JPH01213033A - Satellite relay communication device - Google Patents

Abstract

PURPOSE:To prevent the interference of both signals by transmitting an order signal at a TV signal sending side only for the time of the synchronizing signal of a TV signal and transmitting the order signal at a TV signal receiving station side for only the time synchronized with the synchronizing signal of the transmitting side TV signal. CONSTITUTION:A TV signal input is modulated by an FM modulator 1, and at the same time, a synchronizing signal is extracted by a synchronizing signal detecting circuit 2. A modulating wave is sent from a modulator for order signal input for the internal of the synchronizing signal. Then, it is sent to a satellite repeater through a synthesizer 4, a transmitter 5 and a demultiplexer 6. A carrier for order signal is received with a receiver 7 through the demultiplexer 6. Besides, the synchronizing signal of a TV signal received with a receiver 10 through a demultiplexer 9 and branched with a distributor 11 is extracted with a synchronous signal extracting circuit 15. The order signal input is sent by the control of the synchronous signal outputted from the circuit 15 from a modulator 14 and a transmitter 13 for the synchronizing signal interval. Thus, the interference of the TV signal and the order signal can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a satellite relay communication device, and in particular, in satellite communication, one-way transmission of T
The present invention relates to a satellite relay communication device that simultaneously transmits a V signal line and a bidirectional meeting line.

[Prior Art] In recent years, a one-way TV signal line and a two-way meeting line have been simultaneously transmitted via - number of satellite repeaters.

However, in conventional satellite relay communication equipment, FM for TV signals
In order to avoid mutual interference between the carrier wave and the carrier wave for the meeting line, it was necessary to analyze the spectrum of the FM carrier wave for the TV signal and place the carrier wave for the meeting line at a frequency with relatively low spectrum density.

In addition, the signal level of the carrier wave for the meeting line is affected by increased interference due to the cross-modulation product of the satellite repeater.
It was necessary to keep it sufficiently low compared to the V signal.

Figure 3 shows that in a conventional satellite relay communication device, NTSC
FIG. 4 is a diagram showing signal levels and frequency spectra when simultaneously transmitting one TV signal FM carrier wave and a meeting line carrier wave according to the PAL system or the S E CAM system.

As shown in the figure, the FM carrier for TV signals occupied most of the passband of the satellite repeater. Therefore, the carrier wave for the meeting line is located at the end of the passband, and the signal level is also kept lower than that for TV signals.

[Problems to be solved] The above-mentioned conventional satellite relay communication device has an FMI for TV signals.
In order to avoid mutual interference between the II transmission wave and the carrier waves for the meeting line, there is a problem in that the degree of freedom in determining the signal level and frequency arrangement of each carrier wave for the TV signal and the meeting signal is very small.

The present invention has been made in view of the above problems.
To provide a satellite relay communication device which prevents mutual interference between an FM carrier wave for a V signal and a carrier wave for a meeting line, and has a large degree of freedom in determining the signal level and frequency arrangement of each carrier wave for a TV signal and a meeting signal.

[Means for Solving Problems] In order to achieve the above object, the satellite relay communication device of the present invention modulates the TV signal at the TV signal transmitting station side, and also modulates the meeting signal only in the period of the synchronization signal of this TV signal. a first transmitting means for outputting the modulated TV signal and the meeting signal as transmission signals;
and a first receiving means for receiving and demodulating the meeting signal transmitted from the TV signal receiving station side, and the TV signal receiving station side receives the meeting signal transmitted from the first transmitting means via the satellite repeater. a second receiving means for receiving the transmission signal and demodulating the TV signal and the meeting signal; and a second receiving means for modulating the meeting signal only in the period of the synchronization signal of the TV signal demodulated by the second receiving means and transmitting the modulated meeting signal. The configuration includes a transmitting means.

The present invention utilizes the fact that the instantaneous frequency displacement of the FM modulated wave for TV signals in the synchronization signal section of the TV signal is narrow, and with the above configuration, the input TV signal of the TV signal transmitting station is The carrier wave of the meeting signal is transmitted from three opposite circles only in the period of the synchronization signal.

[Example] Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1 is a block diagram of a satellite relay communication device according to an embodiment of the present invention, in which (a) is a block diagram of a TV signal transmitting station, and (b) is a block diagram of a TV signal receiving station. FIG. Moreover, FIG. 2 is a diagram showing signal waveforms of each part in the satellite relay communication device of FIG. 1.

In Fig. 1, l is an FM modulator, 2 and 15 are synchronization signal extraction circuits, 3 and 14 are modulators, 4 is a combiner, 5 and 13 are transmitters, 6 and 9 are demultiplexers, 7° 10 is the receiver, 8,16
is a demodulator, ]1 is a distributor, and 12 is an FM demodulator.

First, the operation of the TV signal transmitting station having the above configuration will be explained.

A TV signal input is converted into an FM modulated wave by an FM modulator 1, and at the same time, a synchronization signal extraction circuit 2 separates and extracts a synchronization signal from the TV signal.

Then, based on the output of the synchronization signal extraction circuit 2, a modulated wave is sent out from the modulator 3 for inputting the meeting signal only in the period of the synchronization signal.

On the other hand, the synthesizer 4 combines the TV FM modulated wave and the meeting signal modulated wave, and the transmitter 5 performs frequency conversion and amplification processing. The signal is then transmitted to the satellite repeater via the duplexer 6.

