JPH0529884A - Monitor for oscillator - Google Patents

Abstract

PURPOSE:To improve the reliability of accuracy of monitoring by detecting a frequency deviation between a monitor oscillator and a main oscillator so as to detect a fault of the main oscillator and a monitor circuit itself. CONSTITUTION:The monitor is provided with frequency mixers 4a, 4b comparing an oscillating frequency of a main oscillator 1A with an oscillating frequency of plural monitor oscillators 3a, 3b, low pass filters 5a, 5b extracting respectively a beat frequency component from the output of the mixers, and counters 6a, 6b outputting a frequency deviation detection signal when a coefficient of each bit component exceeds a setting value. An AND circuit 8 discriminates the coincidence between outputs of the counters 6a, 6b to output a frequency deviation detection signal. A level detector 2 detects the level reduction in an output signal of the main oscillator 1A, an OR circuit 10 ORs a level fault signal from the level detector 2 and the frequency deviation detection signal from the AND circuit 8 to output an oscillator fault signal.

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 oscillator output signal.

[0002]

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

Next, the operation will be described. The oscillator 1 generates an output signal having a predetermined frequency, and this output signal is monitored by a level detector. Then, the level detector 2 detects an output interruption or a level decrease from the output signal, and sends out an oscillator failure signal indicating that the oscillator 1 is abnormal.

[0004]

Since the conventional oscillator monitoring device is constructed 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 invention of claim 1 has been made to solve the above problems, and an oscillator monitoring device capable of monitoring not only the level abnormality of the output signal of the main oscillator but also the frequency deviation. Aim to get.

It is another object of the present invention to monitor the frequency shift between the two main oscillators and selectively output a normal oscillation signal on the main oscillator side.

[0007]

According to another aspect of the present invention, there is provided an oscillator monitoring apparatus, wherein each of the frequency mixers compares the oscillation frequency of a main oscillator with the oscillation frequencies of a plurality of monitor oscillators, and the frequency mixers. Low-pass filter for extracting the beat frequency component from the output of the filter, and each counter for outputting a frequency deviation detection signal when the count value of each beat component from the low-pass filter exceeds a set value And an AND circuit that determines the coincidence of the outputs of the counters and outputs a frequency shift detection signal, and causes the level detector to detect a decrease in the level of the output signal of the main oscillator. The OR circuit takes the logical sum of the level abnormality signal and the frequency shift detection signal from the AND circuit to output the oscillator failure signal.

Further, the oscillator monitoring apparatus according to the invention of claim 2 has a switching circuit for selectively switching and outputting the oscillation outputs of the two main oscillators, the oscillation frequency of the main oscillator and the oscillation frequency of the monitor oscillator. Each one of the frequency mixers, a low-pass filter that extracts the beat frequency component from the output of the frequency mixer, and the count value of each beat component from the low-pass filter has a set value. Each counter that outputs a frequency deviation detection signal when exceeding, and an exclusive OR circuit that determines a mismatch of the output of each counter and outputs a monitoring circuit failure signal, and in the case of a mismatch, the above The switching circuit outputs the switching signal due to the frequency shift from the switching signal output AND circuit, causes the level detector to detect the level decrease of the output signal of the main oscillator, and causes the OR circuit to output the switching signal output signal. And take the logical sum of the switching signal and the level error signal from the level detector from the hard circuit, in which to output an oscillator fault signal.

[0009]

In the counter according to the first aspect of the present invention, the frequency difference between the monitor oscillator and the main oscillator is detected, and the AND circuit detects the coincidence of the frequency deviations, and the exclusive OR circuit detects the discrepancy of the frequency deviations. By detecting
The failure of the main oscillator and the monitoring circuit itself is detected to improve the reliability of monitoring accuracy.

The counter according to the invention of claim 2 is
The frequency difference between the two main oscillators is detected by the exclusive OR circuit to selectively output the oscillation signal of the normal main oscillator, and also the failure of the monitoring circuit itself can be detected.

[0011]

EXAMPLES Example 1. An embodiment of the invention of claim 1 will be described below with reference to the drawings. In FIG. 1, reference numeral 1A is a main oscillator, 2 is a level detector for detecting an output cutoff or a level drop of the main oscillator 1A and sending a level abnormality signal, 3a
3b is a monitor oscillator for frequency comparison with the main oscillator 1A, 4a and 4b are frequency mixers for frequency comparison, 5
a and 5b are low-pass filters that extract only the beat component from the outputs of the frequency mixers 4a and 4b, and 6a and 6b count the beat component, and when the count value exceeds a preset count value, the frequency It is a counter that outputs a deviation detection signal.

Further, 7 is a reset pulse generator for periodically resetting the counters 6a, 6b, 8 is an AND circuit for detecting the coincidence of two counter outputs (frequency deviation detection signals), and 9 is a disagreement of the two counter outputs. And an OR circuit 10 that outputs a fault signal of the monitoring circuit and outputs an oscillator fault signal by ORing the level abnormality signal and the frequency shift detection 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 a deviation occurs in the oscillation frequency of the main oscillator 1A, the main oscillator 1A and the monitor oscillator 3a, The sum and difference components of the respective oscillation frequencies with 3b are output. Further, 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 the reset pulse of the reset pulse generator 7 as shown in FIG. 3 (b), as shown in FIG. 3 (c). When the preset count value is exceeded within the reset period, a frequency shift detection signal as shown in FIG. 3D is sent out. 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 output the frequency deviation detection signal, so that the AND circuit 8 detects the frequency deviation. It is confirmed that the signals match, 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. 4 (a), 4 (b) and 4 (c). As shown, no frequency offset 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 deviation, a frequency deviation detection signal is output from either of the two counters 6a and 6b. , AND circuit 8 does not match, and the oscillator failure signal is not output. On the other hand, the exclusive OR circuit 9 detects the mismatch and outputs the monitoring circuit failure signal.

