GB1572308A - Directional radiation transmitting apparatus - Google Patents

Description

(54) DIRECTIONAL RADIATION TRANSMITTING APPARATUS (71r We, PAYTHEON COMPANY, a corporating organized under the laws of the State of Delaware, United States of America, do hereby declare the inention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a directional radiation transmitting apparatus com- prising an array of electromagnetic or sonar transducers. This application is divided out of application No. 50142/77 (Serial No.

1 572 307) of which the specification (herein after referred to as the parent specification) is concerned with a receiving apparatus. Refenrence may be made to the introductory part of the parent specification for the background against which the present invention is to be seen, the transmitting apparatus of the present invention being analogous or complementary to the receiving apparatus disclosed and claimed in the parent specification.

According to the present invention, there is provided directional radiation transmitting apparatus, comprising an array of radiating elements, a memory having locations for the storage of signals, each of the locations being identified by an address, means connected to the memory for coupling the signals to the radiating elements of the array, and an address generator including a counter circuit, and a combiner, the address generator being arranged to produce repetitively sequences of partial addresses, the counter circuit counting these sequences cyclically, the combiner being arranged to combine the partial addresses with the counts of the counter circuit to produce addresses selecting said locations from which signals are read out, and the coupling means including selecting means responsive to addresses from the address generator to select the radiating element to which each read-out signal is fed.

The invention will be described in more detail, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a block diagram of apparatus embodying the invention; and Fig. 2 is a timing diagram showing contents of a memory of Fig. 1.

Referring now to Fig. 1, there is shown a block diagram of a transmitting system 176 which comprises à waveform generator 178, an analog-to-digital converter hereinafter referred to as A/D 180 and a memory 100 into which digitized samples provided by the A/D 180 are written .The samples are read out of the memory 100, multiplied by weighting coefficients in a multiplier 96 and routed to transducer channels by a selector switch 182. Each transducer channel comprises a digital-to-analog converter here inafter referred to as a DIA 184, a bandpass filter 186, an amplifier 188, and a transducer unit 147F which has a terminal A connected to a sonar transducer via a trans mit/receive circuit.The bandpass filter smooths the samples, now in analog form by virtue of the D/A 184. An address generator 46A comprises the elements illustrated in Fig.

1 and other elements which are illustrated in Fig. 3 of the parent specification. The elements which are not illustrated in Fig. 1 herein are a counter, (counter 108 in the said Fig. 3), which will be called the R-counter, and a random access memory (RAM), (RAM 110 is the said Fig. 3). The R-counter counts modulo R at N times the sampling rate where R is the number of transducers and N is the number of mathematical operations peormed per sampling interval.The R-counter addresses the RAM which, in respect of each mathematical operation, provides the following: 5(1) A partial address for the memory 100 which partial address is furnished to an adder 114 and is established as explained in the parent specification in accordance with the relative propagation times between the transducers for the selected direction.

(2) A corresponding weighting coefficient fed on line 122 to the multiplier 96.

t3)A corresponding address on line 121 which selects, via the switch 182, which transducer channel receives the sample read out of the memory 100 and multiplied by a corresponding weighting coefficient in the multiplier 96.

A counter 116 (Fig. 1) counts overflow pulses from the R-counter and counts modulo K where the value of K is explained below. The address generator 46A further comprises a multiplier 190 coupled between the counter 116 and the adder 114, and a source 142 of a digital number R. The number on line 128 from the counter 116 is multiplied by R by the multiplier 190. The product on line 128A is added to the partial address from the RAM to provide the address for the memory 100 on line 125.

The transmitting system 176 operates in this respect in a manner analogous to the receiving system of Figs. 1 to 3 of the parent specification. Recapitulating, the address generator 46A is seen coupled to the memory 100 via line 125, to the multiplier 96 via the line 122 and to the selector switch 182 via the line 121, the lines 125, 122 and 121 carrying the same types of signals as are disclosed with reference to the correspondingly numbered lines of Fig. 3 of the parent specification. The clock signal from the clock 106 (see in Fig. 3 of the parent specification) of the address generator 46A is coupled to the waveform generator 178.

