JP5628508B2 - Underwater detector and its reception characteristic correction method - Google Patents

Description

  The present invention provides a plurality of receptions for amplifying echo signals transmitted from a plurality of ultrasonic transducers into the water having a predetermined bandwidth and returned from the water and received by the respective ultrasonic transducers. The present invention relates to an underwater detection device such as a tide meter, ship speed meter, Doppler sonar, and fish finder provided with a circuit, and a method for correcting reception characteristics thereof.

  Patent Document 1 describes an ultrasonic transducer that has nine channels and enables detection in six directions on a horizontal plane. This ultrasonic transducer has an equilateral triangular lattice structure having a large number of transducers arranged at a predetermined pitch with respect to each vertex of an equilateral triangle, that is, three directions every 120 ° on a horizontal plane, and the pitch direction. By sequentially giving a predetermined phase difference to each other, an ultrasonic transmission beam having a predetermined directivity is transmitted in a predetermined depression angle direction in water. In reception, a reception beam having a predetermined directivity corresponding to the transmission beam is formed, and echo signals returned from underwater are sequentially received in the reception beam. The receiving circuit is composed of nine channels, and, for example, Doppler measurement processing is executed based on echo signals received on each channel.

JP 2006-17629 A

  By the way, when the reception beam is formed by the ultrasonic transducer described in Patent Document 1, the frequency characteristic varies among the reception circuits constituting the reception channel, that is, in a specific direction due to the amplitude difference or phase difference between the circuits. Unnecessary side lobes are generated, and as a result, the underwater detection accuracy may be reduced.

  The present invention has been made in view of the above, and provides an underwater detection apparatus and a reception characteristic correction method thereof that suppress a variation in frequency characteristics of reception circuits of each channel and generate a reception beam with few unnecessary side lobes. It is for the purpose.

The invention according to claim 1 is a plurality of ultrasonic transducers and an ultrasonic signal having a predetermined bandwidth transmitted from each of the ultrasonic transducers into the water, and returns from the water to each ultrasonic transducer. And a plurality of receiving circuits for amplifying the echo signals received in the underwater detection device, in the test mode, the test signals having different frequencies set in advance within the predetermined bandwidth A test signal supplying means for supplying to the input side of the circuit, and an output signal for each of the set number of frequencies in each receiving circuit based on a complex spectrum of each frequency of the output signal of each receiving circuit corresponding to the test signal to obtain correction information for correcting the characteristics related to the amplitude and phase in the frequency domain, the characteristic analyzing means for calculating a correction filter coefficient expressed from the correction information in the time domain, leaving the the respective receiving circuits Is obtained by a correction means for correcting by the correction filter coefficients of the corresponding frequency echo signal including each frequency being.

According to a fourth aspect of the present invention, an ultrasonic signal having a predetermined bandwidth transmitted from a plurality of ultrasonic transducers into the water and amplifying an echo signal received from each ultrasonic transducer returned from the water. In a reception characteristic correction method in an underwater detection device comprising a plurality of receiving circuits, a test signal having a frequency different from a preset number within the predetermined bandwidth is input to each receiving circuit in a test mode. The characteristics relating to the amplitude and phase of the output signal for each of the set number of frequencies in each receiving circuit are corrected based on the test signal supplying process supplied to the side and the output signal of each receiving circuit corresponding to the test signal A characteristic analysis step of obtaining correction information, and a correction step of correcting an echo signal including each frequency output to each receiving circuit with the correction information of the corresponding frequency. .

  According to these inventions, in the test mode, test signals having different frequencies set in advance within a predetermined bandwidth are supplied to the input side of each receiving circuit. Then, based on the output signal of each receiving circuit corresponding to the test signal, correction information that corrects the characteristics related to the amplitude and phase of the output signal for each set number of frequencies in each receiving circuit is analyzed and obtained. The correction information is information for correcting variation between frequency characteristics of the receiving circuit. The obtained correction information is used for underwater detection. That is, the echo signal including each frequency output to each receiving circuit is corrected with the correction information of the corresponding frequency. Therefore, variations in the frequency characteristics of the reception circuits of the respective channels are suppressed, and a reception beam with few unnecessary side lobes is generated.

According to a second aspect of the present invention, in the underwater detection device according to the first aspect, the characteristic analyzing unit selects one of the plurality of receiving circuits and uses the characteristic of the selected receiving circuit as a reference. It is characterized in that it converts the characteristic of another receiving circuit.

