JPH04373220A - Satellite communication system and equipment - Google Patents

Abstract

PURPOSE:To simplify the configuration of a base station by eliminating the need for an IF switch having been required in a conventional system when a satellite is selected in a base station accessing plural satellites. CONSTITUTION:A ground base station 1 in the satellite communication system using plural satellites for a common service area for the service converts a transmission base band signal into a frequency of an IF band for each satellite by a MODEM circuit and accesses a relevant satellite via antennas 41-44 for each satellite. The ground base station 1 converts the reception radio wave for an RF band into a frequency of an IF band depending on each satellite, IF bands of satellites 91-92 are synthesized, the result is demodulated into a base band signal and the satellite to be communicated with the base station 1 is selected by the changeover of the IF band.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite communication system in which a service area is provided using a plurality of satellites. In particular, when a feeder link frequency is shared by a plurality of satellites and satellite identification uses the directivity of the base station antenna, it is related to the method of configuring the base station.

0002

2. Description of the Related Art A satellite communication system in which a service area is provided using a plurality of satellites will be described with reference to FIGS. 3 and 4. In the present invention, the number of satellites is assumed to be two for simplicity. FIG. 3 shows an example of a system configuration of a satellite communication method when a plurality of satellites are used, and FIG. 4 shows an example of frequency allocation of feeder links and service links in that case.

In FIG. 3, 1 is a base station, 21 is a satellite A, 22 is a satellite B, 31 is a slave station A, and 32 is a slave station B. In this case, the slave station A31 uses the satellite A21 to access the base station. The slave station B32 is shown communicating with the base station 1 using the satellite B22.

In FIG. 4, (a) shows the feeder link frequency arrangement of satellite A21, and (b) shows the feeder link frequency arrangement of satellite B22.
shows the feeder link frequency arrangement. Also (c)
indicates the service link frequency allocation of satellite A21, and (
d) shows the service link frequency allocation of satellite B22. This figure shows an example in which bandwidth B is used as both the service link and feeder link bands. As shown in Fig. 4, the antennas 41 and 42 of the base station 1 have sharp directivity, so two satellites can share the same feeder link frequency, but the antennas of the slave stations do not have very sharp directivity, so they can be used as a service link. The same frequency cannot be shared.

[0005] If the above-described configuration is used, if one of the satellites becomes temporarily unusable due to, for example, a sun transit, the mobile station can switch the frequency used, and the base station can switch the antenna system to which it is connected. Communication can be continued by switching.

FIG. 5 shows an example of the configuration of a base station according to the conventional method for realizing the above method. In the figure, 6 is IF
A group of modulators covering the bandwidth B, 7 is an IF switch circuit that switches the connection destination of the modulated signal, 81 and 82 are combiners, and 91 and 92 are frequency converters that convert the IF band to the RF band. Also, 101 and 102 are large power amplifiers, 41 and 42 are directional antennas, 111 and 11
2 is a transmitter/receiver duplexer, 121 and 122 are low noise amplifiers, and 131 and 132 are frequency converters for converting the RF band into the IF band. 141 and 142 are distributors, 15
16 is an IF switch circuit that switches the demodulation destination of the signal, and 16 is a demodulator group that covers the IF bandwidth B. In the above configuration, subscript 1 indicates a circuit for accessing satellite A21, and subscript 2 indicates a circuit for accessing satellite B22.

By switching the IF switch circuits 7 and 15, it is possible to select a satellite to which the signal group from the baseband section 5 should be connected.

[0008]

[Problem to be solved by the invention] As shown in FIG.
In the conventional base station configuration, the IF switch circuit 7
and 15 are required. This is an IF switch that has contacts for the number of communication channels in communication band B (the number of modulators in modulator group 6 and demodulator group 16), and this scale increases as the number of satellites increases. .

The present invention is directed to this large-scale IF switch circuit 7.
The purpose is to configure a base station that does not require the following.

0010

[Means for Solving the Problems] According to the present invention, a base station includes a modulation/demodulation circuit that can set a transmission or reception frequency to an arbitrary frequency in an IF band, and a base station that transmits a signal in the IF band to a plurality of IF bands with different frequencies. a circuit for distributing signals into groups, a circuit for synthesizing signals of a plurality of IF band groups having different frequencies, and a frequency conversion circuit for converting between each of the IF band groups having different frequencies and a single RF band; A plurality of antennas and RF circuits capable of accessing different satellites are provided, and when switching satellites to be accessed using the same modulation/demodulation circuit, satellite switching is realized by changing only the transmission or reception IF frequency of the modulation/demodulation circuit.

[0011]

[Operation] Since the RF circuit to be connected is selected by changing the IF frequency of the modulation/demodulation circuit, an IF switch circuit is not required. Also, the combiner and divider of the modulation/demodulation circuit group can be realized with half the number of conventional systems.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of the configuration of a base station used in the satellite communication system according to the present invention will be described with reference to FIGS. 1 and 2. In the present invention, for the sake of simplicity, it is assumed that the number of satellites is two, and the system configuration of the satellite communication system is assumed to be the configuration example shown in FIG. 3.

