JPH04311117A - Voice signal communication system - Google Patents

Abstract

PURPOSE:To reproduce a voice signal without generating cut off of the head of speaking on the receiving side at the time of switching transmission by transmitting coded voice signal after applying a delay equipment to a time required for synchronization establishment to the coded voice signal on the transmitting side. CONSTITUTION:A voice signal digitally coded by a coding circuit 2 is temporarily stored in a memory buffer circuit 5, and after the lapse of a delay time previously set by a delay time setting circuit 6 the stored voice signal is sent to a modulator 7. A synchronizing flag signal is inserted into the delay time. The synchronizing flag signal indicates the start of the coded voice signal after the lapse of a prescribed time from the end of the signal. The transmitting signal modulated by the modulator 7 is sent to an output amplifier 8 and power- amplified and the amplified signal is radiated from an antenna 9 to air. Since the output of the coded voice signal is delayed on the transmitting system side A only by the time required for the synchronization establishment on the receiving system side B, the voice signal can be reproduced without generating cut off of the head of speaking on the receiving system side B.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio signal communication system for transmitting digitally encoded audio signals by radio telephone, satellite communication, etc.

0002

2. Description of the Related Art Conventionally, audio signals in wireless communication have been transmitted using modulation techniques such as AM modulation and FM modulation. In recent years, with the development of digital signal transmission technology, wireless communication that digitally encodes and transmits audio signals has also come into use.

However, in the case of communication systems that transmit modulated waves only during calls, such as the press-talk system or voice control, when the transmitting side shifts from the receiving state to the transmitting state, the demodulation and coding of the modulated signal on the receiving side is It takes time to reproduce the synchronization signal. In this case, truncations at the beginning of the audio signal often occur. For this reason, for example, in the press talk system, it is necessary to start the conversation after a certain break period after the press talk.

0004

[Problems to be Solved by the Invention] As described above, in the conventional voice signal communication system, it takes time to demodulate the modulated signal and reproduce the coded synchronization signal, and the disadvantage is that the beginning of the voice signal is cut off. was there.

[0005] This invention was made to solve the above-mentioned drawbacks, and an object of the present invention is to provide an audio signal communication system that can reproduce audio signals without cutting off the beginning of speech on the receiving side when switching transmission. do.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an audio signal communication system that transmits and receives digitally encoded audio signals. a transmission delay means that applies a delay equivalent to the time required for establishment to the encoded audio signal before transmitting it; and a synchronization means that establishes synchronization of the received signal within the delay time when switching from the transmission state to the reception state. It is composed of:

[0007]

[Operation] In the audio signal communication system with the above configuration, the time required for establishing synchronization on the transmitting side and on the receiving side is
Since the output of the encoded audio signal is delayed,
On the receiving side, synchronization is established before the beginning of a speech, thereby making it possible to reproduce the audio signal without cutting off the beginning of a speech.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 shows its configuration, where A is a transmitting system and B is a receiving system.

In the transmission system A, the audio signal input from the microphone 1 is sent to an encoding circuit 2 such as PCM or ADPCM, where it is digitally encoded. When starting a call (when switching from receiving state to transmitting state), press voice control switch 3 or press talk switch 4.
is set to the on state, and a transmission switching signal is generated.

The audio signal digitally encoded by the encoding circuit 2 is temporarily stored in the memory buffer circuit 5, and is sent to the modulator 7 after a delay time preset by the delay time setting circuit 6 has elapsed. At this time, a synchronization flag signal is inserted within the delay period. This synchronization flag signal indicates that the encoded audio signal will start a predetermined time after the end of the synchronization flag signal. The transmission signal modulated by the modulator 7 is sent to the output amplifier 8, where the power is amplified and radiated into the air from the antenna 9. The delay time setting circuit 6, modulator 7, and output amplifier 8 are switched to a transmission mode by a transmission switching signal.

