JPH02210911A - Frequency counter - Google Patents

Abstract

PURPOSE:To keep the required measuring frequency resolution and to attain frequency measurement with high accuracy without multiplication of the frequency of a signal to be measured and the setting of a wave number by measuring the frequency through the use of the signal to be measured and a sampling value of a reference signal. CONSTITUTION:The input signal to be measured is synchronized with a synchronizing circuit comprising D FFs 1, 2 together with a sampling signal. Moreover, the number of waves of the signal to be measured is counted continuously by a counter 3, inputted to a D FF 4 as a 1st sampling means together with an output from the FF 2 and the number of waves of the sampled signal to be measured is outputted to an arithmetic circuit 10. Moreover, similarly, a reference signal generated from a reference signal generator 5 and the calculated value of the sampling reference signal are outputted via D FFs 6, 7, a binary counter 8 and a D FF 9 as a 2nd sampling means to the circuit 10. Then a ratio of both sampling differences to be inputted to the circuit 10 is operated to measure the frequency. Thus, the frequency of both the measures signals is measured with high accuracy.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a frequency counter used to receive radio waves from a moving object and measure Doppler frequency, and is particularly suitable for use in fields where measurement time is a problem. Regarding frequency counters.

[Conventional technology]

Different examples of conventional frequency counters of this type are shown in FIGS. 2 and 3, respectively.

The frequency counter shown in FIG. 2 has a gate signal generation circuit 11 that generates a fixed time for a sampling signal, and uses the output of this gate signal generation circuit 11 to generate an AND gate 1.
2 is opened to gate the signal under test, and the wave number of the signal under test during this period is counted by a wave number counter 13.

In this configuration, the measurement frequency r is the gate signal generation circuit 11
From the gate time T and the count value N of the wave number counter 13, it can be determined by the relationship f-N/T.

On the other hand, the frequency counter shown in FIG. 3 synchronizes the signal under test and the sampling signal using D-type flip-flops 21 and 22, and passes the synchronized signal and the signal under test through an AND gate 23 to a wave number counter 24. Count. The output of this wave number counter 24 is compared with a wave number set value N in a comparator 25, and when this set value is counted, a gate signal is output. This gate signal opens the AND gate 27 to allow the reference signal 26 to pass through, and this reference signal is counted by the counting counter 28.

With this configuration, the frequency can be obtained by measuring the average period of the signal under test. That is, the measurement frequency f
is the wave number setting value N2, the frequency fcL of the reference signal, and the count value X of the reference signal, f = N X f cLg /
It becomes X.

[Problem to be solved by the invention]

Among the conventional frequency counters mentioned above, the counter shown in Fig. 2 cannot make the gate time T longer than necessary due to the requirements of the sampling period. It is necessary to multiply f equimetrically.

In addition, the measurement frequency resolution of the counter in Fig. 3 is independent of the frequency of the input signal under test, and can be improved by increasing the frequency f of the reference signal (CLK), but the wave number setting value N changes depending on the sampling period. You need to change the settings.

Furthermore, in both counters, the starting point of measurement is the starting point of the sampling signal, and the end time of measurement is the end point of the gate time, so there is inevitably a time when the frequency of the signal under test is not measured, which may affect the measurement accuracy. There is a problem that the amount of energy is reduced.

An object of the present invention is to provide a frequency counter that solves the above-mentioned problems and realizes highly accurate measurement.

[Means to solve the problem]

The frequency counter of the present invention includes a synchronization circuit that synchronizes a signal under test and a reference signal with a sampling signal to generate a clock signal, a progressive counter that continuously counts the signal under test, and an output of the progressive counter. a first sampling means that samples the reference signal based on the clock signal; a progressive counter that continuously counts the reference signal;
a second sampling means for sampling the output of the progressive counter based on the clock signal;
and an arithmetic circuit that calculates the frequency of the signal under test based on the output of the second sampling means.

In this arithmetic circuit, the difference between the current sampling value and the previous sampling value in each of the wave number of the signal under test and the count value of the reference signal is determined, and the frequency of the ratio measurement signal is calculated from the ratio of the two.

[Effect]

In the above-mentioned configuration, the sampling values of the signal under test and the reference signal are used for calculation, so the required measurement frequency resolution is maintained without having to multiply the frequency of the signal under test or set the wave number setting, and high accuracy is achieved. frequency measurement.

〔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.

The input signal under test is synchronized with the sampling signal by a synchronization circuit composed of a D-type flip-flop 1.2. In addition, the wave number of the signal under measurement is determined by a progressive counter,
Here, it is continuously counted by a binary counter 3 and output to a D-type flip-flop 4. and,
The synchronized sampling signal serves as a clock signal for the D-type flip-flop 4 as a first sampling means, and the wave number of the sampled signal under test is output to the arithmetic circuit 10. Similarly, the reference signal generated from the reference signal generator 5 is synchronized with the sampling signal by a synchronization circuit constituted by a D-type flip-flop 6.7. Further, the reference signal is continuously counted by a progressive counter (binary counter) 8 and outputted to a D-type flip-flop 9 as second sampling means. The synchronized sampling signal becomes a clock signal for the D-type flip-flop 9, and the count value of the sampled reference signal is output to the arithmetic circuit 10.

The arithmetic circuit 10 calculates the wave number N (k) of the currently sampled signal under test, the wave number N (k-1) of the previously sampled signal under test, and the count value of the currently sampled reference signal. The following calculation is performed using X (k) and the count value X (k-1) of the previously sampled reference signal to calculate the frequency f of the signal under test.

However, f　CLK is the frequency of the reference signal.

Therefore, in this frequency counter, the resolution of the measurement frequency can be improved by increasing the frequency of the reference signal. Further, since there is no need to multiply the frequency of the signal under test or set a wave number setting value, counting can be easily performed. Furthermore, since counting is performed while the sampling signal, the signal under test, and the reference signal are each synchronized, highly accurate counting can be performed.

〔Effect of the invention〕

As explained above, the present invention samples the wave number of the signal under test and the count of the reference signal based on a synchronized clock, and measures the frequency by finding the ratio of the difference between these sampling values. By increasing the frequency of the necessary reference signal, it is possible to improve the resolution of the measurement frequency without multiplying the frequency of the signal under test or setting the wave number setting value. Furthermore, since counting is performed using a clock signal synchronized with the sampling signal or the signal under test, there is also the effect that the frequency of the signal under test can be measured with high precision.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the frequency counter of the present invention, and FIGS. 2 and 3 are block diagrams showing different conventional frequency counters. 1.2... D-type flip-flop, 3... Binary counter, 4... D-type flip-flop, 5... Reference signal, 6.7... D-type flip-flop, 8...
Binary counter, 9...D type flip-flop, 1
0... Arithmetic circuit, 11... Gate signal generation circuit, 1
2...And gate, 13...Wave number counter, 21
．． 22... D-type flip-flop, 23... AND gate, 24... Wave number counter, 25... Comparator,
26...Reference signal, 27...And gate, 2°8
...counter. bondage

Claims (1)

[Claims] 1. A synchronization circuit that synchronizes the signal under test and the reference signal with a sampling signal to generate a clock signal, a progressive counter that continuously counts the signal under test, and an output of the progressive counter as the clock signal. a progressive counter that continuously counts the reference signal; a second sampling means that samples the output of the progressive counter based on the clock signal; 1. A frequency counter comprising: an arithmetic circuit that calculates the frequency of a signal under measurement based on the output of the sampling means of No. 2.