JP2525103B2 - FM multiplex broadcast receiver - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FM multiplex broadcasting receiver, and more particularly to a mobile FM multiplex broadcasting receiver having a data structure in which one frame is composed of a plurality of data blocks (packets).

[0002]

2. Description of the Related Art In mobile FM multiplex broadcasting, one frame of data is composed of a plurality of data blocks, and a sync signal (fleming code) is not present only at the beginning of the frame as in the prior art, but each Four types of block identification codes (BIC) that act as synchronization signals are added to the beginning of the data block. Therefore, in the mobile FM multiplex broadcast receiver, as shown in FIG. 2, the frame synchronization is obtained by detecting the change point of the block identification code. That is, the block identification code is as shown in FIG.
There are four types of BIC1 to BIC4 as shown in, and BIC4 → BIC1 and BIC1 → BIC3 during one frame.
There are four transition points, BIC4 → BIC2 and BIC2 → BIC3. The position of the block data in the frame can be known by detecting this change point, and frame synchronization can be achieved by setting the frame counter to an appropriate value.

[0003]

As described above, in frame synchronization, the value of the frame counter is set to an appropriate value in accordance with the change point detected by the block identification code,
It is performed by incrementing the frame counter by the block synchronization signal. For this purpose, it is first necessary for the blocks to be synchronized. Otherwise,
The value of the frame counter is set to a different value,
This is because counting up more than necessary can occur.

Here, a particular problem is when the block synchronization enters a non-synchronized state, which is lost due to deterioration of the reception state or the like. At this time, the conventional FM multiplex broadcast receiver 1
Then, as shown in FIG. 3, the block counter 3 is reset in response to the block identification code detected by the BIC detection circuit 2 from the input data to try to synchronize the blocks. When the output of the block counter 3 which outputs the block synchronization signal is delayed from the accurate timing, as shown in FIG. 4, a section where there is no block synchronization signal occurs between about two blocks. Therefore, when the frame counter 4 is caused to count using the output of the block counter 3, the value of the frame counter 4 becomes one less than the originally supposed value, and there is a problem that frame synchronization is lost. Further, some block identification codes detected after the block synchronization is lost are erroneously detected due to the same pattern that happens to be present in the data, and the value of the frame counter 4 is increased until the block synchronization becomes the synchronization state again. May be an even more incorrect value.

Therefore, a main object of the present invention is to provide an FM multiplex broadcasting receiver in which the value of the frame counter becomes an accurate value even if the block synchronization is lost.

[0006]

According to the present invention, there is provided an FM multiplex broadcast receiver for receiving data in which one frame is composed of a plurality of data blocks in which a block identification code is added to the beginning of each block. A first counter, which is reset in response to the identification code and is stepped by a clock signal synchronized with the input data, and outputs a first block synchronization signal when the block synchronization of the input data is achieved, the first block synchronization A second counter reset in response to a second block synchronization signal obtained based on the signal and the count value of the signal itself and stepped by the clock signal; and a second counter receiving the count value of the second counter. A timing signal generation circuit for generating a block synchronization signal, and a first block synchronization signal and a second block Characterized in that it comprises a third counter which is incremented by at least one of the signals, FM
It is a multiple broadcast receiver.

[0007]

In the above prior art, when the output of the block counter is delayed, the count of the frame counter is counted by using both the block counter output and the block identification code separated from the input data as the count signal of the frame counter. Although it is possible to maintain the value accurately, conversely, when the output of the block counter is advanced, this causes a problem that the count value of the frame counter is excessively advanced. Further, as described above, since the block identification code separated from the input data has a false signal detected by the same pattern that happens to exist in the data, the block identification code can be directly used as the count signal of the frame counter. Has a problem.

Therefore, in the present invention, a first counter for block synchronization and a second counter for generating a signal for incrementing the frame counter, which is a third counter, are separately provided, and The first counter outputs the first block synchronization signal to the second counter when the block synchronization with the input data is achieved, and the second counter outputs the first block synchronization signal output from the first counter or It is reset by the second block synchronization signal generated by the timing signal generation circuit based on the output of the second counter itself. On the other hand, if the second counter is ahead of the normal timing as the step count signal of the frame counter, which is the third counter, only the second block synchronization signal from the timing signal generation circuit is used. When the second counter is behind the normal timing, the first block synchronization signal output from the first counter is used together with the second block synchronization signal.

[0009]

According to the present invention, since the first counter for block synchronization and the second counter for generating the count signal of the third counter (frame counter) are separately provided, the block synchronization is achieved. The first one when it comes off
It is possible to prevent the influence of the disturbance of the counter of the above from affecting the count value of the frame counter. Further, even if the block synchronization is once lost and the synchronization state is re-entered, the first block synchronization signal of the first counter may be used as the count signal of the frame counter depending on the advance or delay of the second counter. By controlling not to use it, the count value of the frame counter can always be maintained at a normal value.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the detailed description of the embodiments below with reference to the drawings.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An FM multiplex broadcast receiver 10 of the embodiment shown in FIG.
Has terminals 12 and 14, and received data (input data) is inputted to the terminal 12 and a clock signal synchronized therewith is inputted to the terminal 14. The BIC detection circuit 16 detects four types of block identification codes included in the input data as shown in FIG. BIC detection circuit 16
Detection signal is supplied to the synchronization detection circuit 18, and the synchronization detection circuit 18 outputs the first detection signal from the first counter 20.
Block synchronization control is performed between the block synchronization signal of 1) and the detection signal from the BIC detection circuit 16. First counter 2
0 is reset by the reset signal from the synchronization detection circuit 18 and is advanced by the clock signal supplied from the terminal 14. That is, if it is determined that the detection signal output from the BIC detection circuit 16 and the first block synchronization signal output from the counter 20 are asynchronous,
The synchronization detection circuit 18 resets the counter 20 in response to the detection signal from the BIC detection circuit 16.

Further, a synchronization state signal indicating the synchronization state of block synchronization is supplied from the synchronization detection circuit 18 to the AND circuit 22, and the AND circuit 22 also receives the counter 20.
The first block sync signal from Therefore, when the block synchronization is in the synchronization state (because the synchronization state signal becomes high level), the AND circuit 22 causes the counter 20 to
The first block synchronization signal, which is the output of, is output as it is. As the count input signal of the second counter 24,
As with the first counter 20, the clock signal from the terminal 14 is applied. The output of the counter 24 is given to the timing signal generating circuit 26, and the timing signal generating circuit 26 generates various timing signals based on the output of the counter 24. This timing signal generation circuit 2
The second counter 24 is fed by either the second block synchronization signal fed back from 6 or the output of the AND circuit 22 described above, that is, the first block synchronization signal.
Is reset.

The timing signal generation circuit 26 further includes
In addition to generating other control signals, it also generates a gate signal indicating the degree of delay or advance of the synchronization timing between the counter 24 and the input data. This gate signal is the counter 2
For example, when the value of 4 is in the first half of the total block count number, it is a low level signal, and in the latter half, it is a high level signal. The gate signal is supplied to another AND circuit 28. The above-mentioned AN is applied to the other input of the AND circuit 28.
The output signal of the D circuit 22 is given, and
When the gate signal is at high level, the AND circuit 28 outputs A
The output signal from the ND circuit 22, that is, the first block synchronizing signal is gated and given to the OR circuit 30. This is because when the first block synchronization signal is supplied from the AND circuit 22 when the count value of the counter 24 is in the first half of the total block count number, the timing of the counter 24 advances with respect to the input data. If the second block synchronization signal is supplied from the AND circuit 22 when the count value of the counter 24 is in the latter half of the total block count number, the timing of the counter 24 becomes the input data. This is because it can be judged that it is behind.

In this way, the output signal (first block synchronizing signal) of the AND circuit 22 gated by the AND circuit 28 and the timing signal (second block) generated by the counter 24 and the timing signal generating circuit 26 (second block). The count input signal of the frame counter 32, which is the third counter, is ORed with the synchronization signal). The frame counter 32 supplies a change point signal indicating the BIC change point to the synchronization detection circuit 18, and accordingly, the synchronization detection circuit 1
In 8, the frame synchronization control is performed with the change point detected from the output of the BIC detection circuit 16. That is, BIC
When it is determined that the change point detected by the detection circuit 16 and the change point output from the counter 32 are asynchronous, the synchronous detection circuit 18 supplies the load signal and the load count value to the counter 32 to set the counter 32 to a predetermined value. Set to the value of.

