JPH01318369A - Voice multiplex reception equipment for nicam system - Google Patents

Abstract

PURPOSE:To satisfactorily demodulate a second voice signal by demodulating the output of a band-pass filter, which has such characteristic that a first voice carrier wave passes through this filter, and the output of a band-pass filter which has such characteristic that a video carrier wave passes through this filter together with a second voice carrier wave. CONSTITUTION:A band-pass filter 3-1 has such selectivity characteristic that the second voice carrier wave and the video carrier wave pass through the filter 3-1, and the first voice carrier wave has a level difference from the second voice carrier wave, and the output is applied to a video intermediate frequency and video detecting circuit 5-1 as the differential output to take out beat components of the second voice carrier wave and the video carrier wave, and a QPSK signal is obtained through a BPF 8. A band-pass filter 3-2 has a selectively characteristic to have a peak in the first voice carrier wave, and the output is processed by a video intermediate frequency and video detecting circuit 5-2 and removes noise components like a video signal component through a high-pass filter 7 to obtain an FM signal. Thus, an adverse influence of the first voice carrier wave upon the second voice carrier wave is reduced to satisfactorily demodulate a digital signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a receiving device for PCM audio multiplex broadcasting of a ground station, of which experimental broadcasting has now begun in Europe.

A-7 Prior Art Conventional television audio multiplex broadcasting in Europe is the West German system. In this West German system audio multiplexing, a first audio carrier wave of 33.4 MHz is frequency-modulated by a first audio signal.
The second audio carrier wave of 33.16 MHz is frequency-modulated by the second audio signal and transmitted. On the other hand, the circuit configuration up to the audio intermediate frequency stage of the receiving device is a quasi-parallel circuit that has bandpass filters and video intermediate frequency/video detection circuits in the video signal path and the audio signal path, respectively.
The configuration shown in the figure is common.

In the figure, 1 is a tuner, 2 is a bandpass filter with the selectivity characteristics shown in FIG. 4A, 3 is a bandpass filter with the selectivity characteristics shown in FIG. In the circuit, an audio trap circuit 6 is connected to the output end of the video intermediate frequency/video detection circuit 4 to connect a video signal, and a bypass filter (HPF) 7 is connected to the output end of the video intermediate frequency/video detection circuit 5. F by doing
They each receive an M (audio) signal.

3 Heh.

N I CAM (Ne
a'rInstantaneous Compand
Even in audio multiplex broadcasting using the Audio Muj'tiplex (quasi-instantaneous companding audio multiplexing) system, the audio signal is a two-carrier system similar to the West German system described above, so the circuit configuration shown in Figure 3 can be applied. I can do it.

By the way, in the NICAM system audio multiplex broadcasting in Northern Europe, the second audio signal is Q
A PSK digitally modulated signal is transmitted. Therefore, in order to make the bandpass filter 3 compatible with the NICAM system, it can be realized by changing the 33.16 MHz point to 33.05 MHz, and from the output end of the video intermediate frequency/video detection circuit 5 shown in FIG. is 5.5 MHz F
An M signal and a 5.85 MHz QPSK signal are output.

Problems to be Solved by the Invention However, in the conventional circuit configuration as described above, when demodulating a digital signal modulated using the QPS method,
．． There was a problem in that malfunctions such as frame synchronization failures were likely to occur due to the influence of the 5 MHz (7) FM signal.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, it is an object of the present invention to provide an audio multiplex broadcast receiving apparatus in which digital signals are not adversely affected by FM signals.

Means to solve problems The audio multiplex reception device according to the present invention receives FM signals.

A bandpass filter and a video intermediate frequency/video detection circuit are provided for each QPSK digital signal, and FM
The bandpass filter for obtaining the signal shall have a characteristic that allows at least one audio carrier wave to pass through, and the other bandpass filter shall have a characteristic that allows the other audio carrier wave and video carrier wave to pass, and the output of each bandpass filter shall be By detecting the wave and passing it through a filter, each QPS
The present invention is characterized in that a signal and an FM signal can be obtained.

