JPS62197776A - Target signal detecting circuit - Google Patents

Abstract

PURPOSE:To reduce a frequency at which a noise signal is detected by mistake and a frequency at which a target signal can not be detected and increase a reliability by calculating the quantity of a scatter in the phase, frequency or period of received signals, multiplying the quantity of the scatter by a threshold value and extracting the target signals. CONSTITUTION:Received signals 101 before a detection and a rectification and inputted from an input terminal 1 and fed to a delay circuit 11 and a period variance calculating circuit 13. In the circuit 11, the signals 101 are delayed by approximately half a time width for which a period variance value is calculated and outputted to a gate circuit 12 as delayed signals 102. In the circuit 13, the period of the signals 101 is measured in every AC cycle and the period variance value within a prescribed time width is calculated at constant time widths to output a calculated value to a comparing circuit 14 as a period variance value signal 104. Provided with a threshold value 105 determined in advance, the circuit 14 compares the signals 104 with the value 15 and outputs a result to the circuit 12 as a comparison signal 106. The signals that have passed the circuit 12 are fed to an output terminal 2 as target detecting signals 103.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention emits sound waves into water,
The present invention relates to a target signal detection circuit applied to an active sonar device that receives echoes from a single target object.

[Conventional technology]

As shown in FIG. 3(a), the conventional target signal detection circuit of this type sets a certain signal level as a threshold value 111 for the received signal 11O, and detects the reception level exceeding this threshold value 111. It was configured to detect 600 as a reference signal.

[Problems to be Solved] As mentioned above, in the conventional circuit that detects the target signals 112 and 113 based on the level of the received signal, the third [j(
As shown in b), if the signal level is higher than the threshold value 111, even the noise signal 114 will be detected as a target signal; The signal 113 has a problem in that it is not detected even if the target signal level is higher than the surrounding noise level, and thus lacks reliability.

The present invention has been made in view of the problems mentioned in 1.
It is an object of the present invention to provide a highly reliable target signal detection circuit that has a low frequency of erroneously detecting a noise signal as a target signal and a low frequency of failing to detect a target signal.

[Means for Solving Problems] In order to achieve the above object, the present invention emits pulsed sound waves with a predetermined time width into water, and receives sound waves including the sound waves reflected by a target object existing in the water. , in a target signal detection circuit that converts this received sound wave into a received signal by acoustic-electrical conversion and detects a target signal representing a sound wave reflected by the target object from among the received signals, or a circuit that calculates the amount of variation in any one of the phase 1 frequency or period of the received signal in a time width smaller than or equal to that, and a comparison circuit that compares the variation amount with a predetermined threshold; The configuration includes a gate circuit that outputs a received signal when the variation amount is less than the threshold value based on the output from the comparison circuit as the target signal.

[Example] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a target signal detection circuit according to this embodiment.

The target signal detection circuit of this embodiment includes a delay circuit 11, a gate circuit 12, a cycle dispersion calculation circuit 13, and a comparison circuit 14. The delay circuit 11 is a period dispersion calculation circuit 1
This function has a function of delaying the input signal by a time approximately equal to the calculation processing time required in step 3. Gate circuit 1
2 has a function of passing or blocking the input signal according to the comparison signal output from the comparison circuit 14. The zero period dispersion calculation circuit 13 measures the period of each AC cycle of the input signal, It has a function of calculating the dispersion value (variation bk) of the period within each predetermined time width. The comparison circuit 14 compares the periodic dispersion value calculated by the periodic dispersion calculating circuit 13 with a predetermined threshold value, and outputs a signal for controlling passing or blocking of the input signal to the gate circuit 12. It has the following.

Next, I will explain the operation.

A pulsed sound wave with a predetermined time width is emitted into the water, the l'f wave containing the sound wave reflected by a target object existing in the water is received, and the received sound wave is converted into an acoustic/electrical signal before detection and rectification. A received signal 101 is input from input terminal l and sent to delay circuit 11 and period dispersion calculation circuit 13.

