JP2847973B2 - Audio PCM 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 a voice PCM using satellites.
The present invention relates to distribution of broadcast and television signals and to a broadcast receiver.

[0002]

2. Description of the Related Art In recent years, services using a communication satellite CS are expanding, and voice PCM broadcasting is one of them. This system occupies a bandwidth of 27 MHz for one transponder which is usually used for transmitting a television signal including video and audio for one channel, and occupies a satellite broadcasting BS.
This is for digitally multiplexing and transmitting six channels of high quality PCM audio equivalent to. In this system, considering the input / output nonlinear characteristics of the transponder of the communication satellite,
It is planned to transmit the digitally multiplexed voice PCM signal after MSK modulation. An audio PCM broadcast receiver for receiving this is constituted by a block diagram as shown in FIG. References: “Multi-channel PCM
Speech Satellite Broadcasting "NHK Giken R & D Published February 15, 1990 by Kameda and Kawai In FIG. 2, reference numeral 10 denotes an IF input terminal of an audio PCM broadcast receiver. The terminal 10 is applied with a first intermediate frequency signal which is converted from a 12 GHz band radio wave from a satellite received by an antenna to a 1 GHz band by a down converter and guided indoors by a coaxial cable. 11 is a tuning circuit, 12 is a band pass filter, 13 is an MSK demodulator,
15 is a high-order multiplex decoder, 16 is a PCM decoder, 17 is D
/ A converter, 18 is a low-pass filter LPF, 1
Reference numerals 9 and 20 denote audio output signal terminals.

A 1 GHz band MS is selected by a tuning circuit 11.
The K signal is converted to a second intermediate frequency. The band-pass filter 12 is a filter for extracting only the MSK signal and removing noise and signals of other channels, and generally employs a Gaussian filter having excellent phase group delay characteristics. The MSK demodulator 13 plays a role of extracting I and Q baseband signals orthogonal to each other. Inputting the baseband signal, the high-order multiplex decoder 14
MSK demodulated digitally multiplexed audio signals for 6 channels are separated into respective channels,
It performs a function of correcting a bit error due to deterioration of the transmission system by digital processing. The separated digital signals for one channel are input to the PCM decoder 16, where interleaving, range bit processing, and control signal processing are performed. D
The / A converter 17 converts a digital signal into an analog signal, and outputs the audio baseband signals R and L to output terminals 19 and 20 via the LPF 18.

On the other hand, a satellite television receiver used for purposes such as satellite-based video distribution and television broadcast reception has a configuration as shown in FIG. In FIG. 3, reference numeral 40 denotes an input terminal of the first intermediate frequency signal. A channel selection circuit 41 has a function of selecting a channel from a number of first intermediate frequency signals and receiving one channel. Reference numeral 50 denotes a band pass filter, which is used as a channel filter. Reference numeral 51 demodulates the FM signal selected by the FM demodulator to obtain a detection output signal. Reference numeral 53 denotes a video signal processing circuit that performs processing such as de-emphasis on the demodulated detection output signal, and outputs a 1 Vp-p video signal to a video signal output terminal 54. 52 is QPS
The K demodulator plays a role of demodulating a QPSK-modulated audio signal on a 5.7 MHz subcarrier and extracting I and Q baseband signals orthogonal to each other. I,
The Q baseband signal is converted into a PCM-coded digital signal by differential conversion. 16 is a PCM decoder, P
Interleave, range bit processing, and control signal processing are performed on the CM-encoded digital signal. The D / A converter 17 converts a digital signal into an analog signal,
The audio baseband signals R and L are output to output terminals 19 and 20 via the LPF 18.

[0005]

As described above, the voice P
Since both the CM broadcast receiver and the satellite television receiver are terminals of a system for transmitting data using satellites, a receiver that can be integrated and enjoy both media can be considered. At this time, there is a problem that the decoding process of the PCM code and the like are both necessary and overlap.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to share an audio PCM broadcast receiver and a satellite television receiver.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an audio PCM broadcast receiver according to the present invention receives a radio wave from a satellite and converts the frequency of the radio wave into a first intermediate frequency signal having an input signal. A first band-pass filter that receives an output of the first band-pass filter, an MSK demodulator that receives an output signal of the first band-pass filter, and an MSK. A high-order multiplex decoder that receives an output signal of the demodulator and selects one channel, and a first multiplex decoder that receives a radio wave from a satellite and converts the frequency.
A second band-pass filter that receives an output of a second tuning circuit that receives an intermediate frequency signal as an input signal and passes only a desired FM signal, and an FM demodulation that receives an output signal of the second band-pass filter as an input A video signal processing circuit that inputs a detection output signal of an FM demodulator and outputs a video signal; a QPSK demodulator that inputs a detection output signal of the FM demodulator and demodulates an audio subcarrier; Decoder and Q
A switch for switching the output signal with the PSK demodulator and outputting one of them, and a PCM for inputting the output signal of the switch and
An audio signal processing circuit for decoding the encoded audio signal to obtain an audio signal.

[0008]

According to the present invention, a desired channel is selected by the first tuning circuit from the input first intermediate frequency signals from the satellite, and a second intermediate frequency signal is obtained. The MSK signal of the audio PCM broadcast passes through the first band-pass filter to remove noise and the like and is subjected to MSK demodulation. The mutually orthogonal I and Q baseband signals output from the MSK demodulator are guided to a high-order multiplex decoder. The high-order multiplex decoder has functions of separating digitally multiplexed audio signals of six channels into respective channels and correcting bit errors due to deterioration of the transmission system. The separated audio digital signal for one channel is
The signal is selected by the switch and guided to the audio signal processing circuit. The audio signal that has been PCM-encoded in the audio signal processing circuit is decoded, and an audio baseband signal is obtained.

On the other hand, the television signal and the FM signal by the audio subcarrier input to the second tuning circuit are tuned, and then pass through a second band-pass filter to remove noise and the like to perform FM demodulation. Guided to the vessel. The FM signal selected by the FM demodulator is demodulated to obtain a detection output signal. Upon input of this signal, the video signal processing circuit performs processing such as de-emphasis to obtain a video signal. The detection output signal is QPS
The signal is also input to the K demodulator, and the audio subcarrier is demodulated to obtain I and Q baseband signals orthogonal to each other.
The I and Q baseband signals are differentially converted into one channel PCM encoded audio digital signals. This audio digital signal is selected by the switch, and is guided to the audio signal processing circuit. As in the case of the audio PCM broadcast, the audio signal that has been PCM-encoded in the audio signal processing circuit is decoded to obtain an audio baseband signal. In this way, the audio signal processing circuit can be shared by the audio PCM broadcast receiver and the satellite television receiver.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a voice P in one embodiment of the present invention.
It shows a CM broadcast receiver. In FIG. 1, 10
Is an input terminal of the first intermediate frequency signal, 11 is a tuning circuit, 12
Is a bandpass filter, 13 is an MSK demodulator, 15 is a high-order multiplex decoder, 30 is a switch, 35 is an audio signal processing circuit, 16 is a PCM decoder, 17 is a D / A converter,
8 is a low-pass filter LPF, 19 and 20 are audio output signal terminals, 40 is an input terminal of the first intermediate frequency signal, 41 is a tuning circuit, 50 is a band pass filter, 51 is an FM demodulator, 53 is a video signal The processing circuit 52 is a QPSK demodulator.

[0011] With regard to the receiver configured as described above,
The operation will be described below. The input terminal 10 is applied with a first intermediate frequency signal which is obtained by converting a 12 GHz band radio wave from a satellite received by an antenna into a 1 GHz band by a down-converter and guided indoors by a coaxial cable. The 1 GHz band MSK signal is converted to a second intermediate frequency by the tuning circuit 11. Bandpass filter 12
Is a filter for extracting only the MSK signal and removing noise and signals of other channels. Generally, a filter having a Gaussian characteristic having excellent phase group delay characteristics is employed.
The MSK demodulator 13 plays a role of extracting I and Q baseband signals orthogonal to each other. Upon inputting the baseband signal, the high-order multiplex decoder 14 separates the MSK-demodulated digitally multiplexed audio signals for the six channels into respective channels, and performs digital processing to reduce bit errors caused by deterioration of the transmission system. Performs the function of correcting When a correct higher-order multiplexed signal is input and decoded correctly, the higher-order multiplex decoder 14 outputs a synchronization detection signal 31 for a higher-order frame. The separated digital signals for one channel are selected by the switch 30 and guided to the audio signal processing circuit 35.

As a signal for controlling input switching of the switch 30, a synchronization detection signal 31 of the high-order multiplex decoder 14 is used.
That is, when a high-order multiplexed signal is input to the high-order multiplex decoder 14, the synchronization detection signal 31 is output. The signal is converted to an audio signal processing circuit 35
To lead. The audio signal processing circuit 35 includes a PCM decoder 16, a D / A converter 17, a low-pass filter LP
F18. The PCM decoder 16 performs interleaving, range bit processing, control signal processing, and the like.
The D / A converter 17 converts a digital signal into an analog signal, and outputs audio baseband signals R and L to output terminals 19 and 20 via an LPF 18.

