JPH0799470A - Automatic frequency control system - Google Patents

Abstract

PURPOSE:To provide an automatic frequency control system in which equipments of each earth station are simplified and the economy is improved. CONSTITUTION:A reference earth station 1 is provided with a pilot signal transmission means 2 sending a pilot signal P1 to a satellite 80, a pilot signal reception means 3 receiving the pilot signal P2 sent from the satellite 80 via a repeater, a pilot signal frequency deviation detection means 4 detecting a frequency deviation of the received pilot signal P2, and a transmission frequency conversion means 5 correcting a transmission frequency of an SCPC carrier S1 based on the frequency deviation of the pilot signal P2 detected by the pilot signal frequency deviation detection means 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic frequency control system applied to the SCPC system which is one of satellite communication systems.

[0002]

2. Description of the Related Art Generally, in a satellite communication system based on the narrow band communication of the SCPC system, when transmitting an SCPC carrier wave from a reference earth station to each earth station via a satellite,
Since the carrier wave undergoes frequency fluctuations at the satellite repeater,
An automatic frequency control method is used to correct this frequency fluctuation using a pilot signal.

Conventionally, this kind of automatic frequency control method is performed by correcting the reception frequency of the reception frequency converter 203 by an automatic frequency controller 210 provided in each earth station 200, as shown in FIG. It was Specifically, a pilot signal is oscillated from the pilot oscillator 101 of the reference earth station 100, and is transmitted from the antenna 104 to the satellite 150 via the transmission frequency converter 102 and the high power amplifier 103. Then, the satellite 150 receives and the satellite 15
The pilot signal that has undergone frequency fluctuations at the repeater of 0 is received by the antenna 201 of each earth station 200, and is input to the reception frequency converter 203 via the low noise amplifier 202. This pilot signal is input from the reception frequency converter 203 to the automatic frequency controller 210 and compared with the reference frequency of the reference frequency oscillator in the automatic frequency controller 210. From this comparison, the frequency deviation due to the frequency fluctuation in the satellite 150 is obtained, and the frequency deviation information is input from the automatic frequency controller 210 to the reception frequency converter 203.

As a result, the output frequency is changed in the reception frequency converter 203, and the SCPC from the reference earth station 100 is changed.
When the carrier wave is received, it is corrected to a normal frequency by the reception frequency converter 203 of each earth station 200 and input to the demodulator 204. As a technique similar to this technique, Japanese Patent Laid-Open Nos. 61-251240 and 58-58
There are techniques described in JP-A-178639 and JP-A-58-75935.

[0005]

However, in the above-mentioned conventional automatic frequency control system, since it is necessary to provide the automatic frequency controller 210 in all the earth stations 200 on the receiving side, the equipment of each earth station 200 is complicated. become. For this reason,
There is a problem that the manufacturing cost of each earth station 200 becomes high and the economy is poor. In particular, a very small earth station (VSA) that requires a large number of stations and must focus on the economical efficiency of the equipment.
When T) is applied to the earth station 200, a great economic demerit occurs.

The present invention has been made in view of the above problems, and an object thereof is to provide an automatic frequency control system capable of simplifying the equipment of each earth station and improving the economical efficiency.

[0007]

In order to achieve the above object, the automatic frequency control method of the present invention uses the pilot signal transmitted from the reference earth station and received via the relay of the satellite to repeat the relay. In the automatic frequency control method for compensating for the frequency deviation generated in the transmitter, the pilot signal transmitting means for transmitting the pilot signal to the satellite is transmitted to the reference earth station, and the satellite transmitted from the satellite via the repeater. Pilot signal receiving means for receiving the pilot signal, pilot signal frequency deviation detecting means for detecting the frequency deviation of the pilot signal received by this pilot signal receiving means, and frequency of the pilot signal detected by this pilot signal frequency deviation detecting means Based on the deviation, the SCPC (Songle Channel Per
Carrier) Transmission frequency conversion means for correcting the transmission frequency of the carrier wave is provided.

Further, in the automatic frequency control system according to a second aspect of the present invention, in the first aspect, the pilot signal transmitting means converts a pilot oscillator for oscillating a transmission pilot signal into a predetermined frequency. A transmission frequency converter, the pilot signal receiving means has a reception frequency converter for converting a reception pilot signal into a predetermined frequency, and the pilot signal frequency deviation detecting means receives from the reception frequency converter. The transmission frequency converting means detects a difference between the frequency of the pilot signal and the frequency of the transmission pilot signal from the pilot oscillator, and outputs a control signal corresponding to the frequency difference. And a modulator for generating and outputting the SCPC carrier wave from the modulator based on the control signal. It is constituted with a transmission frequency converter for correcting the wavenumber.

[0009]

According to the above automatic frequency control method, the pilot signal transmitted from the pilot signal transmitting means of the reference earth station and transmitted from the satellite via the repeater of the satellite is
It is received by the pilot signal receiving means. The pilot signal received by the pilot signal receiving means has its frequency deviation detected by the pilot signal frequency deviation detecting means, and based on this frequency deviation, the transmission frequency-corrected SCPC carrier wave is transmitted by the transmission frequency converting means. Sent to satellite.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an automatic frequency control method according to an embodiment of the present invention. In the present embodiment, when the SCPC carrier wave is transmitted from the reference station 1 to the earth station 90 via the satellite 80, the reference station 1 automatically controls the frequency of the transmitted SCPC carrier wave.

The reference earth station 1 includes pilot signal transmitting means 2 for transmitting the pilot signal P1 to the satellite 80,
The pilot signal receiving means 3 for receiving the pilot signal P2 transmitted via the repeater mounted on the satellite 80, the frequency difference detector 4 as the pilot signal frequency deviation detecting means, and the SCPC carrier wave S1. Satellite 80
For transmitting to the PCC carrier wave transmission unit 5 and the satellite 80
And an SCPC carrier wave receiving unit 6 for receiving the SCPC carrier wave S2 transmitted from

The pilot signal transmitting means 2 comprises a pilot oscillator 21 which oscillates the pilot signal P1. A transmission frequency converter 22 is provided on the output side of the pilot oscillator 21, and the transmission frequency of the pilot signal P1 from the pilot oscillator 21 is appropriately converted. A high power amplifier 23 is provided on the output side of the transmission frequency converter 22, and the pilot signal P1 from the transmission frequency converter 22 is amplified and sent to the antenna 70.

The pilot signal receiving means 3 has an antenna 7
0, a reception frequency converter 32 for converting the reception frequency of the pilot signal P2 received via the low noise amplifier 31 into a predetermined frequency. The pilot signal P2 whose frequency is converted by the reception frequency converter 32 is output to the frequency difference detector 4.

The frequency difference detector 4 is the reception frequency converter 3
2 detects the difference between the frequency of the received pilot signal P2 from the transmitter 2 and the frequency of the transmitted pilot signal P1 from the pilot oscillator 21, and the control signal C corresponding to the frequency difference is SC.
It has a function of outputting to the PC carrier wave transmission unit 5.

The SCPC carrier wave transmission section 5 is composed of a modulator 51 for forming and outputting the SCPC carrier wave S1 and a transmission frequency converter 52 as a transmission frequency conversion means. The transmission frequency converter 52 has a function of correcting the transmission frequency of the SCPC carrier S1 based on the control signal C from the frequency difference detector 4. That is, the control signal C from the frequency difference detector 4 is the received pilot signal P.
2 shows the frequency deviation with respect to two transmission pilot signals P1. Specifically, since the control signal C indicates the frequency variation generated by the repeater of the satellite 80, the correction performed by the transmission frequency converter 52 is the frequency variation generated by the repeater of the satellite 80. Correction will be performed. In this way, the output is formed by the modulator 51, and the transmission frequency converter 52 is formed.
The frequency-corrected SCPC carrier wave S1 is amplified by the high power amplifier 23 and transmitted to the receiving side earth station 90 via the antenna 70 and the satellite 80.

The SCPC carrier receiver 6 is composed of a reception frequency converter 61 and a demodulator 62. The reception frequency converter 61 has a function of appropriately converting the frequency of the SCPC carrier S2 received via the antenna 70 and the low noise amplifier 31 based on the pilot signal S1 from the pilot oscillator 21, and the demodulator 62 is , The reception SCPC carrier S2 from the reception frequency converter 61 is demodulated.

Next, the operation of this embodiment will be described.
The pilot signal P1 oscillated from the pilot oscillator 21 of the reference station 1 is frequency-converted by the transmission frequency converter 22, and then amplified by the high power amplifier 23. The pilot signal P1 amplified by the high power amplifier 23 is transmitted from the antenna 70 to the satellite 80.

The satellite 80 receives the pilot signal P1 from the reference station 1 and uses it as the pilot signal P2.
However, since the pilot signal P1 undergoes frequency fluctuation in the repeater of the satellite 80, the pilot signal P1 will be transmitted to the reference station 1 as the pilot signal P2 having frequency fluctuation.

The pilot signal P2 from the satellite 80 is received by the reception frequency converter 32 via the antenna 70 and the low noise amplifier 31. The reception pilot signal P2 is converted to a predetermined frequency by the reception frequency converter 32 and then output to the frequency difference detector 4.

In the frequency difference detector 4, the frequency of the received pilot signal P2 that has undergone this frequency fluctuation is compared with the frequency of the transmitted pilot signal P1 from the pilot oscillator 21 that has not undergone frequency fluctuation, and these frequencies are compared. The difference is detected, and the control signal C corresponding to the frequency difference is output to the transmission frequency converter 52.

In the transmission frequency converter 52, the frequency of the SCPC carrier S1 formed by the modulator 51 is corrected based on the control signal C from the frequency difference detector 4. That is, for the SCPC carrier wave S1 from the modulator 51,
The pilot signal S1 generated by the repeater of the satellite 80 is corrected by the amount of frequency fluctuation. In this way, the SCPC carrier wave S whose frequency is corrected by the transmission frequency converter 52
1 is amplified by the high power amplifier 23 and transmitted to the satellite 80 via the antenna 70.

SCPC carrier wave S transmitted from the reference station 1.
1 is received by the repeater of the satellite 80 and the satellite 8 is transmitted to the earth station 90.
Sent from 0. At this time, the repeater of the satellite 80 causes the SCPC carrier wave S1 to undergo frequency fluctuations. As described above, since the reference station 1 has corrected the frequency fluctuations, the SCP transmitted to the earth station 90 is corrected.
The C transmission wave S1 will be transmitted as a carrier wave having a normal frequency.

As described above, according to the automatic frequency control system of the present embodiment, the reference station 1 corrects the frequency of the SCPC carrier S1 in response to the frequency fluctuation caused by the repeater of the satellite 80, and transmits it to the earth station 90. Therefore, it is not necessary to specially provide an automatic frequency control device for correcting the frequency of the SCPC carrier S1 in each earth station 90 on the receiving side. Therefore, the device of each earth station 90 can be simplified, the manufacturing cost of the earth station 90 can be reduced, and the economic efficiency can be improved. In particular,
If it is applied to a very small earth station (VAST) 90, which requires a large number of stations and requires great importance to the economical efficiency of the device, a great economic effect is produced.

[0024]

As described above, according to the automatic frequency control system of the present invention, the frequency of the SCPC carrier wave is corrected at the reference earth station, so that the above-mentioned automatic frequency controller is specially provided for each receiving earth station. Since it is not necessary to provide the device, the equipment of each earth station can be simplified. As a result, the manufacturing cost of the earth station can be reduced, and the economic efficiency can be improved. In particular, if the present invention is applied to a very small earth station (VSAT), which requires a large number of stations and places importance on the economical efficiency of the apparatus, a great economic effect is produced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an automatic frequency control method according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an automatic frequency control method according to a conventional example.

[Explanation of symbols]

 1 Reference Earth Station 2 Pilot Signal Transmitting Means 3 Pilot Signal Receiving Means 4 Pilot Signal Frequency Deviation Detecting Means 5 Transmission Frequency Converting Means 80 Satellites 90 Earth Stations P1, P2 Pilot Signals S1, S2 SCPC Carriers

Claims (2)

[Claims] 1. An automatic frequency control system for compensating a frequency deviation generated in the repeater by using a pilot signal transmitted from the reference earth station and received via a repeater of a satellite, Pilot signal transmitting means for transmitting the pilot signal to the satellite, pilot signal receiving means for receiving the pilot signal transmitted from the satellite via the repeater, and pilot signal receiving means for receiving the pilot signal Based on the pilot signal frequency deviation detecting means for detecting the frequency deviation of the pilot signal and the frequency deviation of the pilot signal detected by the pilot signal frequency deviation detecting means, the SCPC (Sng
le Channel Per Carrier) A transmission frequency conversion means for correcting the transmission frequency of a carrier wave is provided. 2. The pilot signal transmitting means includes a pilot oscillator that oscillates the transmission pilot signal, and a transmission frequency converter that converts the transmission pilot signal into a predetermined frequency, and the pilot signal receiving means includes the reception pilot. The pilot signal frequency deviation detecting means has a reception frequency converter for converting a signal to a predetermined frequency, and the pilot signal frequency deviation detecting means is a difference between the frequency of the reception pilot signal from the reception frequency converter and the frequency of the transmission pilot signal from the pilot oscillator. And a frequency difference detector for outputting a control signal corresponding to the frequency difference, wherein the transmission frequency conversion means is a modulator for forming and outputting an SCPC carrier, and a modulator for outputting the control signal based on the control signal. And a transmission frequency converter that corrects the frequency of the SCPC carrier wave. Method.