JPH01135134A - Signal control system - Google Patents

Abstract

PURPOSE:To prevent interference between signals by detecting an oscillated signal from a reference frequency oscillator and controlling an output signal based thereupon. CONSTITUTION:A detector 10 detects the output level of the reference frequency oscillator 7 and a control circuit 8 uses a signal from the detector 10 to discriminate the normality of the signal level of the reference frequency oscillator 7 so as to turn on/off the power supply 11 of an amplifier 9. That is, when the oscillation signal level from the reference frequency oscillator 7 is normal, the power supply 11 is turned on and even in case of detecting a fault, the power supply 11 is quickly turned off to stop the signal output. Even in case of the fault of the reference frequency oscillator 7, the signal output is controlled quickly and surely to prevent signal interference.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is applicable to microwave communication devices in which the transmission capacity is increasing in order to effectively utilize frequencies. The present invention relates to a signal control method that prevents interference.

[Prior Art] FIG. 2 is a block diagram showing an output signal control method in a conventional heterodyne type microwave communication device.

That is, in a heterodyne type microwave communication device in which a voltage controlled oscillator (VCO) 4 and a frequency converter 3 convert the high frequency signal into a high frequency band, and further amplify and output the high frequency signal by a high frequency amplifier 9, the reference frequency oscillator 7 A phase detector 6 detects the phase difference between the oscillation signal and a signal obtained by downgrading the oscillation signal of the VCO 4, and the detected voltage is applied to the VCO 4.
A feed pad is added to the varactor diode for frequency control of 4.
This keeps the oscillation frequency stable.

The above-mentioned stabilization circuit is generally called an APC circuit, but
Conventionally, this APC circuit determines whether the circuit is normal or abnormal based on the voltage detected by the phase detector 6 for signal control in the event of an abnormality.
Method for controlling F If the A10 circuit's phase detection voltage goes out of the normal operating range and the APC alarm is activated, the vCO frequency will become unstable and there is a risk of interfering with other signals with adjacent frequencies. Ta.

Particularly in digital communication systems, interference with adjacent channels, even for a short time, causes a huge number of code errors, which is a very serious problem.

The present invention has been made in view of these problems, and it is an object of the present invention to provide a signal control method that can reliably control and prevent signal interference even when a failure occurs in the reference frequency oscillator.

[Means for Solving Problems] To achieve the above object, the present invention provides a hetero gain system that converts an intermediate frequency band signal into a high frequency band using a voltage controlled oscillator and a frequency converter, and further amplifies and outputs the high frequency signal using an amplifier. In the type microwave communication device,
The oscillation signal level of the reference frequency oscillator provided to stabilize the voltage controlled oscillator is detected, and if the oscillation signal level is normal, the above amplifier is activated, and if the oscillation signal level is abnormal, the above amplifier is activated. This is a method of stopping the signal and controlling the signal output.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment. In the drawing, 1 is an input terminal, 2 is an output terminal, and a frequency converter 3 and a high frequency amplifier 9 are connected between these terminals.

The frequency converter 3 converts an intermediate frequency signal (input from the input terminal 1) into a high frequency signal based on a local signal from a voltage controlled oscillator (VCO) 4.

Then, the high frequency amplifier 9 amplifies the converted high frequency signal and outputs it to the output terminal 2.

7 is a reference frequency oscillator, and a phase detector 6 detects the phase difference between its oscillation signal and a signal obtained by downgrading the oscillation signal of the VCO 4, and the detected voltage is fed back to the VCO 4 through the DC amplifier 5 to keep the oscillation frequency constant. The oscillation signal is kept as a local signal of the frequency converter 3.

A detector 10 detects the output level of the reference frequency oscillator 7. 8 is a control circuit that determines whether the signal level of the reference frequency oscillator 7 is normal or abnormal based on the signal from the detector 1o;
Based on this, turn on the power supply 11 of the amplifier 9.
do. That is, when the oscillation signal level of the reference frequency oscillator 7 is normal, the power supply 11 is turned on, and when an abnormality is detected, the power supply 11 is immediately turned off to stop signal output.

With such a system, even when the reference frequency oscillator 7 fails, the signal output can be controlled quickly and reliably, and signal interference can be prevented. That is, as shown in FIG. 3, spectrum 1 of channel (ch) 1
2 and the spectrum 14 of the adjacent ch2, if a failure occurs in the reference frequency oscillator 7 as described above on the chi side, in the conventional control method, the frequency will become unstable immediately after the reference signal is disconnected. It becomes stable, and as shown in the spectrum 13 of chi shown in the figure, the output is cut off after a frequency shift occurs. Therefore, the spectrum 13 and the spectrum 14 of ch2 were interfering with each other. On the other hand, according to the method of the present embodiment, the output is cut off before a frequency deviation like the spectrum 13 occurs, so that interference with the spectrum 14 can be prevented.

Note that the control circuit 8 also uses the voltage level detected by the phase detector 6 as a factor in control judgment, as in the conventional case.

[Effects of the Invention] As explained above, according to the present invention, since the oscillation signal of the reference frequency oscillator is detected and the plow output signal is controlled accordingly, the signal can be output immediately even when the reference frequency oscillator fails. This has the effect of preventing interference between signals.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a conventional example, and FIG. 3 is a diagram explaining interference between adjacent channels. Input terminal 2: Output terminal 3: Frequency converter 4: Voltage controlled oscillator (V CO
) 5: DC amplifier 6: Phase detector 7: Reference frequency oscillator 8: Control circuit 9: Amplifier 10: Detector 11: Power supply agent Patent attorney Kihira Watanabe Figure 1

Claims (1)

[Claims] For stabilizing the voltage controlled oscillator in a heterodyne microwave communication device that converts an intermediate frequency band signal into a high frequency band using a voltage controlled oscillator and a frequency converter, and further amplifies and outputs the high frequency signal using an amplifier. Detecting the oscillation signal level of a reference frequency oscillator provided at A signal control method featuring