JP2598013B2 - Waveform processing method - Google Patents

Description

The present invention relates to a waveform processing method, and more particularly, to a waveform processing method for detecting a beat signal based on sampling.

(Prior Art) Conventionally, in order to detect a beat signal of two AC signals, a beat signal is directly recorded on a recorder or a difference signal between the two AC signals is converted to a DC level through a converter. It was necessary to obtain a digital signal by converting the signal into a signal and further converting it into an analog-digital signal.

Such a conventional waveform processing method requires a converter for converting the difference signal into a DC level signal,
Also, when the frequency difference between the two AC signals is large, the level change of the difference signal also becomes fast, and the conversion response speed of the converter becomes a problem, and it becomes difficult to extract a beat signal with high accuracy.

(Problems to be Solved by the Invention) As described above, the conventional waveform processing method does not employ a method of directly processing and detecting a beat signal. Therefore, a beat signal is detected with high accuracy and simple processing. It was impossible.

The present invention has been made in order to eliminate such a conventional drawback, and an object of the present invention is to provide a waveform processing method for detecting a beat signal of two AC signals by a simple arithmetic processing using a computer.

[Configuration of the invention]

Waveform processing method according to the present invention (means for solving the problem), the beat signal of the AC signal and the reference AC signal of frequency f ₀ of the frequency f f _S = 2nf
By extracting sampling points for each π phase of the reference AC signal from sampling points obtained by sampling at a sampling frequency f _S satisfying ₀ (n is an integer), the beat signal is This is to detect.

Beat signal V generated by the difference of the AC signal (created for) the frequency f and the reference AC signal of frequency f ₀ is expressed by the following equation.

_{V = Vsin2πft-Vsin2πf 0 t =} Vsin (2π (f 0 + Δf) t) -Vsin2πf 0 t ...... (1) where _{Δf = f-f 0 ...... (} 2) Sampling frequency F that satisfies the signal V wherein _S sampling.

(F ₀ / f _S ) × 2π = π (3) Therefore, f _S = 2f ₀ (4) where the sampling period T is Becomes

Since the sampling cycle is T, expansion is performed by substituting t = T into equation (1), and using the relation of equation (5), V = V (sin t cos 2πΔft + cos πsin 2πΔft) −Vs
in π.

Since cos π = 1 and sin π = 0, V = −Vsin 2πΔft (6), and a signal depending on the beat frequency Δf is extracted. With this sample the difference signal at a beat signal V of the waveform of the AC signal and the reference AC signal of the reference frequency f ₀ of the frequency f for each [pi (180 degrees), the envelope of the beat signal V is obtained.

However, when sampling the beat signal V, it is not possible to determine at which phase of the reference AC signal of the reference frequency f ₀ the sampling is being performed, so a frequency that is an integral multiple of 2f ₀ is used as the sampling frequency. That is, a sampling value whose polarity changes from (+) to (−) or from (−) to (+) is detected as a reference of phase 0, and a sampling value obtained by multiplying the sampling value by an integer is used as a sampling value of phase π. By calculating, a sampling value of the envelope of the beat signal can be obtained.

Thus, among the sampled values at f _S = 2nf _0, f _S
= 2nf ₀ only satisfies the expression (6), and only the sampling values satisfying the expression (6) can be extracted by the above method.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 3 is a conceptual diagram of a processing device for explaining a waveform processing method according to the present invention. A difference signal between an AC signal having a frequency f and a reference AC signal having a frequency f ₀ is obtained by a differential amplifier 1, and the difference signal is reduced to a normal input signal level by an auxiliary transformer 2, and the analog input card 3 is input. This difference signal is an analog within the input card 3 is sampling and binarized by a quantization unit 4 is performed according to the sampling frequency f _S is specified by the control unit 8, such as a microprocessor. The output of the quantizing unit 4 is sent to a positive / negative determining unit 6 where a positive / negative determination is made.
The output unit 7 outputs the digital signal as a sine wave beat signal. The control unit 8, the positive / negative determination unit 6, and the output unit 7 can be configured as a microprocessor.

Figure 1 is the beat signal and the sampling frequency is a signal of the difference between the AC signal and the reference AC signal of frequency f ₀ of the frequency f
a waveform diagram showing a relationship between f _S serve to explain the principles of the present invention. According to the figure, the reference AC signal having the frequency f ₀ changes in the envelope of the beat signal represented by the frequency of the frequency difference Δf = f−f ₀ .

Π That reference AC signal from the AC signal and the difference signal in which samples the beat signal at a sampling frequency fs seeking sampling points of the reference alternating waveform of frequency f ₀ of the frequency f, for each 180 ° phase By extracting the sampling points, an envelope of the beat signal can be obtained. At this time, the sampling frequency f _S satisfies the expressions (3) and (4). However, since the sampling point is not always at the 90 ° phase point, the sampling frequency f _S needs to be a value satisfying f _S = 2nf ₀ (n: integer value) (7).

Frequency at a sampling frequency f _S which defines in this way
sampling the reference AC signal having a f _0, the sampling value X _0, X _1, obtaining ...... X _n.

FIG. 2 is a flowchart showing a procedure for detecting a beat signal using the sampling value thus obtained.

First, input the sampling values X ₀ and X ₁ of two adjacent points,
(Step 101), it is detected whether there is a polarity change from plus to minus or from minus to plus (step 102). If there is a change in polarity, the sampling point of the sampling value having the smaller absolute value is set as a reference, and that point is set as a reference of phase 0 (steps 104 and 105).

Then enter the next sampling value (step 10
6), it is determined whether or not the sampling value is a sampling of phase π / 2 (step 107). If the point is the sampling point of the phase π / 2, the next sampling value is inputted as a reference point of the sampling of the phase π (step 108) (step 109), and it is determined whether or not the sampling point is the phase π. (Step 110) If the sampling point is the phase π, this point is recorded as the sampling value of the beat signal (Step 111).

Then, when the sampling of a predetermined number of sampling values is completed, the sampling is completed (step 112). Thus _{n × 2π · f 0 / f} S = π ...... (8) by sampling at a sampling frequency f _S satisfying the extracted sampling points for each [pi phase of the reference AC signal from the determined sampling points The beat signal is detected by using it as the sampling value of the beat signal.

In FIG. 1, X ₀ is a sampling point of π / 2 phase (X ₂ )
And X ₂ is shown as a reference point for finding a sampling point for each phase π.

〔The invention's effect〕

As described in detail based on the above embodiments, according to the present invention, a sampling value of a beat signal can be obtained by a simple arithmetic processing from a sampling value sampled at a relatively low sampling frequency f _S , whereby the beat signal is obtained. It can be easily detected.

[Brief description of the drawings]

FIG. 1 is a waveform diagram for explaining sampling of an AC input signal performed according to the present invention, FIG. 2 is a flowchart for executing a waveform processing method according to the present invention, and FIG.
FIG. 1 is a conceptual diagram of a processing device for executing the present invention. 1 ... Differential amplifier, 2 ... Auxiliary transformer, 3 ... Analog input card, 4 ... Quantization unit, 6 ... Positive / negative determination unit, 7 ...
... output unit, 8 ... control unit.

Claims (1)

(57) [Claims] 1. A frequency signal a beat signal V f _S = 2nf ₀ is the difference between the AC signal and the reference AC signal of frequency f ₀ of f (n is an integer) obtained by sampling at a sampling frequency f _S satisfying Π of the reference AC signal from the sampling points
A waveform processing method wherein a sampling point for each phase is extracted and used as a sampling value of the beat signal to obtain an envelope of the beat signal.