JPH0625782B2 - Frequency discrimination circuit - Google Patents

Description

TECHNICAL FIELD The present invention relates to a frequency discriminating circuit capable of discriminating frequencies in a short time.

[Conventional technology]

In a circuit for identifying a plurality of frequencies in the same circuit by setting from the outside, conventionally, this has been done by counting the number of pulses included in a fixed time.

[Problems to be solved by the invention]

However, the conventional identification method as described above requires a long time for counting the number of pulses, and since the number of pulses is erroneously counted when noise is superimposed on the signal, sufficient accuracy is not obtained. There was a problem that I could not do it.

The present invention has been made in order to solve such a problem, and an object thereof is to obtain a frequency discriminating circuit capable of discriminating a frequency accurately in a short time.

[Means for solving problems]

A frequency discriminating circuit according to a first aspect of the present invention includes a frequency setting section for setting a frequency for discriminating; pulse cueing means for outputting a trigger pulse corresponding to a central portion of a peak or a trough of a pulse of an input signal; The sampling means for sampling the input signal, the timing setting means for controlling the timing of sampling by the sampling means in response to the frequency set by the frequency setting unit when activated by the trigger pulse, and the sampling means. Sampling level judging means comprising level judging means for outputting an error pulse when the level is different from the reference value corresponding to the peak or the valley of the pulse; and corresponding to the frequency set by the frequency setting part when activated by the trigger pulse. A timer that measures the measurement time and one measurement by this timer For each interval, an error limit value corresponding to the frequency set by the frequency setting unit is set, and the error limit value and the count value of the error pulse are compared to output a discrimination signal. It is a thing.

A frequency discriminating circuit according to a second aspect of the present invention is a sampling level which comprises sampling means for sampling an input signal and level determination means for outputting an error pulse when the level captured by the sampling means is different from a reference value. Determining means; a frequency range estimating means for estimating an approximate frequency range from the level captured by the Kokizana sampling; and a duty ratio measured from the level captured by the Kokizana sampling, and measuring the duty ratio from the edge of the pulse to the peak or valley. Pulse cueing means for obtaining an interval to the central portion; sampling width setting means for setting sampling widths respectively corresponding to a plurality of cycles obtained from at least the output of the frequency range estimating means;
Sampling level determination means is activated at the time of start-up and sampling is performed every time, and thereafter, when the sampling width is set by the sampling width setting means, sampling is performed with a plurality of sampling widths starting from the central portion of the peak or valley of the pulse. And the arithmetic processing means for calculating the frequency by the sampling width with the smallest error pulse number.

[Action]

In the first aspect of the present invention, the pulse cueing means detects the central portion of the peak or valley of the pulse of the input signal and outputs the trigger pulse. The trigger pulse is supplied to the sampling level determination means and the timer, and the sampling level determination means starts sampling by this, and outputs an error pulse when the taken level is different from the reference value. Further, the timer also starts timing with the trigger pulse, and when the timer times out, the arithmetic processing means compares the error limit value with the count value of the error pulse and outputs the determination signal.

Further, in the second aspect of the present invention, first, the arithmetic processing means performs all-out sampling, and at this time, the approximate frequency range is estimated from the level taken in by the frequency range estimating means. Further, the pulse cueing means measures the duty ratio from the taken-in level to obtain the interval from the edge of the pulse to the center. Then, the sampling width setting means sets sampling widths corresponding to a plurality of periods obtained from the output of the frequency range estimating means, and the arithmetic processing means performs sampling with these sampling widths, and the sampling width with the smallest error pulse number. Calculate the frequency by

〔Example〕

FIG. 1 is a diagram for explaining an embodiment of the frequency discriminating circuit of the first invention of the present invention.

In this figure, 1 is a frequency setting unit, 2 is a pulse cueing unit, 3 is a sampling level determining unit, 3a is a sampling unit, 3b is a level determining unit, 3c is a timing setting unit for setting sampling, and 4 is a measurement. A timer for suppressing arithmetic processing during time, 5 is arithmetic processing means, 5a is a decoder, 5b is an error counter, and 5c is a comparator.

Next, the operation will be described.

First, the frequency to be discriminated is set in the frequency setting unit 1. Next, when there is an input pulse, the pulse cueing means 2 is activated, and the input pulse is sampled every time,
For example, the interval between pulse peaks is measured by detecting the rising edge and the falling edge of the input pulse, and the interval from the pulse rising edge to the center is calculated. Then, thereafter, a trigger pulse is generated at the position of the center of the pulse peak. In addition,
The method of obtaining the interval from the rise of the pulse to the center is not limited to this, and for example, it is estimated by a method of obtaining the center of the peak (or valley) of the pulse based on the frequency set by the frequency setting unit 1. May be.

On the other hand, the output of the frequency setting unit 1 is also input to the timing setting unit 3c in the sampling level determining unit 3, and the timing setting unit 3c is set by receiving the trigger pulse from the pulse cueing unit 2. A sampling pulse having a frequency equal to the frequency (or a cycle of which is an integral multiple) is sent to the sampling means 3a. The sampling means 3a performs sampling with a sampling pulse, and the level determination means 3b determines whether the taken-in level is "H" or "L".

In this embodiment, the pulse locating means 2 detects the central portion of the crest (“H”) of the pulse, and the trigger pulse is output by this, so the sampling means 3 a
When at least a signal of the frequency set by the frequency setting unit 1 is input to the, the level to be captured is, for example, the second level.
As shown in FIG. 7A, the reference value should always be "H" regardless of the passage of time.

Further, as shown in FIG. 2B, when the level to be taken in does not always become "H", an error pulse is output from the level judging means 3b each time, and the error counter 5b in the arithmetic processing means 5 is outputted. Entered in. This must actually take into account the adverse effects of noise, etc.
This is because it is not possible to immediately determine that the frequencies are different because the error pulse is output. Therefore, the arithmetic processing means 5 sets the error limit value by the decoder 5a when the frequency to be discriminated first is set, and suppresses the arithmetic processing output from the timer 4 during the measurement time corresponding to the frequency to be discriminated. The comparator 5c is configured to be latched by a latch signal for

Then, when the measurement time ends and the timer 4 times up, the latch of the comparator 5c is released and comparison is performed. At this time, the count value of the error pulse output from the error counter 5b is the decoder 5a. When it is larger than the error limit value output from the comparator 5, a determination signal indicating that a signal different from the frequency set by the comparator 5c is input is obtained. Therefore, the frequency can be discriminated from this discrimination signal.

Now, for example, when discriminating a signal of 100 Hz, 10
It is assumed that a 1 Hz signal is input. In this case, in the conventional pulse count method, the difference is only 1 count even if it is measured for 1 second, and it is not easy to make an accurate determination if the influence of noise is taken into consideration.

However, according to the method of the present invention, the count value of the error pulse output from the sampling level determination means 3 in one second is 0 when the signal is 100 Hz, whereas it is 0 when the signal is 101 Hz. The count value of the error pulse becomes about half (about 50) of the total number of samples. Therefore, it is possible to accurately distinguish signals of close frequencies, and
It is possible to distinguish in a short time.

Note that each block in FIG. 1 does not necessarily have to have a hardware configuration, and may have a software configuration using a program.

However, in the configuration shown in this embodiment, even if the input signal is an integer multiple of the set frequency, it is determined to be the same. Therefore, when the input signal is completely unknown, some measure is required. Become.

FIG. 3 is a diagram for explaining one embodiment of the frequency discriminating circuit of the second invention of the present invention.

In this figure, the same reference numerals as in FIG. 1 indicate the same parts,
6 is arithmetic processing means, 6a is pulse cueing means, 6b is frequency range estimating means, 6c is sampling width setting means, 7
Is an indicator.

Next, the operation will be described.

First, when the arithmetic processing means 6 is activated, the arithmetic processing means 6
Activates the sampling level discriminating means 3 and carries out sampling as shown in FIG. 4 (a).

Next, the input pulse (the exact frequency is 1005.5 Hz, which is still unknown at this point) captured by the frequency range estimating means 6b is subjected to all-round sampling to detect the rising and falling points. And measure the period at an approximate frequency range, eg 1000-101
Estimated to be in the 0 Hz range. On the other hand, the pulse locating means 6a measures the interval of the crests of the input pulse in the same manner as the pulse locating means 2 of FIG. 1 described above, and from the rising edge of the pulse to the center as shown in FIG. 4 (b). Calculate the interval.

Next, the operation of further narrowing down the frequency range of the input pulse will be described.

The sampling width setting means 6c is the frequency range estimating means 6b.
Of the output of 1000 to 1010 Hz and a sampling width in a large range of a period with the same Hz order, for example, 100
0,1001,1002, ..., 1008,1009Hz
10 types are calculated and set.

Next, the arithmetic processing means 6 uses the output of the pulse cueing means 6a and the output of the sampling width setting means 6c to perform the above first
In the same manner as in the embodiment of the invention, the frequency discrimination (sampling) is performed ten times starting from the center of the pulse peak.
And the frequency range is limited to, for example, 1005 to 1006 Hz with the smallest error pulse as shown in FIG. 4 (c).

Next, the sampling width setting means 6c again sets 1005
For the frequency range of up to 1006Hz, for example, after setting about 10 kinds of sampling width in the order of 0.1Hz,
Frequency discrimination is performed 10 times, and there are the fewest error pulses as shown in FIG. 4 (d), for example, 1005.5 Hz.
Frequency is calculated and displayed on the display 7.

Therefore, it can be seen that the frequency of the input signal is 1005.5 Hz.

〔The invention's effect〕

As described above, the first invention of the present invention is: a frequency setting section for setting a frequency for performing discrimination; pulse cueing means for outputting a trigger pulse corresponding to a central portion of a peak or a valley of a pulse of an input signal; The sampling means for sampling the input signal, the timing setting means for controlling the timing of sampling by the sampling means in response to the frequency set by the frequency setting section when activated by the trigger pulse, and the level captured by the sampling means Sampling level judgment means comprising level judgment means for outputting an error pulse when it differs from a reference value corresponding to a peak or a valley of the pulse; a measurement time corresponding to the frequency set by the frequency setting part when activated by the trigger pulse And a timer for measuring the time and each measurement time by this timer , The error limit value corresponding to the frequency set by the frequency setting unit is set, and the error limit value is compared with the count value of the error pulse to output a discrimination signal. There is an effect that it is possible to accurately determine the frequency in a short time with a circuit having such a configuration.

Further, as described above, the second invention of the present invention comprises a sampling means for sampling an input signal and a level determination means for outputting an error pulse when the level captured by the sampling means is different from a reference value. Determining means; a frequency range estimating means for estimating an approximate frequency range from the level captured by the Kokizana sampling; and a duty ratio measured from the level captured by the Kokizana sampling, and measuring the duty ratio from the edge of the pulse to the peak or valley. Pulse cueing means for obtaining the interval to the central portion; sampling width setting means for setting sampling widths respectively corresponding to a plurality of cycles obtained from at least the output of the frequency range estimating means; Sampling every step After that, when the sampling width is set by the sampling width setting means, sampling is performed with a plurality of sampling widths starting from the center of the peak or valley of the pulse, and the frequency is calculated with the sampling width with the smallest number of error pulses. Since it is composed of the arithmetic processing means, the frequency of the unknown input signal can be easily known.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of the frequency discrimination circuit of the first invention of the present invention, FIGS. 2 (a) and 2 (b) are waveform diagrams for explaining the operation, and FIG. FIG. 4 is a diagram for explaining an embodiment of the frequency discriminating circuit of the second invention of the present invention, and FIGS. 4 (a) to 4 (d) are waveform diagrams for explaining the operation. In the figure, 1 is a frequency setting unit, 2 is a pulse cueing unit, 3 is a sampling level determining unit, 3a is a sampling unit, 3b is a level determining unit, 3c is a timing setting unit, 4 is a timer, 5 is an arithmetic processing unit, 5a is a decoder,
5b is an error counter, 5c is a comparator, 6 is an arithmetic processing means, 6a is a pulse cueing means, 6b is a frequency range estimating means, 6c is a sampling width setting means, and 7 is a display.

Claims (3)

[Claims] 1. A frequency setting section for setting a frequency for performing discrimination; pulse cueing means for outputting a trigger pulse corresponding to a central portion of a peak or a trough of a pulse of an input signal; sampling for sampling the input signal. Means, timing setting means that is activated by the trigger pulse and controls the timing of sampling by the sampling means corresponding to the frequency set by the frequency setting unit, and the level captured by the sampling means is the pulse Sampling level determination means comprising level determination means for outputting an error pulse when the reference value corresponding to a peak or a valley is different; measurement time corresponding to the frequency set by the frequency setting part when activated by the trigger pulse A timer that measures the time and one measurement time by this timer The error limit value corresponding to the frequency set by the frequency setting section is set, and the error limit value is compared with the count value of the error pulse to output a discrimination signal. A frequency discriminating circuit characterized by the above. 2. A frequency discriminating circuit according to claim 1, wherein the sampling level discriminating means carries out sampling at a frequency for discriminating. 3. Sampling level judging means comprising sampling means for sampling an input signal and level judging means for outputting an error pulse when the level taken in by the sampling means is different from a reference value; Frequency range estimating means for estimating an approximate frequency range from the level taken in by; the duty ratio is measured from the level taken in by the above-mentioned sampling and the interval from the edge of the pulse to the central part of the peak or valley is obtained. Pulse cueing means; sampling width setting means for setting sampling widths respectively corresponding to a plurality of cycles obtained from at least the output of the frequency range estimating means; and activating the sampling level determination means at the time of starting sampling Done, then When the sampling width is set by the sampling width setting means, sampling is performed with the plurality of sampling widths starting from the central portion of the peak or valley of the pulse, and the frequency is calculated by the sampling width with the smallest number of error pulses. A frequency discriminating circuit comprising: