JPS58178640A - Satellite communication system - Google Patents

Abstract

PURPOSE:To compensate the variation of the quality of an SCPC system line, by switching the SCPC system transmission electric power modulated by a narrow band signal in steps in accordance with the existence of a large power carriers. CONSTITUTION:The titled system is composed of plural earth stations 2-7 which transmit SCPC system telephone using a television signal and one carrier in each telephone channel by using the same repeater of a satellite 1. A command station 2 transmits/receives both television and telephone signals to concentrically control the SCPC telephone operated by demand assignment multiple access (DAMA) system. At the concentrated control, the command station 2 detects the existence of a television signal, superposes the detected information to a DAMA system common control signal to send the superposed signal and switches the transmitting electric power of the SCPC telephone by two steps. Other earth stations 3-5 receives a command signal included in a common control signal transmitted from the command station 2 and switch the SCPC transmitting electric power by two steps.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to satellite communication systems, particularly broadband signals such as television, etc.
The present invention relates to a satellite communication system that uses the same satellite repeater to transmit narrowband signals such as telephone signals using the CPC system.

As satellite communications have developed and come to be used for a variety of purposes, there has also been an increasing demand for the use of the same satellite repeater to transmit different types of information using multiple transmission methods. . For example, television and 5epc telephone calls are transmitted using separate satellite repeaters on Intelsat satellites, but television and 5epc telephone calls are transmitted between multiple earth stations using the same satellite repeater.
There is a demand for a dedicated communication system that can transmit CPC telephone calls. On the other hand, although the scale of satellites has increased,
There is a limit to the output of a satellite repeater, and for the economical configuration of a satellite communication system, effective use of the output of the satellite repeater is an important issue in system design. It is important that communication capacity is often limited by the output of the satellite repeater rather than the frequency bandwidth. Therefore, it is desirable that the satellite repeater be operated at an operating point close to the saturated output, as long as other conditions, such as interference noise due to cross-modulation, permit. [7 However, broadband signals such as television, multiplex telephones, and high-speed data may cause problems! When a high-power carrier wave such as a high-power carrier wave and a low-power carrier wave modulated by a narrowband signal such as a telephone signal operate near the saturated output, satellite relay for the low-power carrier wave is The effective gain of the device is
A phenomenon appears in which the effective gain of the repeater becomes lower than that for a high-power carrier wave. As a result.

The gain of a repeater for a small-power carrier is the same as the so-called small-signal gain of the repeater in the absence of a high-power carrier, whereas when a high-power carrier is added, the saturation effect reduces the small-signal gain mentioned above. The effective gain (large signal gain) for the high power carrier wave, which is several dB lower than the gain, is further lowered by several dB.

Therefore, in a method of keeping the transmission power of the earth station constant as in the normal satellite communication system, the satellite repeater output of the low power carrier wave of the 5CPC system, that is, the damage input of the other earth station, varies greatly depending on the presence or absence of the high power carrier wave. As a result, 5 cp
There is a problem in that the communication quality of the c method varies significantly.

An object of the present invention is to eliminate the above-mentioned problems and provide a simple satellite communication system that compensates for line quality fluctuations in the 5CPC system by switching the transmission power of the 5CPC system in stages depending on the presence or absence of high-power carrier waves. That's it.

The satellite communication system of the present invention modulates the narrowband signal and
In a satellite communication system in which communication is performed between a plurality of earth stations via the same repeater of a satellite using a plurality of small power carrier waves of a PC system and at least one high power carrier wave modulated with a wideband signal, the plurality of A transmitting means @1, wherein a command station among the earth stations that transmits a command signal specifying transmission conditions of the 5 cpc method switches the transmission power of the low power carrier wave in at least two stages according to the command signal; comprising a detection means for detecting all usage conditions of the high-power carrier wave, and a command signal transmission means for generating the command signal from the output of the detection means and transmitting it to the first transmission means and each other earth station. , a commanded earth station other than the command station that transmits the low-power carrier wave has a second transmitting means that switches the transmission power of the low-power carrier wave to at least two stages according to the command signal; and command signal receiving means for receiving the command signal.

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a system configuration diagram of an embodiment of the present invention.
It consists of eight earth stations that transmit television signals and 5CPC telephones using the same repeater. 2 transmits and receives both television and telephone calls, and uses *Demand Assigned Multiple Access (DAMA)
) method, a command station that performs 0 centralized control of 5cpc telephones detects the presence or absence of the '1'-fv'' signal and sends this information on the DAMA common control signal, and also increases the transmission power of 5cpc telephones to 1 in 2 stages. 3 is for TV transmission and 5 is for TV transmission.
Earth station using CPC telephone, 4 is TV reception and SC
An earth station that uses PC telephones, 5, is an earth station that uses only 5CPC telephones, and these stations that use 5CPC telephones receive command signals included in the common control signal from command station 2, and 5C
PC transmission power f: This is a commanded earth station that switches between two stages. 6 is a mobile station that transmits and receives only television, and 7 is an earth station exclusively for television reception. In the figure, among the arrows indicating the transmission and reception of radio waves between satellite 1 and each earth station, the solid line indicates a 5 cpc telephone carrier wave containing a common control signal.

The dashed line indicates the television carrier.

Figure 2 is a block diagram of the command station 2 in Figure @1, where 20 is an antenna (ANT) used for both transmission and reception, 21 is a low noise amplifier (LNA), and 22 is a receiving signal at an intermediate frequency. (I
F) Down converter (D/C) to convert to band, 2
3 is a 5cpc intermediate frequency amplifier (5CPCIFA) that amplifies a 5cpc telephone carrier wave, 24d 5CPCF
A divider that branches the O output <D IV),
25 separates and detects the 5cpc pilot signal and converts the AFC signal and AGC signal to D/C22°5CP.
Pilot receiving equipment (PIL) supplied to CIFA 23
REC), 26 is a common control Kl signal receiving board (C8CRX) that receives common control signals for DAMA control.
, 27 is a telephone output signal (T
PRX) t-Receive channel unit (RXC) to take out
IU), 28 is a television intermediate frequency amplifier (TVIFA) that branches the output of the D/C 22 and amplifies the television signal, 29
is a detection signal 1 that detects the presence or absence of a TV signal from its output.
01 and the AGCgN signal of TVIFA 28, and 30 is a TV demodulator (T) that demodulates the TV output signal (TVRX) from the TV output signal.
V OEM), Ttonff20. LNA21, D
/C22, TV HPA29o! The AGCDET 30 and AGCDET 30 constitute a detection means for detecting the presence or absence of a television carrier wave. In addition, 31 is a pilot signal oscillator (PIL O8
C), 32 is 5 modulated with telephone power signal (TPTX)
A transmission channel unit (TXCHU) that generates a CPC type transmission IFgs signal, 33 a common control signal transmission board (C8CTX) that transmits a DAMA type common control signal,
34 is a combiner (COMB) that combines the pilot signal 1 speech signal and the common control signal; 35 is a transmission intermediate frequency amplifier (TX IFA) that amplifies this IF output and switches the gain to t-2 stages according to the command signal 102; 36 is a TV modulator (TVMOD) 38 that modulates a carrier wave with a TV input signal (TVTX) and generates an IF signal, and an up/down converter (U/C) that converts the output of the TXIFA 35 into a radio frequency.
, 37 is a transmission power amplifier (HPA) that amplifies the output to the required transmission power, and 39 is a DAMA central control device 1 (DAMA) that allocates frequencies to each earth station using the 5 cpc method.
Antenna 20, PIL 08C31, TX
CHU32, C8CTX33, C0MB54, T
The first with XIFA35, U/C36 and HPA37
The DAMA 39 and the C3CTX 33 constitute a command signal sending means. DAMA39 is 5PA
Similar to the DE method, the common control signal t-C3 of the TDMA method
In addition to transmitting control signals such as call/response from each earth station via CTX 33'i, C3cRX26-'? '
In addition to the function of receiving and controlling the frequency of the synthesizer local oscillator of RX CHU27 and TX CHU32,
The detection signal 101 from AGCDET 29 has a function that changes the number of channels that can be assigned from fewer when the TV is in use and more when there is no TV carrier, and a function that increases the transmission power of the 5 cpc carrier when there is a TV carrier and increases the number of channels that can be assigned when the TV carrier is present. When there is no command signal sound, which is small and switches in two stages, is generated and sent to each commanded earth station via C8CTX33t along with the TXIFA35h and DAMA common control signals.

FIG. 3 is a block diagram of an embodiment of the commanded earth station 5 of FIG. 1, in which antennas (ANT) 50. Low noise f amplifier 41i (LNA) 51. Down converter (D/C) 52
, intermediate frequency amplifier (IFA) 53° divider (DIV) 5
4. Pilot receiving device (PILREC)55. Common control signal receiving board (C8CRX) 56 and slave station DAMAf
The llJli device (LOCDAMA) 57 constitutes a command signal receiving means.

Also, common control signal sending 1g board (C8CTX) 58, sending channel unino) (TXCHU) 59. Combiner (CO
MB)60. Transmission intermediate frequency amplifier (TXIFA) 6
1, Ayp: l Anhar-1 (U/C) 61, a transmitting power amplifier (HPA) 63, and an antenna 50 constitute a second transmitting means, which is sent from the command station together with a common control signal, and transmits the above-mentioned command. The transmission power is switched between two stages according to the command signal 103 received and demodulated by the signal receiving means. In addition.

