JPS63227140A - Signal detecting system - Google Patents

Abstract

PURPOSE:To reduce the influence of underwater noise by sending out an ultrasonic signal obtained by applying a sound signal with analog modulation, into the water, and providing a level deciding means for a received demodulating signal and a timer for deciding the detection of a signal and its end. CONSTITUTION:An underwater communication is executed by sending out an ultrasonic signal which is applied with analog modulation by a sound signal, into the water, in a transmitting part, and demodulating said signal in a receiving part. In such a case, when the level of an input signal becomes higher than a prescribed level, a demodulating circuit inputs a carrier detecting signal (b), starts a first timer 21, and when the signal (b) is continued longer than a time time T1, a comparing circuit 22 decides it to be signal detection, and by turning on a power amplifier control signal (c), the output of voice is started. After the voice output is started, when the level of the input signal becomes lower than the prescribed level, the signal (b) is turned off, a second timer 24 is started, and when the signal (b) is turned off longer than a timer time T2, a comparing circuit 25 decides it to be a signal disconnection and stops the output of the voice. In such a way, the influence of underwater noise can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a signal detection method, and more particularly to signal detection in a receiving section of underwater communications using ultrasonic signals.

Recently, there has been an increase in dangerous underwater work such as on the ocean floor due to ocean development, and Scuba divers account for a large proportion of the divers engaged in this work. In addition, the number of 5-cuba dippers for leisure is rapidly increasing.

However, at present, there is no means of communication between fellow Diapers or between the Diapers and the mother ship at sea, so a wireless means of communication is desperately needed from the standpoints of safety and work efficiency. Compared to the diving method in which the diver wears a diving suit and receives air from a ship at sea, wireless communication is essentially preferred as the communication method for the 5 Cuba Diper, which carries an air cylinder on its back and does not require a lifeline. Of course. Unlike in the air, electromagnetic waves and light cannot be used as communication means in water, and ultrasonic waves (or sound waves) are usually used as the wave motion.

When considering wireless communication using ultrasonic waves for a 5ucba Diaper, the man-machine interface between the human and the transmitting/receiving device (because the person is holding a mouthpiece for inhaling air from a cylinder, it is difficult to speak freely). Conventionally, a helmet that covers the entire head is used, air is supplied into the helmet, a microphone is placed near one lip, and earphones are placed near both ears. The method used is implemented. Another method was to supply air to the face using a face mask that covers only the face rather than the entire head, and to use a lip microphone and bone conduction earphones.

However, in the former case, a helmet is required, which is bulky and inconvenient, and in the latter case, there is a risk of water entering through the gap between the mask and the face, making it impossible to move the jaw sufficiently. be. In any case,
This method was very dangerous because it caused fear in the diapers.

In order to solve the above-mentioned problems, the present applicant previously proposed an underwater communication system that can be carried by 5CUBA Dipers and perform wireless communication between 5CUBA Dipers or between 5CUBA Dipers and a mother ship. (Gan Sho 61-285349). This underwater communication system has a switch at the transmitting end that can operate in multiple modes in all directions, outputs the sound corresponding to the switch input from a sound synthesis circuit that stores in advance, and converts this signal into analog modulation to generate an ultrasonic signal. The receiving section demodulates the ultrasonic signal and outputs an audio signal.

Purpose The present invention is an improvement on the underwater communication system previously proposed by the above applicant, and is particularly aimed at providing a signal detection system that can reduce the influence of underwater noise. .

In order to achieve the above object, the present invention provides an underwater communication system in which a transmitter transmits an ultrasonic signal analog-modulated with an audio signal, and a receiver demodulates the ultrasonic signal to output an audio signal. , a device for determining the level of a signal, a first timer for determining detection of the signal, and a second timer for determining the end of the signal.

Hereinafter, the present invention will be explained based on examples.

FIG. 1 is an electrical block diagram for explaining an example of an underwater communication device as an example of a device to which the signal detection method according to the present invention is applied. In the figure, 1 is an input switch, 2 is an encoder, 3 is an is a speech synthesis circuit, 4 is a modulation circuit, 5 is a power amplifier, 6 is a circulator, 7 is a transducer, 8 is a preamplifier, 9 is a demodulation circuit, 10 is a decoder, 1
1 is a bone conduction earphone, 12 is a judgment circuit, a human power switch 1 is attached to the arm of the dialer, etc., and a corresponding code is output from the encoder circuit 2 to the output circuit 3 of the audio stand 1 by operating the switch corresponding to a command. . The voice synthesis output circuit 3 reads out the corresponding pre-recorded voice data from the ROM, performs D/A conversion, and sends it to the modulation circuit 4 as an analog voice output. As a voice synthesis method, there is a method that uses PCM data, but there is also a method that uses PCM data.

By using data compressed using the ADPCM method or the Percoll method, the capacity of the ROM for recording audio data can be reduced. The modulation circuit 4 subjects this signal to AM modulation, for example, the signal is amplified by the power amplifier 5, and the ultrasonic signal is transmitted through the circulator 6 and from the ultrasonic transducer 7 into the water as analog audio data.

In the receiving section, the signal received by the ultrasonic transducer 7 is input to the preamplifier section 8 via the circulator 6 and amplified. After the signal is detected by the demodulation circuit 9, it is amplified by the power amplifier 10, and the dialer can listen to this signal using the bone conduction earphone 11.

In order to cope with amplitude fluctuations of the ultrasonic signal underwater, AGC (automatic gain control) is applied to the preamplifier section 8 from the demodulation circuit 9 in order to stabilize the demodulated output. Furthermore, when the signal level exceeds a specified value, the demodulation circuit 9 sends out a carrier detection signal and inputs it to the determination circuit 12. Judgment circuit 12
When it is determined that a signal has been input, the power amplifier control signal C is turned on, the power amplifier 10 is operated, and an audio signal is output. When the determination circuit 12 determines that the signal has ended, the power amplifier 10 is turned off to prevent the generation of unnecessary noise such as underwater noise.

FIG. 2 is a diagram schematically showing an example of an ultrasound signal waveform, and this diagram shows AM modulation. As for the ultrasonic frequency, for example, a signal of 50 KHz is used as a carrier. An unmodulated signal of a prescribed length is sent out in order to pull in the AGC before generating the audio signal, but this length only needs to be sufficiently longer than the time required to pull in the AGC.

FIG. 3 is a diagram showing the output waveform of the preamplifier 8, which shows that AGC pull-in is performed in the portion before the voice section. Note that FIG. 4 schematically shows the output waveform of the power amplifier 10.

5 is an electrical block diagram for explaining an example of the determination circuit 12 shown in FIG. 1, and FIG. 6 is a time chart for explaining the operation of the circuit shown in FIG. , 20
is an ON detection circuit, 21 is a first timer, 22 is a first comparison circuit, 23 is an FF detection circuit, 24 is a second timer,
25 is a second comparison circuit, 26 is a control signal generation circuit, and when the level of the input signal shown in FIG. 6(a) becomes higher than a specified level, a carrier detection signal (b) is inputted;
When the first timer 21 is started and the carrier detection signal (b) continues longer than the first timer time (T1), the first comparison circuit 22 determines that the signal has been detected and the power amplifier control signal Turn on (c) and start outputting audio. When the carrier detection signal (b) turns OFF in a time shorter than the time of the first timer 21, the first timer 2
Reset 1.

If the level of the input signal becomes lower than the specified level after starting audio output, the carrier detection signal (b) becomes O
becomes FF and starts the second timer 24. When the carrier detection signal (b) remains OFF for a period longer than the time (T2) of the second timer 24, the second comparison circuit 25 determines that the signal is disconnected, and sets the power amplifier control signal (c) to 0FFL,
Interrupt audio output. If the level of the input signal becomes higher than the specified level again in a time shorter than the time of the second timer 24 and the carrier detection signal (b) is turned on, the second timer 21 is reset and the audio output is Do not interrupt.