According to a third aspect of the present invention, in the underwater detection device according to the first or second aspect, the test signal supply unit supplies the test signal to each receiving circuit a plurality of times, and the characteristic analysis unit performs the correction. The information is obtained by averaging the characteristics of the output signal corresponding to the test signal a plurality of times. According to this configuration, the correction accuracy can be improved.

  According to the present invention, it is possible to suppress variations in the frequency characteristics of the reception circuits of the respective channels, and to generate a reception beam with less unnecessary side lobes.

1 is an overall block diagram showing an embodiment of a schematic configuration of a Doppler velocimeter to which an underwater detection device according to the present invention is applied. (A) is a top view which shows a transmission surface, (b) is the sectional view on the AA line in (a). FIGS. 2A and 2B are diagrams illustrating a positional relationship between the vibrators illustrated in FIG. 2A, in which FIG. 2A is a plan view and FIG. It is a wiring diagram explaining the wiring of each vibrator shown in FIG. It is a block diagram which shows the structure pattern of the 1st-3rd group of TD1. (A) is a block diagram which shows phase control, (b) is a figure which shows the advancing direction of the transmission beam projected in the horizontal direction at the time of performing the phase control shown to (a). It is drawing for demonstrating the outline | summary of a correction | amendment algorithm.

FIG. 1 is an overall block diagram showing an embodiment of a schematic configuration of a Doppler velocimeter to which an underwater detection device according to the present invention is applied. The underwater detection device includes an ultrasonic transducer 1 that transmits and receives an ultrasonic signal, a transmission / reception switch 2 that switches a transmission / reception operation of the ultrasonic transducer 1, and a plurality of vibrations that constitute the ultrasonic transducer 1. A transmission drive signal generation circuit 4 that generates a transmission signal (transmission beam) to be input to the child, a transmission amplifier 3 that amplifies the transmission drive signal, and an echo signal received by each transducer of the ultrasonic transducer 1 A reception analog circuit 9 that performs signal processing, a correction filter 10 that corrects variations in the reception analog circuit 9 as will be described later, a control unit 5 that performs a test operation, a correction signal generation unit 6 that generates a test signal, A switch 8 that switches between a reception signal from the sonic transducer 1 and a test signal, and a correction calculation unit 7 that performs a predetermined process on the result information obtained by the test operation and calculates a correction filter coefficient are provided. . In addition, the underwater detection device includes a reception beam forming circuit 11 that forms a reception beam, and a Doppler processing unit 12 that calculates the velocity of the hull and the like from the Doppler component of the reception signal and displays the velocity on the display unit 13.

First, the ultrasonic transducer 1 will be described. In the ultrasonic transducer 1, for example, a plurality of ultrasonic transducers having a plane parallel to the horizontal plane as a transmission surface are allocated to a predetermined number of channels, for example, 9 channels, and arranged in an array. The ultrasonic transducer 1 is mounted on, for example, the ship bottom, and the wave transmission surface is exposed in water.

Here, the detailed structure of the ultrasonic transducer 1 will be described with reference to FIG. 2, FIG. 3, and FIG. Fig.2 (a) is a top view which shows a transmission surface, FIG.2 (b) is the sectional view on the AA line in Fig.2 (a). 3A and 3B are diagrams showing the positional relationship between the vibrators shown in FIG. 2A. FIG. 3A is a plan view and FIG. 3B is a partially enlarged plan view. FIG. 4 is a wiring diagram for explaining the wiring of each vibrator shown in FIG. Although channel numbers are omitted in FIGS. 3A and 4, the arrangement of the vibrators is the same as that shown in FIG.

The ultrasonic transducer 1 has an equilateral triangular lattice structure in which a transducer 100 is arranged at each vertex of an equilateral triangle having one side perpendicular to the bow-stern direction. If the arrangement pitch of the transducers 100 in the bow-stern direction (interval between transducer rows) is d, the length of one side of the equilateral triangle, that is, the distance between the centers of the transducers 100 is (2/3 ^1/2 ) d. It is. The pitch d is set in advance by the wavelength λ of the transmission signal and the depression angle θ that is an angle formed by the horizontal direction and the detection direction. Details will be described later.

As shown in FIG. 2B, the ultrasonic transducer 1 is formed of a substrate 101 made of a ferroelectric material or the like and having a piezoelectric effect, and electrodes 102 formed on opposite sides of the substrate 101. Is done. In other words, each vibrator 100 is formed by forming the electrodes 102 at opposite positions on both surfaces of the piezoelectric substrate 101. The piezoelectric substrate 101 vibrates at a frequency peculiar to the substrate when a predetermined voltage is applied between the electrodes 102 on both sides. That is, the portion sandwiched between the electrodes 102 of the piezoelectric substrate 101 functions as a piezoelectric vibrator.

In this embodiment, the vibrator 100 is divided into nine channels, and the vibrators 100a to 100c, 110e to 100g, and 100h to 100j of each channel are arranged with the positional relationship shown in FIGS. Has been. In FIGS. 2A and 3B, symbols are given only to the transducers representing each channel, and only the channel numbers to which other transducers belong are shown.

As shown in FIG. 3B, equilateral triangles having a side length of (2/3 ^1/2 ) d with the centers of the first, second, and third channel vibrators 100a to 100c as vertices are formed. The side connecting the second and third channel vibrators 100b and 100c is perpendicular to the bow-stern direction, and the first channel vibrator 100a is disposed on the bow side with respect to this side. The fourth channel vibrator 100e is disposed at a position opposite to the second channel vibrator 100b with the third channel vibrator 100c interposed therebetween, and the fifth channel vibrator 100f has the third channel vibrator 100c interposed therebetween. It is disposed at a position opposite to the first channel vibrator 100a. The sixth channel vibrator 100g is arranged at a position that forms an equilateral triangle having a side length of (2/3 ^1/2 ) d together with the fourth channel vibrator 100e and the fifth channel vibrator 100f, in other words. For example, the sixth channel vibrator 100g is disposed at a position symmetrical to the third channel vibrator 100c with the line connecting the fourth and fifth channel vibrators 100e and 100f as a line symmetry reference. The seventh channel vibrator 100h is disposed at a position opposite to the fifth channel vibrator 100f with the sixth channel vibrator 100g interposed therebetween, and the eighth channel vibrator 100i has the sixth channel vibrator 100g interposed therebetween. It is disposed at a position opposite to the fourth channel vibrator 100e. The ninth channel vibrator 100j, together with the seventh channel vibrator 100h and the eighth channel vibrator 100i, is arranged at a position constituting an equilateral triangle having a side length of (2/3 ^1/2 ) d. In other words, the ninth channel transducer 100j is disposed at a position symmetrical to the sixth channel transducer 100g with the line connecting the seventh and eighth channel transducers 100h and 100i as a line symmetry reference. The ninth channel transducer 100j forms an equilateral triangle having a side length of (2/3 ^1/2 ) d with the first channel transducer 100a at the opposite position of the eighth channel transducer 100i. The second channel vibrator 100b is disposed at a position, and the fourth channel vibrator 100e is formed at a position where an equilateral triangle having a side length of (2/3 ^1/2 ) d is formed with the second channel vibrator 100b. Is arranged. The ultrasonic transducer 1 is formed by repeating a predetermined number of such nine-channel transducer array patterns vertically and horizontally.

The vibrators 100a to 100c, 100e to 100g, and 100h to 100j formed in this way are wired in the wiring pattern shown in FIG. The first channel vibrators 100a arranged in a direction perpendicular to the bow-stern direction are connected in parallel by wiring patterns L12, L13, L14, and L15, and the wiring patterns L12 to L15 are connected to the port P1. . Similarly, the second channel vibrator 100b is connected in parallel to the port P2 through wiring patterns L21, L22, L23, L24, and L25, respectively, and the third channel vibrator 100c is connected to the wiring patterns L31, L32, L33, L34, and L35 is connected in parallel to port P3. The fourth channel vibrator 100e is connected in parallel to the port P4 through wiring patterns L41, L42, L43, L44, and L45, and the fifth channel vibrator 100f is connected to the wiring patterns L51, L52, L53, L54, and L55, respectively. Are connected in parallel to the port P5, and the sixth channel vibrator 100g is connected in parallel to the port P6 through wiring patterns L61, L62, L63, L64, and L65, respectively. Further, the seventh channel vibrator 100h is connected in parallel to the port P7 by wiring patterns L71, L72, L73, L74, and L75, respectively, and the eighth channel vibrator 100i is a port by wiring patterns L81, L82, L83, and L84, respectively. The ninth channel vibrator 100j is connected in parallel to P8 and connected in parallel to the port P9 through wiring patterns L91, L92, L93, and L94, respectively. The ports P <b> 1 to P <b> 9 are connected to each line of the bus line with the transmission / reception switch 2. The other terminals of the vibrators 100a to 100c, 100e to 100g, and 100h to 100j are grounded, for example, for each channel or common. As a result, all the vibrators are connected to the first channel to the ninth channel. The wiring pattern described above is realized by forming a wiring pattern electrode on one surface of the piezoelectric substrate 101 in the case where the electrodes 102 are formed on both opposing surfaces of the piezoelectric substrate 101. When used, it is realized by connecting the terminals of the vibration elements by wiring pattern electrodes or conductor wires formed on the surface of the insulating substrate.

In this embodiment, the ultrasonic transducer 1 has nine channels of transducers 100 divided into three groups. Specifically, the first channel vibrator 100a to the third channel vibrator 100c are set as the first group, the fourth channel vibrator 100e to the sixth channel vibrator 100g are set as the second group, and the seventh channel vibrator is set. 100h to the ninth channel vibrator 100j are in the third group.

FIG. 5 is a plan view showing arrangement patterns of the first to third groups of the ultrasonic transducer 1. As shown in FIG. 5, the first group transducer 110a, the second group transducer 110b, and the third group transducer 110c have a positional relationship in which the center-to-center distance is 2d and arranged in an equilateral triangular lattice. In the ultrasonic transducer 1, the transducers of each group are arranged at a pitch d in a direction parallel to the bow-stern direction and in a direction of ± π / 6 with respect to the bow-stern direction. . Specifically, the first group transducer 110a, the second group transducer 110b, and the third group transducer 110c are arranged with a pitch d in the order parallel to the bow-stern direction, and the bow-stern direction. Are arranged in the order of ± π / 6 with a pitch d in the order of the first group transducer 110a, the third group transducer 110c, and the second group transducer 110b.

  The transmission drive signal generation circuit 4 generates a transmission drive signal for the transducer to transmit a transmission signal having a desired frequency in accordance with the control signal input from the control unit 5, and the phase of the transmission drive signal output for each group Take control. In the present embodiment, as described later, since transmission drive signals having opposite phases (phase difference π) are used, one type of transmission drive signal is output from the transmission drive signal generation circuit 4. Specifically, as shown in FIG. 6A, phase control is performed so that two predetermined groups have opposite phases. Here, the two predetermined groups are the second group transducer 110b and the third group transducer 110c. In place of the above method, the transmission drive signal generation circuit 4 may generate transmission drive signals having opposite phases.

6A is a block diagram showing phase control, and FIG. 6B is a diagram showing the traveling direction of the transmission beam projected in the horizontal direction when the phase control shown in FIG. 6A is performed. It is. As shown in FIG. 6A, the reference transmission drive signal and the transmission drive signal whose phases are different by π (rad: radians) are included in the first group transducer 110a, the second group transducer 110b, and the third group transducer. Any two group transducers of the group transducer 110c, in this embodiment, a reference transmission drive signal is input to the second group transducer 110b, and a phase difference π (rad) is transmitted to the third group transducer 110c. A credit driving signal is input.

When a transmission drive signal having a phase difference π (rad) is input to the second group transducer 110b and the third group transducer 110c, the ultrasonic signal is transmitted in the bow direction, as shown in FIG. Predetermined for a total of six directions: stern direction, direction rotated from the bow direction to port, starboard direction ± π / 3 (rad), and direction from bow direction to port, starboard direction ± 2π / 3 (rad) Is transmitted with an included angle θ. That is, six transmission beams TxBeam1 to TxBeam3 and TxBeam1 'to TxBeam3' are set.

  The operation of the transmission drive signal generation circuit 4 will be described. As described above, the ultrasonic signal transmitted from the ultrasonic transducer 1 is a broadband signal having a predetermined wavelength range. In the present embodiment, a transmission signal in which a plurality of wideband signals encoded by the two-phase phase shift keying (BPSK) method are connected is used. This method is described in, for example, a patent application (Japanese Patent Laid-Open No. 2007-292668) related to the present applicant.

  The echo signal (reception signal) received by each transducer 100 is captured by the reception analog circuit 9 and guided to the Doppler processing unit 12 through the correction filter circuit 10. The reception beams in the three directions are received so as to sequentially give a phase difference of 2π / 3 [rad] to the first group transducer 110a, the second group transducer 110b, and the third group transducer 110c. Formed with. The reception beams for the remaining three directions can be formed by reversing the phase shift direction as necessary.

