374,000 (£234,700) in speaking fees alone. Speaking of his deep regard for American automobiles, he revealed "my wife drives a couple of Cadillacs". In Michigan he announced, "I love this state. The trees are the right height."
There was a flurry when it turned out they had gone on holiday taking the family dog on top of the car. He responded, "Peta [People for the Ethical Treatment of Animals] are not happy that my dog likes fresh air." He once declared that "corporations are people too". As so often, you can work out roughly what he means but are baffled by the way he says it. Though it's hard to pick the bones out of this: "I believe in an America where millions of Americans believe in an America that's the America millions of Americans believe in."
David Letterman said: "He looks like you would see his picture on a packet of men's briefs." And he's a practising, active Mormon, a fact that the Democrats are so far too fastidious to exploit. But that might change if things turn nasty. Sorry, when things turn nasty.
✒One of the speakers here is Seth Shostak who runs the Search for Extra-Terrestial Intelligence in California. This is not a quest for little green men, but a scientific attempt to discover if we can detect radio signals from other worlds. Not long ago, Seth told me, he bumped into John Cleese who was with Keanu Reeves. Cleese inquired: "We are here for a reason, aren't we?"
"I replied: 'If you'd asked me that question 100m years ago, I'd have said you were just another dinosaur. And, frankly, nothing has changed.' I don't think he was too pleased by that."
✒Channel hopping last weekend (my host has several hundred on his cable system) I came across an American MasterChef lookalike, but with the somewhat more aggressive title of Chopped! So the presenters can say Apprentice-like to the losers: "You're chopped!" But what the two shows have in common is that you would not want to eat the dishes. The winner on Sunday had made a dessert out of granola bars, solidified brown sugar, and roasted tomatoes. It looked quite disgusting.
✒Did anyone call to your attention the fact that the Titanic sank exactly 100 years ago? I'm pretty aged now, and in 1956, as a schoolboy, crossed the Atlantic with my family on the old Queen Elizabeth. It was the last year more people crossed by sea than by plane, which was far more expensive. Rationing had not quite disappeared in Britain, and to a growing boy it was a miracle that we could eat as much food as we could possibly want – even in third class. Luckily we didn't hit an iceberg, so there was no need for Cunard employees to batten down the hatches and keep us from the lifeboats. It was a fabulous way to travel, as I remind myself as we taxi to the runway, strapped into a chair fit for an eight-year-old, to tuck into lasagne made from recycled in-flight magazines.
✒More labels etc next week. In the meantime, I loved the story from Stephen Prasher about his friend who owns a bookshop in Essex. A customer wanted George Orwell's Dining Out in Paris and London, and would accept nothing else.


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Gzjjby.com is a 1 year old domain, situated in United States. The domain is linked to the IP address 126.96.36.199 which is provided by the hosting company Defender cloud international llc.
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by Paul Sanders
Computer technology changes quickly, and a great laptop computer may seem out of date after only a few years. Of course, you may be generally happy with your laptop and just want some performance or memory upgrades, or you might be buying a new laptop for yourself and want to hand off your computer to someone else who might find it useful. While laptop parts aren't as easily interchangeable as desktop computer parts, you can still do a few upgrades that will extend the life of your laptop. Check your laptop computer's user manual and look for these upgrade possibilities.
Swap out the hard drive. Computer storage space gets cheaper every year, and programs for your laptop computer require more and more of it. If your hard drive seems cramped, you may be able to install a new one rather easily.
Add RAM to boost performance. Your laptop computer has several slots for new memory sticks. You can fill in any empty slots or replace existing RAM with larger sticks. Be sure to write down the precise type of RAM that your laptop computer uses before you shop for new memory sticks. For example, you laptop may accept DDR2 or DDR3 RAM.
Install a faster processor. Replacing a CPU should be done delicately, but installing a new one is relatively simple. Check the socket number on the motherboard for your laptop computer and find a compatible processor with a higher speed or multiple cores to give your laptop PC a big performance boost.
Upgrade the graphics processor. The graphics processing unit (GPU) handles the video and display tasks for your laptop. Many laptop computers have separate graphics processors on a separate graphics card that can be upgraded. If your laptop PC uses a card, a new graphics card can be added or installed in a PC card slot on the motherboard.
Get a new battery. After a few years of constant use, your laptop computer's batteries may not hold a charge like they used to. Getting a new battery can give your laptop all new life.