Further, the received carrier wave for the meeting signal is received by the receiver 7 via the splitter 6. After the receiver 7 performs frequency conversion, the demodulator 8 reproduces the signal into a meeting signal.

The above is the operation on the TV signal transmitting station side.

Next, the operation of the opposing TV signal receiving station will be explained.

On the TV signal receiving station side, the TV signal FM carrier wave and the meeting signal carrier wave are received by a receiver 10 via a splitter 9. After the receiver 10 performs frequency conversion, the distributor 11 branches the signal into two components: an FM carrier wave for TV signals and a carrier wave for meeting signals.

One of the outputs of the distributor 11 is demodulated and reproduced by the FM demodulator 12 into a TV signal, and the other output is sent to the demodulator 1.
6t is thereby reproduced as a meeting signal.

In addition, the synchronization signal extraction circuit 15 separates and extracts only the synchronization signal from the reproduced TV signal, and
Create a synchronization signal with timing synchronized with the V signal. On the other hand, the meeting signal input is converted by the modulator 14 into a modulated wave for the meeting signal. However, the modulated wave is sent out only during the synchronization signal period under the control of the synchronization signal output from the synchronization signal extraction circuit 15. And transmitter 13
The signal undergoes frequency conversion and amplification processing, and is transmitted via the duplexer 9 to which satellite repeater.

The above is the operation on the TV signal receiving station side.

FIG. 4 is a diagram showing the signal level and frequency spectrum when the satellite relay communication device of FIG. 1 is used to simultaneously transmit an FM carrier wave for a TV signal and a carrier wave for a meeting line. Here, (a) in the same figure shows the spectrum of the synchronization signal section, and (b) of the same figure shows the spectrum of the image signal section.

Next, a specific frequency relationship will be explained.

The highest frequency of the normal meeting signal is 3.4kHz
Then, the synchronization signal repetition frequency of the TV signal is approximately 15
kHz, which is higher than the Nyquist sampling frequency. Therefore, although the meeting signal received by the opposing station is in a burst form, it is fully possible to reproduce it into the original signal.

Further, the synchronization signal extraction circuits 2 and 15, like mono-multivibrator circuits, emit free-run signals at a frequency close to the synchronization signal even when there is no TV signal input to obtain an output signal.

In this way, in the present embodiment, between the three satellite communication earth stations A and B which are facing each other, earth station A transmits the FM carrier wave of the TV signal and the carrier wave of the meeting signal which is transmitted only during the period of the synchronization signal of the TV signal. The signal is transmitted to the satellite repeater, and earth station B receives it to obtain the TV signal and meeting signal.
The carrier wave of the meeting signal is transmitted to the satellite repeater only during the period of the synchronization signal of this TV signal.

That is, on the TV signal transmitting station side, a carrier wave modulated by the negotiation signal is transmitted only during the time of the synchronization signal of the TV signal, and is combined with the FMIIG transmission wave for the TV signal and transmitted.

On the other hand, on the TV signal receiving station side, the received TV signal FM
The TV signal is demodulated from the carrier wave, and the carrier wave modulated by the negotiation signal is emitted only at a time synchronized with the synchronization signal of the TV signal on the transmitting station side using the synchronization signal.

Further, in this case, it is assumed that the frequencies of the carrier waves of the two meeting signals are different, and the two carrier waves pass through the same satellite repeater.

[Effects of the Invention] As explained above, the present invention has the advantage of providing a satellite relay communication device having the following features.

■The spectrum of the FM carrier wave for TV signals that passes through the satellite repeater is narrow, and the carrier wave of the meeting signal is T.
No interference from carrier waves.

(2) Since the carrier wave due to the meeting signal exists only in the synchronization signal section of the TV signal, it does not affect the image signal portion of the TV signal.

(2) There is a wide degree of freedom in determining signal levels and frequency allocation for each carrier wave for TV signals and meeting signals.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a satellite relay communication device according to an embodiment of the present invention, Fig. 2 is a diagram showing signal waveforms of various parts in the satellite relay communication device of Fig. 1, and □ Fig. 3 is a diagram of conventional satellite relay communication Figure 4 is a diagram showing the signal level and frequency spectrum when simultaneously transmitting the FM carrier wave for TV signals and the carrier wave for meeting lines in the equipment. FIG. 3 is a diagram showing a signal level and frequency spectrum when carrier waves for a meeting line are simultaneously transmitted. 1: FM modulator 2.15: Synchronization signal extraction circuit 3.14: Modulator 4 =Synthesizer 5.13: Transmitter 6.9: Demultiplexer 7.10: Receiver 8.16: Demodulator 11: Distributor 12: FM demodulator

Claims (1)

[Claims] The TV signal transmitting station modulates the TV signal and
a first transmitting means that modulates the meeting signal only in the period of the synchronization signal of the TV signal and outputs the modulated TV signal and the meeting signal as transmission signals;
and a first receiving means for receiving and demodulating the meeting signal transmitted from the signal receiving station side, and the TV signal receiving station side receives the transmission transmitted from the first transmitting means via the satellite repeater. a second receiving means that receives the signal and demodulates the TV signal and the meeting signal; and a second transmitter that modulates and transmits the meeting signal only in the period of the synchronization signal of the TV signal demodulated by the second receiving means. A satellite relay communication device characterized by comprising: means.