JPH0196578A - Active sonar device - Google Patents

Abstract

PURPOSE:To reduce the influence of a background noise greatly and to improve detecting ability and azimuth determination accuracy by taking a narrow-band frequency analysis. CONSTITUTION:A couple of right and left reception directional beams are generated and a received signal through the right and left beams is processed by Fourier transformation to obtain a right and a left beam complex spectrum by the narrow-band frequency analysis. Components of equal frequency of those right and left complex spectra are complex-added and the absolute value of the amplitude of the composite addition complex spectrum is obtained. The respective frequency elements of the absolute-value spectrum are amplified by anatomic gain controller (AGC). Then a maximum value is detected in the spectrum after the AGC amplification and complex spectra of the same frequency element with the maximum spectrum having the maximum value are selected from the complex spectrum received through the right and left beams to obtain the vector angle difference between the right and left beam complex spectra. Then a target azimuth is calculated from the vector angle difference.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an actifuner device, and in particular, to an actifuner device that makes it possible to measure a target direction from the phase difference between echoes received by two left and right receiving beams. The present invention relates to an active sonar device.

[Conventional technology]

Conventionally, this type of active sonar device has a configuration as shown in FIG. The basic operation of the conventional seven-tape sonar device will be explained below with reference to FIG.

The transmitter circuit 1 pulse-modulates a sine wave, performs power amplification, and outputs a transmit signal 51. The transmission/reception conversion circuit 2 supplies a transmission signal 51 to the transducer 3 during the transmission period, and during the reception period, the underwater acoustic signal converted into a stain signal by the transducer 3,
is output as a received signal 53.

The reception operation for determining the direction will be explained below.

The received signal 53 is added after being given a delay set for each output of each element of the transducer 3 in the directivity synthesis circuit 4, and is added to the left and right sides of the same characteristic separated by d(-), as shown in FIG. The beams are combined into an R beam and an L beam directivity pattern to form an R signal 54 and an L signal 55.

Bandpass filters 5 and 6 pass R signal 54 and L signal 5.
5, and outputs 56 and 57. Since the frequency of the reverberating sound is frequency-shifted from the transmission frequency due to the Doppler effect, the passband width is determined from the maximum set value of the relative velocity of the transducer 3 and the target and the transmission frequency.

Output 56 and output 57 are AGC circuits 18 and 1, respectively.
9 compresses the dynamic range, resulting in an output cuff of 0 and an output cuff of 1.

The adding circuit 20 adds the output cuff 0 and the output cuff 1 and outputs the full beam output cuff 2. The detection circuit 21 detects the envelope of the full beam output cuff 2, which is an AC signal, and generates an intensity signal 7.
Outputs 3. This intensity signal serves as an input to the feedback circuit 22 in addition to serving as a display luminance signal. The feedback circuit 22 integrates the input intensity signal 73, compares it with a reference voltage, and controls the feedback signal 74 so as to reduce the difference.

The phase detection circuit 23 detects the phase difference between the output cuff 0 and the output cuff 1 and outputs it as a phase difference signal 75.

The direction calculation circuit 24 sets the value of the phase difference signal 75 as θ and calculates the third direction.
The direction δ of the target in the figure is calculated using the following formula (1) and (21), and is output as the direction signal 76.

2yrfd 8inδ θ=c(rad)...Scream...Scream...(1) f: Transmission frequency (H2) d: Distance between the acoustic centers of R and L beams (C) C: Speed of sound
(-/sec) Equation (1) is converted to obtain the following equation (2).

-1c・θ 6=81° (,,fd) (racl)°---
-----=-(2) Equations (1) and (2) 2 are approximated by assuming that there is no Doppler shift of the echo sound from the target.

The intensity signal 73 and the azimuth signal 76 are displayed as distance (time elapsed after transmission) versus azimuth versus intensity, as shown in FIG. 4, and are used for detecting echoes and measuring their distance and azimuth. Fourth
In the figure, the background noise portion is displayed distributed in random directions, and the echo sound portion is displayed with a stable direction and high intensity.

Since there is a limit to the range of direction α that can be detected with a pair of left and right beams, in order to be able to detect a wider range of directions, multiple pairs of left and right beams are formed by changing the angle by α to obtain the required range. Cover.

[Problem that the invention seeks to solve]

The above-mentioned conventional active sonar devices are susceptible to background noise because they utilize all of the frequency bands passed by the bandpass filter in the adult process of the intensity and orientation signals, resulting in detection of low-level reverberations. It has the disadvantages of low performance and low accuracy in determining the orientation of the measured target.

