JPS6236932A - Satellite broadcast receiver - Google Patents

Abstract

PURPOSE:To attain demodulation of multiplex stereo signal by means of an existing FM stereo receiver by providing a converter converting a sound carrier frequency of a satellite broadcast into a frequency of ground FM broadcast. CONSTITUTION:A sound tuning voltage generating circuit is operated to change the local frequency of a sound local oscillation mixer 6A and the frequency is tuned to the sound carrier of the multiplex stereo, terminals (a,c) of a switch 12 are shorted to conduct a transistor 13 thereby operating a frequency converter 7C. On the other hand, a voltage interrupting analog switches 17L, 17R is generated across a resistor 20 to eliminate L/R outputs and no sound output of the stereo amplifier is given. In this case, an input selector of the stereo amplifier is changed over and the output of the FM stereo receiver is ouputted, then the output of the frequency converter 7C is demodulated by the FM stereo receiver and outputted from the stereo amplifier as the L/R output.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a satellite broadcast receiving apparatus capable of receiving American C-band satellite broadcasting.

Conventional technology In the C band, stereo broadcasting is often performed using two waves, and many receivers have a two-wave stereo broadcast reception function (matrix system and discrete system), but Ma) IJ Adding a 2-wave receiver is expensive, so there are not many models that actually have a 2-wave 2-wave receiving function.

Problems to be Solved by the Invention If the system is made to support the three stereo systems of satellite broadcasting and terrestrial FM broadcasting, there are problems in that the cost increases and the circuit becomes complicated.

An object of the present invention is to provide an inexpensive receiving device that can receive three stereo broadcasts.

Means for Solving the Problems In the present invention, the FM audio signal converted to the IF frequency is not detected, but is converted to the frequency band of terrestrial FM broadcasting by the output of the audio local frequency generation circuit and output. be.

According to the present invention, by converting the %FMFM audio signal to the frequency of M broadcasting and using an existing FM stereo receiver, it is possible to listen to multiplex audio stereo, and there is no need to provide a new receiver.

Embodiment 3 Hereinafter, a satellite broadcast receiving apparatus according to an embodiment of the present invention will be explained with reference to the drawings. In Fig. 1, 1 is a low-noise frequency converter attached to a parabolic antenna.
Convert to ~1,450MH2 and power 1''. 2 is 2n
A tuner called a d-mixer tunes to any one of the channels 1 to 24 and supplies an intermediate frequency (IF) output to an intermediate frequency amplifier (IF amplifier) 3.

This frequency converter 1 and tuner 2 are connected by a high frequency cable with little loss. 4 is an FM detector. The frequency characteristic of the output of the FM detector 4 extends from 8 to 9 MHz, and in addition to the video signal at 4.2 MHz-i, there are 1 to 20 audio carrier waves between 5.6 and 8.5 MHz. It is included. The number and frequency of audio carrier waves differ for each channel, and many types of stereo broadcasts are sent, and the stereo systems also include matrix, discrete,
There are multiplexes and many types. 6 is a buffer amplifier that clamps and outputs only one video signal component. 6
A is a local oscillator and mixer of the audio carrier, for example, an audio carrier of 6.8 MHz and a local frequency of 176 MHz.
Hz mixed to form a 10.7 MHz IF signal.

This is amplified by seven audio IF amplifiers and detected by eight FM detectors. The local frequencies of the six audio local oscillators/mixers are controlled by an audio tuning voltage generation circuit 10. 6B is also composed of the same audio local oscillator and mixer as 6A, and is controlled by the audio tuning voltage generation circuit 1o so that the former six audio local oscillators and mixers have a different local frequency. 7B is the same audio IF amplifier as the audio IF amplifier 7A, and 8B is the same FM detector as the 8 FM detectors, for discrete and stereo.

