CN106291578A - The method that laser Doppler shift based on two-way one-way communication tests the speed - Google Patents

Abstract

A kind of method that the present invention relates to Doppler range rate measurement based on two-way one-way communication.Two places use the mode of two-way one-way communication, and the laser instrument of two places sends signal simultaneously, and detects reception simultaneously, the frequency of the signal received two places is added and is averaged, i.e. can get Doppler frequency shift, then by Doppler frequency shift and the relation of speed, can be in the hope of the relative velocity of two places.The present invention uses the communication means of two-way one way, relative to traditional Doppler range rate measurement, under identical transmitting power, can transmit longer distance.

Description

Laser Doppler frequency shift speed measurement method based on two-way one-way communication

technical field

The invention relates to the fields of free-space laser communication and laser velocity measurement, more specifically, a laser Doppler velocity measurement method based on two-way one-way communication.

technical background

In 1964, Yang (YEN) and Cumnis (Cumnis) first measured the distribution of water laminar flow by using laser Doppler frequency shift, which opened the prelude to the development of laser Doppler velocimetry technology. Laser Doppler velocimetry (LDV) uses a photodetector to detect the frequency shift between the scattered light or reflected light on the surface of an object and the reference light to obtain the speed information of the object. Compared with traditional contact measurement, LDV is a non-contact measurement, which is a non-interference flow field measurement technology with extremely high measurement accuracy. In principle, the LDV response has no hysteresis and can keep up with the rapid pulsation of the object. It can cover a wide speed range from a few milliseconds per second to supersonic speed, and the measurement is not affected by parameters such as object pressure, temperature, density, viscosity, etc. It can also realize one-dimensional, two-dimensional, three-dimensional speed measurement and motion The judgment of the direction has outstanding advantages such as fast dynamic response, high spatial resolution, large measurement range and real-time performance.

Prior art [Zhang Yanyan, Gong Ke, etc., Laser Doppler Velocimetry Technology Progress [J]. Laser and Infrared, 2011, 40(11): 1157-06. The echo signal of the laser and the local reference optical signal of the laser make a difference frequency. When the laser is transmitted over a long distance, the echo signal of the laser will be very weak, and it is difficult for the detector to detect the echo signal. Therefore, a high-power laser and a high-power Sensitivity of photodetectors, which increases the difficulty of implementation.

Contents of the invention

The present invention aims at the existing laser Doppler speed measuring method (the difference frequency signal of the echo signal of the laser detected by the photoelectric detector and the local reference light signal of the laser is used to obtain the moving speed information of the object) which is difficult to realize the long-distance transmission of the laser Insufficient, adopt the way of two-way one-way communication, send in two places at the same time, and detect their respective difference frequency signals at the same time, and obtain the moving speed of the object through the relationship between Doppler frequency shift and speed. The invention adopts the two-way one-way communication mode, and can still measure the moving speed of the object through the Doppler frequency shift of the laser without increasing the performance requirements of the laser and the detector when the laser is transmitted over a long distance.

The technical solution of the present invention comprises the following steps:

A method for laser Doppler frequency shift speed measurement based on two-way one-way communication, comprising the following steps:

Step 1: Transmit the signals of two ranging communication stations, that is, A and B, to each other at the same time, wherein the local signal frequency of A is f _A , and the local signal frequency of B is f _B ;

Step 2: After t ₀ time, A land receives the signal from B land, its frequency is f _AR , make a difference frequency between the local signal of A land and the received signal of A land, and obtain the frequency of the signal after the difference frequency It is f _AR -f _A ; at the same time, B receives the signal from A, and its frequency is f _AR , and the local signal of B and the signal received by B are difference frequency, and the frequency of the signal after the difference frequency is f _BR -f _B ;

Step 3: The frequency f _AR of the signal received by A site = f _B + f _dB , where f _dB is the Doppler frequency shift generated by B site,

