JPS6227681A - Hearing doppler detection circuit for fm transmission - Google Patents

Abstract

PURPOSE:To attain to enhance efficiency such as the reduction of the fatigue of operators and the reduction in the number of operators, by making it possible to discriminate Doppler by hearing. CONSTITUTION:The echo from the object in the sea is received by a transmitter- receiver 5 and the receiving echo 101 is applied to a trigger detector 8 to detect the rising part of the signal 101 while a trigger signal 102 is sent to memory circuits 10, 11. The FM transmission signal 106 from the circuit 10 is sent to a beat detection circuit 14 as a transmission amplitude adjusting signal 107 through an amplitude adjusting circuit 12. The transmission time setting time signal 104 from the circuit 11 is sent to a gate 13 which is, in turn, opened only for a transmission time to permit the passage of the output signal 103 of an amplitude adjusting circuit 9 to be sent to the circuit 14 as a receiving echo amplitude time limit signal 105. When there is Doppler in the signal 101, the output signal of the circuit 104 outputs as the signal having the difference frequency of the signals 105, 107 and the output signal of a 800Hz generation circuit 15 comes to a hearing signal of 800Hz+DELTAf and hearing discrimination becomes possible. Therefore, it is unnecessary to visually observe plural pictures and the reduction in the fatigue of an operator is contrived.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an active sonar for detecting underwater moving objects, and more particularly to an audible Doppler detection circuit for FM transmission of an active sonar.

Active sonar for detecting moving objects underwater.There are two ways to recognize the echoes from a target: a visual method using the CR'l' display, and an auditory method using a hearing receiver or loudspeaker. pcw
In the auditory recognition method using a single frequency such as transmission, by frequency modulating the reverberant sound (e.g. 800 Hz) and listening to the Doppler sound caused by the movement of the object, it is relatively easy to determine whether the object is moving or not. is possible. However, in the case of 1M transmission, since the fundamental frequency is changing, it is not possible to perform Doppler discrimination using only conventional frequency modulation, and it is impossible to discriminate whether an object is a moving object or not. Therefore, as a Doppler detection method in conventional FM transmission, a visual discrimination method using a CRT display such as a Doppler display is widely used. However, this visual discrimination method requires a large number of operators and is disadvantageous in that the operators are highly fatigued.

Regarding this type of FM transmission, Japanese Patent Application Laid-Open No. 48-749
No. 89 is known.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an audible Doppler detection circuit for FM transmission of an active sonar, which can improve efficiency by reducing operator fatigue and reducing the number of operators.

[Summary of the invention]

In order to reduce operator fatigue and reduce the number of operators, Doppler discrimination may be performed by hearing. Therefore, in the present invention, the FM transmission signal and the received echo signal are put into a beat detection circuit, the presence or absence of a beat is detected by both signals, and the audible signal is changed depending on whether a beat is occurring or not, and the received echo signal is It is determined whether the source or target is a moving object.

[Embodiments of the invention]

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

FIG. 1 is a block diagram of a 7M active sonar to which an embodiment of the present invention is applied. In FIG. 1, an FM transmission generation circuit 2 generates a transmission signal within the time set by a transmission time setting circuit 1, and transmits the signal to a transducer 5 via a power amplifier circuit 3 and a transmission/reception switching circuit 4. is converted into sound and transmitted into the ocean.

After the echo from the underwater target is received by the transducer 5 and converted into an electrical signal, the received signal that has passed through the transceiver switching circuit 4 and the preamplifier circuit 6 is subjected to various processing in the signal processor 18. , are displayed on the screen on the CRT display 19. Further, the output signal of the preamplifier circuit 6 is sent to the loudspeaker 20 via the direction detection circuit 7, and is listened to as a raw received sound.

Furthermore, the output signal of the preamplifier circuit 6 via the azimuth detection circuit 7, that is, the received echo signal 101 (see FIG. 2), has its voltage level adjusted to a constant level by the amplitude adjustment circuit 9, and is then passed through the hearing detection time setting gate 13. sent to. On the other hand, the trigger detector 8 detects the rising edge portion of the received echo signal 101 and transfers the trigger signal 102 (see FIG. 2) to the memory circuit 10.1.
Send to 1.