The output of the 8 FM detectors is left audio R, the output of FM detector 8B is right audio R, and in the case of matrix stereo, F
The output of the M detector 8A is L+R, and the output of the FM detector 8B is LR. The audio matrix processing circuit 9 performs matrix processing using an external switch (not shown).
Switches whether to output the outputs of 8A and 8B to that 6th page. By supplying the video output from the buffer amplifier 5 to a monitor television, the audio output, and the R output to a stereo amplifier, stereo audio and images can be viewed and viewed.

On the other hand, when transmitting multiplexed stereo signals in satellite broadcasting, the method is the same as in terrestrial FM broadcasting, so the desired audio carrier wave is transmitted to the audio local oscillator/mixer 6A.
The output of the audio local oscillator/mixer 6A is converted to, for example, 88 MHz (any FM band can be used) using the full frequency converter 7C, and the output is taken out using an antenna (or wire).1 A normal FM stereo receiver. 11 antenna and set the tuning frequency to 88 MHz. In this way, there is no need to incorporate a demodulator for multiplex stereo broadcasting into the satellite broadcasting receiver.

Now, in such a case, it is better to automatically stop audio other than multiplex stereo broadcasting, so
As shown in the figure, when the DC power supply 11 is supplied to the frequency converter 7G through the switching transistor A-7 and the switch 12 that determines whether or not to multiplex is switched, the satellite broadcast receiver
The output may be stopped and the frequency converter 7C may be operated. That is, in FIG. 2, 11 is a DC power supply, resistors 14 and 16 are resistors that provide bias to make the transistor 13 conductive, 16 is a capacitor for noise removal, and 17L and 1
7R is an analog switch, 18L and 18R are resistors that determine the output impedance, and switch 17L.

This prevents the output impedance from increasing when 17R is open. The resistor 19 and the resistor 20 are resistors that provide a switching voltage to make the analog switches 17L and 17Ri conductive. When the switch 12 is short-circuited between terminals a and b, and all settings except multiplex are specified, the transistor 13 is not conductive, so the frequency converter 7C does not operate, and no voltage is applied across the resistor 20. The analog switches 17L and 17R are electrically connected, and the audio matrix processing circuit 9 is connected to output the R output to the outside.

Operate the audio tuning voltage generation circuit 10'jz, and the audio localer 7
,,-.

By changing the local frequencies of the six speakers, oscillators, and mixers,
When tuned to the audio carrier wave of multiplex stereo, switch 12 short-circuits terminals a and c, transistor 13 is made conductive, and frequency converter 7Ci is operated. On the other hand, at this time, a voltage is generated across the resistor 2o that cuts off the analog switches 17L and 17R, so the R output is no longer output. That is, the audio output of the stereo amplifier is no longer output. At this time, if the input selector of the stereo amplifier is switched to output the output of the FM stereo receiver 11, the output of the frequency converter C is demodulated by the FM stereo receiver 11 and the L signal is output.

It is output from the stereo amplifier as an H output.

As described above, according to this embodiment, by converting the audio carrier wave of satellite broadcasting to the frequency band of terrestrial FM broadcasting,
Multiplex stereo can be demodulated (received) by the existing FM stereo receiver 11.

Effects of the Invention As described above, according to the present invention, by providing a converter that converts the audio carrier wave of satellite broadcasting to the frequency of terrestrial FM broadcasting, it is possible to demodulate multiplex stereo using an existing FM stereo receiver. can.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a satellite broadcast receiving apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram illustrating the operation of the main parts of the apparatus. 1... Frequency converter, 2... Tuner, 3... IF amplifier, 4... FM
Detector, 5, buffer amplifier, 6A, 6B...
...Audio local oscillator and mixer, 7A, 7B River...Audio IF amplifier. 8A, 8B...Audio detector, 9...Audio matrix processing circuit, 10...Audio tuning voltage generation circuit, 7C...Frequency conversion circuit.

Claims (1)

[Claims] It is characterized by comprising two audio local frequency generation circuits, and a converter that converts an FM audio signal converted to an IF frequency into a terrestrial FM broadcasting frequency using one of the audio local frequencies, and outputs the frequency. Satellite broadcast receiver.