  The correction signal generation unit 6 is a circuit that can generate a test signal having a frequency set by the control unit 5. The correction signal generator 6 may be a known integrated circuit that digitally generates a sine wave.

  In the test mode, the switch 8 switches the signal path so that a correction sine wave can be supplied from the correction signal generator 6 to the input side of the reception analog circuit 9.

  The correction calculation unit 7 performs FFT processing on the signal output from the correction filter 10 to calculate a filter coefficient (frequency domain), and performs IFFT (inverse Fourier transform) processing on the calculation result, thereby correcting the filter coefficient (time domain). Is calculated.

  FIG. 7 is a diagram for explaining the outline of the correction algorithm. In FIG. 7, step A is a step of detecting a spectrum in the reception analog circuit of each channel in the test mode. Step B is a step of selecting a reference channel. Step C is a step of detecting the frequency characteristics of each receiving circuit, that is, the amplitude ratio and the phase difference. Step D is a step of performing an averaging process on a plurality of measurement results. Step E is a step of calculating filter coefficients. Step F is a step of executing IFFT.

  When the present invention shifts to the test mode, the correction algorithm is executed as follows. The transition to the test mode is automatically performed when the power is turned on after the underwater detection device is manufactured, shipped, or mounted on the hull, in response to an instruction from an operator, or in a mounted state. The test mode may be performed once or a plurality of times.

  The correction algorithm is executed under the following conditions. That is, in this embodiment, as described above, reception systems for nine channels ch1 to ch9 are provided (see FIG. 7), and a broadband ultrasonic signal is used as the ultrasonic wave for detection. Therefore, the correction signal, which is a test signal, sets n frequencies at equal intervals within the band range of the broadband ultrasonic signal. The test is performed N times (N is an integer of 1 or more) and averaged.

  In step A, first, a correction signal (test signal) is supplied from the correction signal generator 6 to the reception analog circuit, sampled by the AD converter, passed through the correction filter and FFT, and the spectrum at the frequency of the correction signal is obtained. Perform detection. However, as an initial setting of the test mode, the control unit 5 sets values that have an amplitude “1” and a phase “0” as initial values for the correction filter.

  In step A, the frequency of the correction signal is generated by sequentially changing from f1 to fn, and is sequentially supplied to the reception analog circuit. Such processing is repeated N times. As a result of spectrum detection processing by FFT, the data from the 1st to the Nth 1ch to 9ch are obtained as the first ch1 (I, Q) to the Nth ch9 (I, Q) for the frequency fn. (See [1] in FIG. 7).

  When all the supply of the correction signal is completed, in the process B, the selection of the reference channel is executed by the correction calculation unit 7. That is, a channel serving as a reference for obtaining an amplitude ratio and a phase difference is selected from the obtained signals. For example, data having the maximum amplitude value is extracted from the data acquired in the process A, and the channel having the maximum value is selected as the reference channel.

  When the selection of the reference channel is completed, in step C, the correction calculation unit 7 calculates the amplitude ratio and phase difference with respect to the reference channel for each channel. This calculation process is performed for all frequencies f1 to fn and measurement times 1 to N.

Specifically, it is performed as follows. In this example, channel ch1 is the reference channel. Let the corresponding spectrum at a certain frequency be a _i + jb _i (subscript i is the channel).

Now, assuming that the amplitude of ch_i is ch_i_pow,
ch_i_pow = √ (a _i + jb _i ) × (a _i + jb _i ) ^* (1)
It becomes. In addition, the code | symbol * in (Formula 1) shows a complex conjugate. Therefore, the amplitude ratio pow_1i of ch_i with reference to ch1 is
pow_1i = (ch_i_pow) / (ch_1_pow) (2)
It becomes.

Next, the phase difference θ_1i based on ch1 is
θ_1i = tan ⁻¹ (Im [(a _i + jb _i ) × (a ₁ + jb ₁ ) ^* ] / Re [(a _i + jb _i ) × (a ₁ + jb ₁ ) ^* ]) (3)
Obtained from When pow_1i is replaced with V and θ_1i is replaced with θ, (pow_1i, θ_1i) in a certain channel is expressed as f (V, θ). Accordingly, f1 (V, θ) to fn (V, θ) are obtained corresponding to each frequency and for each of the measurement times (1 to N times) (see [2] in FIG. 7).

