JPH04370772A - Signal characteristics measurement device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal characteristic measuring device for measuring the amplitude ratio and/or phase difference of two repetitive signals having the same frequency.

0002

2. Description of the Related Art Conventionally, it has been required in various fields to measure the amplitude ratio and phase difference of repetitive signals such as sinusoidal waveform signals having the same frequency. FIG. 3 is a schematic diagram of torque measurement to illustrate an example of a field in which it is required to determine the phase difference between two repetitive signals.

A power source 1 and a power absorption source 2 are connected by a rotating shaft 3. Two gears 4 and 5 having the same pitch are attached to the rotating shaft 3,
The teeth of each gear 4, 5 are detected by each magnetic sensor 6, 7. At this time, the force generated in the power source 1 and the absorption source 2
The rotating shaft 3 rotates in an elastically twisted state due to the resistance at , and the signals picked up by the magnetic sensors 6 and 7 have the same frequency f (angular frequency ω = 2πf) but different phases. The torque is determined by detecting this phase difference φ.

FIG. 4 is a schematic diagram showing a state in which a transmission relationship of a predetermined system is determined. A sine wave signal Ac of amplitude A and frequency f (angular frequency ω=2πf) generated by the signal generator 8
osωt is input to the system 9 for calculating the transfer function, and a signal Bco having a different amplitude and phase with respect to the input signal Acosωt is input.
Assume that s(ωt+φ) is output. At this time, these two signals Acosωt, Bcos(ωt+φ)
By finding the amplitude ratio B/A and the phase difference φ while sweeping the frequency f, the transfer function of the system 9 can be found.

[0005] In various fields as exemplified above,
To measure the amplitude ratio of repeated signals such as two sine wave signals having the same frequency, for example, there is a method of holding the peak of each repeated signal and comparing the two peak values held, or A method has been adopted in which the Fourier transform is performed to obtain each amplitude and then compared. In addition, to measure the phase difference between the above two repetitive signals, there are two methods: binarize each repetitive signal and divide the time difference between the two binarized signals by the period of the signal, or use Fourier transform to measure the phase difference. A method of determining the phase difference, etc. is adopted.

[0006]

[Problem to be solved by the invention] 2.
The amplitude ratio and phase difference of two repetitive signals are determined, but each of the above methods requires a signal of at least one period or more of the above repetitive signal in order to determine the amplitude ratio and phase difference. There is a problem in that measurement time takes a long time when the frequency of the repetitive signal is low.

The present invention solves the above problem and determines the amplitude ratio and/or of two repetitive signals without waiting for one cycle of the repetitive signals.
Another object of the present invention is to provide a signal characteristic measuring device capable of determining a phase difference.

[0008]

Means for Solving the Problems To achieve the above object, the signal characteristic measuring device of the present invention is a signal characteristic measuring device for measuring the amplitude ratio and/or phase difference of two repetitive signals having the same first frequency. In the characteristic measuring device, a signal generator that generates two sine wave signals having the same second frequency and having phases different from each other by 90 degrees, and each of the two sine wave signals for each of the two repetitive signals. a multiplier that multiplies , and an output from the multiplier,
a filter for extracting one component of the first frequency or the second frequency from each signal containing components of both the first frequency and the second frequency; and The present invention is characterized by comprising an arithmetic circuit that calculates the amplitude ratio and/or phase difference between the two repetitive signals based on the signals.

[0009] Here, a frequency is selected in which the second frequency is the same as or similar to the first frequency.

0010

[Operation] The signal characteristic measuring device of the present invention was completed by paying attention to the following principle. FIG. 1 is a diagram illustrating the principle of a signal characteristic measuring device according to the present invention. Two input sine wave signals Acosωt, Bc with the same frequency f (angular frequency ω=2πf) and whose phases differ from each other by φ
Multiply os(ωt+φ) by exp(−jω0 t). Here, this angular frequency ω0 is ω0 = ω or ω0
Suppose that ≒ω.

When Acosωt is multiplied by exp(-jω0 t), the signal S1 becomes

0012

[Math 1]

##EQU1## This results in a signal having two angular frequencies, ω-ω0 and ω+ω0. The signal shown in equation (1) is input to a filter that allows only one of the signal components having each of these frequencies to pass through. Here, for example, the component of angular frequency ω-ω0 is passed and the angular frequency ω+ω0 is
shall be cut. As a result, the signal S2 that has passed through this filter is

[0014]

[Math 2]

[0015] Also, in the same way as above, Bcos
When (ωt+φ) is multiplied by exp(-jω0 t), the signal S3 becomes

[0016]

[Math 3]

When this signal is input to a filter having the same characteristics as above, the signal S4 outputted from the filter is

[
0018

[Math 4]

[0019] The above (2) obtained in this way,
When the ratio S4/S2 of the two signals expressed by equation (4) is found,

[0020]

[Math 5]

The amplitude ratio B/A can be found by finding this absolute value, and the real part Re=(B/A)c
Ratio Im between osφ and imaginary part Im=(B/A)sinφ
The phase difference φ is determined by calculating /Re=tanφ. If you want only the phase difference φ here, or
For example, if the amplitude A is known, instead of finding S4/S2, find the conjugate complex number S2* of equation (4) above, and
4×S2* may be calculated. That is,

0022
]

[Math 6]

##EQU1## If the amplitude A is known, the amplitude B, and therefore the ratio B/A, can be found, and the phase difference φ can also be found. The present invention employs the above principle, and thereby the amplitude ratio and/or phase difference can be determined in a period shorter than one period T (T=1/f=2π/ω).

[0024]

[Examples] Examples of the present invention will be described below. FIG. 2 is a block diagram showing an embodiment of the signal characteristic measuring device of the present invention. The same frequency f (angular frequency ω
) and whose phases differ from each other by φ
cosωt and Bcos(ωt+φ) are input to A/D converters 11 and 12, respectively, and sampled at predetermined sampling intervals to obtain digital signals D1 and D2. Note that here, each digital signal D1, D2 is obtained by sampling at every interval. For the sake of simplicity, the digitized signals D1, D2, etc. will also be described below, for example.

[0025]

[Math 7]

[0026]

[Math. 8]

Let us express it in the same way as a continuous function, as shown in the following. The signal D1 output from the A/D converter 11 is input to multipliers 13 and 14, and the signal D2 output from the A/D converter 12 is input to multipliers 15 and 16. Also,
The signal generator 17 outputs frequency f (angular frequency ω) and a frequency f0 (angular frequency ω0) that is similar to the frequency f0 (angular frequency ω0), which have a phase of 9
Two signals shifted by 0°

[0028]

[Math. 9]

[0029]

[Math. 10]

is output, and the signal D3 is sent to the multipliers 13 and 15.
Then, the signal D4 is input to multipliers 14 and 16. Each of the multipliers 13, 14, 15, and 16 multiplies each of the two input signals to produce the following signals D5, D6, D7, respectively.
D8 is output.

[0031]

[Math. 11]

[0032]

[Math. 12]

[0033]

[Math. 13]

[0034]

[Math. 14]

The signals D5, D6, D7, D8 output from the multipliers 13, 14, 15, 16 are input to the filters 18, 19, 20, 21, respectively. These filters 18, 19, 20, and 21 are filters that pass the signal of angular frequency ω−ω0 and cut the signal of angular frequency ω+ω0.
From 9, 20, 21, the following signals D9, D10,
D11 and D12 are output.

[0036]

[Math. 15]

[0037]

[Math. 16]

[0038]

[Math. 17]

[0039]

[Math. 18]

Signals D9, D10, D11, and D12 output from each filter 18, 19, 20, and 21 are input to an arithmetic circuit 30. In this arithmetic circuit 30, the signal D9 is applied to the multipliers 31 and 33, and the signal D10 is applied to the multipliers 32 and 3.
4. Signal D11 is input to multipliers 31, 34, signal D12 is input to multipliers 32, 33, and each multiplier 31, 32, 33,
34, each of the two input signals is multiplied, and the following signals D13, D14, D15, and D16 are generated.

[0041]

[Math. 19]

[0042]

[Math. 20]

[0043]

[Math. 21]

[0044]

[Math. 22]

The above four signals D13, D14, D15,
Two signals D13 and D14 among D16 are addition signals input to the adder 35.

[0046]

[Math. 23]

##EQU1## is generated and input to the divider 36. Furthermore, two signals D15 and D16 among the four signals D13, D14, D15, and D16 are input to a subtracter 37 to produce a subtracted signal.

[0048]

[Math. 24]

##EQU1## is generated and input to the divider 38. In addition, each signal D9, D output from the filters 20, 21
10 is input to each squaring circuit 39, 40, and their respective outputs are added together by an adder 41 to produce a signal.

[0050]

[Math. 25]

##EQU1## is generated and input to the dividers 36 and 38. Each divider 36, 38 receives two input signals D.
17, D19; D18, D19 are divided, and each signal

[0052]

[Math. 26]

[0053]

[Math. 27]

##EQU1## is generated. Each of these signals D20, D
21 are respectively input to squaring circuits 42 and 43 and squared, added together in an adder 44, and then square rooted in a square rooter 45 to obtain a signal.

[0055]

[Math. 28]

is output, which causes two input signals D
1, the amplitude ratio B/A of D2 is determined. Further, the signals D20 and D21 outputted from the dividers 36 and 38 are input to the divider 46 and the signals

[0057]

[Math. 29]

##EQU1## is generated, and from this the phase difference φ between the two input signals is determined. In this way, by calculating both the real part and the imaginary part according to the principle shown in FIG. 1, the A/
The amplitude ratio B/A and/or phase difference φ of the two input signals Acosωt and Bcos(ωt+φ) can be determined for each sampling in the D converters 11 and 12.

In the above embodiment, the arithmetic circuit 30 calculates both the amplitude ratio B/A and the phase difference φ, but when calculating only the amplitude ratio B/A, for example, the arithmetic circuit 30 The configuration can be modified in various ways depending on the case where only the phase difference φ is to be determined. In addition, filters 18, 19, 20,
21 extracts a signal with an angular frequency ω-ω0, but it may be configured to extract a signal with an angular frequency ω+ω0 instead. In addition, in the above embodiment, the two input signals Acosωt and Bcos(ωt+φ) are first input to A/
Although the amplitude ratio B/A and the phase difference φ were obtained by D conversion and digital calculation, some or all of these calculations may be replaced with analog calculations. As described above, the signal characteristic measuring device of the present invention is not limited to the above-mentioned embodiments, and can be configured in various ways.

[0060]

Effects of the Invention As explained above in detail, the signal characteristic measuring device of the present invention has two input signals whose phases are 90° to each other.
By multiplying two different sine wave signals and extracting a single frequency component signal from the resulting mixture of multiple frequency components, the two input signals can be combined in a period shorter than one period of the input signal. The amplitude ratio and/or phase difference of

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the principle of a signal characteristic measuring device of the present invention.

FIG. 2 is a block diagram showing an embodiment of the signal characteristic measuring device of the present invention.

FIG. 3 is a schematic diagram of torque measurement.

FIG. 4 is a schematic diagram showing a state in which a transfer function of a predetermined system is determined.

[Explanation of symbols]

11, 12 A/D converter 13, 14, 15, 16 Multiplier 18, 19, 20, 21 filter 30 Arithmetic circuit

Claims (2)

[Claims] [Claim 1] Two components having the same first frequency
In the signal characteristic measuring device for measuring the amplitude ratio and/or phase difference of two repetitive signals, the signal generator generates two sine wave signals having the same second frequency and having phases different from each other by 90°; a multiplier that multiplies each of the two repeated signals by each of the two sine wave signals, and each signal output from the multiplier that includes components of both the first frequency and the second frequency. a filter that extracts one component of the first frequency or the second frequency from the filter; and a calculation that calculates the amplitude ratio and/or phase difference of the two repeated signals based on the signal output from the filter. A signal characteristic measuring device comprising a circuit. 2. The signal characteristic measuring device according to claim 1, wherein the second frequency is the same as or similar to the first frequency.