JPH03115879A - Method and circuit for processing signal of active sonar apparatus - Google Patents

Abstract

PURPOSE:To discriminate a Doppler frequency by converting a detection signal into a pulse of a one-bit signal of 1 or 0 by comparing the level of the detection signal with a prescribed level, and by verifying the sequence of a pulse train. CONSTITUTION:Each of signal detecting circuits 5-1 to 5-3 verifies whether outputs of successive band-pass filter are LFM reception signals, from a signal train inputted thereto, and outputs a maximum value when the list of the input signal train is complete and in conformity with the sequence, while outputting a minimum value when the signal train is random. For instance, '3' is outputted when all of the input trains are '1', while '1.5' is outputted when two out of the input trains are '1', and '0' is outputted when they are in other order than the foregoing. An output of the signal detecting circuit 5-1 is sent to a maximum value detecting circuit 8 via delay circuits 7-1 and 7-2, while an output of the signal detecting circuit 5-2 is sent thereto via a delay circuit 7-3, and an output of the signal detecting circuit 5-3 is sent thereto directly. The maximum value detecting circuit 8 extracts the system of the signal detecting circuit showing the maximum value of the outputs of the signal detecting circuits and outputs a Doppler frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to reception signal processing of an active sonar device, and in particular to reception signal processing for detecting the presence or absence of Doppler in reception signal processing of LFM (Linear Frequency Modulated Wave) signals. Related to signal processing circuits.

[Conventional technology]

Conventionally, this type of active sonar device uses PCW (Pulsed CCW) to detect target Doppler.
continuous wave) signals were used.

Figure 5 is a diagram showing the Doppler effect. When the active sonar device moves in a straight line at a speed v1 and a projectile moves at a speed v2, the relationship between the transmission frequency FHz and the reception frequency F' Hz is expressed by the following equation. .

where C is the phase velocity of the wave and Rn is the relative velocity of the active sonar device and the projectile.

In conventional receiving circuits using PCW signals, it is difficult to obtain a large gain through signal processing, and as an alternative, there is a received signal processing method using a cross-correlation receiving method using frequency-modulated LFM signals or the like. In this case, L
Doppler detection is difficult with only FM signals, so P
CW signals were also used.

[Problem to be solved by the invention]

In the conventional active sonar receiving circuit described above, L
By preparing two receiving circuits, one for FM signal processing and the other for PCW signal processing, signal detection can be performed using LFM.
Doppler detection was performed using PCW signals. When using the PCW signal and the LFM signal at the same time, it is necessary to separate the frequencies of these signals to prevent mutual interference and widen the reception band and transmission band. Furthermore, since the receiving circuit simultaneously processes the LFM signal and the PCW signal, there is a drawback that the circuit size becomes large.

An object of the present invention is to provide a signal processing method and circuit for an active sonar device that eliminates the above-mentioned drawbacks.

[Means for Solving the Problems] A signal processing method for an active sonar device according to the present invention divides the LFM reception band of the input signal into a plurality of parts, detects the signal components of each divided band, and determines the level of the detected signal. is compared with a predetermined level, converted into a 1-bit signal pulse of 1 or 0, and the order of the pulse train is verified to determine Doppler.

Further, the signal processing circuit of the active sonar device of the present invention includes: a signal band filter that divides the LFM reception band of the input signal into a plurality of parts; a detection circuit that detects the output of each signal band filter; and both ends of the input signal. Two frequency band filters, an average value circuit that calculates the average of the outputs of these two band filters, and a comparison circuit that compares the average value circuit output with each detection circuit output and outputs a signal when the input exceeds a predetermined level. a first delay circuit that delays the output of the comparison circuit; a signal detection circuit that detects whether the pulse trains of the output of the comparison circuit and the output of the first delay circuit are output in order; and a second delay circuit that delays the output of the signal detection circuit. The second delay circuit is characterized by comprising a delay circuit, and a maximum value detection circuit that detects the maximum value of the output of the second delay circuit and detects the maximum value and its band.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of a signal processing circuit of the present invention. The signal processing circuit of this active sonar device is
Signal band filter (F6) 1-1° (F5) I-2, (F4) I- that divides the LFM reception band of the input signal into a plurality of parts, that is, divides the LFM reception signal into narrow bands.
3, (F3) l-4, (F2) 1-5, and a detection circuit (DT) 2-1 that detects the output of each of these band filters.
．． 2-2.2-3.2-4.2 to 5, and two bandpass filters (F 1 ) for detecting the levels of both end frequencies of the input signal, that is, the levels outside the LFM reception band 1-6.
(F7) 1-7, an average value circuit (AVG) 6 that calculates the average of the outputs of these two bandpass filters, and compares the output of the detection circuit and the output of the average value circuit, and detects only signals larger than a predetermined level. Comparison circuit (C) that extracts and converts it into a 1-bit signal, that is, outputs a signal when the input is at a predetermined level or higher 3-1. 3-2.3-3.3-4
．． 3-5, and a delay circuit (D) that delays the output of the comparison circuits 3-2 to 3-5 by the pulse width according to each band filter.
4-1.4-2.4-4-4.4-5.4-6.4-7
and a signal detection circuit (S l ) that detects whether the pulse trains of the comparator circuit output and the delay circuit output are output in order.
5-L (S2) 5-2. (S3) 5-3
and a delay circuit (D) 7-1. which delays the output of the signal detection circuit 5-1.5-2. 7-2.7-3 and delay circuit 7-
2.7-3 and a maximum value detection circuit (PD) 8 that detects the maximum value among the outputs of the signal detection circuit 5-3 and detects the maximum value and its band, that is, detects the system having the maximum value. have.

Next, the operation of this embodiment will be explained.

