JPS61230434A - Active and standby changeover system - Google Patents

Abstract

PURPOSE:To obtain a digital signal with less error by synchronizing respectively an output of a local oscillator of the transmission and reception side to an output of the 1st and 2nd highly stable oscillator so as to eliminate the deviation of the frequency at the transmission and reception side. CONSTITUTION:An output of a VCXO of the transmission side and that of the reception side are synchronized respectively with the output of the 1st and 2nd highly stable oscillators 17, 18. Thus, VCO11-1-13-1 of the transmission side and VCXO14-1-16-1 of the reception side are oscillated respectively at the same frequency. When an active receiver 15 is changed over into a standby receiver 14 because of a fault of, e.g., an active transmitter 12, since no deviation of the intermediate frequency exists in the standby receiver, the locking time of a PLL circuit is almost neglected and a digital signal with less error is obtained. Since the deviation of the oscillating frequency between the local oscillator of the transmission and reception sides does not exist in this way, the digital signal with less error is obtained independently of the changeover of the active and standby receivers.

Description

[Detailed Description of the Invention] [Summary] The present invention provides outputs of local oscillators on the transmitting side and receiving side to first and second high-stability oscillators, respectively, when switching between active and backup systems used in a microwave digital radio line. By synchronizing each with the output of the oscillator, it is possible to obtain a digital signal with fewer errors.

[Industrial application field]

The present invention relates to an improvement in a working protection switching system used in microwave digital radio lines.

In general, there are various types of active backup configurations for wireless lines, but for example, in the case of a band where the use of frequencies is particularly restricted, two types of digital signals are transmitted at the same frequency with different polarization planes, and it is used as a backup wireless device. There is a 50% set backup method that allows switching between two active wireless devices with different planes of polarization.

In such a working protection switching system, since digital signals are being transmitted, there is a need for a protection switching system that can extract digital signals with fewer errors even when switching between the working transceiver and the protection transceiver.

[Conventional technology]

FIG. 3 shows a block diagram of a conventional example of a 50% set reserve switching system.

In the figure, the transmitting side during normal operation transmits the digital signal -1 applied to the terminal IN-1 to the baseband switch 1, for example.
In addition to the working transmitter 3, a modulated wave is obtained through the transmitter 3. This modulated wave is mixed in the microwave section 3-2 with the output of the transmitting local oscillator 3-1 composed of a crystal oscillator, and is mixed with the output of the transmitting local oscillator 3-1, which is made up of a crystal oscillator, and is then mixed with the output of the transmitting local oscillator 3-1, which is made up of a crystal oscillator, to a predetermined frequency fO.
and is converted into an output and sent to a high frequency switch 5. The signal is transmitted to the outside through an antenna, for example, with vertical polarization V.

On the receiving side, the received wave that has passed through the high frequency switch 6 is mixed with the output from a receiving local oscillator 8-1 composed of a crystal oscillator in the working receiver 8 and converted into an intermediate frequency wave. Then, a carrier wave regeneration circuit (not shown) in the intermediate frequency section (IP section in the figure) of the receiver 8 regenerates a carrier wave component from this wave, and uses this regenerated carrier wave to convert the received wave into a digital signal - 1 is taken out and transmitted from the terminal OυT −1 through the baseband switch 10.

Incidentally, the working transmitter 2 and the working receiver a7 also transmit the digital signal -2 to the outside in the same manner as described above, and the standby transmitter 4 and standby receiver 9, for example, stand by in an operating state (all frequencies are fo).

Here, when a failure occurs in the active transmitter 3, the baseband switchers 1 and 10 and the high frequency switcher 5.6 operate, and the digital signal -1 is transmitted to the backup transmitter 4. It is transmitted from the terminal o'r-i through the standby receiver 9.

Furthermore, the transmitting local oscillator 2-1.3-1.4-1 and the receiving local oscillator? Since the crystal oscillators constituting -1, 8-1, and 9-1 each operate independently, the oscillation frequencies differ within tolerance due to changes over time or deviations in initial settings.