Received data (input data) and counter 20
In a normal state in which the AND circuit 22 is synchronized with
The block synchronization signal output from the block synchronization signal and the block synchronization signal fed back from the timing signal generation circuit 26 are completely coincident in timing. However, once the synchronization is lost, the counter 20 and the counter 24 are in an asynchronous operation state. At this time, since the output of the AND circuit 22 is in the asynchronous state, the block synchronization signal is not output, and the counter 24 self-runs by the second block synchronization signal generated by itself. During this period, the counter 20 enters the synchronous capturing operation with the input data, and as described above, the irregular block synchronizing signal is output to the output of the counter 20. The unstable sync signal is not supplied to the counter 24.

Then, when the synchronization with the input data is restored thereafter, the correct first block synchronization signal with the synchronized state restored is output to the output of the AND circuit 22. At this time, if the timing relationship with the second block synchronization signal generated by the counter 24 which has been running until then is deviated, the AND circuit 28 is controlled by the gate signal from the timing signal generation circuit 26. Thus, the count value of the frame counter 32 can be maintained at an accurate value. This is based on the premise that the count value of the free-running counter 24 does not usually deviate more than a correct value even while the block synchronization is lost. Therefore, when the count value of the counter 24 is in the first half of the total block count number, it can be determined that the counter 24 is ahead of the correct state. Therefore, the first block synchronization signal (AND circuit 22 output) generated by the counter 20 is generated. ) Can be controlled by the gate signal so as not to be given to the frame counter 32 so that the count value of the frame counter 32 does not advance too much. Conversely, when the count value of the counter 24 is in the latter half of the total block count number, the counter 2
Since 4 can be judged to be behind the correct state, A
The first block synchronization signal output from the ND circuit 22 can be controlled by the gate signal so as to be output to the frame counter 32 so that the count value of the frame counter 32 is not delayed too much.

[Brief description of drawings]

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

FIG. 2 is an illustrative view showing a general data structure in FM multiplex broadcasting.

FIG. 3 is a block diagram showing a conventional FM multiplex broadcast receiver.

FIG. 4 is a timing diagram showing conventional synchronization signal generation.

[Explanation of symbols]

 10 ... FM multiplex broadcast receiver 12, 14 ... Terminal 16 ... BIC detection circuit 18 ... Synchronization detection circuit 20 ... First counter 22, 28 ... AND circuit 24 ... Second counter 26 ... Timing signal generation circuit 30 ... OR circuit 32 ... Third counter (frame counter)

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Masanori Saito, 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside Broadcasting Research Institute of Japan Broadcasting Corporation (72) Toru Kuroda 1-10-11 Kinuta, Setagaya-ku, Tokyo Broadcasting Technology Institute of Japan Broadcasting Corporation (72) Inventor Shigeki Moriyama 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside Broadcasting Technology Laboratory of Japan Broadcasting Corporation (72) Tomohiro Saito 1-10-11 Kinuta, Setagaya-ku, Tokyo (72) Inventor Tadashi Isobe 1-10-11 Kinuta, Setagaya-ku, Tokyo (72) In-house Broadcasting Research Institute of Japan Broadcasting Corporation (72) Sator Yamada 1-1-10 Kinuta, Setagaya-ku, Tokyo (56) Reference JP-A 63-87039 (JP, A) JP-A 2-137432 (JP, A) JP-A 5-63692 (J , A) JP 50-161104 (JP, A) JP 58-20204 (JP, A) JP 1-291542 (JP, A) JP 1-208923 (JP, A) JP 63-60633 (JP, A) JP-A-5-268211 (JP, A)

Claims (2)

(57) [Claims] 1. An FM multiplex broadcast receiver for receiving data in which one frame is composed of a plurality of data blocks in which a block identification code is added to the head of each data, and reset in response to the block identification code. A first counter that outputs a first block synchronization signal when the input data is in block synchronization and is stepped by a clock signal synchronized with the input data, the first block synchronization signal and its own A second counter reset in response to a second block synchronization signal obtained on the basis of a count value and incremented by the clock signal; and a second counter receiving the count value of the second counter.
Signal generation circuit for generating the block synchronization signal of the first block synchronization signal, and the first block synchronization signal and the second block synchronization signal
An FM multiplex broadcast receiver comprising a third counter stepped by at least one of the block synchronization signals of 2. Depending on the count value of the second counter, both the first block synchronization signal and the second block synchronization signal are given to the third counter, or the second block is supplied. The FM multiplex broadcast receiver according to claim 1, further comprising control means for controlling whether or not to apply only a synchronization signal.