CN111351585B - Phase measurement method using sawtooth wave phase modulation - Google Patents

Abstract

The invention discloses a phase measurement method using sawtooth wave phase modulation, firstly, setting a phase to be measured as a signal carrying the phase, then, carrying out phase modulation through periodic sawtooth wave, carrying out Fourier transformation on the modulated signal in one period, and obtaining a phase value. The invention adopts sawtooth wave to carry out phase modulation, the modulation and demodulation processes are convenient, specific phase information can represent physical quantities such as length, optical path, refractive index and the like, and the change information of the corresponding physical quantity can be obtained through measuring the phase change, so that the invention can be widely applied to various measurement fields related to the phase.

Description

Phase measurement method using sawtooth wave phase modulation

Technical Field

The invention belongs to the technical field of phase measurement, and relates to a phase measurement method using sawtooth wave phase modulation.

Background

The measurement of the phase has the advantage of high resolution, and can measure tiny phase changes below one thousandth and one ten thousandth of wavelength. There are various methods for measuring phase, mainly including: heterodyne method, phase shift method and phase modulation method. The heterodyne method is to generate two paths of electric signals with a certain tiny frequency difference, electromagnetic waves or light waves, beat frequencies are generated between the two paths of electric signals, and the phase of the beat frequency signals is the phase information to be measured. The phase shift method is to use a phase shifter to generate several fixed phase shifts according to a certain step length (such as pi/4), and calculate the phase value by the signals under different phase shifts. The phase modulation method has the characteristics of low cost and simple design. The common phase modulation method is to periodically change the phase in a sine form, then extract the direct current signal (or frequency doubling signal) and the single frequency signal in the modulated signal, and the two signals are mutually orthogonal, so as to calculate the phase information therefrom, which belongs to indirect measurement and has large workload.

Disclosure of Invention

Object of the invention

The purpose of the invention is that: the phase measurement method using sawtooth wave to conduct phase modulation is provided, the sawtooth wave is used for conducting phase modulation, phase information is obtained through direct demodulation of a phase-locked amplifier, and modulation and demodulation processes are convenient.

(II) technical scheme

In order to solve the above technical problems, the present invention provides a phase measurement method using sawtooth wave phase modulation, which includes the following steps:

first, let the phase to be measured be

The signals carrying this phase are:

wherein A (t) and B (t) are amplitude and bias respectively,

is the phase information to be extracted;

next, the phase modulation is performed by the periodic sawtooth wave, the modulation period is set as T, and the modulation amplitude is set as

Then the phase change over a complete period is:

the modulated signal becomes in one period:

then, the X and Y signals are obtained by Fourier analysis as follows:

x and Y are independent of the signal bias B, X, Y signals are mutually orthogonal, and the amplitude ratio is

Then, there are: />

Wherein, in

The following are the cases:

(III) beneficial effects

The phase measurement method using sawtooth wave phase modulation provided by the technical scheme adopts sawtooth wave for phase modulation, the modulation and demodulation processes are convenient, specific phase information can represent physical quantities such as length, optical path, refractive index and the like, and the change information of the corresponding physical quantities can be obtained by measuring the phase change, so that the method can be widely applied to various measurement fields related to the phase.

Drawings

FIG. 1 is a schematic diagram of a conventional gas turbine

Analog waveform in this case.

Detailed Description

For the purposes of clarity, content, and advantages of the present invention, a detailed description of the embodiments of the present invention will be described in detail below with reference to the drawings and examples.

The phase measurement method using sawtooth wave phase modulation comprises the following steps:

first, let the phase to be measured be

The signals carrying this phase are:

wherein A (t) and B (t) are amplitude and offset respectively, which may change with time, and phase information therein is directly extracted by phase modulation

Next, the phase modulation is performed by the periodic sawtooth wave, the modulation period is set as T, and the modulation amplitude is set as

Then the phase change over a complete period is:

the modulated signal becomes a single period (the modulation period T is short, and the signal amplitude a and the bias B can be considered as unchanged in a short time):

then, by fourier analysis, the X and Y signals can be found as:

observing the above formula, the method has the following characteristics: x and Y are independent of the signal bias B, X, Y signals are mutually orthogonal, and the amplitude ratio is

Then, there are:/>

at the position of

Is as follows:

thus, only one phase-locked amplifier (or other method) is used for demodulating and obtaining X and Y signals, thereby calculating the phase information to be measured

The foregoing is merely a preferred embodiment of the present invention, and it should be noted that modifications and variations could be made by those skilled in the art without departing from the technical principles of the present invention, and such modifications and variations should also be regarded as being within the scope of the invention.

Claims (2)

1. A phase measurement method using sawtooth wave phase modulation, comprising the steps of:

first, let the phase to be measured be

The signals carrying this phase are:

wherein A (t) and B (t) are amplitude and bias respectively,

is the phase information to be extracted;

next, the phase modulation is performed by the periodic sawtooth wave, the modulation period is set as T, and the modulation amplitude is set as

Then the phase change over a complete period is:

the modulated signal becomes in one period:

then, the X and Y signals are obtained by Fourier analysis as follows:

x and Y are independent of bias B, X, Y signals are mutually orthogonal, and the amplitude ratio is

Then, there are:

2. the phase measurement method using sawtooth phase modulation according to claim 1, wherein, in

The following are the cases:

/>

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