JPH04200038A - Digital microwave radio communication equipment - Google Patents

Abstract

PURPOSE:To receive a transmission data correctly without out of synchronism even when a momentary interruption of a transmission signal sent from a sender side or a momentary phase change takes place at the changeover from an active system into a standby system and to reproduce the data by adopting a delay detection system for a demodulation circuit of a standby system reception circuit section. CONSTITUTION:A demodulation circuit 46 adopting the delay detection system is provided to a standby system reception circuit section 40b of a receiver RX and the 2nd demodulation circuit 46 is used at the changeover from an active system reception circuit section 40a to the standby system reception circuit section 40b to demodulate a transmission signal. Thus, even when a momentary interruption of a transmission signal or a momentary phase change takes place due to the changeover of a changeover switch 3 of a transmitter TX, no bit error in the transmission signal takes place or should a bit error take place, it is kept within a range of error correction capacity of an error correction circuit 44a, then the transmission signal is continuously demodulated without any hindrance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a digital microwave radio communication device used in a backbone communication channel of a digital communication network.

(Prior Art) In recent years, with the increase in communication needs and the development of communication technology, various communication systems have been developed, one of which is a digital microwave wireless communication system. This type of system uses, for example, a carrier wave consisting of a microwave with quadrature phase shift m (Q
It wirelessly transmits digital data by modulating it using the PSK (PSK) method or the multi-value quadrature amplitude modulation (multi-value QAM) method, and is cheaper and higher quality than analog wireless transmission systems or wired digital transmission systems. Data transmission is possible.

By the way, in this type of system, service is not interrupted when repairing deterioration of transmission quality or line disconnection caused by fading in the transmission line or failure of equipment that makes up the transmission line, or when testing and repairing equipment or lines. To ensure this, important equipment on the transmission path is usually equipped with spare equipment. There are two methods for arranging this spare device: a system spare method and a set spare method. Among these, the set backup method is a method in which a backup device is prepared for each device constituting the system, and when a failure occurs, the current device is switched to the backup device for relief.

FIG. 4 shows an example of the configuration of a system that employs this set reserve method, where TX represents a transmitting device and RX represents a receiving device. The transmitting device TX includes an active transmitting circuit section la and a backup yarn feeding circuit section 1b, which have the same configuration, and these transmitting circuit sections la.

1b is configured to be switched by a changeover switch 3. Note that 2 is a signal splitter. On the other hand, receiving device RX
similarly includes a working receiving circuit section 4a and a standby receiving circuit section 4b, which have the same configuration, and these receiving circuit sections 4a, 4b
is configured to be switched by changeover switches 5 and 6. Further, the demodulation circuits of the working receiving circuit section 4a and the standby receiving circuit section 4b generally employ circuits employing a synchronous detection method with excellent error rate characteristics.

FIG. 5 shows an example of the configuration of a demodulation circuit employing a synchronous detection method. In the figure, a multilevel QAM signal output from an intermediate frequency amplifier (not shown) is branched into two, and then sent to two synchronous detectors 711 for in-phase and quadrature phases.
, 71Q, where they are each synchronously detected.

The in-phase and quadrature component baseband signals obtained by these synchronous detectors 711.7IQ are introduced into discriminators 721 and 72Q, respectively. These discriminators 72'I and 72Q each include, for example, an A/D converter. And these identifiers 72I.

72Q, each of the above baseband signals is A/D converted in synchronization with the clock regenerated from the one span signal by the clock regeneration circuit 73, and the output thereof is inputted to the differential logic circuit 74 as identification data. . The differential logic circuit 74 performs differential logic processing on the identification data, thereby obtaining demodulated digital data.

Further, the identification data output from each of the above-mentioned discriminators 721 and 72Q is input to the carrier wave regeneration circuit 75. This carrier wave regeneration circuit 75 has a logic circuit, a DC amplifier with a built-in loop filter, and a voltage controlled oscillator (VCO), and the reference carrier wave is regenerated by this circuit 75.

The second reference carrier wave is branched by a phase shift divider 76 into an in-phase reference carrier wave and a 90° phase-shifted reference carrier wave, and then supplied to the synchronous detectors 711 and 710, respectively. It is done.

That is, the demodulation circuit employing this synchronous detection method uses the synchronous detectors 711, 71Q and the carrier regeneration circuit 75 to
) circuit, and this PLL circuit allows multi-value Q
Synchronous detection of the multilevel QAM signal is performed according to a reference carrier whose phase is always locked to the AM signal.

(Problem to be solved by the invention) However, such a conventional system has the following problems when switching the transmitting circuit section of the transmitting device TX and the receiving circuit section of the receiving device RX from the active system to the standby system. was occurring. That is, since the changeover switch 3 of the transmitting device TX is constituted by a coaxial switch, it takes a certain amount of time to switch from the working system to the standby system, which causes instantaneous interruption of the transmission signal. Additionally, there is a delay between the transmission signal transmitted from the active transmission circuit section 1a and the transmission signal transmitted from the protection transmission circuit section 1b due to differences in modulation frequency and transmission frequency and variations in equipment between systems. There is a time difference. Therefore, in the standby receiving circuit section 4b of the receiving device TX, the phase of the regenerated carrier wave for synchronous detection changes instantaneously due to the instantaneous interruption of the transmission signal, the frequency difference and the delay time difference between the transmission signals, and the PLL circuit The limit of synchronization pull-in was exceeded, resulting in loss of synchronization. - Once synchronization occurs, the data transmitted will have bit errors until synchronization is reestablished, causing a lot of damage to a large number of end users, especially when used on a backbone communication channel. This turned out to be very unfavorable.

Therefore, it is an object of the present invention to correctly transmit data without losing synchronization even if a momentary interruption or instantaneous change in phase occurs in the transmission signal sent from the transmitting side when switching from the working system to the standby system. An object of the present invention is to provide a digital microwave radio communication device capable of receiving and reproducing data.

Another object of the present invention is to provide a digital microwave wireless communication device that can simplify the switching sequence and shorten the time required for switching.

Furthermore, another object of the present invention is to be able to correctly receive and reproduce transmitted data without causing synchronization when switching from the working system to the protection system, and to ensure that the error rate remains high even after switching to the protection system. An object of the present invention is to provide a digital microwave wireless communication device capable of receiving and reproducing data with excellent characteristics.

[Configuration of the Invention (Means for Solving the Problems)] In order to achieve the above object, the present invention adopts a configuration in which the demodulation circuit of the working system receiving circuit section adopts a synchronous detection method, and the standby system receiving circuit section The demodulation circuit is configured to employ a delay detection method.

The present invention is also characterized in that the switching circuit for switching between the active receiving circuit section and the standby receiving circuit section on its input side is configured by a leak type switch.

Furthermore, in order to achieve the above-mentioned other object, the present invention adopts a configuration in which the demodulation circuit of the working system receiving circuit section adopts a synchronous detection method, and also employs a synchronous detection method as the demodulation circuit of the standby system receiving circuit section. A circuit that uses the delayed detection method and a circuit that uses the delayed detection method, and is equipped with a selection circuit for the detection circuit, and this selection circuit allows the circuit that uses the delayed detection method to is selected, and after the switching is completed, a circuit employing the above-mentioned synchronous detection method is selected.

Another feature of the present invention is that the switching circuit for switching between the working receiving circuit section and the standby receiving circuit section on its input side is configured by a leak type switch. , , (Work, Use) As a result, according to the present invention 4, since it is constituted by the demodulation circuit of the standby system receiving circuit section or a circuit adopting a delay detection method that does not need to be synchronized with the received signal. , even if momentary interruptions or instantaneous changes in phase occur in the transmission signal sent from the transmitting side4 when switching from the working system to the reserve system, synchronization may be lost due to these instantaneous interruptions or instantaneous changes in phase. Never. - Therefore, the occurrence of data errors is suppressed within the permissible range, thereby making it possible to correctly receive and reproduce transmitted data.

In addition, by configuring the microwave switching circuit located on the input side of each receiving circuit with a leak type switch, the demodulation circuit of the protection receiving circuit is activated in advance when switching from the working system to the protection system. I can do something. Therefore, even if the switching from the working system to the protection system in the receiving side equipment and the switching from the working system to the protection system in the transmitting side equipment are performed almost simultaneously, the error correction capability of the protection system receiving circuit section is A bit error exceeding -
1, which allows data transmission to continue accurately without
Ru.

In other words, there is no need to make the timing for switching from the active system to the protection system on the receiving side equipment different from the timing for switching from the active system to the protection system on the sending side equipment. Therefore, the switching sequence can be simplified and the time required for switching can be shortened.

According to still another aspect of the present invention, a delay detection type circuit and a synchronous detection type circuit are provided as demodulation circuits in the backup reception circuit section, and during the switching period from the working system to the protection system, the delay detection type circuit is used. is selectively used, and after the switching is completed, the synchronous detection type circuit is selectively used. Therefore, when switching from the working system to the backup system, the delayed detection circuit allows data reception to continue without causing synchronization, and after the switching is completed, the synchronous detection circuit allows the received data to continue to be received. Since demodulation is also performed, it is possible to receive data with excellent error rate characteristics.

(Embodiment) FIG. 1 shows the configuration of a digital microwave wireless communication system in an embodiment of the present invention. In this figure, the same parts as those in FIG. 1 will be described with the same reference numerals.

The transmitting device TX includes a working transmitting circuit section 1a, a standby transmitting circuit section 1b, a signal distributor 2, a changeover switch 3, a control circuit 14, and a changeover request switch 15. The active transmitting circuit section 1a and the standby transmitting circuit section 1b have the same configuration, and are each composed of transmitting digital signal processing circuits 11a and llb, modulation circuits 12a and 12b, and transmitting microwave circuits 13a and 13b. . As the changeover switch 3, a microwave diode changeover switch having a switching time shorter than one bit period of transmission data is used. The control circuit 14 is configured using, for example, a microcomputer as the main control unit, and when the switching request switch 15 is operated or an alarm is generated from the active transmission circuit section 1a, the control circuit 14 changes the current switching sequence according to a predetermined switching sequence. Executes switching control from the system to the standby system.

On the other hand, the receiving device RX includes changeover switches 5 and 6, a working receiving circuit section 4a, a standby receiving circuit section 40b, and a control circuit 4.
8. Among the changeover switches 5.6, the changeover switch 5 for changing over the microwave is constituted by a leak switch.

A leak switch is configured so that when switched to one side, an input signal leaks to the other side and is output.

The active receiving circuit section 4a and the backup receiving circuit section 40b differ in configuration in the following points. That is, the active receiving circuit section 4a includes a microwave receiving circuit 41a, a demodulating circuit 42a employing a synchronous detection method, and a difference calculation circuit 43a.
, an error correction circuit 44a, and a received digital signal processing circuit 45a.

On the other hand, the standby receiving circuit section 40b performs differential calculation processing on the microwave receiving circuit 41b, a first demodulating circuit 42b employing a synchronous detection method, and the demodulated signal output from the first demodulating circuit 42b. A difference calculation circuit 43a, a second demodulation circuit 46 employing a delayed detection method, and a switching circuit 4
7, an error correction circuit 44b, and a reception digital signal processing circuit 45b. The switching circuit 47 is composed of, for example, a semiconductor switch, and selectively switches between the output of the difference calculation circuit 43a and the output of the second demodulation circuit 46 according to a switching instruction from the control circuit 48, and supplies the output to the error correction circuit 44b. It is.

The control circuit 48 includes a microcomputer as a main control section, and executes switching control according to a predetermined control sequence when a switching request signal arrives from the transmitter TX via the control channel.

The second demodulation circuit 46 employing the delay detection method is configured as shown in FIG. 2, for example. That is, the modulation signal is split into two, one of which is split into two signals whose phases are different by 90 degrees from each other by a no-blitt circuit 80, and then sent to multipliers (double balanced mixers) 811 and 81, respectively.
0 local port. On the other hand, the other branched modulated signal is delayed by 1 bit in a delay circuit 85 and becomes a reference carrier wave. Then, this reference carrier wave is branched by a phase shift divider 86 into an in-phase reference carrier wave and a 90° phase-shifted reference carrier wave, and the multiplier 811 divides the reference carrier wave into a reference carrier wave whose phase is shifted by 90 degrees.
．． 81Q high frequency port.

In these multipliers 811 and 81Q, the in-phase reference carrier wave and the anti-phase reference carrier wave supplied from the hybrid circuit 80 are multiplied by the reference carrier wave, and the baseband signal obtained thereby is formed by an A/D converter. It is input to discriminators 821 and 820. These identifiers 8
21.820, the signal level of the baseband signal output from the multiplier 811.81Q is identified in synchronization with the clock reproduced by the clock reproduction circuit 83, and the identified output is input to the differential logic circuit 84. Ru.

The differential logic circuit 84 performs predetermined logic processing on the identification output, thereby obtaining demodulated data.

Next, the operation of the system configured as above will be explained.

In the steady state, the changeover switch 3 of the transmitting device TX and the changeover switches 5 and 6 of the receiving device RX are switched to the working transmitting circuit section la side and the working receiving circuit 4a side, respectively. Then, the digital data input to the transmitter TX in this state is subjected to predetermined transmission digital processing in the transmission digital signal processing circuit 11a of the active transmission circuit section 1a, and then is converted into, for example, 1.
The signal is modulated according to the 6QAM method, further converted into a microwave signal by the transmission microwave circuit 13a, and transmitted from the antenna.

On the other hand, in the receiving device RX, the microwave arriving from the transmitting device TX is received by the antenna and then introduced into the active receiving circuit section 4a via the changeover switch 5.

In this working receiving circuit section 4a, the received microwave signal is first frequency-converted into an intermediate frequency signal by a receiving microwave circuit 41a, and then synchronously detected by a demodulation circuit 42a employing a synchronous detection method, and further by a differential calculation circuit. 43a
Difference calculation is processed in . The demodulated baseband signal thus obtained is subjected to 2-bit error correction processing in an error correction circuit 44a, and then subjected to predetermined digital signal processing in a reception digital signal processing circuit 45a, thereby reproducing digital data. Ru.

Now, suppose that in this state, for example, a maintenance person operates the switching request switch 15 of the transmitter TX in order to inspect at least one device in the current system. Then, the control circuit 14 of the transmitter TX and the control circuit 48 of the receiver RX execute switching control as follows. That is, while the current system is operating, the control circuit 14 repeatedly monitors the occurrence of an alarm and monitors the operation of the switching request switch 15 in steps 9a and 9b, respectively, as shown in FIG. In this state, when the switching request switch 15 is operated as described above, the control circuit 14
In step 9C, the switching request signal is inserted into the control channel in the transmission signal frame and transmitted to the receiving device RX.

In response, the control circuit 48 of the receiving device RX determines whether a switching request signal has arrived from the control channel output of the receiving digital signal processing circuit 45a of the active system receiving circuit section 4a in step 10a as shown in FIG. I'm monitoring it. When the arrival of the switching request signal is detected in this state, the control circuit 48
In step 10b, the switching circuit 47 is switched from the side of the first demodulation circuit 42b which employs the synchronous detection method to the side of the demodulation circuit 46 which employs the delayed detection method, and in step 10c, the changeover circuit 5 is switched to the side of the working system receiving circuit section 4a. The switch is then made to the side of the standby system receiving circuit section 40b.

Then, in step 10d, it is determined whether the switching has been completed, and if it is confirmed that the switching has been completed, in step 10e, a switching response signal is inserted into the control channel in the transmission signal frame and sent back to the transmitter TX.

The control circuit 14 of the transmitting device TX monitors the return of the switching response signal in step 9d, and when the switching response signal is returned from the receiving device RX, the control circuit 14 performs steps from step 9d to step 9e.
, and then switch the selector switch 3 to the active transmission circuit section 1.
Switch from the a side to the standby transmission circuit section 1b side.

In this way, both the transmitting device TX and the receiving device RX are switched from the active system to the backup system, and thereafter data transmission continues using the pre-tin system transmitting circuit section 1b and the backup system receiving circuit section 40b.

By the way, when the changeover switch 3 in the transmitter TX is switched, the transmission data is cut off for a part of the 1-bit period. In addition, the active transmission circuit section 1
Since the carrier wave frequency of a and the carrier wave frequency of the standby transmission circuit section 1b generally do not match, the phase of the transmission signal changes instantaneously between before and after switching. However, in the standby receiving circuit section 40b of the receiving device RX, since the demodulating circuit 46 employing a delay detection method is operating, the above-mentioned instantaneous interruption of the signal or instantaneous change in phase may occur at the time of switching. However, the transmitted signal can be demodulated without any problem.

In some cases, the switching timing of the changeover switch 3, that is, the momentary signal interruption period or the identification timing of the transmitted data, may coincide. In this case, even if the second demodulation circuit 46 employs the delay detection method, a bit error occurs in the corresponding bit of the transmitted data. As mentioned earlier, in the delayed detection method, the received signal is detected according to the reference carrier wave delayed by 1 bit, so the 1-bit error mentioned above spreads to the next bit, resulting in a 2-bit error or a 2-bit error. Sign. However, since this 2-bit error is corrected by the error correction circuit 44b at the subsequent stage, it is possible to obtain error-free demodulated data as a result.

Further, when the switching from the working system to the protection system is completed as described above, the control circuit 48 of the receiving device RX performs step 10f in FIG. Then, it is determined whether synchronization of the first demodulation circuit 42b employing the synchronous detection method has been established. and,
When it is confirmed that synchronization has been established after switching, the control circuit 48 switches the switching circuit 47 from the second demodulation circuit 46 side to the first demodulation circuit 42b side in step 10g.