The delay circuit 11 outputs the received signal 1 for approximately 1/2 of the time width in which the periodic dispersion calculation circuit 13 calculates the periodic dispersion value.
01 is delayed and sent to the gate circuit 12 as a delayed signal 102.
Output to.

In the period dispersion calculation circuit 13, the period of each AC cycle of the received signal 101 is measured, and the period dispersion value within the time width (predetermined time width) of the pulsed sound wave emitted into the water is calculated for a constant time width. , this calculated value is used as the periodic dispersion value signal 10
It is output to the comparator circuit 14 as 4.

The comparator circuit 14 receives a predetermined threshold value 105 from the threshold 1 input terminal 3, compares the periodic dispersion value signal 104 with this threshold value 105, and uses the comparison result as a comparison signal 106. Output to gate circuit 12.

Based on the comparison signal 106, the gate circuit 12 allows the d transmission signal 102 to pass when the periodic dispersion value signal 104 is smaller than the threshold value 105, and passes the d transmission signal 102 when the periodic dispersion value signal 104 is larger than the threshold value 105. prevent passage. The signal that has passed through the gate circuit 12 in this manner is sent to the output terminal 2 as a target detection signal 103.

Figure 2 shows the output signals from each of the circuits described above. (a) shows the periodic dispersion of the received signal 101, (b) shows the periodic dispersion of the received signal lO1, and (e) shows the periodic dispersion of the received signal 101. Value signal 104. (d) of the figure shows the delayed signal 102. In the figure (e), the comparison signal 106. FIG. 4(f) shows the target detection signal 103.

As shown in FIG. 2(b), in the received signal 101, where the target signals 1ota and 101b overlap t,
Compared to the other 31 tones only, the periods are more consistent and the dispersion is smaller. therefore.

As shown in FIG. 2(c), by setting an appropriate threshold value for the periodic dispersion value signal 104 and extracting a portion smaller than this threshold value, the target signals 1ota, 101
b is a G target detection signal 103a as shown in FIG. 2(f),
It can be detected as 103b.

In this way, the target signal can be accurately detected without erroneously detecting a portion where the signal level is simply high even though it is a noise signal, or without detecting a target signal with a low signal level.

Note that in the above-described embodiment, the amount of variation in the period of the received signal is calculated as the periodic dispersion value, and the target signal is detected based on this periodic dispersion A1. However, the amount of variation in the phase or frequency of the received signal is calculated, The target signal may be detected by comparing the calculated value with a predetermined threshold value. In this case as well, the target signal portion of the received signal has little variation in phase or frequency, so the target signal can be detected accurately. can be detected.

[Effects of the Invention] As explained above, the present invention calculates the amount of variation in the phase, frequency, or period of the received signal, and extracts the target signal by applying a threshold value to this amount of variation. , it is possible to reduce the frequency of erroneously detecting high-level noise as a target signal and the frequency of failing to detect a low-level target signal, which has a significant effect in improving reliability.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 show an embodiment of the present invention,
Figure 1 is a block diagram showing the target signal detection circuit, and Figure 2 is a diagram showing the output signals from each component circuit. Me, the same figure (
c) is a periodic dispersion value signal, (d) is a delayed signal, and (
Fig. 3(e) shows a comparison signal, Fig. 3(f) shows an i1 target detection signal, and Fig. 3 shows a conventional example. lTwo-person terminal? : Output terminal 1-3: Threshold input terminal 11: d detour 12: Gate circuit 13:
Period dispersion calculation circuit 14: Comparison circuit 101: Received signal 102: i# extension signal 103: Target detection signal 104: Period dispersion value signal

Claims (1)

[Claims] A pulsed sound wave with a predetermined time width is emitted into water, a sound wave including the sound wave reflected by a target object existing in the water is received, and this received sound wave is converted into a received signal by acoustic-electrical conversion, and this received signal is In a target signal detection circuit that detects a target signal indicating a sound wave reflected by the target object, the phase, frequency, or period of the received signal in a time width that is approximately the same as or less than the predetermined time width. a circuit that calculates the amount of variation in any one of the values; a comparison circuit that compares the amount of variation with a predetermined threshold; A target signal detection circuit comprising: a gate circuit that outputs a received signal as the target signal.