JPH0119678B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a television audio multiplex control signal device for a television receiver.

By converting the audio multiplex signal processing circuit of television receivers from analog circuits to digital circuits, the number of peripheral components in conventional analog circuits has been reduced, and the control signal system also needs to be digitalized. ing. The present invention attempts to digitize the control signal processing section of an audio multiplex signal processing circuit.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an audio multiplex signal processing circuit according to an embodiment of the present invention. In Fig. 1, 1 is the SIF (sound intermediate frequency) detection output, which is an analog composite signal.
The signal is input to an analog/digital converter (hereinafter referred to as A/D converter) 2 and converted into a PCM digital signal.

This digital composite signal 3 is input to a digital band pass filter (hereinafter referred to as DBPF) 4, and a 31.5kHz sub-channel FM signal 5 is extracted. The 31.5 kHz sub-channel FM signal 5 of this digital signal is input to the digital rectifier circuit 6, and as can be easily understood from the waveforms of the signals 5 and 7 described for operation explanation in FIG. Wave rectification is performed by digital circuit means.
The signal 7 thus full-wave rectified by the digital rectifier circuit 6 is input to the digital comparator 8. The digital comparator 8 holds a threshold level 9, which is a level at which the received SIF detection output can be received well, as its comparison reference data, and if the comparator input 7 exceeds this threshold level 9, When
A level detection pulse 10 is output.

By the way, the A/D converter 2, the DBPF 4, the digital rectifier circuit 6, and the digital comparator 8 are connected to the sampling frequency of the A/D converter 2.
Operates based on sam. Therefore, the output of the digital rectifier circuit 6 takes discrete values as shown in the waveform of FIG. 2a. Also, the comparator output from the digital comparator 8 is shown in Fig. 2b.
The signal will be as shown in .

Now, input the comparator output as shown in Fig. 2b to the level judgment circuit 11, and
It is determined whether a comparator output pulse is obtained for [sec]. That is, 1/2・sam
If a pulse input is obtained even once during the [sec] period, it is determined that the mode is multiplexed, and the 1/2・sam
If there is no pulse input during the [sec] period, it is determined that the mode is monaural mode. Then, when it is determined that the mode is multiplex mode, a determination output pulse is output.

If the output pulse of the level determination circuit 11 is immediately used as a monaural/multiple mode determination output, there will be a major problem. In other words, if pulse noise of a level that exceeds the threshold level of a single digital comparator 8, such as that generated by a car or radio equipment, is mixed into the input of the digital comparator 8, the output of the comparator 8 is multiplexed. A pulse indicating mode reception is generated, and as a result, even if the reception mode is actually monaural mode, a pulse erroneously indicating multiple mode is obtained as the output of the level determination circuit 11.

Therefore, in the present invention, a pulse circuit 13 is further provided at the output of the level determination circuit 11. This pulse circuit 13 includes a means for delaying a pulse indicating the multimode reception state of the level determination circuit 11 for a predetermined period of time, and a means for delaying the pulse indicating the multimode reception state of the level determination circuit 11, and a means for delaying the pulse indicating the multimode reception state of the level determination circuit 11, and a pulse that should be newly input after a predetermined period of time if the multimode is selected. and a means for comparing the signals and confirming that pulses indicating the multi-mode reception state are continuously input. This delay time is caused by, firstly, the periodicity of the sub-channel FM signal 5, and secondly, the time interval of about 0.3 seconds when the broadcasting station switches the broadcasting mode between monaural mode and multiplex mode. It is determined based on the point at which the mode is switched. Therefore, in this embodiment, a delay circuit having a delay time of 0.5 seconds was used. Therefore, the pulse indicating multiple mode input to the pulse circuit 13 at time t is 0.5 sec pulse circuit 13.
When a similar pulse indicating the multiplex mode is input at time t+0.5 [sec], the pulse circuit 13 outputs a pulse signal indicating the multiplex mode. On the other hand, if there is no pulse indicating multiple mode at time t+0.5 [sec], the pulse circuit 13 outputs a signal indicating monaural mode.

As described above, according to the present invention, by digitizing the multiplex determination circuit and configuring it on the same IC chip as other audio processing units,
Compared to the conventional analog system, the number of peripheral parts can be significantly reduced, resulting in significant cost reductions.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a television audio multiplex control signal processing device according to an embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining the device. 2...A/D converter, 4...Digital band pass filter, 6...Digital rectifier circuit,
8...Digital comparator, 11...Level judgment circuit, 13...Pulse circuit.

Claims (1)

[Claims] 1 The audio multiplex composite signal detected from the TV audio intermediate frequency signal is set to the sampling frequency.
An analog-to-digital converter that converts analog to digital signals into SAM's PCM signals, and a subchannel from the audio multiplex composite signal digitally converted by this analog-to-digital converter.
A digital band pass filter that extracts the FM signal, a digital rectifier circuit that performs full-wave rectification of the sub-channel FM signal, and a rectified output of this digital rectifier circuit that is input, and whether or not this rectified output is below a set threshold level. A digital comparator outputs a pulse indicating that a rectified output exceeding the threshold level can be obtained.
Determine whether or not a comparator output pulse is obtained during the sam period, and determine whether the comparator output pulse is 1/
2. A level determination circuit that outputs a pulse signal indicating a multimode reception state when obtained during the sam period, and a level determination circuit that delays the output pulse signal of the level determination circuit by a predetermined time and returns to the same reception mode after a predetermined time. and a pulse circuit that outputs a pulse signal indicating a reception mode determined to be the same when an output pulse signal of the level determination circuit indicating that the reception mode is the same is obtained. Device.