64 is a reception channel unit (RXCHU) that demodulates the telephone reception output (TPRX), and the LOCDAMA
57 receives the output of C3CRX56 and TXCHU59,
It is configured to set the frequency of the R,X CHU 64.

As explained above, according to this embodiment, each earth station that transmits a 5 cpc carrier wave changes its transmission power based on the command signal from the command station depending on the presence or absence of the television carrier wave, so the television carrier wave is transmitted near the saturation point of the satellite repeater. Even if amplified, 5CPC@! due to small signal suppression effect! This has the effect of compensating for the drop in the signal and the drop in the bell, resulting in a nearly constant satellite repeater output, and resulting in a nearly constant telephone quality regardless of the presence or absence of a television.

Furthermore, since the number of used channels of 5 cpc can be switched by the DAMA central control unit, it is also effective in terms of effective use of the repeater output.

In the above embodiment, a system consisting of one television wave and a 5 epc telephone is explained, but a high power carrier modulated with a broadband signal other than television, such as high-speed data or broadband multiplexing, and a 5 cpc telephone may also be used. is not limited to one wave, but there are two or more waves, and depending on the usage situation, the transmission power of the 5CPC waves may be switched to three or more levels. or,
5cpc is a broadly defined 5cpc system that uses multiple low-power carrier waves modulated with narrowband signals, not only for telephone calls, but also for data/music transmission or multiple telephone calls with a small number of communication paths.
The 5CPC utilization stations may include transmission-only stations (command signals are received) or reception-only stations. Furthermore, in one embodiment, 5cpc operated in L) AMA system was explained, but 5cpc with fixed channel allocation instead of DAMA was explained.
It may also be applied to the CPC system, in which case each earth station can not only switch the transmission power of the 5 cpc wave but also transmit it according to the command signal.

As shown in FIG. 2, the command station in this embodiment has television transmitting and receiving equipment, but the command station does not necessarily have high-power carrier wave receiving equipment, and can receive information from other stations that have receiving equipment. It can also be used as a means for detecting the usage status of high-power carrier waves. The method of switching the transmission power is not limited to the method of the embodiments shown in FIGS. 2 and 3, and may be performed in a high frequency band instead of an intermediate frequency, and may also be performed by inserting and switching an attenuator.

Furthermore, one high-power carrier wave can be divided into two depending on the type of transmission signal.
In a case where transmission power is switched in stages, the transmission power of 5CPC or the transmission power and the number of used channels may be switched depending on the usage situation.

As explained in detail above, according to the satellite communication system of the present invention, high power carrier waves and 5 cpc
When sharing the low-power carrier wave of the 5cpc system, even if the high-power carrier wave is operated near the saturation output of the satellite repeater, it is possible to maintain almost the same line quality as the 5cpc system regardless of the usage situation. This has the effect of creating a simple system configuration with high utilization efficiency of the outputs of both layer repeaters.

[Brief explanation of the drawing]

FIG. 1 is a system configuration diagram of an embodiment of the present invention. FIG. 2 is a block diagram of an embodiment of a command station, and FIG. 3 is a block diagram of an embodiment of a commanded earth station. 1...Satellite, 2...Command station, 3.4.
5... Commanded earth station, 20.50...
Antenna, 21.51 ...Low noise amplifier% 2
2.52...down converter, 23,28,
35,53.61...Intermediate frequency amplifier, 24.
54...Distributor, 25.55...Pilot receiving device, 26.56...Common control signal receiving board, 27.64:...Receiving channel unit , 29...detection amplifier, 30...TV demodulator, 31...pilot signal oscillator,
32.59...Transmission channel unit, 33
．． 58...Common control signal transmission board, 34.60...
...Synthesizer, 36.62 Up converter, 37.
63...Transmission power amplifier, 38...TV modulator, 39...DAMA central control unit, 5
7...Slave station DAMAfllJIl device. , -1'/ Figure 2 Figure 3

Claims (1)

[Claims] A satellite repeater for transmitting signals between a plurality of earth stations using a plurality of low power carriers in a 5 cpc format modulated with a narrowband signal and at least one high power carrier modulated with a wideband signal. In a satellite communication system that performs satellite communications, a command station that sends out a command signal specifying transmission conditions for the SC PC system among the plurality of earth stations controls the transmission power of the low-power carrier at least according to the command signal. a first transmitting means that can be switched to two stages; a detecting means that detects the usage status of the high-power carrier wave; and an output of the detecting means that generates the command signal sound, which is transmitted to the first transmitting means and each other. a command signal transmitting means for transmitting a command signal to an earth station, the commanded earth station transmitting the low power carrier excluding the command station transmits the transmission power of the low power carrier to the command signal in at least 42 steps; A satellite communication system comprising: a second transmitting means that can be switched; and a command signal receiving means that receives the command signal sent from the command station.