Thus, the receiving device RX demodulates the transmission signal using the first demodulation circuit 42b.

That is, when switching from the active receiving circuit section 4a to the standby receiving circuit section 40b, the receiving device RX performs delayed detection only during the period from the start of the switching until the synchronization of the first demodulating circuit 42b is established. Demodulation is performed by the second demodulation circuit 46 that employs the synchronous detection method, and after the synchronization of the first demodulation circuit 42b is established, the error rate characteristics are determined by the first demodulation circuit 42b that employs the synchronous detection method. Excellent demodulation is performed.

As described above, in this embodiment, the demodulation circuit 4 employing the delay detection method in the standby receiving circuit section 40b of the receiving device RX
6 is provided, and this second demodulation circuit 46 is used to demodulate the transmission signal when switching from the active receiving circuit section 4a to the standby receiving circuit section 40b.
Even if a momentary interruption of the transmission signal or an instantaneous change in phase occurs due to switching of the changeover switch 3, two pit and two errors in the transmission signal will not occur at all, or even if they occur, the error correction circuit 4
Since the error correction capability (2-bit error correction) of 4a is within the range, the transmitted signal can be continuously demodulated without any problems.

Also, after switching, the first demodulation circuit 42. After the synchronization of b is established, the second demodulation circuit 4 employing the delayed detection method
6 to the first demodulation circuit 42b that adopts the synchronous detection method, and since then demodulation is performed by this first demodulation circuit 42b. Therefore, even after switching to the 100-system, synchronous detection with excellent error rate characteristics can be achieved. The first demodulation circuit 42b employing the method
It is possible to demodulate the transmitted signal.

Furthermore, the receiving device RX of this embodiment has a changeover switch 5.
Since a leak type switch is used as the switch, the received transmission signal is supplied to the standby receiving circuit section 40b without momentary interruption when the changeover switch 5 is switched. Therefore, bit errors in the transmission signal do not occur when the changeover switch 5 is switched, and as a result, the working receiving circuit section 4
It is possible to smoothly switch from the receiving circuit section 40a to the standby receiving circuit section 40b. Therefore, even if the changeover switch 3 of the transmitting device TX is changed over, for example, without a sufficient period of time after the changeover of the changeover switch 5, only the bit error caused by the changeover switch 3 will occur in the transmission signal. That is, bit errors are detected by the error correction circuit 44. This can be suppressed to within 2 bits that can be corrected by b, and there is no problem in data demodulation. In other words, the transmitter TX
There is no need to carry out control to sufficiently delay the switching timing of the changeover switch 3 of the transmitter RX from the changeover timing of the changeover switch 5 of the receiver RX.
The switching control of the control circuit 14 can be simplified.

Incidentally, if a leak type switch is not used as the selector switch 5, in other words, if a non-leak type switch, which is commonly used as a microwave switch, is used, the received transmission signal will be lost even when the selector switch 5 is switched. As a result, the total number of bit errors occurring in the received transmission signal at the time of switching is 4 bits, which exceeds the error correction capability of the error correction circuit 44b. Therefore, the transmitter TX
The switching timing of the changeover switch 3 is the changeover timing of the changeover switch 5.
must be delayed sufficiently from the switching timing of
The control circuit 14 of the transmitting device TX requires control for this purpose, which results in complicated control.

Note that the present invention is not limited to the above embodiments. For example, in the above embodiment, the first demodulation circuit 42b employing the synchronous detection method and the second demodulation circuit 46 employing the delay detection method are provided as the demodulation circuits of the standby receiving circuit section 48 of the receiving device RX, and the switching During the period, the first demodulation circuit 42
b, and after the switching is completed, the demodulation circuit is switched to the first demodulation circuit to perform the demodulation, or only the demodulation circuit 46 employing the delay detection method is provided, and during the period of switching to the prediction system. Alternatively, demodulation may be continuously performed using a differential detection method. In this way, the error rate characteristics will deteriorate compared to the case of switching to the demodulation circuit 42b using the synchronous detection method, or the circuit configuration can be simplified by making the demodulation circuit 42b using the synchronous detection method unnecessary. I can do it.

Furthermore, in the above embodiments, the present invention has been explained as an example in which the present invention is applied when switching from the active system to the standby system, but the present invention can also be applied when returning from the standby system to the active system as an application example. It is possible.

In addition, various modifications may be made to the type of changeover switch, the configuration of the demodulation circuit employing the delayed detection method, the configuration of the demodulation circuit employing the synchronous detection method, the switching control procedure, the control contents, etc., without departing from the gist of the present invention. It can be implemented by

[Effects of the Invention] As described in detail above, according to the present invention, the demodulation circuit of the working receiving circuit section is configured to adopt the synchronous detection method, and the demodulating circuit of the protection receiving circuit section is configured to use the delayed detection method. By adopting this configuration, even if a momentary interruption or momentary change in phase occurs in the transmission signal sent from the transmitting side when switching from the active system to the backup system, synchronization will not occur. It is possible to provide a digital microwave wireless communication device that can correctly receive and reproduce transmitted data.

According to another aspect of the present invention, the demodulation circuit of the active receiving circuit is configured using a synchronous detection method, and the demodulating circuit of the protection receiving circuit is configured using a circuit using a synchronous detection method and a delay detection method. This selection circuit selects the circuit that employs the delayed detection method during the period of switching from the working system to the standby system, and after the switching is completed. By selecting a circuit that employs the above-mentioned synchronous detection method, it is possible to correctly receive and reproduce transmitted data without causing synchronization when switching from the working system to the preliminary system, and when switching to the preliminary system. Accordingly, it is possible to provide a digital microwave radio communication device that can receive and reproduce data with excellent error rate characteristics even after the data has been transferred.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram showing the configuration of a digital microwave wireless communication system in an embodiment of the present invention, and FIG.
The figure is a circuit block diagram showing the configuration of a demodulation circuit employing the delay detection method used in the same system, Figure 3 is a flowchart showing the switching control procedure and control contents of the system shown in Figure 1, and Figure 4 is a FIG. 5 is a schematic diagram of a digital microwave wireless communication system used in the conventional explanation, and is a circuit block diagram showing the configuration of a demodulation circuit that employs a synchronous detection method. TX: transmitting device, RX/receiving device, 1a: working system transmitting circuit section, lb: standby system transmitting circuit section, 2: signal distributor, 3, 5.6: changeover switch, 4a: working system Receiving circuit section, 40b...-standby receiving circuit section, lla, llb
... Transmission digital signal processing circuit, 12a, 12b.
...Modulation circuit, 13a, 13b...Transmission microwave circuit, 14...Control circuit of transmitter, 15...Switching request switch, 41a, 41b...Reception microwave circuit, 42a, 42b...・Demodulation circuit adopting synchronous detection method, 43a, 43b...Difference calculation circuit, 44a, 44
b...Error correction circuit, 45a, 45b...Reception digital signal processing circuit, 4
6... Demodulation circuit adopting delayed detection method, 47...
Switching circuit, 48... Control circuit of receiving device, 711.7
IQ...Synchronous detector, 72I, 72Q. 82I, 82Q: Discriminator, 73.83: Tarock regeneration circuit, 74.84: Differential logic circuit, 75: Carrier wave regeneration circuit, 76: Phase shift divider, 85: Delay circuit. Applicant's agent Patent attorney Takehiko Suzue

Claims (4)

[Claims] (1) Comprising a working system receiving circuit section, a standby system receiving circuit section, and a switching circuit that switches these receiving circuit sections to operate selectively, and performs synchronous detection on the demodulation circuit of the working system receiving circuit section. What is claimed is: 1. A digital microwave wireless communication device, characterized in that the demodulation circuit of the standby receiving circuit section is configured to employ a delay detection method. (2) Digital microwave wireless communication according to claim (1), characterized in that the switching circuit for switching between the active receiving circuit section and the standby receiving circuit section on its input side is constituted by a leak type switch. Device. (3) A working system receiving circuit section, a standby system receiving circuit section, and a switching circuit that switches these receiving circuit sections to operate them selectively, the demodulation circuit of the working system receiving circuit section being synchronously detected. In addition, the standby system reception circuit section has a circuit that employs a synchronous detection system and a circuit that employs a delayed detection system as a demodulation circuit, and when switching from the working system to the standby system, the standby system is A circuit that uses the delayed detection method is selected during a period until synchronization of the circuit that uses the synchronous detection method in the system receiving circuit section is established, and after that, a circuit that uses the synchronous detection method is selected. A digital microwave wireless communication device characterized by comprising a selection circuit. (4) Digital microwave wireless communication according to claim (3), characterized in that the switching circuit for switching between the active receiving circuit section and the standby receiving circuit section on its input side is constituted by a leak type switch. Device.