According to the present invention, in order to obtain a QPS signal, a level difference is provided between the first audio carrier wave and the second audio carrier wave in one of the bandpass filters, and a level difference is provided between the second audio carrier wave and the 5-Heno video carrier wave. By obtaining the second audio intermediate frequency signal as the beat component of the second audio intermediate frequency signal, good demodulation of the digital signal can be obtained.

EXAMPLE An example of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 shows a block diagram of one embodiment, and FIG. 2 shows a characteristic diagram of the bandpass filter shown in FIG. 1.

In FIG. 1, tuner 1. Bandpass filter 2° video intermediate frequency/video detection circuit 4. The trap circuit 6 is the same as that shown in FIG. 3-1 is a bandpass filter, QPSK
It has selectivity characteristics to allow the second audio carrier wave and video carrier wave modulated by the digital signal to pass through. Here, the first audio carrier wave (33.4 MHz) has a level difference of 3 dB or more with respect to the second audio carrier wave (33.05 MHz). The output of this bandpass filter 3-1 is applied as a differential output to the video intermediate frequency/video detection circuit 5-1, and the beat components of the second audio carrier wave and video carrier wave are extracted and sent to the BPF 8 and further to the Duode 6-2 circuit. (not shown) to the QPS.

On the other hand, the bandpass filter 3-2 for the first audio carrier has a selectivity characteristic having a peak at the first audio carrier as shown in FIG. 2B, and only the first audio carrier component is output from its output end. , the next stage video intermediate frequency/video detection circuit 5-
2 and further passes through a bypass filter 7 to remove miscellaneous components such as video signal components and obtain a first audio signal (FM signal).

According to this configuration, the FM modulated first audio signal, Q
A bandpass filter 3-1, respectively, for the PSK audio signal.
3-2 and video intermediate frequency/video detection circuits 5-j, 5-
2 and obtain the first audio carrier wave and the second audio carrier wave from the output ends of the respective circuits, the negative effect of the first audio carrier wave on the second audio carrier wave is particularly small (
However, good demodulation of digital signals becomes possible. In the above embodiment, the bandpass filter 3-2 has a characteristic of passing only the first audio carrier wave component, but similarly to the bandpass filter 3-2, it also passes the video carrier 7 wave component. The p-th audio signal may be demodulated by the beat component of the recarrier wave.

Effects of the Invention As described above, according to the present invention, in an audio multiplex broadcast receiving device in which the first audio signal is an FM modulated signal and the second audio signal is a digitally modulated signal, a bandpass filter is provided for the first audio signal, the bandpass filter for the first audio signal has a characteristic of passing at least the first audio carrier wave, and the bandpass filter for the second audio signal has a characteristic of passing the video carrier wave together with the second audio carrier wave, By demodulating the outputs of the respective bandpass filters, the second audio signal can be demodulated particularly well.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an N I CAM audio multiplex receiver according to an embodiment of the present invention, and FIG. 2A is a block diagram. 1 is a characteristic diagram of the bandpass filter in Fig. 1, Fig. 3 is a block diagram of a conventional audio multiplex receiver, and Fig. 4 A
, B is a characteristic diagram of the bandpass filter shown in FIG. 3-1.3-2...Band filter, 5-1.5
-2...Video intermediate frequency/video detection circuit.

Claims (1)

[Claims] In a receiver for audio multiplex broadcasting in which the first audio signal is an FM modulated signal and the second audio signal is a digitally modulated signal, a bandpass filter is provided for each audio signal, and a bandpass filter for the first audio signal is provided. has the characteristic of passing at least the first audio carrier wave, and the bandpass filter for the second audio signal has the characteristic of passing the video carrier wave together with the second audio carrier wave, and the output of each bandpass filter is demodulated and 1. A NICAM audio multiplex receiver, characterized in that it obtains a first audio signal and a second audio signal.