JPS6311882A - Sonar receiver - Google Patents

Abstract

PURPOSE:To improve searching to a weak signal, by providing an adaptive filter automatically tuning with the frequency spectrum of an input sonic wave to a listening system. CONSTITUTION:An input sonic wave is received by a receiver 1 to be converted to an electrical signal which is, in turn, inputted an FFT (fast Fourier transform) circuit 31 through an A/D converter 2 to be subjected to spectrum analysis and the analytical result is supplied to convolution operation circuit 32 and CPU34. CPU34 determines the impulse response train of a filter and reads impulse response train frequency characteristic data to supply the same to the circuit 32. The circuit 32 performs the multipulication of input data from the circuit 31 and CPU 34 to obtain desired filter output which is, in turn, supplied to an IFFT (inverse FFT) circuit 33. The circuit 33 converts input data to a time region value to supply the same to a frequency converting circuit 5 which then converts input frequency to preset listening frequency. The output of the circuit 5 is listened in a high S/N state by a headphone 8 through a D/A converter 6 and an amplifier 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sonar receiving device, and more particularly to a sonar receiving device with improved detection and identification functions for weak input signals.

[Conventional technology]

Passive and active sonar are equipped with a sonar receiving device that converts input sound waves into audible frequencies and allows the sonar operator to listen to them using terminal equipment such as headphones to detect and identify targets. In many cases, the target audible sound is received by converting the input to a predetermined audible frequency.

[Problem that the invention seeks to solve]

In the above-mentioned conventional receiver, the signal processing performed on the video system, especially the signal processing performed with consideration to improving the S/NI No. 4-to-noise ratio of the received signal, is not applied to the audio system. Currently, we rely solely on the experience and skill of the operator, and for this reason, we have no choice but to respond to weak signals with low S/N only by detecting and identifying them using the video system. Another problem is that the operation of the listening system itself requires highly trained operators.

The purpose of the present invention is to eliminate the above-mentioned drawbacks and improve the S/N of the hearing system of a sonar receiver, thereby ensuring that the hearing system performs the same detection and identification processing as the video system for weak signals. It is an object of the present invention to provide a listener receiving device which can significantly increase the discrimination function and greatly reduce the level of listening skill required of an operator.

[Means for solving problems]

The device of the present invention is a sonar receiving device in which the hearing system includes an adaptive filter that automatically tunes to the frequency spectrum of an input sound wave.

〔Example〕

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

FIG. 1 is a block diagram showing an embodiment of the sonar receiving device of the present invention. The embodiment shown in FIG. 1 includes a receiver 1. A
/D converter 2. Adaptive filter 3, control circuit 41 frequency conversion circuit 5. The adaptive filter 3 is configured to include a D/A converter 6, an amplifier 7, headphones 8, etc.
sform) circuit 31, convolution multiplication circuit 32, FF
T (Inverse FFT) circuit 33 and CPU 3
It is composed of 4th grade.

The receiver 1 is an active or panship sonar sensor that receives input sound waves, converts them into electrical signals, and supplies the electrical signals to the A/D converter 2 .

The A/D converter 2 samples the input at a predetermined sampling frequency, digitizes it with a predetermined number of bits, and supplies this quantized data to the FFT circuit 31 .

The FFT circuit 31 converts the input signal in the time domain into data in the frequency domain, that is, performs spectrum analysis, and supplies the result of this spectrum analysis to the display/recorder of the sonar device for video display, and also performs convolution calculation. The signal is supplied to the circuit 32 and the CPU 34.

The CPU 34 functions as the CPU of the adaptive filter 3 while receiving control commands from the control circuit 4 regarding basic setting conditions in reception processing, such as active detection or passive detection, commands regarding listening operations, sonar operational specifications, etc. . The adaptive filter 3 adaptively controls its center frequency and bandwidth with respect to the frequencies of the spectral components of the signal input as a whole, and functions as a bandpass filter puncture in frequency domain processing. Filtering performed in the frequency domain can be done by obtaining the product of the input sequence converted to the frequency domain and the frequency characteristics of the impulse response sequence, that is, by obtaining a convolution operation, and then converting it to time domain data using IFFF processing. Frequency domain transformation is generally performed by FFT.

When the CPU 34 obtains information regarding the center frequency fO of the bandpass filter to be constructed from the FFT circuit 31, the CPU 34 determines the bandwidth ΔB from this and the preset condition of fo/ΔB, and based on this, determines the impulse response of the filter to be constructed. Determine the column. The characteristics of the filter to be configured, and hence the impulse response, are set in advance in relation to the center frequency and bandwidth, and the frequency domain transformation data thereof is stored in the built-in memory. The CPU 34 reads this impulse response string frequency characteristic data and supplies it to the convolution calculation circuit 32.

The multiplication circuit 32 multiplies the input data from the FFT circuit 31 and the CPU 34 to obtain a desired filter output and supplies it to the IFFT circuit 33.

The IFFT circuit 33 converts the input data into a time domain value again by IFFT and supplies it to the frequency conversion circuit 5. In this way, the adaptive filter 3 performs filter processing that operates adaptively to the input frequency.

As is well known, 1 filter processing in the frequency domain can increase the calculation speed compared to processing in the time domain, and the processing frequency domain can be expected to expand accordingly.

In this way, the signal input output from the adaptive filter 3 is
The signal is supplied to the frequency conversion circuit 5 in a state where the S/N ratio has been significantly improved in accordance with the characteristics of the adaptive filter 3.

The frequency conversion circuit 5 converts the input frequency into a preset listening frequency and supplies the output to the D/A converter 6.

The D/A converter 6 performs analog conversion of the digital input and supplies it to the amplifier 7.

Amplifier 7 amplifies the input to a predetermined level and outputs it to headphones 8.
The operator listens to the audible output through headphones 8 in a high S/N state. In this way, similar to the video system, Pc
Auditory processing predicated on improving s/H can be implemented in the form of adaptive filter insertion that automatically tunes to the frequency spectrum of the input sound waves.

〔Effect of the invention〕

As explained above, according to the present invention, in a sonar receiving device, an adaptive filter that automatically tunes to the frequency spectrum of an input sound wave is included in the listening system to perform listening processing, thereby achieving a high S/N even in the case of a weak signal. Hearing becomes possible,
When used in combination with a video system, it is possible to realize a sonar receiving device that can significantly improve detection performance and greatly ease the operator's requirements for briquetting.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention. 1... Receiver, 2... A/D converter, 3... Adaptive filter, 4... Control circuit, 5...・Frequency conversion circuit, 6...
・D/A converter, 7...Amplifier, 8...
...Headphones, 31...FFT circuit, 32
...Convolution operation circuit, 33...I
FFT circuit, 34...CPU. town map

Claims (1)

[Claims] What is claimed is: 1. A sonar receiver comprising an adaptive filter that automatically tunes to the frequency spectrum of an input sound wave.