SUMMARY OF THE INVENTION The object of the present invention is to eliminate the above-mentioned drawbacks, to provide an active sonar device that significantly reduces the influence of background noise and significantly improves detection ability and orientation accuracy.

[Means for solving problems]

The active sonar device of the present invention includes a means for forming a pair of left and right reception directional beams, and a means for forming a pair of left and right receiving directional beams, and Fourier transforms the signals received through the left and right beams to obtain left and right beam complex spectra by narrowband frequency analysis. means for complex adding the same frequency components of the left and right complex spectra, means for converting the amplitude of the complex spectrum resulting from the complex addition into an absolute value, and each frequency element of the absolute value spectrum. means for AGC amplification;
means for detecting the maximum value from the spectrum after GC amplification;
means for selecting a complex spectrum having the same frequency element as the maximum spectrum having the maximum value from the complex spectra received through the left and right beams; and means for obtaining a vector angle difference between the selected left and right beam complex spectra. , and means for calculating a target orientation from the vector angle difference.

〔Example〕

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. The configuration of the embodiment shown in FIG. 1 includes a transmission circuit 1, a transmission/reception conversion circuit 2, a transducer 3 as a means for forming left and right beams, a directional synthesis circuit 4, a bandpass filter 5, 6, and a narrowband frequency analysis circuit. A-to-D converter circuit 7.8 and Fourier transform circuit 9, 1 to obtain left and right beam complex spectra.
0. An adder circuit 11 that performs complex addition of the same frequency components of the left and right beam complex spectra, and an amplitude calculation circuit 12 that calculates the absolute value of the amplitude of the complex spectrum output from the adder circuit 11.
, an AGC circuit 13 for AGC amplifying the output of the amplitude calculation circuit 12. A maximum value detection circuit 14 that detects the maximum value from the spectrum after AGC amplification, a selection circuit 15 that selects from the received complex spectrum a complex spectrum having the same frequency element as the maximum spectrum having the maximum value, and selected left and right beams. It is configured to include a phase calculation circuit 16 that obtains a vector angle difference between complex spectra, and an orientation calculation circuit 17 that calculates a target orientation from the vector angle difference.

In the configuration of the embodiment shown in FIG. 1, transmitting circuit 1. Transmission/reception conversion circuit 2. Transducer/receiver 3. Since the bandpass filters 5 and 6 of the directional synthesis circuit 4 are the same as those in the conventional example shown in FIG. 2, a detailed explanation thereof will be omitted.

Each of the A-D conversion circuits 7 and 8 is a bandpass filter 5.
The outputs 56 and 57 of 6 and 6 are converted from analog signals to digital signals, and outputted as a digital signal 58 and an L digital signal 59. Fourier transform circuit 9
and 1o performs Fourier transform on these signals and outputs an R Fourier transform output 60 and an L Fourier transform output 61.

R7-! J engineering transform output 60 and L Fourier transform output 61
are expressed as frequency domain signals shown by the following equations (3) and (4), respectively.

R Fourier transform output 60"j"(-n) +"g(-
n+1).

...j'R(n-s), ni'B(n)・
・・・・・・・・・・・・・・・・・・(3) L Fourier transform output 6"""L(-n), Fh(-n+t).

... PL (n-t), 1'''t, (n) ...
(4) In the Fourier transform, the range from the negative maximum Doppler to the positive maximum Doppler is frequency-analyzed into 21+1 frequency elements. Due to the nature of Fourier transform, each frequency element is output as a complex vector and is expressed by the following equations (5) and (6).

In this case, the magnitude of the complex vector, i.e. ν(!!I
ts)2 + (Eel)2 represents the intensity of the frequency element, and the argument is tan-” ((imaginary part)/(real part)
) represents the phase angle of the frequency element.

The adder circuit 11 performs complex addition of the same frequency elements of the R Fourier transform output 60 and the L Fourier transform output 61 to obtain a full beam Fourier transform output 62. The full beam Fourier transform output 62 is expressed by the following equation (7).

Full beam Fourier transform output 62 = F(, ), F(-1
+1).

"" F(-1), F(0), F(1)...F(n-
1) , F(n) ・・・・・・・・・・・・
...(7).

The amplitude calculation circuit 12 outputs a full beam Fourier transform output 62
The amplitude is calculated using the following equation (8) for each frequency element to obtain a series of full beam vectors 63.

Full beam vector 63 = F(-n), FC-n
+t) #...F(-t), F(0)s"(1)・
・・・'(n-1),”(n) ・・・・・・・・・
(8) Here, (-n<1(n).

The AGC circuit 13 performs AGC amplification in the time axis direction for each frequency element of the full beam vector 63 to equalize the background noise level, and generates a standardized full beam vector 64.
Output. FIG. 5 is an explanatory diagram showing the functions of the AGC circuit 130. As shown in FIG. 5, the time constant of the AGC circuit 13 is such that the output level remains constant for background noise N that changes slowly over time other than the echo P, but for the pulse width of the echo P. It is assumed that the optimization settings are made so that the gain hardly changes.

The standardized full beam vector 64 obtained in this way is expressed by the following equation (9).

Standardized full beam vector 64 = A(-n).

A(n+x), -A(-t), A(o), A(1)・
・・・A(n-1)A(n) ・・・・・・・・・・・・
...(9) The maximum value detection circuit 14 is a standardized full beam vector 6
The one having the maximum value is selected from among the four series, and its level is output as an intensity signal 65, and a maximum value elenote signal 69 indicating which frequency element the maximum value was detected is output.

As an example, the series A of standardized full beam vectors 64 (
i) If the element of i=fn (-n≦i≦n) is the maximum, output the intensity signal 65=AM and the maximum value element signal 69=m.

The selection circuit 15 selects a frequency element equal to the frequency element of the maximum value detected by the maximum value detection circuit 14 from the series of the R Fourier transform output 60 and the L Fourier transform output 61 under the control of the maximum value element signal 69, and calculates the direction. It is output as an input signal 66.

The direction calculation input signal 66 is expressed by the following equation (10).

Direction calculation input signal 66=”R(”)l”L(ffl)
(10) The azimuth calculation circuit 16 calculates the phase difference signal 67 from the two vectors of the azimuth calculation input signal 66 using the following equation (11).

, ′″′7 Phase difference signal 67 ” L PRHX FLCFFI3
=-jan'・・・・・・・・・・・・・・・・・・
(11) This phase difference signal 67 corresponds to θ in equation (9),
The azimuth calculation circuit 17 calculates δ obtained by substituting the phase difference signal 67 into θ in equation (2), and outputs it as an azimuth signal 68.

In this way, the signal-to-noise ratio, detection ability and orientation accuracy can be significantly improved.

〔Effect of the invention〕

As explained above, by performing narrowband frequency analysis, the present invention significantly improves the signal-to-noise ratio of reverberations and background noise, improves the detection ability for low-level reverberations, and improves the azimuth accuracy of the measured target. This has the effect of significantly improving.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional active sonar device. 3 is an explanatory diagram of a receiving beam pair, FIG. 4 is an explanatory diagram showing a display example of an active sonar device, and FIG. 5 is an explanatory diagram showing the function of the AGC circuit in the embodiment of FIG. 1. DESCRIPTION OF SYMBOLS 1... Transmission circuit, 2... Transmitter/receiver converter, 3... Transducer/receiver, 4... Directivity synthesis circuit, 5, 6... Band pass filter, 7.8... A- D conversion circuit, 9.10...
・7-Rie transform circuit, 11...addition circuit, 12...
Amplitude calculation circuit, 13...AGC circuit, 14...Maximum value detection circuit, 15...Selection circuit, 16...Phase calculation circuit, 17...Azimuth calculation circuit, 18.19...AG
C circuit, 20...addition circuit, 21...detection circuit, 2
2... Feedback circuit, 23... Phase detection circuit, 24...
・Azimuth calculation circuit. Agent Patent Attorney Oto Uchihara

Claims (1)

[Claims] means for forming a pair of left and right reception directional beams (hereinafter abbreviated as left and right beams); and means for Fourier transforming the signals received through the left and right beams to obtain left and right beam complex spectra by narrowband frequency analysis. means for complex adding the same frequency components of the left and right beam complex spectra, means for converting the amplitude of the complex spectrum resulting from the complex addition into an absolute value, and each frequency element of the absolute value spectrum. AGC (Automatic G
ainControl) means for amplifying, means for detecting a maximum value from the spectrum after the AGC amplification, and selecting a complex spectrum having the same frequency element as the maximum spectrum having the maximum value from the complex spectra received via the left and right beams. An active sonar device comprising: means for obtaining a vector angle difference between said selected left and right beam complex spectra; and means for calculating a target heading from said vector angle difference.