JP2995374B2 - AGC circuit by frequency - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AG for suppressing reverberation in an active sonar device which emits sound waves into water and detects and displays a target object from the reverberation sound (echo).
It relates to a C (AutoGain Control) circuit.

[0002]

2. Description of the Related Art FIG. 4 is a processing block diagram of an AGC circuit implemented for each frequency in a reception processing circuit of the conventional active sonar device of FIG.

In a conventional active sonar device, a sound wave is emitted from a transmitter 1 in water, a reverberation sound (echo) from a target 2 is received by a receiver 3, and a preprocessor 4 performs frequency conversion and the like. After the processing, the received data 101 for each frequency divided by the frequency analysis circuit 5 for each frequency is provided to the AGC circuit 6 for each frequency. In the AGC circuit 6 for each frequency, AGC is performed on the reception data 101 for each frequency as follows.

The received data 101 for each frequency is multiplied by K (K is a constant determined by a time constant: K <1) by a multiplier 7 and given to an adder 8. The register 10 receiving the output signal of the adder 8 stores the previous moving average value 102,
This value is multiplied by (1−K) in a multiplier 9 (K is a constant determined by a time constant: K <1) and is given to an adder 8. The adder 8 adds the received data multiplied by K and the previous moving average value multiplied by (1−K).

The new moving average value 103 output from the adder 8 is stored in the register 10 and the new moving average value
Output to The divider 11 receives the received data 10 for each frequency.
1 is divided by the new moving average 103 and the result is output to the post-processor 12 as AGC output data 104 for each frequency. The above operation is carried out by the AGC circuit 6 for each frequency, but when processing the first received data 101 for each frequency, the initial value (constant data) of the register 10 is set to the initial value setting unit 1.
Load from 4.

In the post-processor 12, the AGC output data 104
, And outputs the video data to the display 13 as video data. The display unit 13 displays the input video data as an image.

[0007]

In the conventional AGC circuit implemented for each frequency, the initial value of the register for storing the moving average value of the AGC circuit is the same for each frequency, so that the optimum value for the reverberation characteristics is obtained. AGC was not performed, and the reverberation suppression time was different for each frequency. As shown in FIG. 5, the frequency characteristics of the reverberation are sin (2πfT) / (2) depending on the transmission pulse width (T) and the transmission frequency (f) from the transmitter.
πfT), and the level attenuates while fluctuating with time.

Therefore, when the S / R ratio (signal-to-reverberation ratio) is poor, reverberation having a Doppler (echo) is masked by reverberation until the reverberation level of each frequency converges by AGC, and extraction is difficult.

It is an object of the present invention to provide a frequency-dependent AGC circuit which can extract a reverberation sound (echo) having a Doppler without being masked by reverberation even when the S / R ratio is poor.

[0010]

According to the present invention, in a frequency-dependent AGC circuit implemented for each frequency in a reception processing circuit of an active sonar device, reception data is multiplied by K (K is a constant determined from a time constant: K <1), a first multiplier that multiplies the previous moving average by (1−K), a received data multiplied by K, and a previous moving average that is multiplied by (1−K) , A register which is provided with output data of the adder and which gives the previous moving average value to the second multiplier, and stores data for setting an initial value of the register. And a divider for dividing received data by the output data of the adder, thereby obtaining an AGC circuit for each frequency.

In the present invention, instead of the ROM, an initial value setting register for storing data or n.
Alternatively, an average value detection circuit which can store (n is a natural number) received data and detect the n average values may be used.

[0012]

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

FIG. 1 is a block diagram showing one embodiment of the present invention. The target 2 by emitting sound waves into the water from the transmitter 1
After receiving the reverberation sound (echo) from the receiver 3 and subjecting the preprocessor 4 to processing such as frequency conversion, the frequency analysis circuit 5
Received data 10 for each frequency divided into respective frequencies
1 is output to the AGC circuit 6 for each frequency. AG by frequency
The C circuit 6 receives the received data 10 for each frequency as follows.
AGC is carried out for 1.

The received data 101 for each frequency is multiplied by K (K is a constant determined by a time constant: K <1) by the multiplier 7 and output to the adder 8. The previous moving average value 102 is stored in the register 10, and this value is multiplied by (1−K) (K is a constant determined by a time constant: K <1) in the multiplier 9 and output to the adder 8. The adder 8 adds the previous moving average value multiplied by K times the received data (1-K).

The new moving average value 103 output from the adder 8 is stored in the register 10 and is also stored in the divider 11.
Output to The divider 11 receives the received data 10 for each frequency.
1 is divided by the new moving average 103 and the result is output to the post-processor 12 as AGC output data 104 for each frequency.

