JP2577836B2 - Oscillator monitoring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillator monitoring device for monitoring the frequency and level of an output signal of an oscillator.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing a conventional oscillator monitoring apparatus. In FIG. 5, reference numeral 1 denotes an oscillator, and reference numeral 2 denotes a level detector for detecting output cutoff or level drop of the oscillator 1.

Next, the operation will be described. Oscillator 1 generates an output signal having a predetermined frequency, and this output signal is level detected.
Monitored by output unit 2 . Then, the level detector 2 detects an output disconnection or a level drop from the output signal, and sends out an oscillator failure signal indicating that the oscillator 1 is abnormal.

[0004]

Since the conventional oscillator monitoring apparatus is configured as described above, there is a problem that the level abnormality of the output signal of the oscillator 1 can be monitored, but the frequency deviation cannot be monitored. .

The present invention solves the above-mentioned problems.
To monitor the frequency shift between the two main oscillators.
And selectively output the normal oscillation signal on the main oscillator side.
The purpose is to make it.

[0006]

An oscillator monitor according to the present invention is provided.
The viewing device selectively switches the oscillation output of the two main oscillators
And a switching circuit for outputting the oscillation frequency and the oscillation frequency of the main oscillator.
Frequency for comparing the oscillation frequency of the monitoring oscillator
A beat frequency component from the output of the mixer and the frequency mixer.
Respectively, and a low-pass filter for extracting
When the count value of each beat component exceeds the set value,
A counter for outputting a detection signal;
Reset pulse generator that periodically resets
Determine the match of the output of each counter and generate a monitoring circuit fault signal.
Output circuit and the counter output
An exclusive OR circuit to be determined, and an output of the exclusive OR circuit.
A switch signal output interface that calculates the logical product of the outputs of the counters.
And the output signal of each of the main oscillators
A level detector for detection and an AND circuit for outputting the switching signal
Switching signal from road and level error from the above level detector
ORing with the signal to output the oscillator fault signal
Both have an OR circuit that outputs a switching signal to the switching circuit.
It is a thing.

[0007]

The counter according to the present invention has two main oscillators.
The exclusive OR circuit detects the frequency shift of
While selectively outputting the oscillation signal of the main oscillator,
Failure of the visual circuit itself can be detected.

[0008]

[Embodiment 1] An embodiment of the present invention will be described below with reference to the drawings. FIG.
, 1A is a main oscillator, 2 is a level detector that detects an output cutoff or level drop of the main oscillator 1A and sends out a level abnormal signal, 3a and 3b are monitor oscillators for performing frequency comparison with the main oscillator 1A, 4a , 4b are frequency mixers for frequency comparison, and 5a, 5b are frequency mixers 4a, 4b
Low-pass filter that extracts only the beat component from each output of
Reference numerals a and 6b denote counters that count the beat component and output a frequency shift detection signal when the count exceeds a preset count value.

Reference numeral 7 denotes a reset pulse generator for periodically resetting the counters 6a and 6b, 8 an AND circuit for detecting coincidence of two counter outputs (frequency shift detection signals), and 9 a mismatch between the two counter outputs. An exclusive OR circuit 10 for detecting an error signal and outputting a monitoring circuit failure signal is an OR circuit for obtaining an OR of the level abnormality signal and the frequency deviation detection signal and outputting an oscillator failure signal.

Next, the operation will be described. The two monitor oscillators 3a and 3b oscillate at the same frequency as the main oscillator 1A, and when the oscillation frequency of the main oscillator 1A shifts, the main oscillator 1A and the monitor oscillators 3a and 3a are output to the output sides of the respective frequency mixers 4a and 4b. The components of the sum and difference of the respective oscillation frequencies with respect to 3b are output. Also, based on the sum and difference components, the low-pass filters 5a and 5b extract frequency difference components (so-called beat components) as shown in FIG. 3 (a), which are input to the counters 6a and 6b. The beat component is counted.

Here, each of the counters 6a and 6b is periodically reset by a reset pulse as shown in FIG. 3B of the reset pulse generator 7, as shown in FIG. 3C. When the count value exceeds a preset count value within the reset period, a frequency shift detection signal as shown in FIG. 3D is transmitted. When the monitoring system including the monitor oscillators 3a and 3b and the frequency mixers 4a and 4b is normal, the outputs of the two counters 6a and 6b both transmit a frequency shift detection signal. A signal match is confirmed, and through the OR circuit 10,
An oscillator fault signal is output. When the count value of the beat component does not exceed the count value set within the reset cycle, the results are as shown in FIGS. 4A, 4B and 4C. As shown, no frequency shift signal is output.

On the other hand, when the main oscillator 1A is normal and one of the two monitor oscillators 3a and 3b has a frequency shift, a frequency shift detection signal is output from one of the two counters 6a and 6b. , AND circuit 8 does not match, and no oscillator failure signal is output. On the other hand, exclusive OR circuit 9 detects a mismatch, and outputs a monitoring circuit failure signal.

Embodiment 2 FIG. FIG. 2 shows another embodiment of the present invention , which comprises two main oscillators 1B and 1C, which are switched and used as an active and a standby configuration. To explain this, 11a and 11b are a monitor oscillator 3, a frequency mixer 4
a switching signal output AND circuit for detecting a match between a frequency shift detection signal from two systems of frequency shift monitoring circuits consisting of a and 4b and an output of an exclusive OR circuit 9 for detecting a mismatch between two counter outputs; 12 is two main oscillators 1
This is a switching circuit for selectively outputting the output signals of B and 1C. The other blocks that are the same as those shown in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

Next, the operation will be described. First, when any one of the two main oscillators 1B and 1C has a frequency shift, a frequency shift detection signal is output to one of the outputs of the two counters 6a and 6b by the same operation as in the first embodiment. Is done. For this reason, the output signals of the counters 6a and 6b become inconsistent, the inconsistency is detected by the exclusive OR circuit 9, the gate of the switching signal output AND circuit 11a or 11b is opened, and the frequency shift detection signal is output by the OR circuit 10a. , 10b to the switching circuit 12. For this reason, the switching circuit 12 controls the normal main oscillator 1B,
Alternatively, it is automatically switched to the 1C side and output.

If the two main oscillators 1B and 1C are normal and the monitor oscillator 3 has a frequency shift,
The outputs of the two counters 6a and 6b both transmit a frequency shift detection signal. Therefore, the exclusive OR circuit 9 does not detect a mismatch, and the switching signal output AND circuits 11a and 11b
Is not opened, and no switching signal is sent.
On the other hand, at this time, since a match is detected by the AND circuit 8, the monitoring circuit failure signal is sent to the outside.

[0016]

As described above, according to the present invention , the frequency difference between the two main oscillators and one monitor oscillator is detected, and the abnormality caused by the frequency shift of each oscillator can be monitored mutually. The switching circuit selectively outputs the oscillation signal of one of the normal main oscillators when the displacement detection signals do not match. Therefore, both the abnormality detection of the main oscillator and the output of the oscillation signal from the normal main oscillator are performed. There is an effect that what can be realized is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an oscillator monitoring apparatus according to an embodiment of the present invention .

FIG. 2 is a block diagram showing an oscillator monitoring apparatus according to another embodiment of the present invention .

FIG. 3 is a signal waveform diagram showing operation timing when the frequency of the main oscillator is normal.

FIG. 4 is a signal waveform diagram showing operation timing when a frequency of the main oscillator is abnormal.

FIG. 5 is a block connection diagram showing a conventional oscillator monitoring device.

[Explanation of symbols]

 1A, 1B, 1C Main oscillator 2 Level detector 3, 3a, 3b Monitoring oscillator 4a, 4b Frequency mixer 5a, 5b Low-pass filter 6a, 6b Counter 7 Reset pulse generator 8 AND circuit 9 Exclusive OR circuit Reference Signs List 10 OR circuit 11a, 11b AND circuit for switching signal output 12 Switching circuit

Claims (1)

(57) [Claims] An oscillator output of two main oscillators is selectively turned off.
A switching circuit for switching and outputting, and an oscillation frequency of the main oscillator
And each cycle to compare the oscillation frequency of the monitor oscillator
The beat frequency from the output of the wave number mixer and the frequency mixer
A low-pass filter for extracting each component, and
When the count value of each beat component exceeds the set value,
A counter for outputting a number shift detection signal,
A reset pulse generator for periodically resetting the
The output of each of the above counters is judged to match,
And an AND circuit that outputs a signal
An exclusive OR circuit for determining a match, and an output of the exclusive OR circuit.
Switching signal output that takes the logical product of the force and the output of each of the above counters
AND circuit and the level of the output signal of each main oscillator
Level detector for detecting the lower position,
Switching signal from the load circuit and the level from the level detector
OR operation with an abnormal signal to output an oscillator fault signal
And an OR circuit that outputs a switching signal to the switching circuit.
Oscillator monitoring device equipped with