JPH0116392B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for forming receiving beams having directivity in each direction in, for example, an underwater detection device that detects in a wide range of directions. It relates to a device that changes in each direction at high speed.

As a device for forming a directional received beam, a device that performs phase synthesis is generally used in many cases.
That is, a large number of transducers are arranged on the same plane, and the phase relationship of each transducer is adjusted to form a directional receiving beam in a specific direction. For example, as shown in FIG. 1, the received signals of a large number of oscillators Z ₁ to Zn are phase-shifted on a plane F by respective phase shifters S ₁ to Sn. Then, the phase shift amount of each phase shifter _S1 to Sn is set to 2π/λ(n-1)d Sinθ n=1, 2, 3,...n, and the signal after phase shift is By adding them in addition circuit A, it is possible to form a directional characteristic in the θ direction.

In the above, in order to change the pointing direction θ, it is sufficient to change the phase shift time of the phase shifters S ₁ to Sn. By the way, in order to vary the directivity direction θ over a wide range, it is necessary to greatly vary the phase shift times of the phase shifters S ₁ to Sn. In a normal phase shifter, it is impossible to change the phase shift time to such a large extent. Therefore, conventionally, when changing the pointing direction θ, as shown in _FIG.
Phase shifters S 1 ' to Sn' are provided separately from the phase shifters S ₁ ' to Sn', and the phase shift times of the phase shifters S ₁ ' to Sn' are set so that the output of the adder circuit A' forms a directional characteristic in the θ direction. do.
Therefore, in this configuration, it is necessary to prepare a phase shifter specific to each direction of directivity, so in order to change the direction in a wide range at every fixed angle, it is necessary to prepare a very large number of phase shifters. Requires a phaser. This has the disadvantage that the device becomes extremely large and expensive.

The present invention provides a device that can continuously and rapidly change the directivity direction of a received beam in a wide range of directions with an extremely simple configuration without using a large number of phase shifters as described above.

Examples of the present invention will be described below.

FIG. 3 shows a diagram for explaining the principle of the present invention, and in the diagram, Z ₁ to Zn indicate vibrators arranged in the same manner as in FIG. 1. After each received signal of the vibrator Z ₁ to Zn is amplified by each preamplifier P ₁ to Pn, each of the mixing circuits M ₁ to Mn corresponds to each of the mixing circuits M ₁ to Mn from the signal generator SG. The local oscillator signal transmitted by the transducer and the signals received by the transducers _Z1 to Zn are mixed. Then, the mixed outputs of the mixing circuits _M1 to Mn are led to the adding circuit Σ and added. The output of the adder circuit Σ is guided to a filter circuit FF to extract a specific frequency component.

In the above, the i-th oscillator is Si(t)=Ei Sin(ωt+Ai)...(1) Also, the local oscillation signal mixed with this received signal in the mixing circuit Mi is Ui(t)=Vi Sin( ωct+Bi) ...(2) Then, the mixed output in this case is Ci(t)=Si(t)・Ui(t) =Ei Sin(ωt+Ai) ×Vi Sin(ωct+Bi) =1/2Ei Vi｛Cos[ (ω-ωc)t + (Ai-Bi)]-Cos[(ω+ωc)t + (Ai+Bi)]} ...(3) As is clear from equation (3), the mixed signal Ci(t) is the received signal It is composed of a difference frequency and a sum frequency component between Si(t) and the local oscillator signal Ui(t). Since the adder circuit Σ sends out the added output of the mixed output expressed by equation (3) for each mixer circuit _M1 to Mn, the filter circuit
Assuming that the difference frequency component of the mixed output is extracted in the FF, the output of the filter circuit FF is CT (t) = _o 〓 〓 ⁱ⁼¹ 1/2Ei Vi Cos {(ω−ωc)t+(Ai+Bi)} …
...(4)

In equation (4), when Ai=Bi (5), each output of the mixing circuits _M1 to Mn becomes in phase, and the filter output Ct becomes maximum. Therefore,
At this time, the filter output Ct is the i-th oscillator Zi
The received signal has a phase difference Ai with respect to the first oscillator.
This shows that directivity is formed in the direction θ that causes . In other words, the phase difference Bi and Ai of the local oscillator signal in equation (2)
By setting , a directional reception beam can be formed in the θ direction, and by changing the phase difference Bi, the directional direction θ can be changed.

In Fig. 3, if the arrangement interval of vibrations Zi to Zn is d and the wavelength of the received signal is λ, then in equation (1), Ai = 2π/λ(i-1)d Sinθ ...(6) Therefore, , the local oscillation signal Ui(t) for forming directivity in the θ direction is obtained by substituting equation (6) into equation (2) as Ui(t)=Vi Sin{ωct +2π/λ(i-1) d Sinθ} ...(7) As is clear from equation (7), the directivity characteristic θ of the received signal can be changed by changing θ of the phase term in the local oscillator signal Ui(t).