7 is an electrical block diagram for explaining another example of the determination circuit 12 shown in FIG. 1, and FIG. 8 is a time chart for explaining the operation of the circuit shown in FIG. In the figure, the same reference numerals as in the case of FIG. 5 are given to parts having the same function as in the example shown in FIG. Therefore, in this example,
The method for turning on the power amplifier control signal (c) is the same as the example shown in FIG. 5, but the method for turning it off is different from the example shown in FIG. In this example, after starting audio output, the level of the input signal (a) becomes lower than the specified level, and the carrier detection signal (b) becomes OF.
When F is reached, the second timer 24 is activated, the power amplifier control signal (c) is changed to FFL, and the output of the audio is interrupted. The carrier detection signal (b) is detected by the second timer 24
When it is turned on again in a shorter time than the
Determining that a short signal interruption has occurred, the second comparator circuit 25 turns the power amplifier control signal (c) ON again, resumes audio output, and resets the second timer 24. If the carrier detection signal (b) remains OFF for a time longer than the time set by the second timer 24, it is determined that the signal has ended.

Note that in the above description, an example of AM modulation is used as a modulation method, but an FM modulation method may also be used.

It is also possible to perform software processing of these operations using a μCPU or the like. Furthermore, in the embodiment shown above, the same transducer was used for transmission and reception by connecting the transmitting section and the receiving section with a circulator, but it is easily possible to use two transducers for transmitting and receiving separately. I can understand.

As is clear from the above description, according to the present invention, it is possible to prevent unnecessary noise from being output due to underwater noise etc. in underwater communication, and furthermore, even if a temporary drop in signal level occurs, The effect on audio output can be reduced.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining an example of an underwater communication device as an example of a device to which a determination circuit according to the present invention is applied, FIG. 2 is a diagram showing an example of an ultrasonic signal waveform, and FIG. 3 is a diagram showing an example of an ultrasonic signal waveform. , FIG. 4 is a diagram showing an example of the output waveform of the power amplifier 10, FIG. 5 is a diagram showing an example of the determination circuit shown in FIG. 1, and FIG. 5 is a time chart for explaining the operation of FIG. 5, FIG. 7 is a diagram showing another example of the 1 judgment circuit, and FIG. 8 is a time chart for explaining the operation of the circuit of FIG. 7. It is. 1...Input switch, 2...Encoder, 3...
Speech synthesis circuit, 4... Modulation circuit, 5... Power amplifier, 6... Circulator, 7... Transducer, 8... Preamplifier, 9... Demodulation circuit, 10...
·Power Amplifier. 11... Bone conduction earphone, 12... Judgment circuit, 2
0...ON detection circuit, 21...first timer, 22...
...First comparison circuit, 23..OFF detection circuit, 24.
...Second timer, 25...Second comparison circuit, 26.
...Control signal generation circuit. Patent Applicant Ricoh Co., Ltd. Agent Takano Yobe (j;J,",,1!1',':,
1,''r

Claims (4)

[Claims] (1) In an underwater communication system in which a transmitting section sends out an ultrasonic signal analog-modulated with an audio signal, and a receiving section demodulates the ultrasonic signal and outputs an audio signal, means for determining the level of the signal; the first to determine the detection of a signal;
1. A signal detection method comprising: a timer; and a second timer for determining the end of a signal. (2) When the level of the input signal is higher than a prescribed level and continues longer than the time of the first timer, it is determined that a signal has been detected and output of audio is started. The signal detection method described in section (1). (3) After starting audio output, when the level of the input signal is lower than a specified level and continues longer than the time of the second timer, it is determined that the signal has ended and the audio output is interrupted;
Claim 1 (1) characterized in that the audio output is not interrupted when the level of the input signal is again higher than the prescribed level in a time shorter than the time of the second timer.
) or (2). (4) After starting audio output, when the level of the input signal is lower than the specified level and continues longer than the second timer time, it is determined that the signal has ended and the audio output is interrupted, and the second Claim (1) or (1) characterized in that the audio output is restarted when the level of the input signal is higher than the predetermined level again in a time shorter than the time of the timer. The signal detection method described in section 2).