The waveform generator 178 is synchronized through the clock signal of the address generator 46, and provides a signal waveform suitable for transmission by the array or transducers which may be arranged as in Fig. 1 of the parent specification, such a waveform being, for example, a pulsed sinu soid or a linearly-swept frequencymodulated sinusoid. The signal of the generator 178 is fed to the A/D 180 which, in response to the clock signal, samples the signal and converts each sample to a digital number which is presented to the memory 100.The RAM of the address generator 46A provides a set of digital numbers along the line 125 which address the memory 100, the addresses of the slots 82 of the memory 100 being selected in a manner analogous to that described in the parent specification, the digital samples from the A/D 180 being placed in the slots in accordance with the address as provided by line 125. Samples are extracted from the memory 100 in accordance with the addresses on line 125 and weighted by the multiplier 96 with weighting coefficients provided on line 122.The resulting weighted samples from the multiplier 96 are then applied by the selector switch 182 sequentially to each of the D/A's 184, the selection of specific ones of the D/A's 184 being governed by the digital signal on line 121 in a manner analogous to the designation of the locations in memory of the sampling system of Fig. 3 of the parent specification. Each D/A 184 converts the digital representation of a signal sample to an analog sample. The analog samples then pass through a filter 186 which has a passband sufficiently narrow to extract, from the train of samples of the shift register 184, the frequency of the sinusoid of the waveform generator 178.The signal samples are provided. via the D/A's 184 to each of the filters 186 at a rate at least twice the bandwidth of the filter 186 (the Nyquist rate), for example, 2i times the bandwidth of the filter 186, to provide a signal having an accurate reconstruction of the waveform of the generator 178 by each of the filters 186. The sinusoid produced by each filter 186 is coupled to a corresponding amplifier 188 to increase the power thereof to a suitable level for transmission from the transducers.

Referring now to Figure 2, there is shown a timing diagram of the memory 100.

Samples of the signal to be transmitted by transducer A are seen stored in the first slot, slot numbered (R+1), slot numbered (2R+;1) up to slot number [(K-l)R+1] where R is the number of transducers only transducers A-F being considered in Figure 2 by way of example. Similarly, samples of the signal to be transmitted by transducer B are stored in the second slot of each group of R slots. The term K represents the number of different signal 'samples to be transmitted by transducer A during an interval of time equal to the frequency of the sonic energy mitted by the array 34. The K intervals of time are repeated periodically at a frequency equal to the frequency of the sonic energy transmitted by transducer A, as well as by the other transducers B-F. Figure 2 also shows a formula for the duration of each of the K intervals in terms of A and c where X is the wavelength of the sonic energy and c is the speed of propagation of the sonic energy in the medium in which the array 34 is immersed. During each of the K intervals, a wave of the sonic energy propagates a fractional wavelength, the fraction being 1/K.

In the typical situation, the fractional wavelength intervals are smaller than an out put sample interval so that, for example, several such fractional wavelength intervals may occur during one output sample inter val, two output sample intervals being shown in the right-hand side of Figure 2. As was disclosed hereinabove, the number K of frac tional wavelength intervals, six or more such intervals, is sufficient to ensure that the radia tion pattern of a beam produced by the array 34 is free of grating lobes and the grating nulls. The address generator 46A addresses the memory 100 via line 125 to sequentially select each of the slots to provide each of the transducers A-F with their respective samples.The R-counter counts modulo-R and, at the conclusion of the first group of R samples, the counter 116 produces a count on line 128 representing the number of fractional wavelength intervals that have been completed. As seen in Figure 1, the member on line 128 is multiplied by R, R being provided by the source 142, with the product of the multiplication being coupled via line 128A to the adder 114. Thereby, a distinction is seen between the operation of the generator 46 of Figure 3 of the parent specification and the generator 46A of Figure 1 herein, in that the address on line 125 of the said Figure 3 increases in units of one upon the occurance of each pulse on line 126 while in Figure 1 herein the increment is in multiples of R. The number of slots in the memory 100 is equal to the product of KandR.

Accordingly, at the conclusion of each fractional wavelength interval, the slot address is advanced so that a separate set of samples for each of the transducers AzF is provided during the next fractional wavelength interval. At the conclusion of K fractional wavelength intervals, the count of the counter 116 reverts to zero to repeat the sequence of the extraction of samples from the memory 100. In this way, it is seen that a signal generated by the generator 178 may be stored in the memory 100, and that the stored signal may thereafter be repetitively coupled from the memory 100 to the array of transducers for radiating a beam of sonic energy having the waveform of the stored signal.In addition, the signal from the generator 178 can be fed on line 145 to a processor in the receiving apparatus for storage, to be utilized as a reference for correlation purposes.

