JPH052020B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a satellite relay device in satellite communication.

[Conventional technology]

Currently, satellite communications are rapidly expanding, and their applications are expanding from voice communications such as telephone calls to a variety of other services such as facsimile and data. In recent years, as satellites have become larger, consideration has been given to providing satellite communication services to mobile objects such as ships and automobiles. Unlike fixed earth stations, there are restrictions on the size of antennas that can be attached to these mobile bodies, and the transmission power cannot be increased very much. Satellites only amplify the radio waves they receive, so a large antenna is required to receive radio waves from moving objects. Similarly, when transmitting to a mobile object, it must come from an earth station with a large antenna. One such system, called MSAT, is being actively researched in the United States. An example of a satellite communication system that provides services to mobile objects is the paper presented at the 1986 international conference ICC'86, TYYan.FM.
Naderi, “A Proposed Architecture for A
Satellite Based Mobile Communicatinos
Network: The Lowest Three Layers”.

[Problem that the invention seeks to solve]

However, the conventional method described above has the drawback that mobile stations cannot directly communicate with each other.

An object of the present invention is to provide a satellite relay device that solves the above-mentioned problems by devising a relay device on a satellite and allows mobile stations to communicate with each other efficiently.

[Means for solving problems]

The satellite relay device of the present invention is used in a satellite communication system in which a plurality of earth stations share a satellite. The amplifier includes a group of amplifiers that independently amplify the outputs of the group of amplifiers, and a combiner that recombines the outputs of the group of amplifiers.

[Effect]

The reason why it is difficult for small earth stations such as mobile devices to communicate with each other is that small earth stations have small transmitting antennas and low transmitting power, so the received power on the satellite is also low, and the receiving earth station's antenna This is because sufficient reception power cannot be obtained because the signal is also small. On the other hand, if the antenna of either the transmitting or receiving earth station is large, either the received power on the satellite will be large or the radio waves at the receiving earth station can be weak, making communication possible. Become. However, the fact that it can be received by a small earth station means that the satellite itself can transmit that much power, so it is only necessary to sufficiently amplify the radio waves from the small earth station. In this case, if radio waves from a large earth station are similarly amplified, the amplifier will become saturated and distortion will occur, so the gain of the amplifier is controlled to be small for such signals. Furthermore, if the receiving earth station is large, the transmission power from the satellite may be small, so the gain of the amplifier is also controlled to be small. This allows small earth stations to communicate with each other without changing the size of the satellite antenna.

〔Example〕

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

FIG. 1 is a block diagram showing one embodiment of the present invention. A received signal from the earth station is inputted from the input terminal 100. This received signal is separated by a separator 1 and extracted for each channel. Assuming that the channels are frequency multiplexed, the separator 1 is composed of a group of filters that extract signals of respective frequencies. The output of the separator 1 is provided by variable gain amplifiers (hereinafter referred to as AMPs) 10, 11, 12,
13. One terminal 110, 111, 1
A command signal from a control station on the ground is input from 12 and 113, and the gain of each AMP is instructed. These signals are stored in memory (hereinafter referred to as RAM) 2
0, 21, 22, and 23 respectively, and D/
A converter (hereinafter referred to as D/A) 30, 31, 32, 33
is converted into an analog signal and determines the gain of each AMP. The signals amplified to an appropriate level by each AMP are combined by a combiner 40.
After being amplified by the AMP 50, it is transmitted from the antenna 200 toward the ground. The combiner 40 separates and combines the signals by frequency division or time division so that the signals do not interfere with each other.

Next, FIG. 2 is a diagram showing the operation of each amplifier shown in FIG. 1. AMP10 is involved in communication from a large earth station to a small earth station, AMP11 is involved in communication from a large earth station to a small earth station, and APM12 is involved in communication from a large earth station to a small earth station.
is involved in communication from small earth station to small earth station,
AMP13 is involved in communication from small earth stations to large earth stations. These are a and a in Figure 2, respectively.
It corresponds to b, c, and d. Received signals R1, R2
Since the signals are from large earth stations, they are received at a relatively high level, but the received signals R3 and R4 are signals from small earth stations, so their reception levels are low. Also, since the transmitted signals T1 and T3 are signals to a small earth station, a high level is required, but the transmitted signals T2 and T4
Since it is a signal to a large earth station, it may be relatively low. Based on the above conditions, AMP10, 11, 12,
The 13 gains must be set to different values for G1, G2, G3, and G4, respectively. These values are determined by commands from the ground control station.

By amplifying each channel with different gains in this way, the large earth station and the small earth station can communicate freely.
When transmitting to a large earth station, transmit signal T
2. It is okay to transmit with an output of T4 or higher, but
This will increase the total output from the AMP50 and cause distortion, so it is better to avoid unnecessary output as much as possible. Also,
If the channel is fixedly assigned to the earth station, the AMP gain does not need to be controlled from the ground and may be a fixed value. Furthermore, in this embodiment, the separator 1 has been described as being composed of a filter, but if the signal is a digital signal, the separator can be used not only to separate signals but also to include a regeneration function. By doing this and reproducing the signal, noise in the uplink to the satellite can be removed. In this case, since the magnitude of the regenerator output is constant regardless of the magnitude of the received power of the satellite, the amplification amount of each of the amplifier groups may be determined by considering only the scale of the receiving station.

〔Effect of the invention〕

As described in detail above, according to the present invention, there is an effect that communication between small earth stations can be easily realized.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a diagram showing the operation of each amplifier shown in FIG. 1. 1... Separator, 10, 11, 12, 13, 50
...Amplifier (AMP), 40...Coupler.

Claims (1)

[Claims] 1. In a satellite communication system in which multiple earth stations share a satellite, a separator that separates and extracts the received signal from each earth station, and an amplifier that amplifies the output of the separator independently according to the scale of the transmitting and receiving earth stations. A satellite relay device comprising: a group of amplifiers; and a combiner for recombining outputs of the group of amplifiers.