  When the amplitude ratio and phase difference for each frequency and each measurement time with respect to the reference channel are calculated, in the process D, the control unit 5 executes an averaging process. In the averaging process, the average value of the measurement times is calculated for f1 (V, θ) to fn (V, θ) obtained in the process C. Therefore, as shown in [3] of FIG. 7, average values f1 (Va, θa) to fn (Va, θa) for each frequency of each channel are obtained. Va and θa indicate the average value of N times as the measurement times of V and θ.

  When the averaging process is completed, a filter coefficient calculation process is executed by the correction calculation unit 7 in the process E. The filter coefficient calculation process calculates filter coefficients from the averaged Va and θa. That is, the filter coefficients f1 (I, Q) to fn (I, Q) are obtained for each channel as shown in the following equation (4).

I = (1 / Va) × cos (−θa)
Q = (1 / Va) × sin (−θa) (4)
When the filter coefficient calculation process is completed, IFFT is executed in the correction calculation unit 7 in the process F. The IFFT process performs inverse Fourier transform, and converts the frequency domain filter coefficient calculated in step E into a time domain coefficient. Further, the correction calculation unit 7 transfers the filter coefficient obtained by the IFFT process to the correction filter as a correction filter coefficient. That is, the correction filter coefficient is generated by the frequency sampling method for the FIR filter (finite impulse response filter).

  In this way, it is possible to suppress the variation in frequency characteristics between the reception analog circuits of each channel by setting the correction filter coefficient, and further suppress the deviation by setting the value n or the value N large. It becomes possible to do.

  In the present invention, instead of using the maximum frequency characteristic as a reference, a channel having a value close to a predetermined value may be used as a reference, or the channel may not be used as a reference and a preset predetermined value may be used as a reference. The ratio and the difference with the predetermined value may be the amplitude ratio and the phase difference.

DESCRIPTION OF SYMBOLS 1 Ultrasonic transmitter / receiver 100,100a-100c, 100e-100j Channel vibrator 110a-110c Group vibrator 2 Transmission / reception switch 3 Transmission amplifier 4 Transmission drive signal generation circuit 5 Control part 6 Correction signal generation part 7 Correction calculation part 8 Switch 9 Receive Analog Circuit 10 Correction Filter 11 Receive Beam Forming Circuit 12 Doppler Processing Unit 13 Display Unit

Claims (4)

A plurality of ultrasonic transducers and an ultrasonic signal having a predetermined bandwidth transmitted from the ultrasonic transducers to the water and amplifying an echo signal received from the ultrasonic transducers returned from the water In the underwater detection device comprising a plurality of receiving circuits
In a test mode, a test signal supply means for supplying test signals having different frequencies of a predetermined number within the predetermined bandwidth to the input side of each receiving circuit;
Based on the complex spectrum of each frequency of the output signal of each receiving circuit corresponding to the test signal, correction information for correcting characteristics related to the amplitude and phase of the output signal for each of the set number of frequencies in each receiving circuit is frequency obtained in the area, and the characteristic analyzing means for calculating a correction filter coefficient expressed from the correction information in the time domain,
An underwater detection device comprising: correction means for correcting an echo signal including each frequency output to each receiving circuit with the correction filter coefficient having a corresponding frequency. The characteristic analysis means selects one of the plurality of reception circuits and converts the characteristic of another reception circuit based on the characteristic of the selected reception circuit. The underwater detection device according to claim 1. The test signal supply unit supplies the test signal to each receiving circuit a plurality of times, and the characteristic analysis unit obtains the correction information by averaging the characteristics of the output signal corresponding to the test signal a plurality of times. The underwater detection device according to claim 1, wherein the underwater detection device is configured as described above. A plurality of receiving circuits that amplify echo signals that are transmitted from a plurality of ultrasonic transducers into the water and have a predetermined bandwidth and that are returned from the water and received by each ultrasonic transducer; In the reception characteristic correction method in the underwater detection device,
In a test mode, a test signal supply process for supplying test signals having different frequencies within a predetermined bandwidth to the input side of each of the receiving circuits;
Based on the complex spectrum of each frequency of the output signal of each receiving circuit corresponding to the test signal, correction information for correcting characteristics related to the amplitude and phase of the output signal for each of the set number of frequencies in each receiving circuit is frequency A characteristic analysis step of obtaining a correction filter coefficient expressed in the time domain from the correction information obtained in the area ;
A correction method for a reception characteristic in an underwater detection device, comprising: a correction step of correcting an echo signal including each frequency output to each reception circuit with the correction filter coefficient having a corresponding frequency.

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