Phase measuring device and apparatuses using the phase measuring device

Patent metadata

Field	Value
Publication number	US-10270633-B2
Application number	US-201515526586-A
Country	US
Kind code	B2
Filing date	Nov 13, 2015
Priority date	Nov 14, 2014
Publication date	Apr 23, 2019
Grant date	Apr 23, 2019

Abstract

The inventive phase measuring device includes a first A/D converter 2 that digitizes a first periodical input signal X at each predetermined sampling timing and outputs the resultant signal as a digital signal Xd, a first zero-crossing identification means operable to detect a sign of Xd, a counting processing unit 4 that counts a difference in the number of times of zero-crossing detection by the first zero-crossing identification means and calculates the difference at each sampling timing, and a fraction processing unit 5 that computes a fraction of the number of times of zero-crossing detection on the basis of Xd at sampling timings immediately before and immediately after determination of zero-crossing by the first zero-crossing identification means. An averaging processing unit 6 performs averaging by adding up and totalizing the outputs from the counting processing unit 4 and the fraction processing unit 5, thereby computing a phase. The inventive device thus implements a digital phase measuring device and a digital phase difference measuring device that allow input of periodical signals in a wide frequency range and that are capable of accurate and real-time measurement.

First claim

What is claimed is:

1. A phase measuring device for measuring a phase of a periodical input signal that changes periodically or a phase difference between periodical input signals by using a digital circuit, the device comprising:
an A/D converter that digitizes the periodical input signal respectively at each predetermined sampling timing and outputs each resultant signal as a digital signal;
a zero-crossing identification means operable to detect a change in sign of the digital signal;
a counting processing unit that counts the number of times of zero-crossing detection by the zero-crossing identification means and calculates the number at each said sampling timing;
a fraction processing unit that computes a fraction F x of the number of times of zero-crossing detection, on the basis of the digital signal at sampling timings immediately before and immediately after determination of zero-crossing by the zero-crossing identification means; and
an averaging processing unit that performs averaging on the basis of a sum of N output values calculated by the counting processing unit and a sum of the fractions F x computed by the fraction processing unit during a corresponding period, to compute a phase of the digital signal.

2. The phase measuring device according to claim 1 , wherein
the periodical input signal includes a first periodical input signal X and a second periodical input signal Y,
the A/D converter includes first and second A/D converters that digitize the periodical input signals X and Y, respectively, at each predetermined sampling timing and output the resultant signals as digital signals Xd and Yd, respectively,
the zero-crossing identification means includes first and second zero-crossing identification means operable to detect changes in sign of the digital signals Xd and Yd, respectively,
the counting processing unit counts a difference between the number of times of zero-crossing detection by the first zero-crossing identification means and the number of times of zero-crossing detection by the second zero-crossing identification means, and calculates the difference at each said sampling timing,
the fraction processing unit computes fractions F X and F Y of the respective numbers of times of zero-crossing detection by the first and second zero-crossing identification means, on the basis of the digital signals Xd and Yd at sampling timings immediately before and immediately after determination of zero-crossing by the corresponding ones of the first and second zero-crossing identification means, and
the averaging processing unit performs averaging on the basis of a sum of N output values calculated by the counting processing unit and a difference between a sum of the fractions F X and a sum of the fractions F Y computed by the fraction processing unit during a corresponding period, to compute a phase difference between the digital signals Xd and Yd, thereby measuring a phase difference between the periodical input signals X and Y.

3. The phase measuring device according to claim 1 , wherein when a sampling rate for driving the A/D converter is represented as f ADC and the number of averaging of the averaging processing unit is represented as N, a phase difference calculation rate of f ADC /N is attained in the averaging processing unit.

4. A displacement measuring device based on a laser heterodyne interferometer, the device causing reflected light, obtained by irradiating a measurement object with laser light, to interfere with reference light, obtained by applying a frequency shift to the laser light, and measuring a displacement of the measurement object from a phase difference between the lights,
the device employing the phase measuring device according to claim 2 , wherein
the reflected light corresponds to the first periodical input signal X and the reference light corresponds to the second periodical input signal Y, and
the phase measuring device includes a computing means that computes the displacement of the measurement object on the basis of an output from the averaging processing unit.

5. The displacement measuring device according to claim 4 , wherein when resolution of the displacement measuring device is represented as d r and a maximum value of a measurable velocity range is represented as v max , the following relationships are satisfied:
d r =λ/(4 N· 2 n )

v max <λ( f ADC −4 f h )/8

where λ is a laser wavelength, N is the number of averaging, n is the number of conversion bits of the A/D converter, f ADC is a sampling rate of the A/D converter, and f h is a frequency of the reference signal.

6. A phase noise measuring device which measures a time history of phase fluctuation of an input signal by comparing the input signal with a high-stability reference signal,
the device employing the phase measuring device according to claim 2 , wherein
the input signal and the high-stability reference signal correspond respectively to one and the other of the first periodical input signal X and the second periodical input signal Y, and
the phase fluctuation of the input signal is measured on the basis of an output from the averaging processing unit.

7. A PLL circuit which generates a phase-locked output signal with respect to a periodical input signal by using a phase comparator, a loop filter, a voltage-controlled oscillator (VCO), and a frequency divider,
the PLL circuit employing the phase measuring device according to claim 2 as the phase comparator, wherein
the input signal corresponds to the first periodical input signal X and an output from the frequency divider corresponds to the second periodical input signal Y.

Assignees

• Aist

Inventors

• KOKUYAMA wataru

Classifications

• G01B9/0201

  using temporal phase variation · CPC title

• G01S13/34

  using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal · CPC title

• H03L7/085

  concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal (H03L7/10 takes precedence; circuits for comparing the phase or frequency of two mutually-independent oscillations H03D13/00) · CPC title

• H03K5/26 Primary

  the characteristic being duration, interval, position, frequency, or sequence · CPC title

• G01S7/4008

  of transmitters · CPC title