JP3042083B2 - Earth station receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an earth station receiver.
In particular, the present invention relates to an earth station receiving apparatus for receiving a frequency division multiplexed signal via a communication satellite.

[0002]

2. Description of the Related Art When a frequency division multiplexed signal is received via a communication satellite, the signal cannot be received if the frequency fluctuation in the communication satellite body becomes relatively large compared to the transmission speed of the signal. For this reason, conventionally, a system pilot signal different from the transmission signal is transmitted from the reference station side of the system, and the earth station receiver compares the system pilot signal with the reference oscillation signal to control the local oscillation frequency. By adding an automatic frequency controller (AFC), demodulation is performed by canceling out frequency fluctuations in the communication satellite body. Also, an AFC function is provided in the demodulator of the earth station receiving device, and the AFC pull-in range is extended beyond the maximum value of the frequency fluctuation of the communication satellite body.

[0003]

As described above, since the AFC is provided in order to cope with the frequency fluctuation in the communication satellite main body, there is a problem that the device configuration is complicated and the cost is high. In addition, when extending the AFC pull-in range, there is a possibility of erroneous synchronization with an adjacent transmission signal. Therefore, it is necessary to set the interval between the transmission signals to be equal to or more than the maximum value of the frequency fluctuation of the communication satellite body. There is a problem that the frequency use efficiency in the transmission band is reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an earth station capable of coping with a frequency fluctuation of a communication satellite main body without providing a dedicated AFC and without extending an AFC pull-in range beyond a maximum frequency fluctuation of the communication satellite main body. A receiving device is provided.

[0005]

According to the present invention, there is provided an earth station receiving apparatus comprising: a frequency converter for converting a received signal into an intermediate frequency signal; and a voltage controlled oscillator for outputting an oscillation signal having a frequency corresponding to an oscillation control voltage. A demodulation unit that demodulates the intermediate frequency signal in accordance with the oscillation signal and outputs a demodulated signal, and a phase comparison unit that detects a phase difference between the oscillation signal and the intermediate frequency signal and generates a phase difference voltage. A sweep control unit that generates a sweep voltage that changes in a predetermined voltage range to sweep the oscillation frequency of the voltage control oscillator, and generates the oscillation control voltage by adding the phase difference voltage and the sweep voltage. An adder that performs synchronization, a synchronization detector that detects when a predetermined signal of the demodulated signal is synchronized with the oscillation signal, and a memory that stores a value of the sweep voltage. Further, at the start of the operation, the sweep control unit greatly changes the sweep voltage so that the oscillation signal sweeps beyond the maximum value of the frequency variation on the communication satellite side, and the synchronization detection unit, from the reference station, When the synchronization between the transmitted system pilot signal and the oscillation signal is detected, the sweep is stopped, the value of the sweep voltage at the time of stopping the sweep is stored in the memory unit, and then the sweep stored in the memory unit is performed. The sweep voltage is changed small around the value of the sweep voltage at the time of stop, the synchronization detection unit,
The sweep is stopped when the synchronization between the desired signal and the oscillation signal is detected.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. The reception signal S1 is mixed with a local oscillation signal from the local oscillation unit 2 by the frequency conversion unit 1 to generate a predetermined intermediate frequency signal S2.
And demodulated by the demodulation unit 3 and output as a demodulated signal S3. Here, the local oscillation unit 2 is, for example, a frequency synthesizer, and a control signal C1 from the control unit 10.
Sends out a local oscillation signal of the frequency designated by.

The earth station receiving apparatus of the present invention oscillates at a frequency corresponding to the oscillation control voltage Vc and outputs an oscillation signal Sv, an oscillation signal Sv and an intermediate frequency signal S2. And the phase difference voltage Vp
, A synchronization detection unit 6 that detects when a predetermined signal is detected from the demodulated signal S3 to synchronize with the oscillation signal Sv, and a sweep voltage Vs that sweeps the oscillation frequency of the voltage control oscillation unit 4. , A summation unit 8 that adds the phase difference voltage Vp and the sweep voltage Vs to generate the oscillation control voltage Vc, and a memory unit 9 that stores the value of the sweep voltage Vs. .

Next, the operation will be described.

First, at the start of operation, a mode selection signal Sm is supplied to the control unit 10 to designate an initial mode. Control unit 1
0 transmits the control signal C1 to the local oscillating unit 2 and designates a local oscillation signal corresponding to the system pilot signal among radio waves from the communication satellite. At the same time, the control signal C is sent to the sweep control unit 7.
Send 2 to specify wide-area sweep mode. Sweep controller 7
Controls the sweep voltage Vs so that the frequency of the oscillation signal Sv of the VCO 4 sweeps beyond the maximum value of the frequency variation of the communication satellite body. The demodulation unit 3 demodulates the intermediate frequency signal S2 according to the oscillation signal Sv. The synchronization detector 6 detects the system pilot signal and outputs the oscillation signal S
The synchronization detection signal Ss is sent to the sweep control unit 7 when synchronization with v is detected. Upon receiving the synchronization detection signal Ss, the sweep control unit 7 stops the sweep, and causes the memory unit 9 to store the value of the sweep voltage Vs at the time when the sweep is stopped.

Next, the control unit 1 is controlled by the mode selection signal Sm.
Specify the operation mode as 0. The control unit 10 controls the control signal C
2 specifies the narrow-range sweep mode to the sweep control unit 7. The sweep control unit 7 reads the value of the sweep voltage Vs at the time of the stop of the sweep stored in the memory unit 9 and changes the sweep voltage Vs to a small value around the voltage value. The demodulation unit 3 outputs the oscillation signal S
The intermediate frequency signal S2 is demodulated according to v. Synchronization detector 6
Detects the desired signal included in the demodulated signal S3 and detects when it synchronizes with the oscillation signal Sv, and sends out a synchronization detection signal Ss to the sweep control unit 7. The sweep control unit 7 stops the sweep receiving the synchronization detection signal Ss.

By doing so, the sweep range in the operation mode can be synchronized if it is equal to or greater than the difference between the transmission frequency of the reference station transmitting the system pilot signal and the transmission frequency of the earth station transmitting the transmission signal. It can be made much smaller than the frequency fluctuation of the normal communication satellite body.
Therefore, there is no possibility of erroneous synchronization with an adjacent transmission signal even if the interval between transmission signals is not widened.

In this embodiment, the mode selection signal is supplied from the outside. However, the mode may be automatically switched to the initial mode when the power is turned on, and the operation mode may be switched to the operation mode when synchronization is established.

[0014]

As described above, according to the present invention, when the operation is started, the sweep control unit is set to the wide-area sweep mode to greatly change the sweep voltage Vs, and the frequency of the oscillation signal of the VCO is changed to the frequency of the communication satellite body. Sweep beyond the maximum value of the fluctuation,
Stop the sweep when synchronized with the system pilot signal, store the value of the sweep voltage at the time of the sweep stop in the memory,
After that, the sweep control unit is set to the operation mode, the value of the sweep voltage at the time of the stop of the sweep stored in the memory is read out, and the sweep voltage is changed small around this voltage value, and the sweep is performed when a desired signal is detected. , The sweep range in the operation mode can be reduced.
Even if the FC circuit is not provided and the interval between the transmission signals is not widened, it is possible to cope with the frequency fluctuation of the communication satellite body without erroneous synchronization with the adjacent transmission signal.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Frequency conversion part 3 Demodulation part 4 Voltage control oscillation part (VCO) 5 Phase comparison part 6 Synchronization detection part 7 Sweep control part 8 Addition part 9 Memory part S1 Reception signal S2 Intermediate frequency signal S3 Demodulation signal Ss Synchronization detection signal Sv Oscillation signal Vc Oscillation control voltage Vp Phase difference voltage Vs Sweep voltage

Claims (2)

(57) [Claims] A frequency converter for converting a received signal into an intermediate frequency signal; a voltage controlled oscillator for outputting an oscillation signal having a frequency corresponding to an oscillation control voltage; and a demodulator for demodulating the intermediate frequency signal according to the oscillation signal. A demodulation unit for outputting a demodulated signal
A phase comparison unit that detects a phase difference between the oscillation signal and the intermediate frequency signal to generate a phase difference voltage, and a sweep voltage that changes in a predetermined voltage range to sweep the oscillation frequency of the voltage control oscillation unit. A sweep control unit for generating, an adding unit for adding the phase difference voltage and the sweep voltage to generate the oscillation control voltage, and detecting when a predetermined signal of the demodulated signal is synchronized with the oscillation signal. An earth station receiving device comprising: a synchronization detecting unit; and a memory unit for storing the value of the sweep voltage. 2. The method according to claim 1, wherein the sweep control section changes the sweep voltage so that the oscillation signal sweeps beyond a maximum value of a frequency variation on the communication satellite side when the operation is started. When the synchronization between the system pilot signal transmitted from the reference station and the oscillation signal is detected, the sweep is stopped, and the value of the sweep voltage at the time of stopping the sweep is stored in the memory unit. The sweep voltage is changed to be small around the value of the sweep voltage at the time of stopping the sweep, and the synchronization detection unit stops the sweep when the synchronization between the desired signal and the oscillation signal is detected. The earth station receiving device according to claim 1.