In receiving system B, a received signal captured by an antenna 10 is amplified by a low noise amplifier (LNA) 11 and then demodulated by a demodulator 12. This demodulated signal is sent to the separation circuit 13. This separation circuit 13 separates the input demodulated signal into a synchronization flag signal part and a digital audio signal part.The synchronization flag signal is sent to the synchronization circuit 14, and the digital audio signal is converted into an analog format by a decoder 15. Ru. At this time, the decoder 15
4, the conversion clock and the digital audio signal are synchronized. The output of the decoder 15 is the audio reproduction circuit 1
6 and is played back acoustically. The operation of the above configuration will be described below with reference to FIG.

Now, assume that the transmission system A is instructed to start transmission, and an audio signal as shown in FIG. 2(a) is input from the microphone 1. This audio signal is converted by the encoding circuit 2 into a pulse train digitally encoded signal as shown in FIG. 2(b), and is stored in the memory buffer circuit 5.

On the other hand, at the start of transmission, the press talk switch 4 is turned on, or the voice control switch 3 is turned on when inputting a voice signal starts, thereby generating a transmission start signal. By this transmission start signal, the delay time setting circuit 6, modulator 7, and output amplifier 8 are switched to the transmission mode.

The audio signal digitally encoded by the encoding circuit 2 is temporarily stored in the memory buffer circuit 5, as shown in FIG.
As shown in (c), the data is read out after the delay time Td preset by the delay time setting circuit 6 has elapsed. At this time, a synchronization flag signal is inserted within the delay period Td as shown in the figure.

[0015] The encoded signal delayed as described above is modulated by a modulator 7 and placed on a carrier wave to become a transmission signal, as shown in FIG. 2(d). This transmission signal is power amplified by an output amplifier 8 and radiated into the air from an antenna 9.

Therefore, in the audio signal communication system having the above configuration, the output of the encoded audio signal is delayed on the transmitting system A side by the time required for establishing synchronization on the receiving system B side. It is possible to reproduce the audio signal without cutting off the beginning of the speech. At this time, the transmitting system A side inserts a synchronization flag signal within the delay time, the receiving system B side separates the synchronization flag signal from the demodulated signal, and detects the end point of the signal. Signal synchronization can be established without delay.

[0017] As means for realizing delay of the encoded signal,
A register may be used instead of the memory buffer circuit 5, and the delay time setting circuit 6 may delay the start of transfer clock input by a set time Td. Furthermore, it goes without saying that the delay time setting circuit 6 may be set by software using a microprocessor and may be functionally equivalent.

[0018] Regarding the above-mentioned delay time Td, a certain audio frame time unit (for example, 20 ms) or more is required, but in order to further conceal the audio signal, 100 ms is required.
Synchronization with some degree of delay may be required. Even in such a case, if the delay time is several 100 ms or less including the demodulation circuit, it can be operated without any practical problems and is extremely effective.

[0019]

As described above, according to the present invention, it is possible to provide an audio signal communication system in which an audio signal can be reproduced without cutting off the beginning of a speech on the receiving side during transmission switching.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an audio signal communication system according to the present invention.

FIG. 2 is a waveform diagram for explaining the operation of the transmission system of the same embodiment.

[Explanation of symbols]

A... Transmission system, B... Receiving system, 1... Microphone, 2... Encoding circuit, 3... Voice control switch, 4... Press talk switch, 5... Memory buffer circuit, 6... Delay time setting circuit, 7... Modulator, 8... Output amplifier, 9... Antenna, 10... Antenna, 11... Low noise amplifier, 12... Demodulator, 13... Separation circuit, 14... Synchronization circuit, 15... Decoder, 16... Audio reproduction circuit.

Claims (2)

[Claims] Claim 1: In an audio signal communication system that transmits and receives digitally encoded audio signals, when switching from a receiving state to a transmitting state, a delay equivalent to the time required to establish synchronization on the transmitting side is applied to the encoded audio signal. 1. An audio signal communication system comprising: a transmission delay means for transmitting a received signal after the signal is received; and a synchronization means for establishing synchronization of a received signal within the delay time when switching from a transmission state to a reception state. 2. The audio signal according to claim 1, further comprising synchronization flag signal insertion means for inserting a synchronization flag signal indicating a start position of the encoded signal within a delay period of the encoded audio signal. Communications system.