JPS6056352B2 - Audio multiplex broadcast pilot signal identification device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for identifying pilot signals indicating program contents in television audio multiplex broadcasting.

The signal components of TV audio multiplex broadcasting include main channel 2 channels (L+R), subchannels (L-R), and a pilot signal, which is a control channel signal that indicates the program content.This pilot signal is used for horizontal synchronization of the TV. Approximately 3.5 times the frequency of the signal + f? 4-, seven, [[
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L is modulated by a single tone of 982.5H2 when broadcasting in stereo, and by a single tone of 922.5H2 when broadcasting in two languages.

Therefore, on the receiving side, the single tone frequency of 982.5H2 or 922.5H2, which is the modulation component of this pilot signal, is detected and identified, and the demodulation operation of the multiplex demodulation circuit is performed according to the content of each stereo, bilingual, or monaural broadcast program. It is configured so that it can be carried out according to the situation.

The number of pilot signal identification times for detecting pilot signals indicating program content and generating identification control signals according to each program content is 982.5H2, 92.
Reed filters are used to detect each frequency of 2.5H2.

However, such reed filters have the disadvantages of being high in cost, susceptible to mechanical shock, and lacking in reliability. An object of the present invention is to provide a highly reliable and inexpensive audio multiplex broadcast pilot signal identification device without using a lead filter.

The pilot signal identification device of the present invention includes a detection means for detecting a display signal, which is a single tone signal indicating program content, from a pilot signal, which is a control channel signal, and a reference signal generation means, which outputs a reference signal having a predetermined frequency. , means for detecting a difference between the single tone frequency that is the detection output of the detection means and the output signal frequency of the reference signal generation means and generating a detection signal according to this difference, and a program based on the detection signal. It is characterized by identifying a display signal which is a single tone signal indicating the content.

A preferred embodiment of the reference signal generating means is characterized by having frequency dividing means for receiving a pilot signal and dividing the frequency of this signal by a predetermined number, and
Counting means for counting the frequency of the difference can be used as the means for generating the detection signal according to the difference.

Hereinafter, the present invention will be explained using the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, in which a composite signal subjected to FM detection from a detector (not shown) is selectively extracted as a pilot signal FA having a carrier wave of 55.07 KHz by a bandpass filter 1. be done. This signal FA is detected into a single tone frequency signal of 982.5 Hz or 922.5 Hz by the W detector 2, and is inputted via a bandpass filter 3 to a waveform shaping circuit 4 such as a Schmitt circuit. Here, the sine wave signal is changed to a rectangular pulse signal F, which has the same frequency as the sine wave signal. On the other hand, the pilot signal f^ is converted into a rectangular pulse signal of the same frequency by the waveform shaping circuit 5, and is applied to the 1'6 frequency divider 6 as shown in the figure, for example, to become the reference signal FQ, which is used to generate the previous pulse. For example, it serves as a data input to a D-FF (delayed flip-flop) 7 to detect the frequency difference with the signal F.

Therefore, the pulse signal FT becomes the clock input of D-FF7, and the output of this D-FF7 includes both pulse signals FQ and FT.
A signal FD will be generated having a frequency difference of . As a means to detect the frequency of this signal,
For example, as shown in the figure, two flip-flops 8 and 9
A so-called 2-bit configuration counter is used in which the 2 bits are connected in cascade.

This counter is periodically reset by the reset signal FR from the reset signal generation circuit 10, and the output content of the second bit flip-flop 9, that is, the content immediately before the reset of the second bit of the counter is the difference frequency (FO). used for the detection of For this purpose, the pulse signal of the waveform shaping circuit 5 is further input to the signal detector 11, the presence of the pilot signal is detected, and the AND gate 12 calculates the AND of the output of the detector 11 and the output of the flip-flop 9. The output is a bilingual control signal.

Further, an AND gate 14 performs a logical product of the inverted signal of the output of the flip-flop 9 by the inverter 13 and the output of the detector 11, and the output thereof becomes a stereo control signal. In this configuration, the frequency of the pulse signal FQ is 55.07/64KHz, that is, 860.47Hz, so the output frequency FD of D-FF7 is 922.5-860.47=62 when broadcasting in two languages. .03Hz 1 stereo broadcast 982.5 - 860.47 = 122.0
It becomes 3Hz.

In this case, if the frequency of the reset signal FR of the reset signal generation circuit 10 is selected to be, for example, 25Hz, then when broadcasting in two languages, the frequency is 62.03/25=2.4&. 12 when broadcasting in stereo
Since the numerical value 2.03/25=4.88 is obtained, 2
It can be seen that the count content Q1 of the second bit of the bit counter is at a high level during bilingual broadcasting, and at a low level during stereo broadcasting. Figure 2 shows the difference signal frequency F.

and the count contents Ql and Q2 of each bit of the counter. This section is extracted and shown. Therefore, during stereo, the output of the AND gate 14 is high level, and the output of the other gate 12 is I low level.

Furthermore, when the signal is in two languages, the gate 12 is at a high level, making it possible to use these gate outputs as control signals for stereo and bilingual broadcasting, and when both gate outputs are at a low level, controlling monaural broadcasting. It is easy to generate a signal. The reason why the pilot signal detector 11 and AND gates 12 and 14 are provided is as follows.
This is to prevent the entire identification circuit from malfunctioning due to noise components such as bass sounds that adversely affect the audio circuit, which is a problem peculiar to televisions. (also known as a signal) to improve reliability.

In the above, the frequency of the reset signal FR was set to 25Hz, but if it were set to 30Hz, the frequency would be 62.0 when there are two languages.
3/30=2.07, 122.03/ during stereo broadcasting
Since the numerical value 30=4.07 is obtained, the output of the second bit flip-flop 9 will be at a high level in the former case and at a low level in the latter case, as in the case of the reset frequency of 25 Hz. Therefore, by providing a 112 frequency divider as the reset signal generating circuit 10 and using a commercial power source as its input, signals can be identified in both 50 Hz and 60 Hz regions without requiring any adjustment. Also,
Similarly, a 30 Hz reset signal can be obtained by dividing the frequency by 112 using the vertical synchronization signal in the television composite signal.

Of course, a built-in oscillator may also be used. Furthermore, the frequency division number of the reset frequency FRl frequency divider 6, the number of bits of the counter, and further the determination of the bits to be read can be determined by appropriately selecting these, and for each numerical value in the above embodiment. These are the most preferred examples, and it is clear that the invention is not limited to these.

Further, although the frequency signal FO to be used as a reference is obtained by a pilot signal, it is also possible to use a built-in oscillator separately. As described above, according to the present invention, a lead filter is not used and it is easy to integrate the device into an integrated circuit, so that a low-cost and highly reliable device can be obtained.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing one embodiment of the present invention, Figure 2A
、． B is a waveform diagram showing the operation of the circuit block in FIG. 1; Explanation of symbols of main parts, 2... AM detector, 6...
...Frequency divider, 7...D-FFl8,9...
...Flip-flop, 10...Reset signal generator.

Claims (1)

[Claims] 1. A pilot signal identification device that detects a pilot signal indicating the program content of audio multiplex broadcasting and generates an identification signal according to each program content, comprising a detection means for detecting a display signal of the program content from the pilot signal. , frequency dividing means for receiving the pilot signal as input and dividing the frequency of the pilot signal, detecting a difference between the output frequency of the detection means and the output frequency of the frequency dividing means, and generating a detection signal according to this difference. and gate means for allowing the detection signal to pass when the pilot signal is present, and identifying the display signal of the program content based on the output of the gate means. Signal identification device.