Example 2. FIG. 2 shows an embodiment of the invention of claim 2, which comprises two main oscillators 1B and 1C, which are switched and used as a working and a standby configuration. Explaining this, 11a and 11b are exclusive OR circuits for detecting a discrepancy between a frequency deviation detection signal from two frequency deviation monitoring circuits including a monitor oscillator 3, frequency mixers 4a and 4b, and two counter outputs. A switching signal output AND circuit for detecting a match with the output of 9 and a switching circuit 12 for selectively outputting the output signals of the two main oscillators 1B and 1C. The same block as that shown in FIG. Are denoted by the same reference numerals, and duplicate description thereof will be omitted.

Next, the operation will be described. First, when one of the two main oscillators 1B and 1C causes 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 that of the first embodiment. To be done. For this reason, the output signals of the counters 6a and 6b do not match, the exclusive OR circuit 9 detects the mismatch, the gate of the switching signal output AND circuit 11a or 11b is opened, and the frequency shift detection signal becomes the OR circuit 10a. , 10b, and is input to the switching circuit 12. Therefore, the switching circuit 12 has the normal main oscillator 1B,
Alternatively, it is automatically switched to the 1C side and output.

If both the main oscillators 1B and 1C are normal and the monitor oscillator 3 has a frequency shift, it is 2
The outputs of the two counters 6a and 6b both output a frequency shift detection signal. Therefore, the exclusive OR circuit 9 does not detect a mismatch, and the AND circuits 11a and 11b for switching signal output are used.
The gate is not opened, so no switching signal is sent.
On the other hand, at this time, since the coincidence is detected in the AND circuit 8, the monitoring circuit fault signal is sent to the outside.

[0019]

As described above, according to the first aspect of the present invention, the frequency difference between the main oscillator and the two monitoring oscillators is detected, and the abnormality due to the frequency deviation of the main oscillator is monitored. Since the deviation detection signal and the level of the output signal of the main oscillator are logically ORed by the OR circuit to detect the level drop, it is possible to monitor the failure of the monitoring circuit itself as well as the abnormality of the main oscillator. There is an effect that what can be obtained.

Further, according to the invention of claim 2, the frequency difference between the two main oscillators and one monitoring oscillator is detected, and the abnormality due to the frequency shift of each oscillator can be mutually monitored. When the detection signals do not match, the switching circuit selectively outputs the oscillation signal of one of the main oscillators that is normal, so both the abnormality detection of the main oscillator and the output of the oscillation signal from the normal main oscillator are both realized. There is an effect that what can be obtained.

[Brief description of drawings]

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

FIG. 2 is a block connection diagram showing an oscillator monitoring device according to an 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 the 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 Monitor oscillator 4a, 4b frequency mixer 5a, 5b Low-pass filter 6a, 6b counter 7 Reset pulse generator 8 AND circuit 9 Exclusive OR circuit 10 OR circuit 11a, 11b AND circuit for switching signal output 12 switching circuit

Claims (2)

[Claims] 1. A frequency mixer for comparing the oscillation frequency of a main oscillator and an oscillation frequency of a plurality of monitoring oscillators, and a low-pass filter for extracting beat frequency components from the output of the frequency mixer. A counter that outputs a frequency deviation detection signal when the count value of each beat component from the low-pass filter exceeds a set value, and a reset pulse generator that periodically resets each counter An AND circuit that determines whether the outputs of the counters match and outputs a frequency shift detection signal; an exclusive OR circuit that determines the mismatch of the outputs of the counters and outputs a monitoring circuit fault signal; A level detector that detects a decrease in the level of the output signal, the level abnormality signal from the level detector, and the frequency deviation detection signal from the AND circuit are ORed to determine the oscillator failure signal. An oscillator monitoring device having an output OR circuit. 2. A switching circuit that selectively switches and outputs the oscillation outputs of two main oscillators, one frequency mixer that compares the oscillation frequency of the main oscillator and the oscillation frequency of the monitor oscillator, and the frequency mixer. A low-pass filter that extracts each beat frequency component from the output of the mixer, and each one that outputs a frequency deviation detection signal when the count value of each beat component from the low-pass filter exceeds a set value. Counter, and a reset pulse generator that periodically resets each counter,
An AND circuit that determines whether the outputs of the counters match and outputs a frequency shift detection signal, an exclusive OR circuit that determines the mismatch of the outputs of the counters and outputs a monitoring circuit fault signal, and In this case, a switching signal output AND circuit that outputs a switching signal due to a frequency shift to the switching circuit, a level detector that detects a level decrease of the output signal of the main oscillator, and a switching from the switching signal output AND circuit An oscillator monitoring device comprising: an OR circuit for ORing a signal and a level abnormality signal from the level detector to output an oscillator failure signal.