[Problem that the invention seeks to solve]

Therefore, for example, when switching from the working transmitter 3 to the backup transmitter 4, the transmission frequency shift is Δf1, and when switching from the working receiver 8 to the backup receiver 9, the intermediate frequency shift is Δf2.
When the free run deviation of the intermediate frequency VCO is Δf3, the deviation in the intermediate frequency when the backup receiver 9 receives the wave from the backup transmitter 4 is (Δf1+Δf2+Δf3).

It is said that the larger the difference in intermediate frequency becomes, the slower the pull-in operation of the phase-locked circuit (hereinafter abbreviated as PLL circuit) in the carrier regeneration circuit in the backup receiver 9 becomes, and the more erroneous digital signals are output. A problem arises.

[Means for solving problems]

The above problem can be solved by the working transmitters (12, 13) and the standby transmitter (11), as shown in the principle block diagram of the present invention in FIG.
) of the local oscillators (12-1, 13-1, 11-1) are synchronized with the output of the first high stability oscillator (17),
The outputs of the local oscillators (15-1, 16-1, 14-1) of the working receiver (15, 16) and backup receiver (14) are
The problem is solved by the pre-switching scheme of the present invention, which is synchronized with the output of the high-stability oscillator (18).

[Effect]

In the present invention, the outputs of the local oscillators on the transmitting side and the receiving side are
By synchronizing with the output of the second high-stability oscillator and the output of the second high-stability oscillator, the frequency deviation Δf on the transmitting side and the receiving side can be reduced.
1 and Δf2 were set to O.

Therefore, the difference in intermediate frequency when switching to the standby receiver due to a failure in the working transmitter is only the difference in the oscillation frequency Δf3 caused by the first and second highly stable oscillators, so the above P
The pull-in operation of the LL circuit becomes faster, and a digital signal with fewer errors can be obtained.

The lock diagram is shown.

In the figure, the local oscillators 11-1 to 16-1 of the working transmitters [12, 13 and the standby transmitter 11, the working receivers 15 and 16, and the standby receiver 4114] are, for example, variable capacitance diodes (
The oscillation frequency can be changed by changing the DC voltage applied to the variable capacitance diode.

Therefore, the outputs of the VCXO on the transmitting side and the VCXO on the receiving side are connected to the first and second high stability oscillators I7 and 18, respectively.
By synchronizing with the output of VCO11-1 on the transmitting side,
, 12-1, 13-1 and receiving side (7) VCXO14-
1, 15-1, and 16-1 oscillate at the same frequency.

For this reason, for example, when the working receiver 15 is switched to the backup receiver 14 due to a failure in the working transmitter 12, there is no shift in the intermediate frequency of the backup receiver, so the synchronization time of the PLL circuit described above can be almost ignored and the error can be ignored. A digital signal with less noise can be obtained.

In addition, even if a failure occurs in the first or second high-stability oscillator and the output is cut off, the PLL circuit will be shut down unless the active backup is switched because the VCXO is used as the X local oscillator. Since the state is maintained as it is, no errors occur in the digital signal.

It is assumed that the high frequency switch 5.6 operates at high speed and that no error in the digital signal occurs due to switching. Furthermore, the ratio of active and standby is not limited to 2:1.

〔Effect of the invention〕

As explained in detail above, since there is no deviation in oscillation frequency between local oscillators on the transmitting side and between local oscillators on the receiving side, it is possible to obtain digital signals with fewer errors by switching between the working receiver and the standby receiver. There is an effect.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the principle of the active/standby switching system, FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 is a block diagram of a conventional example. In the figure, 11 is a backup transmitter, 12.13 is a working transmitter, and 14
15.16 is a working receiver, 17 is a first high stability oscillator, and 18 is a second high stability oscillator.

Claims (1)

[Claims] In a system for switching between working transceivers (12, 13, 15, 16) and standby transceivers (11, 14), local oscillators of the working transmitters (12, 13) and standby transmitters (11) (12-1, 13-1, 11-1)
The output of the local oscillators (15-1, 16-1, 14-1) of the working receiver (15, 16) and standby receiver (14) is synchronized with the output of the high stability oscillator (17) of the
This is a working/standby switching system characterized by synchronizing the outputs of the high stability oscillators (18).