Now, assuming that the directivity direction θ of the received signal is changed to θs in time Ts, θ=θs/Tst (8) where 0≦t≦Ts. Therefore, by substituting equation (8) into equation (7), Ui(t)=Vi Sin{ωct+2π/λ(i-1)d Sin(θs/Tst
)}=Vi Sin2π{fc+(i-1)ABSin Bt/Bt}t...(9) is given. However, ωc=2πfc, A=d/λ, and B=θs/Ts. In equation (9), Fci=fc+(i-1)ABSin Bt/Bt...(10) represents the frequency term of the local oscillator signal Ui(t), and the pointing direction θ is changed from 0 to θs in time Ts. At this time, the frequency Fci of the local oscillator signal Ui(t) changes according to equation (10). Conversely, the frequency of the local signal Ui(t)
By changing Fci according to equation (10), the directivity direction of the received signal given as the output of the filter FF in FIG. 3 can be changed arbitrarily.

Based on the above, this invention provides a filter circuit by changing the frequency of the local oscillator signal Ui(t) guided from the signal generator SG in FIG. ₃ to the mixing circuits M1 to Mn according to equation (10). The purpose is to change the directivity direction θ of the received signal transmitted from the FF from 0 to θs.

In equation (10), when t=0, Sin Bt/Bt=1, so Fci=fc. Also, in equation (9), when t=0, Ui(t)=0. Therefore, t=0, that is, When the directivity direction θ is θ=0, the local oscillation signals guided to the mixing circuits M ₁ to Mn each have a frequency of fc and a same phase. Then, when the pointing direction changes to θ, the frequency of each local oscillator signal changes according to equation (10).

FIG. 4 shows an example of generating a local oscillation signal whose frequency and phase are regulated as described above.

In FIG. 4, a clock pulse sent from a clock pulse source 1 is divided into frequency by a frequency dividing circuit 2.
After being frequency-divided by 2, it is sent to counter 3. Counter 3 counts these clock pulses and sends the counted value to a read-only memory.

The read-only memory 4 has storage addresses corresponding to at least the counting capacity of the counter 3, and the data stored in the counter 3 is sent out as a 1-bit output of either a low level or a high level. This storage output of the read-only memory 4 is latched by a latch circuit 5 and then sent out as an output signal. Latch circuit 5 uses the pulse train of clock pulse source 1 to latch the storage output of read-only memory 4.

Therefore, clock pulse sources 1 to 5a
When the clock pulse shown in is sent out, the counter 3 performs a counting operation using the 1/2 frequency b,
Corresponding to the change in the count value, the latch circuit 5 sends out low-level and high-level rectangular wave outputs as shown in FIG. 5c. As is clear from the above, the repetition period and phase of the rectangular wave c can be arbitrarily set by appropriately writing stored data at each storage address in the read-only memory 4. For example, when the count value of counter 3 changes from time t=0 to t=Ts, a rectangular wave train whose phase matches equation (9) and whose repetition frequency changes match equation (10) is obtained. be able to. Note that the local oscillator signal expressed by equation (9) corresponds to the fundamental component of the rectangular wave train shown in FIG. 5c, to be exact. Therefore, when using the rectangular wave sequence c as a local signal, after mixing the rectangular wave sequence c and the received signal Si(t) of the vibrator Zi, select the rectangular wave sequence c from among the mixed signals. Filter FF to extract the mixed component for fundamental wave sequence c
All you have to do is run it.

Figure 6 shows 7 arrayed on a plane based on the above.
A specific example will be shown in which the directivity direction of the received beam is changed from -θ to +θ using the oscillators Z ₁ to Z ₇ .

In FIG. 6, it is assumed that the arrangement interval of the transducers Z ₁ to Z ₇ is d, and a received signal in the θ direction is received. Now, if the received signal of the vibrator Z ₄ is U ₄ (t) = E Sin2πft, then each received signal U ₁ (t) of the vibrators Z ₁ to Z ₇
to U ₇ (t) are expressed as follows.