FIG. 1 shows an example of the configuration of a base station used in the satellite communication system according to the present invention, and FIG. 2 shows the relationship between the IF frequency and RF frequency of the base station configuration according to the present invention. Figure 2(a) shows the RF frequency for satellite A21, and Figure 2(a) shows the RF frequency for satellite A21.
(b) shows the RF frequency for satellite B22, both of which use the same frequency band B. Figure 2(c)
indicates an IF frequency, and in the present invention, IF bands corresponding to the number of satellites are used as the IF frequency. In this example, IF1 and IF2, each having band B, are used, and are for satellite A21 and satellite B22, respectively.

In FIG. 1, 6 is a modulator group covering IF1 and IF2 in FIG. 5(c), and 8 is a plurality of modulator groups 6.
17 is a 1:2 divider,
181 is a band pass filter for IF1 in FIG. 2(c),
182 is a band pass filter for IF2 in FIG. 2(c),
91 and 92 are frequency converters that convert IF1 and IF2 to the RF band, respectively. Also, 101 and 102
is a large power amplifier, 41 and 42 are directional antennas,
111 and 112 are transmitting/receiving duplexers, 121 and 122
is a low noise amplifier, 131 and 132 are RF
This is a frequency converter that converts the frequency band into IF1 and IF2. 19 is a 2-to-1 combiner, 14 is a distributor, and 16 is a 2-to-1 combiner, and 16 is a
) is a demodulator group that covers IF1 and IF2. In the above configuration, subscript 1 indicates a circuit for accessing satellite A21, and subscript 2 indicates a circuit for accessing satellite B22.

By using the above configuration, it becomes possible to select a satellite to which the signal group from the baseband section 5 should be connected by appropriately selecting the IF frequencies of the modulators 6 and 16.

[0016]

As described above in detail, the present invention has the following effects.

[0017] That is, in a satellite communication system in which a service area is provided using a plurality of satellites and a feeder link frequency is shared by the plurality of satellites,

The base station includes a modulation/demodulation circuit that can set the transmission or reception frequency to any frequency in the IF band, a circuit that distributes the IF band signal to a plurality of IF band groups with different frequencies, and a circuit that can set the transmission or reception frequency to any frequency in the IF band. A circuit that synthesizes signals of IF band groups, and IF band groups with different frequencies and a single RF
It is equipped with a frequency conversion circuit for converting bands, and multiple antennas and RF circuits that can each access different satellites, and when switching satellites to access using the same modulation/demodulation circuit, the transmitting or receiving I
It is now possible to switch satellites simply by changing the F frequency, eliminating the need for large-scale IF switch circuits that were previously required, and making it possible to implement large-scale combiners and dividers in half the size of conventional systems. The configuration of a base station used in a satellite communication system can be simplified.

[Brief explanation of drawings]

FIG. 1 shows an example of the configuration of a base station used in a satellite communication system according to the present invention.

FIG. 2 shows the relationship between IF frequency and RF frequency of the base station configuration according to the present invention, where (a) shows the RF frequency for satellite A, (b) shows the RF frequency for satellite B, and ( c.
) indicates the IF frequency.

FIG. 3 shows an example of a system configuration of a satellite communication method in which a service area is provided using a plurality of satellites.

FIG. 4 shows an example of frequency allocation of feeder links and service links in a satellite communication system when a service area is provided using multiple satellites; (a) shows the feeder link frequency allocation of satellite A; (b) shows the feeder link frequency arrangement of satellite B, (c) shows the service link frequency arrangement of satellite A, and (d) shows the service link frequency arrangement of satellite B.

FIG. 5 shows an example of a base station configuration used in a conventional satellite communication system.

[Explanation of symbols]

1 Base station 21 - 22 Satellite 31 - 32 Slave station 41 - 42 Base station antenna 5 Baseband section 6 Modulator group 7 IF switch circuit 81 - 82 Combiner 91 - 92 Frequency converter 101 - 102 High power amplifier 111 ~11
2 Transmission/reception duplexer 121 - 122 Low noise amplifier 131 - 132 Frequency converter 141 - 142 Distributor 15 IF switch circuit 16 Demodulator group 17 Distributor 181 - 182 Band pass filter 19 Synthesizer

Claims (2)

[Claims] Claim 1: In a satellite communication system that uses multiple satellites to service a common service area, a ground base station converts a transmission baseband signal into a frequency of an IF band for each satellite using a modulation/demodulation circuit, After distributing it to each satellite, it converts it into an RF band and accesses the corresponding satellite through the antenna of each satellite, and the ground base station converts the received radio waves in the RF band from the satellite into the IF band frequency determined for each satellite. A satellite communication system characterized by converting the IF bands of each satellite into baseband signals, demodulating them into a baseband signal, and switching the IF band to switch the satellite communicating with the base station. 2. A base station device that accesses a plurality of satellites, comprising: a modulator (6) that converts a transmission baseband signal into an IF band for each satellite; and a synthesizer (8) that combines the outputs of each IF band. , the output of the synthesizer (8) is
Means for distributing into F band (17, 181, 182) and means for converting each IF band into RF band for each satellite (91
, 92 ) and means ( 101 , 102 , 41 , 42 ) for transmitting RF band signals toward the satellite.
), means (131, 132) for converting received radio waves in the RF band from the satellite into an IF band determined for each satellite, means (19) for synthesizing the outputs, and demodulating one of the outputs for the IF band. demodulator (
16) A base station device characterized in that the base station device has the following and switches the satellite to communicate with by switching the IF band.