The frequency f _BR of the received signal at B site =f _A +f _dA , f _dA is the Doppler frequency shift generated by A site;

Calculate the average Doppler frequency shift generated by A and B, the formula is as follows:

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; A</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}$

In the formula, where c is the speed of light;

Calculate the relative velocity between A and B as v, the formula is as follows:

$\mathrm{<span\; class="notranslate">\; v</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}}{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}}\mathrm{<span\; class="notranslate">\; c</span>}$

In the formula,

Using two-way one-way communication, even at a distance of tens of thousands of kilometers, the relative speed of the two places can be measured by Doppler frequency shift.

The obtained v is the relative instantaneous speed of A and B, so the uniformity of the moving speed of the translation platform can be judged by v.

The present invention has following characteristics:

1. The long-distance transmission of laser light can be realized by adopting the method of sending and detecting difference frequency signals at the same time in two places.

2. When the speed is measured by the Doppler frequency shift in the two places, the instantaneous speed of the object is obtained, so the uniformity of the moving speed of the speed translation platform can be judged.

Technical effect of the present invention:

1. The present invention adopts a two-way one-way communication method to transmit and receive at the same time in two places. Even at a distance of tens of thousands of kilometers, the relative speed of the two places can be measured by Doppler frequency shift.

2. Compared with the existing Doppler speed measurement technology, the present invention can still measure the Doppler frequency shift of the laser without increasing the performance requirements of lasers, detectors and other devices during long-distance transmission. The speed of motion of the object.

Description of drawings

Fig. 1 is a block diagram of the present invention

Fig. 2 is a structural diagram of an embodiment of the present invention.

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings and examples, but the protection scope of the present invention should not be limited thereto.

Fig. 1 is a block diagram of the present invention, and its specific implementation includes the following steps:

Step 1: Transmit the signals of A and B to each other at the same time, wherein the frequency of the signal of A is f _A , and the frequency of the signal of B is f _A .

Step 2: After t ₀ time, A site receives the signal from B site, its frequency is f _AR , and the local signal of A site and the signal received by A site are difference frequency, and the signal after frequency difference can be obtained The frequency is f _AR -f _A ; at the same time, ground B receives the signal from ground A, its frequency is f _AR , and the local signal of ground B and the signal received by ground B are divided by frequency, and the signal after the frequency difference can be obtained The frequency is f _BR -f _B .

Step 3: The frequency f _AR =f _B +f _dB of the received signal at A site, f _dB is the Doppler frequency shift generated by B site, the frequency of the received signal at B site is f _BR =f _A +f _dA , and f _dA is The Doppler shift produced by A. Therefore, the difference frequency signals of A and B are added and averaged to obtain

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; A</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}$

From the relationship between Doppler frequency shift and velocity where c is the speed of light. so, in, The relative velocity v of the two places can be obtained.

Fig. 2 is a structural diagram of an embodiment of the present invention. As can be seen from the figure, the structure of A in the optical path diagram of the present invention includes a first tunable laser 1, a first 1-to-2 fiber beam splitter 2, a first fiber circulator 3, a first fiber collimator 4, a speed control A translation stage 5, a first 2*2 fiber optic directional coupler 6, a first photoelectric balance detector 7, and a first digital oscilloscope 8. The structure of ground B includes a second tunable laser 9, a second 1-to-2 fiber beam splitter 10, a second fiber circulator 11, a second fiber collimator 12, a second 2*2 fiber directional coupler 13, a second Two photoelectric balance detectors 14 and a second digital oscilloscope 15 .

The light field output by the tunable laser 1 is

Among them, A ₁ represents the amplitude of the light field, ω _A represents the frequency of the light wave, Represents the phase noise of the light field. The laser output optical signal is divided into two optical signals with equal light intensity by the first 1-to-2 optical fiber beam splitter 2, one of which is used as the local oscillator signal of A ground, expressed as

The other path enters the port 1 of the first optical fiber circulator 3 as the transmission signal of the optical fiber circulator. So the transmitted signal at A is

The output light field of the tunable laser 9 is

Among them, A ₂ represents the amplitude of the light field, ω _B represents the frequency of the light wave, Represents the phase noise of the light field. The laser output light field is divided into two optical signals with equal light intensity by the second 1-to-2 optical fiber beam splitter 10, one of which is used as the local oscillator signal of the B ground, expressed as

The other path enters the port 1 of the second optical fiber circulator 11 as the transmission signal of the circulator. Therefore, the transmitted signal at B is expressed as

The transmission signal of ground A passes through the first fiber collimator 4 to collimate Gaussian light into parallel light, and after the propagation distance in free space is S(t), after passing through the second fiber collimator 12, it is transmitted to the first fiber ring port 2 of the optical fiber circulator, and is received at port 3 of the first optical fiber circulator, so the optical field of the received optical signal at B is expressed as

Wherein, v is the moving speed of speed control translation platform 5, and translation platform translates to B ground, and the sign of getting v is "+", S (t)=S ₀ -vt, S ₀ is when speed control translation platform 5 is static, The distance between A and B.

It can be seen from the above formula that the frequency of the received signal

Therefore, the received light field of B can be expressed as

The received optical signal E _rB (t) and the local oscillator optical signal E _LOB (t) of the B ground are used as the input signal of the second 2*2 optical fiber coupler 13, and the coupling ratio of the 2*2 optical fiber coupler is 1:1, then The light field of the output signal of the second 2*2 fiber coupler 13 is expressed as

The first balanced photodetector 7 converts the received optical signal into a voltage signal, expressed as

cc represents the complex conjugate of the preceding term, is the amplitude of the signal, where R is the responsivity of the photodetector, D is the photosensitive area of the first balance detector, and r is the detector resistance.

The voltage signal output by the first photoelectric balance detector detector 7 is displayed on the first digital oscilloscope 8, and fast Fourier transform FFT is performed on it, and the frequency corresponding to its peak value is f ₁

f ₁ =f _A +f _dA -f _B +δf ₁

where δf ₁ is the laser phase noise resulting in frequency errors.

Ideally the measured angular frequency ω _A +ω _dA -ω _B , is a constant and does not affect the result, considering the random phase term The resulting frequency error δf ₁

The autocorrelation function of V ₁ '(t) is

definition

because is a random Gaussian variable with a mean value of 0 and a variance of 2πΔυ _B |τ|, where Δυ _B is the linewidth of the tunable laser 9; is a random Gaussian variable with mean 0 and variance 2πΔυ _A |τ|, where Δυ _A is the linewidth of tunable laser 1; su so is also a Gaussian variable.

because and are two irrelevant Gaussian variables with a mean of 0, so

${\mathrm{<span\; class="notranslate">\; C</span>}}_{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; K</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\&upsi;</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\&upsi;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; |</span>}$

The spectral density function of V ₁ '(t) is

${\mathrm{<span\; class="notranslate">\; S</span>}}_{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{<span\; class="notranslate">\; \&Integral;</span>}_{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&infin;</span>}}^{\mathrm{<span\; class="notranslate">\; \&infin;</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; \&tau;</span>}}\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; K</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}<span\; class="notranslate">\; \&lsqb;</span>\frac{\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\&upsi;</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\&upsi;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; )</span>}{{<span\; class="notranslate">\; \&lsqb;</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\&upsi;</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\&upsi;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; f</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; \&rsqb;</span>$

Its spectral width is 4π(Δυ _B +Δυ _A ), so δf ₁ =4π(Δυ _B +Δυ _A )

The transmitted signal of B ground passes through the second fiber collimator 12 to collimate the Gaussian light into parallel light, and after the propagation distance in free space is S(t), after passing through the first fiber collimator 4, it is transmitted to the first fiber ring port 2 of the optical fiber circulator, and is received at port 3 of the first optical fiber circulator, so the optical field of the received optical signal at ground A is expressed as

Because the frequency of the received signal Therefore, the light field of the received optical signal at A can be expressed as

The received optical signal E _rA (t) and the local oscillator optical signal E _LOA (t) of ground A are used as the input signal of the first 2*2 optical fiber coupler 6, and the coupling ratio of the 2*2 optical fiber coupler is 1:1, then The light field of the output signal of the first 2*2 fiber coupler 6 is expressed as

The first balanced photodetector converts the received optical signal into a voltage signal, expressed as

cc represents the complex conjugate of the preceding term, is the amplitude of the signal, where R is the responsivity of the photodetector, D is the photosensitive area of the first balance detector, and r is the detector resistance.

The voltage signal output by the photodetector is displayed on the digital oscilloscope, and fast Fourier transform FFT is performed on it, and the frequency corresponding to the peak value is f ₂

f ₂ =f _B +f _dB -f _A +δf ₂

where _δf2 is the laser phase noise The frequency error caused by

Neglecting the central angular frequency term (ω _B +ω _dB -ω _A )t and the constant term in V ₂ (t) Consider only laser phase noise The formula can be written as

Then the autocorrelation function of v' ₂ (t) is

definition

because is a random Gaussian variable with mean 0 and variance 2πΔυ _A |τ|, is a random Gaussian variable with mean 0 and variance 2πΔυ _B |τ|, so is also a Gaussian variable.

In the same way,

${\mathrm{<span\; class="notranslate">\; C</span>}}_{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; ,</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; K</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&Delta;v</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&Delta;v</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; |</span>}$

The spectral density function of V ₂ '(t) is

${\mathrm{<span\; class="notranslate">\; S</span>}}_{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{<span\; class="notranslate">\; \&Integral;</span>}_{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&infin;</span>}}^{\mathrm{<span\; class="notranslate">\; \&infin;</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; \&tau;</span>}}\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; K</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}<span\; class="notranslate">\; \&lsqb;</span>\frac{\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\&upsi;</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\&upsi;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; )</span>}{{<span\; class="notranslate">\; \&lsqb;</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\&upsi;</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\&upsi;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; f</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; \&rsqb;</span>$

Its spectral width is 4π(Δυ _B +Δυ _A ), so δf ₂ =4π(Δυ _B +Δυ _A )

Therefore, the frequency error due to laser phase noise is δf

δf=δf ₁ +δf ₂ =8π(Δυ _B +Δυ _A ).

Claims (1)

1. A laser Doppler frequency shift speed measurement method based on bidirectional one-way communication is characterized in that: the method comprises the following steps:

the method comprises the following steps: signals of two ranging communication stations, namely A, B two places are transmitted to each other simultaneously, wherein the local signal frequency of A place is f_ALocal signal frequency of B ground is f_B；

Step two: warp t₀After time, the A ground receives a signal from the B ground with frequency f_ARThe local signal of A ground and the received signal of A ground are subjected to difference frequency to obtain difference frequencyThe frequency of the signal being f_AR-f_A(ii) a While B receives the signal from A at frequency f_ARThe local signal of B place and the received signal of B place are made into difference frequency, and the frequency of the obtained signal after difference frequency is f_BR-f_B；

Step three: frequency f of the received signal at earth A_AR＝f_B+f_dB，f_dBIs the doppler shift produced by B ground,

frequency f of B ground receiving signal_BR＝f_A+f_dA，f_dAIs the doppler shift produced at a;

the average doppler shift generated in two places is calculated A, B, and the formula is as follows:

$f_d=\frac{f_{dB}+f_{dA}}{2}$

in the formula,wherein c is the speed of light;

the relative velocity between the two places is calculated A, B as v, and the formula is as follows:

$v=\frac{f_d}{\stackrel{\&OverBar;}{f}}c$

in the formula,