The bandpass filters 1-1 to 15 divide the LFM reception signal among the reception signals, and the bandpass filters 1-6.1-7 outside the LFM reception signal band detect the noise level of the reception signal.

FIG. 2 is a diagram showing the division of the bandpass filter used in this example, f,,f,,f,.

LFM with divided bands having center frequency f,,f,
is the received signal band, fi and f? The band with the center frequency is for noise detection. FIG. 3 shows the frequency components when the received signal receives Doppler, and (a) shows Doppler "low," (b) shows Doppler "no," and (c) shows Doppler "'high."

The detection circuits 2-1 to 2-5 are bandpass filters 1-1 to 1.
-5 output is detected, converted to DC, and comparison circuit 3-1~
Output to 3-5. On the other hand, the average value circuit 6 calculates the average level of the outputs of the bandpass filters I-6 and 1-7, and outputs it as a reference signal for the comparison circuit.

The comparison circuit compares the level of each detection circuit output with the level of the reference signal, and outputs "signal present" if the detection output signal is larger than the reference signal. That is, only the signals that are higher than the level of the reference signal are extracted, converted into 1-bit signals, and output.

Each of the delay circuits 4-1 to 4-7 delays the comparison circuit output signal by a time corresponding to the bandwidth of the bandpass filter (usually, the reciprocal of the bandwidth). That is, the delay circuit 4-1 delays the output signal of the comparison circuit 3-2, and the delay circuit 4-2.4-3
delays the output signal of the comparison circuit 3-3, and the delay circuit 4-4
．． 4-5 delays the output signal of the comparison circuit 3-4, and delay circuits 4-6, 4-7 delay the output signal of the comparison circuit 3-5.

The output signal of the comparison circuit 3-1, the output signal of the delay circuit 4-1, and the output signal of the delay circuit 4-3 are sent to the signal detection circuit 5-1. The output signal of the comparator circuit 3-3, the output signal of the delay circuit 4-4, and the output signal of the delay circuit 4-7 are sent to the signal detection circuit 5-2. The output signal is sent to the signal detection circuit 5-3.

Each signal detection circuit verifies whether the outputs of successive bandpass filters are LFM received signals from the input signal sequence. If the human input signal sequence is completely in order, the maximum value is output, and if the signal sequence is random, the minimum value is output. In this example, three input strings are compared. For example, if the input strings are all 1'', it will be ``3'', and if two input strings are ``1'', it will be ``3''.
”, outputs “1.5”, otherwise outputs “0”.

The output of the signal detection circuit 5-1 passes through delay circuits 7-1 and 7-2, the output of the signal detection circuit 5-2 passes through the delay circuit 7-3, and the output of the signal detection circuit 5-3 directly passes through the delay circuits 7-1 and 7-2. Each is sent to the maximum value detection circuit 8.

The maximum value detection circuit 8 extracts the signal detection circuit system showing the maximum value from among the outputs of the signal detection circuits, and outputs it as a Doppler output. In this example, the Doppler outputs of the three signal detection circuits are Doppler Output Low, Doppler No Doppler, and Doppler High.

Furthermore, the detected maximum value is also simultaneously output as an amplitude output. This amplitude value is used as a video signal on the display.

As an example, FIG. 4 shows signal waveforms at various parts.

FIG. 4(a) shows an example of the frequency spectrum of the input signal, and this example shows the case where there is no Doppler. (b) shows the output level and output time of each band filter F1 to F7, and in this example, F3. F4. (C), which shows that the signals are output in the order of F5, shows the time course of the output level of the signal detection circuit Sl, 52.33, and shows that the output of the circuit S2 has the maximum value. (d) shows the time relationship of the inputs of the maximum value circuit PD.

〔Effect of the invention〕

As explained above, in LFM signal processing, the present invention converts the output of a band filter within the LFM reception band into a 1-bit signal of 1 and O by the outputs of two band filters outside the LFM reception band, and further , by a simple method and circuit configuration of verifying the order of the pulse train.
Even when receiving FM, it becomes possible to distinguish Doppler, eliminating the need to use PCW signals for transmission.

Furthermore, by not performing PCW transmission, it is possible to narrow the transmission and reception bands, and also to reduce wasted time and transmission power due to PCW transmission.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an embodiment of the signal processing circuit of the present invention, Fig. 2 is a diagram showing frequency division of a filter circuit, and Fig. 3 is a diagram showing frequency components of a human signal with and without Doppler. , FIG. 4 is a diagram showing the waveforms of each part in FIG. 1, and FIG. 5 is a diagram showing the Doppler effect. l...Band filter circuit 2...Detection circuit 3...Comparison circuit 4.7...Delay circuit 5...Signal detection circuit 6...Average value Circuit 8...Maximum value detection circuit

Claims (2)

[Claims] (1) Divide the LFM reception band of the input signal into multiple parts,
Detecting the signal components of each divided band, comparing the level of the detected signal with a predetermined level, converting it into a 1-bit signal pulse of 1 or 0, and determining the Doppler by verifying the order of the pulse train. A signal processing method for an active sonar device characterized by: (2) A signal band filter that divides the LFM reception band of the input signal into multiple parts, a detection circuit that detects the output of each signal band filter, two band filters at both end frequencies of the input signal, and these two band filters. An average value circuit that calculates the average of the bandpass filter output, a comparison circuit that compares the average value circuit output with each detection circuit output and outputs a signal when the input is above a determined level, and a first comparison circuit that delays the output of the comparison circuit. a delay circuit; a signal detection circuit that detects whether the pulse trains of the comparator circuit output and the first delay circuit output are output in order; a second delay circuit that delays the signal detection circuit output; and a second delay circuit output. 1. A signal processing circuit for an active sonar device, comprising a maximum value detection circuit that detects a maximum value among the maximum values and detects the maximum value and its band.