JPH0326027A - Redundancy changeover device - Google Patents

Abstract

PURPOSE:To decrease a time of line interruption at the time of switching redundancy to improve the reliability by setting the frequency of a recovered carrier for an on-line system demodulation before a fault takes place to the center frequency of a voltage controlled oscillator (VCXO) of a standby system demodulator. CONSTITUTION:An output frequency of a carrier recover VCXO of each ON-line system demodulator 2 measured by a measuring means 21 is fed to a storage circuit 22 in a redundancy switching controller 4 periodically and stored depending on each ON-line system demodulator 2. When any of the ON-line system demodulators 2 is faulty, the redundancy switching controller 4 sets the output frequency of the carrier recovery VCXO of the faulty ON-line system demodulator 2 to be the center frequency of the carrier recovery VCXO of a standby system demodulator 3. Thus, the frequency is acquired quickly at the redundancy changeover, the time interrupting the line is decreased and a redundancy switching system with high reliability is obtained.

Description

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

[Conventional technology]

FIG. 3 is a block diagram showing a conventional redundant switching method.
In the figure, 1 is an input terminal for a received IF signal, 2 is an N online digital demodulator, 3 is one standby digital demodulator, 4 is a redundant switching controller, 5 is a baseband switch circuit, and 6 is an N online system digital demodulator. This is an output terminal for demodulated digital signals.

Next, the operation will be explained.

The frequency division multiplexed reception IF signal of N waves which is manually inputted from terminal l and subjected to digital modulation (for example, PSK modulation) is demultiplexed to N units of online demodulators 2 and one standby demodulator 3, and then Each frequency-divided wave is demodulated by each online demodulator 2 and output as baseband digital data. The redundant switching controller 4 constantly monitors the operating status of the N online demodulators 2, and selects any one of the online demodulators 2.
When a fault signal is input due to a failure in the standby demodulator 3, the frequency channel of the wave received by the online demodulator 2 is set to the synthesizer of that demodulator, and then the baseband switch circuit 5 is switched on. Switch and
Instead of the digital data output of the online demodulator 2, the digital data output of the standby demodulator 3 is output.

[Problem to be solved by the invention]

Such digital demodulators, especially those operating in continuous mode with a low C/N, usually use a synchronous detection method, which uses the carrier frequency of the received modulated wave and the voltage-controlled oscillator for carrier wave regeneration in the demodulator ( If the initial frequency difference from the output frequency of the VCXO is large, it takes time to synchronize the carrier wave. In particular, when operation at a low bit rate and low C/N is required, it is necessary to narrow the band of the carrier wave regeneration loop, and the reception frequency channel requires several tens of seconds to several minutes to synchronize the carrier frequency. Since it is a new null value and has a large frequency deviation with the input received modulated wave,
The problem was that it took a long time to acquire the frequency, and the line would be disconnected during that time.

This invention was made to solve the above-mentioned problems, and by shortening the synchronization acquisition time of the standby system demodulator and shortening the line disconnection time when redundant switching is performed, extremely reliable reliability can be achieved. The purpose is to obtain a high redundancy switching device for a digital demodulator.

[Means to solve the problem]

The redundancy switching device according to the present invention is provided with a circuit for measuring the output frequency of the carrier wave regeneration VCXO of each online demodulator, and transmits the measurement results to the redundancy switching controller to be stored in L7, and redundancy switching is performed. When performing this, the frequency of the failed online system is set in the standby system demodulator as the center frequency of the standby system carrier wave regeneration VCXO by the redundant switching controller.

[Effect]

The redundancy switching method in the present invention sets the frequency of the regenerated carrier wave of the online demodulator before failure to the center frequency of the VCXO of the standby demodulator, so that the input carrier wave of the standby system demodulator and the VCXO output regenerated carrier wave can be changed. Since the frequency deviation between the two can be made extremely small, the acquisition time of the recovered carrier wave of the standby system demodulator can be shortened.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, the same symbols as in FIG. 3 indicate the same parts,
21 is means for measuring the frequency of carrier wave regeneration VCXO of the online system demodulator 2; 22 is a redundant switching controller 4;
A storage circuit (memory circuit) 23 inside is means for setting the center frequency of the carrier wave reproducing vCX○ of the standby system demodulator 3.

Next, we will explain the operation. In the diagram of kings, the output frequency of the VCXO for carrier wave regeneration of each online system demodulator 2 is measured by the measuring means 21, for example, by directly counting the VCXO output frequency or by measuring the input control voltage of the VCXO. , is periodically sent as one of the monitoring signals from each online system demodulator 2 to the storage circuit 22 in the redundant switching controller 4, and each online system demodulator! It is stored separately in S2. The stored frequency value is updated to the latest value each time the measurement results from the online demodulator 2 are sent. Next, if one of the online demodulators 2 fails,
A fault signal is input from the online demodulator 2 to the redundancy switching controller 4. At this time, the redundant switching controller 4 returns to the standby system! The frequency of the synthesizer for the J unit 3 is set to the frequency of the synthesizer of the failed online system demodulator 2, and the memory circuit 2
The frequency setting means 2 sets the output frequency of the VCXO for carrier wave regeneration of the failed online demodulator 2 stored in the frequency setting means 2.
3, the standby system demodulator 3 carrier wave regeneration VCX
Set as the center frequency of o.

In this embodiment, the frequency can be captured quickly,
Therefore, the time during which the line is disconnected is shortened, and a highly reliable redundant switching system can be obtained.

In addition, in the above embodiment, the case of l:N redundancy switching system in which the number of online demodulators is N and the standby demodulator is one is shown, but the number of online demodulators is N and the standby demodulator is M. The present invention is similarly applicable to the case of a MAN (M.>l), and a 2:N redundancy switching system of a second embodiment in which M=2 is shown in FIG.

〔Effect of the invention〕

As described above, according to the present invention, the output frequency of the vCxO for carrier wave regeneration of the online system demodulator that has failed during redundancy switching is set as the center frequency of the carrier wave regeneration ■CX○ of the standby system demodulator. , the frequency can be acquired quickly, therefore the time when the line is disconnected is shortened,
This has the effect of providing a highly reliable redundant switching method.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a redundant switching device according to one embodiment of the invention, FIG. 2 is a block diagram showing a redundant switching device according to another embodiment of the invention, and FIG. 3 shows a conventional redundant switching system. It is a block diagram. 1 is an input terminal for a received IF signal, 2 is an online digital demodulator, 3 is a standby digital demodulator, 4 is a redundant switching controller, 5 is a baseband switch circuit, 6 is an output terminal for a demodulated digital signal, 21 22 is a means for measuring the frequency of the reproduced carrier wave, 22 is a means for storing the frequency, and 23 is a means for setting the frequency. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In a redundancy switching device for demodulators in digital satellite communication, means for measuring the frequency of the regenerated carrier wave of each online demodulator, means for storing each of the frequencies, and the online demodulator that has failed during redundancy switching. redundant switching means for transmitting the frequency to a standby demodulator; and means for setting the frequency transmitted from the redundant switching means in the standby demodulator to a center frequency for frequency acquisition of its carrier regeneration circuit; A redundant switching device characterized by comprising: