JPS63200627A - Microwave communication system - Google Patents

Abstract

PURPOSE:To simplify the system constitution by providing a signal switch to the pre-stage of a modulator and switching the connection between the modulator and the pre-stage equipment at the reduction in the received electric field and at a fault of the pre-stage equipment to interrupt the faulty equipment. CONSTITUTION:When a reception input electric field of a receiver 1 reaches a threshold level or below, the receiver 1 switches the switch 3 by using a control signal outputted from the demodulator 2 to interrupt the input signal to the modulator 4. Thus, no input signal is given to the modulator 4, a signal from a carrier oscillator 16 is outputted to an output terminal 18 while being not subject to modulation by the modulator 4 through the interruption of the input signal, the signal is sent from the output terminal 8 through the frequency converter 4 and the amplifier 6 to execute squelch transmission. Thus, it is not required to provide especially a high frequency oscillator for squelch and the system is simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a microwave communication system capable of non-modulated wave (squelch) transmission.

[Conventional technology]

In the conventional microwave communication system, as shown in FIG.
After receiving the signal, it is demodulated by the demodulator 22, and then sent to the modulator 23.
The signal is modulated by an amplifier 24, a frequency converter 26, and an amplifier 27 before being transmitted from an output terminal 30.

A switch 25 is provided between the modulator 23 and the frequency converter 26 to switch between the transmission signal and the unmodulated signal from the squelch oscillator 28.
By switching by a control signal or manual operation according to the failure mode of the demodulator 22, only the unmodulated signal from the squelch oscillator 28 is connected to the frequency converter 26 and below, thereby enabling squelch transmission.

[Problem that the invention seeks to solve]

In the above-described conventional microwave communication system that performs squelch transmission, the squelch high-frequency oscillator 28 is absolutely essential in the system configuration for squelch transmission.

For this reason, there are problems in that the system configuration becomes complicated, the probability of failure etc. is high, and the cost becomes high.

An object of the present invention is to provide a microwave communication system that enables squelch transmission without using a squelch oscillator.

[Means for solving problems]

In the microwave communication system of the present invention, a signal switching device is provided before a modulator provided in the microwave communication system, and when the received electric field decreases or the previous stage equipment fails, this modulator and the previous stage equipment The configuration is such that the connection can be automatically or manually switched and cut off.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention.

A demodulator 2 is connected to the receiver 1, and further a modulator 42, a frequency converter 5, and an amplifier 6 are connected via a signal switch 3.
It is configured to transmit from the output terminal 8.

The switch 3 switches the receiver 1.degree. It is configured to be switched by a control signal output from the demodulator 2 and to cut off the input signal to the modulator 4.

Further, as shown in FIG. 2, the modulator 4 has ring modulators 13 and 14 connected to modulation signal input terminals 11 and 12, respectively, which perform modulation using a carrier wave from a carrier wave oscillator 16, and combine the signals by a combiner 17. A normal configuration is adopted in which the signal is output from the output terminal 18.

In this case, the one ring modulator 13 has a phase shifter 15.
The same is true for shifting the phase of the carrier wave from the carrier wave oscillator 16 by . Therefore, in this modulator 4, when the input signal is cut off, the signal from the carrier wave oscillator 16 is outputted to the output terminal 18 without being modulated. This carrier wave signal frequency is the same as the output signal frequency of the squelch oscillator 28 shown in FIG. 3, and therefore squelch transmission is possible by transmitting this carrier wave signal.

Therefore, according to this circuit, when the received input electric field at the receiver 1 becomes below the threshold level,
Alternatively, if the receiver 1 or demodulator 2 fails, the switch 3 is turned off by the control signals output from the receiver 1 or the demodulator 2, and the input signal to the modulator 4 is cut off. Therefore, no input signal is input to the modulator 4, and due to the disconnected state of the input signal, the signal from the carrier wave oscillator 16 remains unmodulated at the output terminal 18 of the modulator 4.
This is output to frequency converter 5. The signal will be transmitted from the output terminal 8 through the amplifier 6, and squelch transmission will be performed.

Therefore, unlike the conventional high-frequency oscillator for squelch, it is not necessary, and the system configuration can be simplified.

Here, it goes without saying that the switch 3 may be manually switched depending on the strength of the received input electric field or a failure of the receiver or demodulator.

〔Effect of the invention〕

As explained above, the present invention provides a signal switch at the front stage of the modulator, and when the received electric field decreases or the front stage equipment fails,
Since the connection between this modulator and the preceding equipment can be automatically or manually switched off, the carrier wave from the modulator can be output as a squelch transmission signal, and a high-frequency oscillator for squelch can be specially configured. It is not necessary to provide
This has the effect of simplifying the system, improving reliability, and lowering costs.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the system of the present invention, and FIG.
The figure is a circuit diagram of a modulator, and FIG. 3 is a block diagram of a conventional system.

Claims (2)

[Claims] (1) In a microwave communication system that includes a receiver, demodulator, modulator, frequency converter, etc., a signal switch is provided before the modulator, and when the received electric field decreases or the front-stage equipment fails, 1. A microwave communication system characterized by being configured such that connection between the modulator and a preceding device can be cut off by switching manually or manually. (2) The microwave communication system according to claim 1, wherein the modulator has a built-in carrier wave oscillator and is configured to output an unmodulated carrier wave when the input signal is interrupted.