These memory circuits 10 and 11 are provided to temporarily store the outputs of the transmission time setting circuit 1 and the FM transmission generation circuit 2, respectively.When the trigger signal 102 is input to the memory 10.11, the memory 10. .11 outputs the stored contents respectively◇The FM transmission signal 106 (see Fig. 2) outputted from the memory 10 is adjusted by the amplitude adjustment circuit 12 so that the voltage level becomes a constant value, and the transmission amplitude adjustment signal is 107 and is sent to the beat detection circuit 14.

Transmission time setting time signal 104 output from memory 11
(see FIG. 2) is sent to the hearing detection time setting gate 13, which is opened for the transmission time, passes the output signal 103 (see FIG. 2) of the amplitude adjustment circuit 9, and sends it to the received echo. It is sent to the beat detection circuit 14 as an amplitude time limit signal 105 (see FIG. 2).

The beat detection circuit 14 eliminates the beat between the transmission amplitude adjustment signal 107 and the reception echo amplitude time limit signal 105, and sends a beat detection signal 108 to the 800 Hz generation circuit 15.

A transmission time setting time signal 104 is sent to the 800 Hz generating circuit 15 from the memory 11, and the listening signal 109 is sent out only during the period of the signal 104.

The hearing signal 109 is sent to the hearing receiver 17 via the amplifier circuit 16.

Here, when there is no Doppler in the received echo signal 101, that is, when the target is not a moving object, the output signal from the beat detector 14 is a one-frequency signal as shown in signal 108A in FIG. A signal with no beat (because no beat occurs) is sent.

Therefore, the output signal of the 800Hz generation circuit 15 is
As shown by signal 109A in the figure, a single audio signal remains at 800 Hz.

When the received echo signal 101 has a Doppler, that is, when the target is a moving object, the output signal from the beat detector 14 is mixed with the signal 105 as shown in the signal 108B in FIG. A signal having a frequency with a difference of 107 frequencies is output. Therefore, 800 in such a case
The output signal of the Hz generation circuit 15 is shifted in frequency by the output signal of the beat detector 14, and becomes the signal 109B in FIG.
As shown in K, the audible signal becomes 800Hz±Δf. By distinguishing between this audible signal and the 800 Hz audible signal, it is possible to determine whether or not the target is a moving object.

In this way, according to this embodiment, it is possible to perform Doppler discrimination by listening to the sound, so there is no need to visually check multiple screens, and it is possible to confirm the target by listening to the sound without looking at a single screen. This has the effect of reducing the number of operators and reducing fatigue.

〔Effect of the invention〕

According to the present invention, even when transmitting FM from an active sonar, it is possible to distinguish Doppler by listening, and it is possible to improve efficiency by reducing operator fatigue and reducing the number of operators. Since it is possible to make judgments using the ears that are present, performance can be greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an FM actuator to which an embodiment of the present invention is applied, and FIG. 2 is a signal waveform diagram of each part of FIG. 1. DESCRIPTION OF SYMBOLS 1... Transmission time setting circuit, 2... FM transmission generation circuit, 3... Electric power Sozu circuit, 4... Transmission/reception switching circuit, 5...
... Transducer/receiver, 6... Advance amplifier circuit, 7... Direction detection circuit. 8...Trigger detector, 9.12...Vibration@adjustment circuit,
10.11...Memory circuit, 13...Hearing detection time setting gate, 14...Beat detection circuit, 15...8
00Hz generation circuit, 16... amplifier circuit, 17... hearing receiver, 18... signal processor, 19... CRT display. 20...High voice.

Claims (1)

[Claims] Acoustically convert the FM transmission signal, transmit it underwater, receive the reflected wave from the target object, convert the reflected wave into an electrical signal, and compare the received echo signal obtained by the conversion with the FM transmission signal. F to determine whether or not the target object is a moving object.
An audible Doppler detecting circuit for FM active sonar, characterized in that the audible Doppler detecting circuit for FM transmission is provided with a beat detecting means for shifting the frequency of the audible signal at the beat frequency of the FM transmitting signal and the received echo signal.