WHAT WE CLAIM IS: 1. A directional radiation transmitting apparatus comprising an array of radiating elements, a memory having locations for the storage of signals, each of the locations being identified by an address, means connected to the memory for coupling the signals to the radiating elements of the array, and an address generator including a counter circuit, and a combiner, the address generator being arranged to produce repetitively sequences of partial addresses, the counter circuit counting these sequences cyclically, the combiner being arranged to combine the partial addresses with the counts of the counter circuit to produce addresses selecting said locations from which signals are read out, and the coupling means including selecting means responsive to addresses from the address generator to select the radiating element to which each read-out signal is fed.

2. Apparatus according to claim 1, where in the coupling means include multiplying means for multiplying individual ones of the signals with weighting coefficients and wherein the address generator provides the weighting 'coefficients in synchonism with the partial addresses.

3. Apparatus according to claim 1, wherein the counter circuit comprises a circuit arranged to count modulo K pulses occurring at the rate of the said sequences, and means for multiplying the number in the counter by R to provide the said counts, where R is the number of radiating elements and KR is the number of locations in the memory.

4. Apparatus according to claim 1, 2 or 3, wherein the coupling means comprise means for combining the signals fed to each radiating element.

5. Apparatus according to claim 1, 2 or 3, wherein the coupling means comprises means in respect of each radiating element for converting a sequence of the signals into a sinusoidal signal for exciting the radiating element.

6. Directional Radiation transmitting apparatus substantially as hereinbefore described with reference to, and as illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   34 is free of grating lobes and the grating nulls. The address generator 46A addresses the memory 100 via line 125 to sequentially select each of the slots to provide each of the transducers A-F with their respective samples. The R-counter counts modulo-R and, at the conclusion of the first group of R samples, the counter 116 produces a count on line 128 representing the number of fractional wavelength intervals that have been completed. As seen in Figure 1, the member on line 128 is multiplied by R, R being provided by the source 142, with the product of the multiplication being coupled via line 128A to the adder 114.Thereby, a distinction is seen between the operation of the generator 46 of Figure 3 of the parent specification and the generator 46A of Figure 1 herein, in that the address on line 125 of the said Figure 3 increases in units of one upon the occurance of each pulse on line 126 while in Figure 1 herein the increment is in multiples of R. The number of slots in the memory 100 is equal to the product of KandR.

   Accordingly, at the conclusion of each fractional wavelength interval, the slot address is advanced so that a separate set of samples for each of the transducers AzF is provided during the next fractional wavelength interval. At the conclusion of K fractional wavelength intervals, the count of the counter 116 reverts to zero to repeat the sequence of the extraction of samples from the memory 100. In this way, it is seen that a signal generated by the generator 178 may be stored in the memory 100, and that the stored signal may thereafter be repetitively coupled from the memory 100 to the array of transducers for radiating a beam of sonic energy having the waveform of the stored signal.In addition, the signal from the generator 178 can be fed on line 145 to a processor in the receiving apparatus for storage, to be utilized as a reference for correlation purposes.

   WHAT WE CLAIM IS: 1. A directional radiation transmitting apparatus comprising an array of radiating elements, a memory having locations for the storage of signals, each of the locations being identified by an address, means connected to the memory for coupling the signals to the radiating elements of the array, and an address generator including a counter circuit, and a combiner, the address generator being arranged to produce repetitively sequences of partial addresses, the counter circuit counting these sequences cyclically, the combiner being arranged to combine the partial addresses with the counts of the counter circuit to produce addresses selecting said locations from which signals are read out, and the coupling means including selecting means responsive to addresses from the address generator to select the radiating element to which each read-out signal is fed.
2. 2. Apparatus according to claim 1, where in the coupling means include multiplying means for multiplying individual ones of the signals with weighting coefficients and wherein the address generator provides the weighting 'coefficients in synchonism with the partial addresses.
3. 3. Apparatus according to claim 1, wherein the counter circuit comprises a circuit arranged to count modulo K pulses occurring at the rate of the said sequences, and means for multiplying the number in the counter by R to provide the said counts, where R is the number of radiating elements and KR is the number of locations in the memory.
4. 4. Apparatus according to claim 1, 2 or 3, wherein the coupling means comprise means for combining the signals fed to each radiating element.
5. 5. Apparatus according to claim 1, 2 or 3, wherein the coupling means comprises means in respect of each radiating element for converting a sequence of the signals into a sinusoidal signal for exciting the radiating element.
6. 6. Directional Radiation transmitting apparatus substantially as hereinbefore described with reference to, and as illustrated in the accompanying drawings.