S ₁ (t) = E Sin (2πft + 6πd / λSinθ) S ₂ (t) = E Sin (2πft + 4πd / λSinθ) S ₃ (t) = E Sin (2πft + 2πd / λSinθ) S ₄ (t) = E Sin (2πft) S ₅ (t) = E Sin (2πft-2πd/λSinθ) S ₆ (t) = E Sin (2πft-4πd/λSinθ) S ₇ (t) = E Sin (2πft-6πd/λSinθ) ...(11) Then, as shown in Fig. 7, the receiving direction θ is set to −
Assuming that it changes from -θs to θs in 2Ts from time Ts to time Ts, the reception direction θ is as a function of time T, θ=θs/Tst (-Ts≦t≦Ts)...(12) It is expressed as Therefore, by substituting equation (12) into equation (11), S ₁ (t) = E Sin (2πft + 6πd / λSinθθs / Tst) S ₂ (t) = E Sin (2πft + 4πd / λSinθθs / Tst) S ₃ ( t)=E Sin(2πft+2πd/λSinθθs/Tst) S ₄ (t)=E Sin(2πft) S ₅ (t)=E Sin(2πft−2πd/λSinθθs/Tst) S ₆ (t)=E Sin(2πft −4πd/λSinθθs/Tst) S ₇ (t)=E Sin(2πft−6πd/λSinθθs/Tst) ...(11)' On the other hand, it is mixed with each of the above received signals in the mixing circuits _M1 to _M7 . The local oscillator signal is U ₁ (t) = V・Sin (2πfct + φ1) U ₂ (t) = V・Sin (2πfct + φ2) U ₃ (t) = V・Sin (2πfct + φ3) U ₄ (t) = V・Sin ( 2πfct + φ4) U ₅ (t) = V・Sin (2πfct + φ5) U ₆ (t) = V・Sin (2πfct + φ6) U ₇ (t) = V・Sin (2πfct + φ7) ... (13) If it is expressed as As explained above, by matching the phases φ ₁ to φ ₇ of the local signals U ₁ (t) to U ₇ (t) with the phases of the received signals S ₁ to S ₇ , the received signals -θs
It can be changed from to +θs. Therefore, equation (13) is U ₁ (t) = V · Sin (2πfct + 6πd / λSinθs / Tst) U ₂ (t) = V · Sin (2πfct + 4πd / λSinθs / Tst) U ₃ (t) = V · Sin (2πfct+2πd/λSinθs/Tst) U ₄ (t)=V・Sin(2πfct) U ₅ (t)=V・Sin(2πfct−2πd/λSinθs/Tst) U ₆ (t)=V・Sin(2πfct−4πd /λSinθs/Tst) U ₇ (t)=V・Sin(2πfct−6πd/λSinθs/Tst) ……(13)′ In equation (13)′, if we set d/λ=A θs/Ts=B, (13)′ is transformed as follows.

U ₁ (t)=V・Sin 2π(fc+3ABSin Bt/Bt)t U ₂ (t)=V・Sin 2π(fc+2ABSin Bt/Bt)t U ₃ (t)=V・Sin 2π(fc+ABSin Bt/Bt) t U ₄ (t)=V・Sin 2πfc・t U ₅ (t)=V・Sin 2π(fc−ABSin Bt/Bt)t U ₆ (t)=V・Sin 2π(fc−2ABSin Bt/Bt) t U ₇ (t)=V・Sin 2π(fc−3ABSin Bt/Bt) t (14) Therefore, as is clear from the above explanation, the local oscillation signals guided to the mixing circuits M ₁ to M ₇ are At time t=0, that is, when the directivity direction of the received signal matches the front direction with respect to the transducer array surface, the phases of each local oscillation signal match, and when -Ts≦t≦Ts, the local oscillation signal Frequency of each number Fc ₁ to Fc ₇
is Fc ₁ = fc+3ABSin Bt/Bt Fc ₂ = fc+2ABSin Bt/Bt Fc ₃ = fc+ABSin Bt/Bt Fc ₄ = fc Fc ₅ = fc−ABSin Bt/Bt Fc ₆ = fc−2ABSin Bt/Bt Fc ₇ = fc−3ABSin Bt/Bt...(15) For example, if fc=50×10 ³ Hz d=λ/2, θs=π/4, Ts=1 msec, A=d/λ=1/2 B=θs/Ts=π/4×10 ³ Therefore, when time t=-Ts, [Fc ₁ ] _t=-Ts = 50×10 ³ +1060 [Hz] Also, when time t=0, Sin Bt/Bt=1, so [Fc ₁ ] _{t =0} =50×10 ³ +1178 [Hz] Also, when time t=Ts [Fc ₁ ] _t=Ts =50×10 ³ +1060 [Hz] Therefore, the pointing direction changes from -45 degrees to +45 degrees in 2 msec.
When changing the local oscillator signal to the mixing circuit _M1 , its frequency _Fc1 changes from a frequency higher than the reference frequency fc by 1060Hz to a frequency higher by 1178Hz, and then returns to a frequency higher by 1060Hz. It changes like that. This frequency change is represented by curve _R1 in FIG. Also, other curves R ₂ to R ₇ are frequencies Fc ₂ to Fc ₇ of other local oscillator signals.
represents a change in

The read-only memory 4' shown in FIG. 6 repeatedly sends out a rectangular wave train whose frequency coincides with each of the frequencies Fc ₁ to Fc ₇ of the local oscillation signal. The read-only memory 4' has seven sets of read-only memories 4 shown in FIG. 4 built-in, and the output terminals ₀₁ to ₀₇ independently read the stored data at the memory address specified by the counter 3. .