On the other hand, the first intermediate frequency signal which has received video distribution or television broadcast using a satellite is guided to an input terminal 40. A channel selection circuit 41 has a function of selecting a channel from a number of first intermediate frequency signals and receiving one channel. 5
0 is a channel filter, which is a band-pass filter that allows only one wave to pass, and a SAW filter or the like is generally used. Reference numeral 51 demodulates the FM signal selected by the FM demodulator to obtain a detection output signal. Reference numeral 53 denotes a video signal processing circuit that performs processing such as de-emphasis on the demodulated detection output signal, and outputs a 1 Vp-p video signal to a video signal output terminal 54. 52 is a QPSK demodulator 5.7M
It plays a role of demodulating a QPSK-modulated audio signal on a subcarrier of Hz and extracting I and Q baseband signals orthogonal to each other. The I and Q baseband signals are converted into PCM-coded digital signals by differential conversion. The digital signal for one channel is supplied to the switch 30
And is guided to the audio signal processing circuit 35.
The signal for controlling the input switching of the switch 30 uses the synchronization detection signal 31 of the high-order multiplex decoder 14 as described above. That is, in this case, the video FM
Since the signal is input, the synchronization detection signal 31 is not output, so that the digital signal output from the QPSK demodulator 52 is guided to the audio signal processing circuit 35. The audio signal processing circuit 35 outputs the audio baseband signals R and L to the output terminal 19,
20.

In the above-described embodiment, the signal for controlling the input switching of the switch 30 uses the synchronization detection signal 31 of the high-order multiplex decoder 14.
It is also possible to use an L synchronization detection signal or a detection signal of the presence / absence of a synchronization signal of the video signal processing circuit 53. Alternatively, it may be manually switched by a remote controller or the like.

The format of the range bits of the PCM-coded audio digital signal is slightly different between the audio PCM broadcast signal and the satellite television signal. That is, the range bits are transmitted from 0 to 7 in the audio PCM broadcast signal, but from 0 to 4 in the satellite TV signal. However, the basic concept of the range bit method is the same, and it is possible to handle both systems by treating the data as transmitted from 0 to 7.

[0016]

As described above, according to the present invention, the audio PC
The functions of the M broadcast receiver and the satellite television receiver can be automatically switched and received, and the audio signal processing circuit can be shared.

[Brief description of the drawings]

FIG. 1 is a block diagram of an audio PCM broadcast receiver according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional audio PCM broadcast receiver.

FIG. 3 is a block diagram of a satellite television receiver in a conventional example.

[Explanation of symbols]

 Reference Signs List 10 Input terminal of first intermediate frequency signal 11 Tuning circuit 12 Bandpass filter 13 MSK demodulator 15 High-order multiplex decoder 16 PCM decoder 17 D / A converter 18 Low-pass filter LPF 19 Audio output signal terminal 20 Audio output Signal terminal 30 Switch 35 Audio signal processing circuit 40 First intermediate frequency signal input terminal 41 Tuning circuit 50 Band pass filter 51 FM demodulator 52 QPSK demodulator 53 Video signal processing circuit

Claims (1)

(57) [Claims] 1. A first tuning circuit which receives a radio wave from a satellite and frequency-converts a first intermediate frequency signal as an input signal, and receives an output signal of the first tuning circuit as an input and outputs a desired signal. A first bandpass filter that allows only the MSK signal to pass therethrough, an MSK demodulator that receives an output signal of the first bandpass filter as an input,
A high-order multiplex decoder for selecting one channel, a second tuning circuit that receives a radio wave from a satellite and converts the frequency, and uses a first intermediate frequency signal as an input signal, and a second tuning circuit. A second bandpass filter that receives an output signal as an input and passes only a desired FM signal, an FM demodulator that receives an output signal of the second bandpass filter as an input, and a detection output signal of the FM demodulator. A video signal processing circuit that outputs a video signal, a QPSK demodulator that receives a detection output signal of an FM demodulator and demodulates audio subcarriers, and receives an output signal of a high-order multiplex decoder and a QPSK demodulator. When receiving an audio PCM broadcast, comprising: a switch that selectively outputs one of them; and an audio signal processing circuit that receives an output signal of the switch and decodes a PCM-coded audio signal to obtain an audio signal. Is a switch More, selects the output signal of the high-order multi-decoder, the switch when receiving television signals, Q
An audio PCM broadcast receiver for selecting an output signal of a PSK demodulator.