JPS639414B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a working/standby switching type digital radio device.

In a digital wireless communication system, transmission is performed using a modulation method such as a PSK modulation method or a QAM modulation method, and the receiving side generally performs synchronous detection by regenerating a carrier wave from the received wave. In such wireless devices, in order to improve reliability, a current/standby switching system is adopted, particularly a hot standby system in which the backup device is also turned on and put into operation. In this case, it is conceivable to provide a transmitting local oscillator in each of the active device and the standby device. However, if the frequency and phase of the respective transmitting local oscillators differ when switching between the active and standby devices, the carrier synchronization circuit on the receiving side will become out of synchronization, so the line will remain momentary until resynchronization is achieved. I will have to cut it off.

In order to prevent such momentary interruptions, it is desirable that the transmission frequency be the same for the active and standby devices, and that the transmission output phase be the same. Therefore, in order to make only the frequencies the same, the configuration shown in FIG. 1 can be considered.
In the figure, Ta and Tb are the active and backup transmitters,
IN is the digital signal input terminal, DDa and DDb are the transmission differential conversion circuits that perform signal processing when using the polyphase PSK modulation method, MDa and MDb are the modulators, LOSC is the transmission local oscillator, and FILa and FILb are the transmission waves. switch, SW is a switching circuit, and ANT is an antenna. Since the transmitting local oscillator LOSC is shared by the active transmitter Ta and the backup transmitter Tb,
Switching circuit SW between active transmitter Ta and standby transmitter Tb
Even if the transmission frequency is switched by , the transmitting frequency will not change, and in the carrier wave regeneration circuit on the receiving side, the worst case will be a phase slip, and the signal will disappear in an extremely short time compared to the case where synchronization occurs. It will be over.

However, since there is only one transmitting local oscillator LOSC, there is a drawback that if a failure occurs in this, the line will be disconnected. In addition, the microwave band carrier wave is transmitted to the current transmitter Ta.
There is a disadvantage that the configuration of cables, waveguides, etc. for distributing the signal and the backup transmitting section Tb is expensive.

The present invention improves the above-mentioned drawbacks, and
The purpose of this is to ensure that the transmission frequency remains the same even when switching between working and standby systems, and to prevent the line from being disconnected even if the reference oscillator for this purpose fails. Examples will be described in detail below.

FIG. 2 is a block diagram of an embodiment of the present invention, in which the same reference numerals as in FIG. 1 indicate the same parts, and COM
is the common part, OSC is the high stability reference oscillator, PHDa,
PHDb is a phase comparator, LPFa and LPFb are low frequency filters, VCXOa and VCXOb are VHF band voltage controlled crystal oscillators, and Ma and Mb are multipliers. Phase comparators PHDa, PHDb for active and backup transmitters Ta, Tb,
Low frequency filter LPFa, LPFb, voltage controlled crystal oscillator
VCXOa and VCXOb constitute a phase locked circuit,
The outputs of the voltage controlled crystal oscillators VCXOa and VCXOb synchronized with the output of the highly stable reference oscillator OSC of the common section COM are multiplied by the multipliers Ma and Mb, and the microwave band carrier wave is applied to the modulators MDa and MDb.

Furthermore, if the highly stable reference oscillator OSC fails, the phase synchronized circuit will output a free-running frequency, and even in that case, sufficient stability can be obtained.
The line will never be disconnected. Also highly stable reference oscillator
Since the OSC does not directly supply microwave band carrier waves to the active and backup transmitters Ta and Tb,
It has the advantage of being simple and inexpensive.

FIG. 3 is a block diagram of another embodiment of the phase-locked circuit, in which phase synchronization is applied in the middle of the multiplication order. controlled crystal oscillator
When multiplying the output of the VCXO by n+m and adding a microwave carrier wave to the modulator MD, the output of the highly stable reference oscillator OSC and the output of the multiplier M1 are compared in phase with the phase comparator PHD, and the comparison output is Wave equipment
This is used as the control voltage for the voltage controlled crystal oscillator VCXO via the LPF.

FIG. 4 is a block diagram of another embodiment of the present invention, in which the same reference numerals as in FIG. 2 indicate the same parts;
PLLa and PLLb are microwave band phase-locked oscillators. This microwave band phase-locked oscillator PLLa,
For example, as shown in Fig. 5, PLLb is composed of a phase comparator MPHD, a low frequency filter MLPF, a microwave band voltage controlled oscillator MVCO, a multiplier Ma,
Phase synchronization is performed using the multiplied output of Mb as the reference input.

In this embodiment, since the microwave band phase synchronized oscillators PLLa and PLLb are used, a high output microwave band carrier wave can be obtained. Also, as in the previous embodiment, even if the highly stable reference oscillator OSC fails, transmission can be continued with PLLa and PLLb synchronized to the highly stable free-running frequency provided by VCXOa and VCXOb, so there will be no disconnection of the line. .

As explained above, the present invention
Ta and the preliminary transmitter Tb are each provided with a phase-locked circuit capable of generating a stable free-running frequency including voltage-controlled crystal oscillators VCXOa, VCXOb, etc., and a multiplier that multiplies the carrier wave frequency of a microwave band or the like. Since the highly stable reference oscillator OSC is shared by both the active transmitter Ta and the standby transmitter Tb, the active transmitter Ta
The transmission frequencies of the and backup transmitter Tb are the same because they are based on the output of the same highly stable reference oscillator OSC, and the transmission frequency does not change due to switching, so the carrier regeneration circuit on the receiving side will suffer from phase slip in the worst case. It only takes a momentary interruption, and resynchronization can be achieved in an extremely short period of time. Furthermore, even if the highly stable reference oscillator OSC fails, the current transmitter Ta
Since the transmission operation can be continued using the free-running frequency of the phase synchronized circuit between the auxiliary transmitter Tb and the backup transmitter Tb, the line will not be disconnected. Furthermore, even if the transmission carrier frequency is in the microwave band or millimeter wave band, the carrier frequency is obtained by multiplying within the working transmitter Ta and the standby transmitter Tb, so the highly stable reference oscillator OSC This has the advantage that the configuration for supplying the reference frequency to each transmitting section Ta and Tb is simple.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a wireless device with a common transmitting local oscillator, FIG. 2 is a block diagram of one embodiment of the present invention, and FIG. 3 is a block diagram of another embodiment of the phase locked circuit. FIG. 4 is a block diagram of another embodiment of the present invention, and FIG. 5 is a block diagram of a microwave band phase-locked oscillation circuit. IN is the digital signal input terminal, Ta is the active transmitter, Tb is the backup transmitter, COM is the common part, OSC is the high stability reference oscillator, DDa, DDb are the transmission difference conversion circuits, MDa, MDb are the modulators, FILa, FILb is a transmitter, PHDa, PHDb is a phase comparator, LPFa,
LPFb is a low frequency filter, VCXOa, VCXOb are voltage controlled crystal oscillators, Ma, Mb are multipliers, PLLa,
PLLb is a microwave band phase-locked oscillator circuit.

Claims (1)

[Claims] 1. In a working/standby switching type digital radio device, the working transmitter and the standby transmitter are equipped with a phase-locked circuit that can generate a stable free-running frequency, including a voltage-controlled crystal oscillator, and an output of the phase-locked circuit. a multiplier that multiplies the carrier frequency of the modulator input, and a highly stable reference oscillator common to the working and standby transmitting units that supplies a reference frequency input to the phase synchronization circuit of the working and standby transmitting units; A digital wireless device characterized by comprising: