JPH0677890A - Voice reception circuit - Google Patents

Abstract

PURPOSE:To prevent cutting of a speech head in the mobile body voice communication using a satellite channel. CONSTITUTION:The circuit is provided with a timing detection circuit 102 outputting a frame pulse when an SOM (message start) and a UW(unique word) are detected from a base band signal obtained with an IF(intermediate frequency) signal demodulated by a demodulation circuit 101 and outputting an SOM pattern when the SOM is detected, a SOM decode circuit 103 decoding at which a sub-frame is started for the burst signal from the given SOM pattern and outputting the result in one-bit or plural bits, and a base band processing circuit 104 synchronizing a frame timing with a reception signal after the UW for a given frame pulse at the time of UW detection or at a timing of the result of SOM detection for a given frame pulse at the time of SOM detection so as to recognize a head of VOICE DATA just after the SOM and a head of the VOICE DATA just after the UW.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for receiving voice from a mobile satellite in a mobile satellite communication system. TECHNICAL FIELD The present invention relates to a voice receiving circuit capable of preventing disconnection of a talk in mobile voice communication using a satellite line.

[0002]

2. Description of the Related Art In voice communication using a mobile satellite communication system, a burst signal is output from a transmitting side by using a method usually called voice activation. Therefore, in the transmission circuit, the preamble (hereinafter referred to as PREAMBLE) is added to the transmission signal so that the reference carrier can be reproduced in the reception circuit.
), And a unique word (hereinafter referred to as UW) must be added so that frame synchronization can be established.

A conventional voice receiving circuit for demodulating an IF (intermediate frequency) signal obtained by modulating such a signal is shown in FIG.
And it demonstrates using FIG. However, the IF in FIG. 3 is a signal in which an analog audio signal is encoded into a digital audio signal (hereinafter referred to as VOICE DATA)
It is a signal obtained by modulating a signal to which LE and UW are added (401 and 402 in FIG. 4), and one frame of 401 and 402 is composed of a plurality of subframes, and burst is also performed in units of this subframe. .

The frame format described above is the PRE.
The relationship between AMBLE and UW is always the same. The one in which the position of the UW changes depending on the subframe in which the burst starts (in this case, it always becomes like 401 in FIG. 4) is most often used, but recently the burst is cut A frame format in which the position of the UW is fixed during communication is also used so that frame synchronization can be maintained even in the case of communication. In this case, since a frame such as 402 in FIG. 4 is also formed, it is necessary to add SOM at the end of PREAMBLE. It is assumed that in the frame formats handled thereafter, the latter UW position is always fixed.

A signal IF of 401 or 402 shown in FIG. 4 is demodulated by a demodulation circuit 301 and a baseband signal D1 is given to a baseband processing circuit 303 and a timing detection circuit 302. When the signal D1 is input, the timing detection circuit 302 first detects the SOM in PREAMBLE at the beginning of the burst (when the frame format is 402), and the PRE of the signal D1 is detected.
The frame pulse FR1 is output at the beginning of VOICE DATA immediately after AMBLE. When UW is further detected after that, VOICE DATA immediately after UW of the signal D1 is detected.
The frame pulse FR2 is output at the beginning of the frame pulse, and the frame pulses FR1 and FR2 are the baseband processing circuit 3
It is input to 03. When SOM is not detected (when the input signal is 401), only the frame pulse FR2 is 303
Give to.

In the baseband processing circuit 303, the PRE
Immediately after AMBLE, the beginning of VOICE DATA, and U
It is recognized that the beginning of VOICE DATA immediately after W is the frame pulses FR1 and FR2, respectively, and the signal D1 is subjected to the baseband processing necessary for VOICE DATA, and the signal D2 shown in FIG. 3 is output. Also, frame synchronization is established only when the frame pulse FR2 is given, and VOICE DA immediately after PREAMBLE is established.
The frame pulse FR3 shown in FIG. 3 is output at the timing of the beginning of TA and the beginning of VOICE DATA immediately after UW.

[0007]

In the case of such a frame fort, the position of the frame is fixed even if the input signal of the receiving circuit disappears, but the frame position shifts after a few frames and the frame synchronization is lost. It may come off. Therefore, it is necessary to transmit a dummy burst for correcting this frame position deviation from the transmitting side every few frames. Once frame synchronization is established by this dummy burst, frame synchronization is always maintained until communication is cut off.

However, when the dummy burst cannot be received by the receiving circuit due to some trouble (for example, shadowing), it is necessary to establish the frame synchronization again, and further, the VO transmitted until the frame synchronization is established.
Since correct baseband processing is not performed for ICE DATA, when the output signal of this receiving circuit is converted into voice, the first part (A part 402 in FIG. 4) is interrupted (this is the beginning of the sentence). There is a drawback).

The present invention solves such a problem, and an object of the present invention is to provide a circuit capable of preventing disconnection of the talk head in mobile voice communication.

[0010]

According to the present invention, there is provided a demodulation circuit for demodulating an intermediate frequency (IF) signal in which a burst signal using a voice activation system is modulated and outputting it as a baseband signal, and a baseband signal for the demodulation circuit. When the message start (SOM) is received and the first frame pulse is output at the timing immediately after that, and when the unique word (UW) is detected, the second frame pulse is output at the timing immediately after that. And a baseband processing circuit that outputs a baseband signal and a frame pulse by performing predetermined baseband processing when receiving the first frame pulse and the second frame pulse. And means for outputting a message start (SOM) pattern to the timing detection circuit Wherein, the message start (SO
M) A pattern is input, the sub-frame is decoded from which the burst signal starts, and the result is output to the baseband processing circuit. An SOM decoding circuit is provided. It is characterized by including means for synchronizing the frame timing with the received signal at the timing of the first frame pulse.

One frame consists of N subframes, and each frame has a message start (S) which has a different pattern depending on which subframe the burst starts.
OM) is preferably added to the end of the preamble, a unique word (UW) for establishing frame synchronization, and voice data in which voice is digitally encoded.

[0012]

The demodulation circuit demodulates the IF signal obtained by modulating the burst signal based on the voice activation system, and outputs it to the baseband processing circuit, the timing detection circuit, and the SOM decoding circuit as a baseband signal. When detecting the SOM from the baseband signal, the timing detection circuit outputs the first frame pulse to the baseband processing circuit at the timing immediately after the SOM, outputs the SOM pattern to the SOM decoding circuit, and further, When the unique word (UW) is detected, the second frame pulse is output to the baseband processing circuit.
The SOM decoding circuit decodes from which subframe the burst signal starts from the input SOM pattern, and outputs the result to the baseband processing circuit with one or more bits. When the first frame pulse is input, the baseband processing circuit synchronizes with the received signal at the timing according to the decoding result, and when the second frame pulse is input, synchronizes with the received signal at the timing.

As described above, the SOM pattern is changed on the transmitting side according to which subframe the burst frame input to the receiving circuit starts, and the SOM pattern is changed on the receiving side.
By decoding the pattern, the frame timing can be synchronized with the received signal at the beginning of the voice data immediately after the preamble, and correct baseband processing can be performed from the beginning of the burst frame without a dummy burst for frame position correction.

[0014]

Embodiments of the present invention will now be described with reference to the drawings. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG.
FIG. 3 is a diagram showing a structure of a frame format in the embodiment of the present invention.

In the embodiment of the present invention, the demodulation circuit 10 which demodulates the IF signal in which the burst signal using the voice activation method is modulated and outputs it as the baseband signal D1.
1 and when the baseband signal D1 is received and SOM is detected, the first frame pulse FR1 is output at the timing immediately after that, and when the unique word UW is detected, the second frame is output at the timing immediately after that. Frame pulse F
Timing detection circuit 102 for outputting R2, first frame pulse FR1 and second frame pulse FR2
And a baseband processing circuit 104 that outputs a baseband signal D2 and a frame pulse FR3 when a predetermined baseband processing is performed. Further, as a feature of the present invention, the timing detection circuit 102 is provided with an SOM pattern. The baseband processing circuit 10 includes a means for outputting, inputs this SOM pattern, decodes from which subframe the burst signal starts, and decodes the result.
4, and the baseband processing circuit 104 includes means for synchronizing the frame timing with the received signal at the timing of the first frame pulse FR1 according to the decoding result.

One frame consists of N subframes, and each frame has a different pattern S depending on from which subframe the burst starts, as shown in FIG.
It consists of PREAMBLE with OM added at the end, a unique word UW for establishing frame synchronization, and VOICE DATE in which voice is digitally encoded.

Next, the operation of the embodiment of the present invention thus constructed will be described. However, the IF signal in FIG. 1 is a signal obtained by adding a PREAMBLE and UW to a signal obtained by encoding an analog audio signal into a digital audio signal, and FIG.
201 and 202 shown in FIG.
1 and 202, one frame consists of a plurality of subframes, and the burst is also performed in units of this subframe. Also, after PREAMBLE in 202, SO
M is added, and this SOM changes according to a certain rule depending on from which subframe the burst starts, and the UW position is always fixed.

The IF signal is demodulated in the demodulation circuit 101, and the demodulation circuit 101 converts the baseband signal D1 into the baseband processing circuit 104, the timing detection circuit 102,
And to the SOM decoding circuit 105. When the signal D1 is input, the timing detection circuit 102 first detects the SOM in PREAMBLE at the beginning of the burst, and detects the VOICE D immediately after PREAMBLE of the signal D1.
A frame pulse FR1 is output at the beginning of ATA, and the detected SOM pattern S1 is given to the SOM decoding circuit 103. After that, when UW is further detected, signal D1
The frame pulse FR2 is output in synchronization with the beginning of VOICE DATA immediately after the UW of, and the frame pulses FR1 and FR2 are input to the baseband processing circuit 104.

When the SOM is not detected (when the input format shown in FIG. 2 is 401), the frame pulse FR2
Only the signal is input to the baseband processing circuit 104. SOM
When the decoding circuit 103 is given the SOM pattern S1, it detects from which subframe this burst frame started, and the detection result is given to the baseband processing circuit 104 by one or a plurality of bits DEC. In the baseband processing circuit 104, first, when the frame pulse FR1 is input at the beginning of the burst, the internal frame counter is loaded with a value corresponding to this subframe by the information of one or more bits DEC, and the frame pulse FR1 The frame timing is synchronized with the received signal at the timing.

Next, when the received signal is continuously input after the burst start, the internal frame counter is loaded to the initial value at the timing of the frame pulse FR2 to synchronize the frame timing with the received signal. And PRE
The beginning of VOICEDATA immediately after AMBLE, and U
It is recognized that the heads of VOICE DATA immediately after W are the frame pulses FR1 and FR2, respectively.
The necessary baseband processing is performed on CE DATA, and as a result, the signal D2 is output. Furthermore, as a frame pulse, VOICE DATA immediately after PREAMBLE
, And the frame pulse FR3 is output at the timing of the beginning of VOICE DATA immediately after UW.

[0021]

As described above, according to the present invention, the SOM pattern is changed on the transmitting side depending on which subframe the burst frame input to the receiving circuit starts.
On the receiving side, by decoding this SOM pattern, the frame timing can be synchronized with the received signal at the beginning of VOICE DATA immediately after PREAMBLE, and correct baseband processing can be performed from the beginning of the burst frame without dummy burst for frame position correction. There is an effect that can be done.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a configuration of a frame format in the embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional example.

FIG. 4 is a diagram showing a configuration of a frame format in a conventional example.

[Explanation of symbols]

 101, 301 Demodulation circuit 102, 302 Timing detection circuit 103 SOM decoding circuit 104, 303 Baseband processing circuit

Claims (2)

[Claims] 1. A demodulation circuit for demodulating an intermediate frequency (IF) signal in which a burst signal using a voice activation method is modulated and outputting as a baseband signal, and a message start (SO) for receiving this baseband signal.
M) is detected, a first frame pulse is output at a timing immediately after that, and a second frame pulse is output at a timing immediately after that when a unique word (UW) is detected. In the voice receiving circuit including a baseband processing circuit that performs a predetermined baseband process and outputs a baseband signal and a frame pulse when receiving the first frame pulse and the second frame pulse, the timing detection Start message on the circuit (SOM)
A SOM decoding circuit is included, which includes means for outputting a pattern, receives this message start (SOM) pattern, decodes from which subframe the burst signal starts, and outputs the result to the baseband processing circuit. The baseband processing circuit includes means for synchronizing a frame timing with a received signal at the timing of the first frame pulse according to a decoding result. 2. One frame is composed of N subframes, and each frame has a message start (S) with a different pattern depending on which subframe the burst starts.
The voice receiving circuit according to claim 1, wherein the voice receiving circuit comprises a preamble added with OM) at the end, a unique word (UW) for establishing frame synchronization, and voice data in which voice is digitally encoded.