The counter 3 counts the output pulses of the 1/2 frequency divider 2 in the same manner as in FIG. 4, and the storage address of the read-only memory 4' is designated by the counted value. Therefore,
The pulse train sent from the frequency dividing circuit 2 to the counter 3 is set to be sufficiently smaller than the period of the rectangular wave train generated by reading out the data stored in the read-only memory 4'. For example, if the repetition frequency of the rectangular wave train used as the local oscillation signal is 50 KHz, the period is 20 μsec, so the period of the counting pulse of the counter 3 is set to about 0.5 μsec. With this setting, the period of the rectangular wave train is set to 1
It can be memorized with an accuracy of 1/40 of a wavelength. or,
When counting for 2 msec with a 0.5 μsec clock, the count value of the counter 3 changes up to 4000, so the read-only memory 4' outputs each data from 0 ₁ to 0 _7.
4000 memory addresses are used.

The rectangular wave trains sent out from each of the output terminals 0 ₁ to 0 ₇ by reading the data stored in the read-only memory 4' are combined with the respective received signals in the mixing circuits M ₁ to M ₇ , and are combined with the respective received signals in the adder Σ. After being added with
A frequency component of a specific frequency is extracted by the filter circuit FF in the same manner as in FIG. Therefore, when the count value of the counter 3 changes once, the received signals in each direction from -θs to θs are sequentially transmitted from the filter FF. Since the counter 3 performs the counting operation in an extremely short period of 2 msec as described above, the direction change of the received signal is also performed within this short period of time. Therefore, the filter FF
The received signals in each direction are sent out on approximately equidistant lines in a time-division manner.
Therefore, when the counter 3 repeatedly performs counting operations, the filter circuit FF sends out received signals in each direction on the equidistant line for each distance.
Note that the stored data sent out from each output terminal ₀₁ to ₀₇ of the read-only memory 4' is latched by each latch circuit ₅₁ to ₅₇ , and then sent to each mixing circuit _M1 to _M7. Ru. filter circuit
The received signals in each direction sent out in time series from the FF are amplified by the video amplifier 6 and then guided to the brightness terminal of the cathode ray tube display tube 7. A fan-shaped lath is formed in the cathode ray tube display 7 by guiding a sweep wave from a sweep circuit 9 to the deflection coil 8 thereof. The sweep operation of the sweep circuit 9 is performed in conjunction with the counting operation of the counter 3. That is,
The transmitter 9 periodically transmits ultrasonic pulses from the transmitter 11 in a wide range of directions, and at the same time sets the counter 3 and the sweep circuit 9 to determine the directivity direction of the received signal and the sweep direction of the cathode ray tube display 7. match. Note that in the wave transmitter 11, the vibrators Z ₁ to Z ₇ may be used for transmitting and receiving waves.

As explained above, in the present invention, when generating a frequency signal (rectangular wave train) to be mixed with a received signal,
Amplitude data for each phase of the frequency signal is stored in a memory circuit having a memory address corresponding to each phase, and the amplitude data is generated by reading out the data from the memory circuit. By mixing this frequency signal (rectangular wave train) and the received signal, the same effect as equivalently shifting the phase of the received signal is obtained. Therefore, it is possible to form a receiving beam in a desired direction without using a large number of phase shifters as in the prior art. In addition, since the memory circuit 4' is a high-density integrated circuit that is commercially available, the circuit configuration can be made much smaller and lighter than conventional devices, and the price can also be made sufficiently low. be able to.

[Brief explanation of drawings]

1 and 2 are diagrams for explaining a conventional device, FIG. 3 shows an embodiment of the present invention, FIG. 4 is a specific example of the signal generator, and FIG. 5 explains its operation. FIG. 6 shows an embodiment that is a more specific version of FIG. 3, and FIGS. 7 and 8 are diagrams for explaining its operation.

Claims (1)

[Scope of Claims] 1. A first ultrasonic transducer in which at least first and second ultrasonic transducers are arranged, and each received signal and phase of the first and second ultrasonic transducers are controlled over time; A device that forms a directional reception beam whose pointing direction sequentially changes by separately mixing the second frequency signals and extracting a specific frequency signal from the summed signal of the mixed frequency signals. A memory circuit is provided in which amplitude data for each phase of the frequency signal is stored in a memory address corresponding to each phase, and a readout circuit reads out data stored in the memory circuit, and the readout circuit is provided with: Therefore, the received beam directivity control device is characterized in that the frequency signal is generated by reading out the data stored in the storage circuit.