The above operation is performed by the AGC circuit for each frequency. When the received data 101 for each frequency is first processed, the initial value is stored in the register 10 in accordance with the transmission pulse width, the transmission frequency and the reception level. ROM where is located
Load from 14.

In the post-processor 12, the AGC output data 104
, And outputs the video data to the display 13 as video data. The display unit 13 displays the input video data as an image.

FIG. 2 shows a frequency-dependent A according to another embodiment of the present invention.
It is a block diagram of a GC circuit. In the embodiment shown in FIG. 2, the ROM 15 is replaced with an initial value setting register 16 in the embodiment shown in FIG.
Is stored in the initial value setting register 16, and the initial value of the register 10 is the value of the first received data 101 stored in the initial value setting register 16.

FIG. 3 is a block diagram of a frequency-dependent AGC circuit according to still another embodiment of the present invention. The embodiment shown in FIG. 3 has n ROMs 15 (n is a natural number) in the embodiment of FIG. The received value 101 for each frequency is stored in the average value detecting circuit 17 for storing the received value 101 for each frequency by replacing the average value detecting circuit 17 for detecting the average value. Is the value of the detection result of the average value detection circuit 17.

[0020]

As described above, according to the present invention, the initial value of the register for storing the moving average value in the AGC circuit implemented for each frequency is set to the transmission pulse width, the transmission frequency and the reception frequency corresponding to each frequency. By setting the set value according to the wave level, the first received data or the average value of the first received data, AGC optimal for reverberation characteristics is performed for each frequency, and the convergence time can be reduced. Therefore, the present invention
Due to this reverberation suppression effect, even when the S / R ratio is poor, an echo having Doppler can be extracted without being masked by reverberation.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a block diagram showing another embodiment of the present invention.

FIG. 3 is a block diagram showing still another embodiment of the present invention.

FIG. 4 is a block diagram showing a conventional AGC circuit.

FIG. 5 is a diagram for explaining frequency characteristics and level characteristics of reverberation in the conventional AGC circuit of FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmitter 3 Receiver 4 Preprocessor 5 Frequency analysis circuit 6 AGC circuit according to frequency 7 Multiplier 8 Adder 9 Multiplier 10 Register 11 Divider 12 Postprocessor 15 ROM 16 Initial value setting register 17 Average value Detection circuit 101 Received data for each frequency 102 Previous moving average 103 New moving average 104 AGC output data

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-1699884 (JP, A) JP-A-4-116488 (JP, A) JP-A-4-9785 (JP, A) JP-A-1- 209392 (JP, A) JP-A-62-245173 (JP, A) JP-A-63-144278 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01S 3 / 80-3 / 86 G01S 5/18-5/30 G01S 7/52-7/64 G01S 15/00-15/96

Claims (3)

(57) [Claims] In a frequency-dependent AGC circuit implemented for each frequency in a reception processing circuit of an active sonar device, reception data is multiplied by K (K is a constant determined by a time constant: K <
1) The first multiplier to perform and the previous moving average value to (1-
K) times the second multiplier, K times the received data and (1
-K) an adder for adding the previous moving average value multiplied by two, a register having output data of the adder and providing the second moving average value to the second multiplier, and an initial value of this register. AGC for each frequency, comprising: a ROM for storing data for setting a value; and a divider for dividing received data by output data of the adder.
circuit. 2. In a frequency-dependent AGC circuit implemented for each frequency in a reception processing circuit of an active sonar device, reception data is multiplied by K (K is a constant determined from a time constant: K <K <
1) The first multiplier to perform and the previous moving average value to (1-
K) times the second multiplier, K times the received data and (1
-K) an adder for adding the previous moving average value multiplied by two, a register having output data of the adder and providing the second moving average value to the second multiplier, and an initial value of this register. An AGC circuit for each frequency, comprising: an initial value setting register for storing data for setting a value; and a divider for dividing received data by output data of the adder. 3. In a frequency-dependent AGC circuit implemented for each frequency in a reception processing circuit of an active sonar device, reception data is multiplied by K (K is a constant determined from a time constant: K <K
1) The first multiplier to perform and the previous moving average value to (1-
K) times the second multiplier, K times the received data and (1
-K) an adder for adding the previous moving average value multiplied by two, a register having output data of the adder and providing the second moving average value to the second multiplier, and an initial value of this register. N (n is a natural number) to set the value
AGC circuit comprising: an average value detection circuit capable of storing the received data and detecting the n average values; and a divider for dividing the received data by the output data of the adder.