JPH0443450B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transmission frequency control system for an earth station in a satellite communication system. In particular, the present invention relates to a transmission frequency control method for earth stations that is used in earth stations equipped with working and backup transmission systems and that compensates for frequency fluctuations when switching from the working system to the protection system.

[Conventional technology]

Conventionally, in the transmission frequency control method, frequency control was performed by comparing the frequencies of the return signal transmitted by the own station and a fixed reference signal.

FIG. 3 is a block diagram of a conventional earth station transmission frequency control device. In FIG. 3, the active system is shown by adding "a" to the code, and the protection system is shown by adding "b" to the code. The transmission data signal is divided into two by a modulator 1 by a distributor 2, one of which is converted to a predetermined transmission frequency by a working frequency converter 3a, and transmitted from an antenna 6 to a satellite via a power amplifier 4a and a switch 5. . This signal is folded back by the satellite, received by the antenna 6, amplified by the low-noise amplifier 7, and divided into two by the distributor 8. One of the signals is converted to a predetermined frequency by the working system frequency converter 9a, and the working system frequency is The signal is input to the controller 10a.

FIG. 4 is a block diagram of a conventional automatic frequency controller of a transmission frequency converter of an earth station. Fourth
In the figure, a frequency error detector 102 detects a frequency error between the signal input to the active automatic frequency controller 10a and the reference signal of the reference frequency oscillator 101, and its polarity. This frequency error component is input to a frequency divider 103 and a selection controller 105, and the polarity is given to a reversible measuring device 107. When the frequency error is larger than a predetermined value, the selection controller 105 operates the reversible measuring device 107 using a divided signal obtained by dividing the frequency error component by the frequency divider 103.
When the frequency error is smaller than a predetermined value, the switch 106 is switched so that the reversible measuring device 107 operates according to a predetermined frequency control signal output from the frequency controller 104. The reversible measuring device 107 up-counts or down-counts based on these signals, and its digital value output is converted into an analog signal by the digital-to-analog converter 109 to control the frequency of the voltage-controlled oscillator 110. This controlled frequency signal is input to the frequency converter 3a shown in FIG. 3, forming a frequency control loop. The switching controller 13 performs switching between active and standby.

In this way, the control loop of the active transmission system that is actually transmitting radio waves constitutes a closed loop and operates normally, but the control loop of the backup transmission system that is not actually transmitting radio waves becomes an open loop and does not operate normally. No control action is performed. In other words, if there is a difference in the characteristics of the standby and working control loops, the frequency error will not necessarily be zero in the standby system even if it is zero in the working system, so the output value of the reversible measuring device 107 will be When is 12 bits, it easily moves to the extremes of ``000'' or ``FFF'' in hexadecimal notation. Therefore, when switching from the active system to the standby system, the frequency of the voltage controlled oscillator 110 is controlled from the maximum or minimum state to a predetermined value by the operation of the control loop, and a transient response may occur.

[Problem that the invention seeks to solve]

If the above-mentioned conventional device is used for both active and backup at an earth station that has active and backup transmission systems, when switching from the active system to the backup system, a large transient response will occur until the control value stabilizes to the correct value. There are drawbacks that occur.

The present invention solves the above-mentioned drawbacks and
It is an object of the present invention to provide a transmission frequency control method for an earth station that does not generate a large transient response even during backup switching and can immediately stabilize the control value to the correct control value.

[Means for solving problems]

The present invention comprises a working system and a backup system, each of which includes means for receiving a return signal of a transmitted signal from its own station at a satellite and detecting an error between the return signal frequency and a reference frequency; In a transmission frequency control method for an earth station, the control means includes a control means for automatically controlling the transmission signal frequency of the own station so that this error is within a predetermined value, and the control means includes a control means for automatically controlling the transmission signal frequency of the own station so that the error is within a predetermined value. It comprises register means for giving frequency information to the control means of the standby system, and means for starting automatic control of the transmission signal frequency according to the information in the register means when the working system is switched to the standby system. It is characterized by

[Effect]

The present invention records information on the frequency of a transmission signal being transmitted in the active system in a registration means, gives the information in this register means to the control means of the protection system, and when the active system is switched to the protection system, this information is recorded. By starting automatic control of the transmission signal frequency in accordance with this, it is possible to smoothly switch between the working system and the standby system without generating a large transient response.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a transmission frequency control device for an earth station according to an embodiment of the present invention. In FIG. 1, the active system is shown by adding "a" to the code, and the protection system is shown by adding "b" to the code. A transmission data signal is input to the modulator 1 from outside the figure. The modulated transmission signal from the modulator 1 is connected to the distributor 2 and distributed to the working system and the protection system. The working system output of the distributor 2 is connected to the working system frequency converter 3a. The output signal converted from the frequency converter 3a to a predetermined transmission frequency is connected to the power amplifier 4a, and the power amplified output signal from the power amplifier 4a is connected to the active system input of the switch 5. Similarly, the standby system output of the distributor 2 is connected to the standby system input of the switch 5 via the frequency converter 3b and the power amplifier 4b. The output signal of the switch 5 is connected to an antenna 6, and a transmission signal is sent from the antenna 6 to the satellite.

This transmitted signal is folded back by the satellite and sent to the antenna 6.
received at The output signal of the antenna 6 is connected to a low noise amplifier 7. The amplified output signal from the low noise amplifier 7 is connected to the input of the distributor 8 and distributed to the working system and the backup system. The working system output of the distributor 8 is connected to the working system frequency converter 9a.
An output signal converted to a predetermined frequency from the frequency converter 9a is connected to the active system input of the switch 11. Similarly, the standby system output of the distributor 8 is connected to the standby system input of the switch 11 via the frequency converter 9b. The output signal of switch 11 is connected to demodulator 12 . The demodulated received data signal from the demodulator 12 is sent out outside the figure.

Further, a switching control signal 201 from the switching controller 13 is connected to the switching devices 5 and 11 to switch between the active system and the standby system.

Here, the feature of the present invention is the automatic frequency control portion surrounded by a dashed line. That is, the switching control signal 201 of the switching controller 13 is connected to the selection register control input of the automatic frequency controllers 10a and 10b, and the input of the selection register is switched to the active system. The output signal of frequency converter 9a is connected to automatic frequency controller 10a. A signal of a predetermined frequency from the automatic frequency controller 10a is connected to the input of the frequency converter 3a. Similarly, the output signal of frequency converter 9b is connected to automatic frequency controller 10b. A signal of a predetermined frequency from the automatic frequency controller 10b is connected to the input of the frequency converter 3b. The output of the selection register of the automatic frequency controller 10a is also connected to the input of the selection register of the automatic frequency controller 10b via the data bus 202a,
The output of the selection register of the automatic frequency controller 10b is transmitted to the automatic frequency controller 1 via the data bus 202b.
Connected to the selection register input of 0a.

The operation of the earth station transmission frequency control device having such a configuration will be explained. FIG. 2 is a block diagram of the automatic frequency controller of the earth station transmission frequency control device of the present invention. show. Active system and standby system automatic frequency controllers 10a, 1
0b are selection registers 108a and 108b, respectively.
are provided and connected by data buses 202a and 202b.

Input data to the selection register 108a of the active system includes data from the reversible measuring instrument 107a that actually transmits radio waves and forms a closed loop, and data from the backup system that forms an open loop on the data bus 202.
The data input via b is input,
Data from the reversible measuring device 107a is selected by a switching control signal 201 from the switching controller 13, and frequency control is performed using this data.

The input data to the backup system selection register 108b is the data input via the data bus 202a that actually performs frequency control, and the backup system reversible measuring device 107b, which is in an open loop.
The data from the switching control signal 2 is input.
01 selects the data that actually performs frequency control, so the digital-to-analog converter 1
The input data of 09a and 109b are the same, and switching of the transmission system does not cause a large transient response. If the backup transmission system is used, digital-to-analog converters 109a, 109
The input data of b becomes the output data of the backup reversible measuring device 107b.

As described above, in the present invention, even if there is a difference in the characteristics of the active and standby transmission systems, the transient response of the transmission frequency at the time of switching is slight and smooth switching is performed.

〔Effect of the invention〕

As explained above, the present invention has an excellent effect of being able to smoothly switch from a working transmission system to a standby transmission system without generating a large transient response. Therefore, there is an advantage that efficient transmission frequency control can be performed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a transmission frequency control device for an earth station according to an embodiment of the present invention. FIG. 2 is a block diagram of the automatic frequency controller. FIG. 3 is a block diagram of a conventional earth station transmission frequency control device. Fourth
The figure is a block diagram of the automatic frequency control device. 1...Modulator, 2,8...Distributor, 3,9...
Frequency converter, 4... Power amplifier, 5, 11, 1
06...Switcher, 6...Antenna, 7...Low noise amplifier, 10...Automatic frequency controller, 12...Demodulator, 13...Switching controller, 101...Reference frequency oscillator, 102...Frequency error detector, 103
... Frequency divider, 104 ... Frequency controller, 105...
...Selection controller, 107...Reversible measuring device, 108...
...Selection register, 109...Digital-to-analog converter, 110...Voltage controlled oscillator, 201...
Switching control signal, 202...data bus.

Claims (1)

[Claims] 1. A working system and a backup system are provided, each of which receives a return signal of its own station's transmission signal at a satellite and detects an error between the return signal frequency and a reference frequency. and control means for automatically controlling the transmission signal frequency of the own station so that this error is within a predetermined value, the control means includes: register means for providing information on the transmission signal frequency of the transmission signal to the control means of the protection system; and means for starting automatic control of the transmission signal frequency according to the information in the register means when the working system is switched to the protection system. A transmission frequency control method for an earth station characterized by comprising: