JPH0549122B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to general measuring instruments, radars, etc., in which multiple input sine wave or cosine wave signals (referred to as trigonometric function signals in the present invention) have the same frequency. The present invention relates to a signal phase difference detection device that detects a phase difference between.

[Conventional technology]

There are various ways to measure phase values or phase differences, such as signal phase measurement in general measuring equipment, or detection of phase changes in signals received by antenna elements or phase differences between signals in direction finders or radars that detect phase differences. This method is well known. Analog methods include finding it from the product of two signals,
Alternatively, as a digital method, the signal is converted into a square wave using a certain threshold value, and the phase difference between the square waves is detected using a phase comparator.

[Problem that the invention seeks to solve]

The above phase difference measuring method does not detect the phase difference instantaneously, but averages the phase difference over several waves of signals. Therefore, when applying this phase difference measurement method to detect the direction of illegal radio waves, there is a problem that it becomes impossible to measure the phase difference for illegal radio waves that are emitted intermittently for a very short period of time. . In addition, a phase comparator that directly measures the phase difference between two signals has a phase difference of ±
When the angle exceeds 180°, it is necessary to distinguish between lead and lag, and it is necessary to add a circuit for this discrimination.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned problems and provide a signal phase difference detection device that can detect instantaneous phase differences. Since trigonometric function signals, which are the subject of the present invention, have mathematically defined characteristics, it is an object of the present invention to utilize these characteristics to obtain a simple phase difference detection method.

[Means for solving problems]

The signal phase difference detection device of the present invention includes means for delaying a plurality of input trigonometric function signals having the same frequency by π/2, and sampling the input trigonometric function signals and their delayed signals simultaneously at at least one specific point in time. means for A/D converting the sampled value; means for calculating a phase angle from the ratio of the sampled value at the specific time point and the sampled value of the delayed signal for each input trigonometric function signal; and means for detecting the phase difference of each input trigonometric function signal from the determined phase angle.

[Effect]

The trigonometric function signal is mutually converted into a sine wave signal and a cosine wave signal due to a phase difference of ±π/2. Therefore, as shown in Figure 2, the input is a sine wave signal S(t)
=Esin(wt+α), sample this signal and the signal delayed by the π/2 delay circuit 3.
When sampled by the sampling pulse 100 at a specific time point t _N in hold circuits 1 and 2, S(t _N )=Esin(wt _N +α) from the former, and C(t _N )= from the latter.
The value Esin (wt _N + α + π/2) = Ecos (wt _N + α) is obtained. Therefore, the phase angle θ(t _N ) (=wt _N +α) of the input trigonometric function signal at time t _N is given by the following equation.

θ(t _N )=tan ^-1 [S(t _N )/C(t _N )] If the polarity of S(t _N )/C(t _N ) is positive, θ(t _N )
is determined in each of the first and third quadrants in the polar coordinate system, and if the polarity of S(t _N )/C(t _N ) is negative, θ(t _N ) is in the second quadrant. and one in each of the fourth quadrants. In which quadrant θ(t _N ) exists can be determined from the individual polarity combinations of S(t _N ) and C(t _N ).

That is, if the polarities of S(t _N ) and C(t _N ) are both positive, θ(t _N ) exists within the first quadrant, and S(t _N ) and C(t _N ) are all negative in polarity, θ(t _N ) exists within the third quadrant. Also, if the polarity of S(t _N ) is positive and the polarity of C(t _N ) is negative, θ(t _N ) exists in the second quadrant, and the polarity of S(t _N ) is If it is negative and the polarity of C(t _N ) is positive, θ(t _N ) will be in the fourth quadrant.

In this way, the instantaneous phase angle of one sine wave signal is found, so the two sine wave signals S ₁ (t) = E ₁ sin (wt
+α ₁ ), S ₂ (t)=E ₂ sin (wt+α ₂ ) phase difference (α ₁ −
α ₂ ) calculates the instantaneous phase angles θ ₁ (t _N ) and θ ₂ (t _N ) at the same time for these two sine wave signals,
It can be determined by taking the difference. In this method, (α ₁ −α ₂ ) is obtained from the signal measurement value at time t _N , but (α ₁ − α ₂ ) itself is the phase difference of the waveform regardless of the time.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit block diagram of an apparatus for detecting a phase difference between two signals as an embodiment. Of the two signals, the signal S ₁ (t) expressed by E ₁ sin (wt + α ₁ )
The signal 102 is directly input to the sample and hold circuit 10, and the signal 102' which has passed through the π/2 delay circuit 14 is input to the sample and hold circuit 11. Similarly, among the two signals, the signal S ₂ (t) 103 expressed as E ₂ sin (wt + α ₂ ) is directly sampled.
to the hold circuit 12 and the π/2 delay circuit 15
The signal 103' that has passed through is sent to the sample and hold circuit 1.
Enter 3. The signals 102' and 103' are −E ₁ cos (wt+α ₁ ) and −E ₂ cos (wt+α ₂ ), respectively.

The sample and hold circuits 10 to 13 sample simultaneously at time _tN using the sampling pulse 101. The A/D converters 16 to 19 are
Output 10 of each sample and hold circuit 10 to 13
a, 11a, 12a, and 13a are converted into digital values by A/D converters 16 to 19, respectively.
As the A/D converter, a polarized A/D converter or an offset binary A/D converter is used, and the positive and negative signs are maintained. The arithmetic processor 20 described below is
In the case of the above-mentioned polarized A/D converter, the quadrant is determined by the polarity, and in the case of the offset binary A/D converter, the quadrant is determined by determining the sign of the sign bit.

The outputs of the A/D converters 16 to 19 are each S ₁
(t _N ), C ₁ (t _N ), S ₂ (t _N ), and C ₂ (t _N ). The arithmetic processor 20 inputs the above signals and calculates S ₁ (t _N ), C ₁ (t _N )
The phase angle θ ₁ (t _N ) of the input signal S ₁ (t) at time t _N from
Then, calculate the phase angle θ ₂ (t _N ) of the input signal S ₂ (t) at time t _N from S ₂ (t _N ) and C ₂ (t _N ), and further calculate [θ ₁
(t _N )−θ ₂ (t _N )], and the phase difference (α ₁ −α ₂ ) between the signals S ₂ (t) and S ₁ (t) can be detected.

The above explanation is about finding the phase difference between two signals, but even in the case of two or more signals, if the phase difference between each signal is found using one signal as a reference, the phase relationship of all the signals can be found.

Modified Embodiment (1) In the embodiment shown in FIG. 1, four A/D converters are provided for measuring the phase difference between two signals. In practice, sampling is often performed only once in one cycle and the phase difference is measured for each cycle. In this case, unless the frequency is very high, the conversion rate of A/D converters has recently become higher, so time-division operation can be performed using only one A/D converter.

(2) Next, in the embodiment, measurement of the phase difference between signals was explained, but in special cases, the phase angle from S ₁ (t _N ), C ₁ (t _N ) to time t _N can also be measured for one signal. can be found. In this case, the sampling time t _N serves as a reference to determine the phase.

As is well known, the π/2 delay circuit uses an operational amplifier for low frequencies, and uses an operational amplifier for high frequencies.
This can be realized using a lattice phase shift circuit or a delay cable.

〔Effect of the invention〕

As explained in detail above, in the present invention, the phase angles of a plurality of trigonometric functions at the same specific point in time are calculated, and the difference between the phase angles of each trigonometric function is calculated to obtain an instantaneous waveform. Since it determines the phase difference, direction detection is possible even for radio waves with an extremely short appearance period. The phase angle of trigonometric functions is
Since the phase difference can be determined at any point during the period of 2π, the phase difference between the two signals can be obtained definitively, and the error of ±π is eliminated when the phase difference between the two signals is determined using a phase comparator as in the conventional method. There is no certainty. Therefore, the circuit configuration is correspondingly simpler.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram of an embodiment of the present invention.
FIG. 2 is a diagram explaining the principle of phase angle measurement. 10-13...Sample/hold circuit, 1
4, 15...π/2 delay circuit, 16-19...
A/D converter, 20... Arithmetic processor, 101...
Sampling pulse, 102, 103...input signal.

Claims (1)

[Claims] 1. A phase shifter for shifting the phase of each of a plurality of input trigonometric function signals having the same frequency by π/2, and simultaneously sample-holding the waveforms before and after the phase shift for each of the input trigonometric function signals. sample and hold means; A/D conversion means for converting the sampled and held signal into a digital signal for each of the input trigonometric function signals; 1. A signal phase difference detection device comprising: calculation means for calculating a phase angle from a ratio of amplitudes and calculating a phase difference between the input trigonometric function signals from the difference in phase angles. 2. The signal phase difference detection device according to claim 1, wherein the A/D conversion means is used in common for each of the input trigonometric function signals while shifting the time.