CN105093195A - Method for on-line correcting low-angle radar electric wave refraction error - Google Patents

Abstract

The invention discloses an online correction method for low-angle radar electric wave refraction error. When the radar measures the target, the distance and angle of the radar measurement parameters are passed through the GPS receiver, the ground atmospheric refractivity measuring instrument, the atmospheric profile database, the control and A device composed of a data processor and related interface circuits obtains radar positioning parameters that eliminate atmospheric refraction errors, uses the parameters to locate targets, and improves radar positioning accuracy. The refraction error correction method of the present invention is simple, has small calculation amount, short time, high precision, high degree of automation and is easy to implement, and can realize the online correction function of electric wave refraction error for radar high-precision positioning.

Description

An Online Correction Method for Low Angle Radar Radio Wave Refraction Error

technical field

The invention belongs to the technical field of radar measurement error correction methods, and in particular relates to an online correction method for low-angle radar electric wave refraction errors.

Background technique

Improving the measurement and positioning accuracy of radar is a necessary condition for applications such as navigation, satellite and measurement and control. With the improvement of the accuracy of the electronic components that make up the radar system and the optimization of related data processing methods, the refraction error of radio waves caused by the atmospheric environment has become the main factor that limits the further improvement of radar measurement accuracy.

When radar detects air targets, radio waves must pass through the atmosphere (including the troposphere and ionosphere) environment. The inhomogeneity of the atmospheric environment causes refraction effects when radio waves propagate in the atmosphere. The radio wave rays propagate along curves instead of straight lines, and the propagation speed is less than the speed of light, which causes refraction errors in radar measurement parameters, which in turn affects radar positioning accuracy. In order to further improve the radar positioning accuracy, it is necessary to correct the electric wave refraction error. Because the horizontal inhomogeneity of the atmosphere is very small, the refraction error only considers the distance error and elevation angle error, but does not need to consider the azimuth angle error. At present, the vast majority of scholars use the measured atmospheric environment parameters to calculate and correct the radio wave refraction error using the ray tracing method based on the integral form. Since this method needs to measure the atmospheric environment parameters and integral calculation, the processing time required is very long, so It is only suitable for radar systems in shooting ranges and experimental bases, but not for radar systems that require online (real-time) correction of radio wave refraction errors in practical applications.

At present, there are two main types of real-time correction methods for radio wave refraction errors. One is to use microwave radiometers to measure the thermal noise of radar radio waves passing through the atmospheric environment, and use Marcor technology to obtain the relationship between thermal noise and refraction errors. Perform refraction error correction. However, this method can only correct the distance refraction error, not the angle refraction error, and the correction parameters are incomplete; second, the refraction error obtained by it is only the error amount from the radar to infinity, not the distance from the radar to the target. The error amount between the two, the correction range is larger than the actual radio wave passing interval, which expands the error amount. The other is a simplified correction method for idealized approximation of some parameters. It not only requires a lot of preliminary data statistics, but also has low correction accuracy, and can only be applied to radar systems in typical areas participating in the statistics.

In order to satisfy the online correction of the radio wave refraction error of the radar system in practical applications and further improve the radar positioning accuracy, it is necessary to develop an online correction method of the low-angle radar radio wave refraction error.

Contents of the invention

The technical problem solved by the present invention is to provide an online correction method for low-angle radar electric wave refraction error. The device composed of the atmospheric profile database, the control and data processor and the relevant interface circuit obtains the radar positioning parameters for eliminating the atmospheric refraction error, uses the parameters to locate the target, and improves the positioning accuracy of the radar.

The present invention adopts following technical scheme for solving the above-mentioned technical problem, a kind of low-angle radar electric wave refraction error online correction method, it is characterized in that comprising the following steps: (1) obtain the geographic location and working position of radar antenna by the GPS receiver at radar antenna place month, and send it to the control and data processor through the data interface; (2) the control and data processor searches and determines the required atmospheric model in the atmospheric profile database according to the geographic location and working month of the radar; (3) the atmospheric model The refractometer measures the ground atmospheric refractivity at the radar, and transmits the measured value of the ground atmospheric refractivity to the control and data processor through the data interface; The parameters of the atmospheric model determined in step (2) are determined to obtain a practical atmospheric profile containing only the unknown height h; (5) the radar measurement parameters are sent to the control and data processor through the data interface; (6) in the control and data processing In the device, according to the determined atmospheric profile and radar measurement parameters, the differential radio wave refraction error correction method is used to calculate the radio wave refraction error, and the radar measurement parameters are corrected to obtain the correction result; (7) The corrected radar measurement parameters are sent to (8) display and store the radar refraction error.

Further limit, the establishment method of described atmospheric profile database specifically comprises the following steps:

(1) According to the geographical location of commonly used radars in my country and the changing characteristics of the radio meteorological environment, the grid technology is used to divide the area by 10 intervals in the range of 700 to 1350 east longitude, and in the range of 0.10 intervals in the range of north latitude 150 to 550 , the number of grids established after division is 26000;

(2) Determine the measured atmospheric profile in each grid, and find out the measured atmospheric profile data of the corresponding grid within 20 years from the detection data of the national atmospheric detection stations according to the current positions of the existing atmospheric profile detection stations in my country, twice a day There are 14,600 sets of data in each station. If there is measured data in the grid, the data in the grid is the measured atmospheric profile data. The measured atmospheric profile data, using the Lagrangian interpolation formula to obtain the atmospheric profile in the grid, and finally make each grid have 20 years of measured data of the atmospheric profile;

(3) To determine the atmospheric model, by comparing various atmospheric models, finally select the high-precision atmospheric profile segmentation model, namely

$\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; G</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>& {\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; \&le;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; m</span>}\\ {\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; \&lsqb;</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span>& <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; 9</span>}\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; m</span>}\\ {\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 9</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; \&lsqb;</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 9</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span>& \mathrm{<span\; class="notranslate">\; 9</span>}\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 60</span>}\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; m</span>}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula, h ₀ is the ground altitude, km; N ₀ is the ground atmospheric refraction index; G is the refraction index gradient from the ground to a height of 1 km, 1/km; N ₁ is the atmospheric refraction index at a ground height of 1 km; where N ₉ is the atmospheric refraction index at an altitude of _9km ; c is the attenuation coefficient of the atmosphere from 1km to 9km above sea level, 1/km; c9 is the attenuation coefficient of the atmosphere above 9km above sea level, 1/km;

(4) Calculation of the atmospheric model coefficients in each grid, using formula (2) to calculate the corresponding coefficients G and C for each detection data in each grid, namely

$\left\{\begin{array}{c}\mathrm{<span\; class="notranslate">\; G</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\\ \mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{<span\; class="notranslate">\; \&Sigma;</span>}}\frac{{\mathrm{<span\; class="notranslate">\; ln</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; ln</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

In the formula, N ₁ is obtained by interpolating the measured detection data, N _i is the atmospheric refraction index at each height h _i within the range of 1km from the ground to 9km above sea level, m is the number of atmospheric refraction index detection data in this range, each detection The N ₉ in the data is also obtained by interpolation from the measured detection data. The national change of C ₉ is not large, so the national annual average value of 0.1434 is adopted, so that a set of N ₀ , N ₁ , and N ₉ can be obtained from each measured atmospheric profile of each grid , G, and C data, and these data are substituted into (1) formula to obtain the atmospheric profile model of the actual detection data;

(5) Statistical statistics of the relationship between the ground refraction index N ₀ of each grid and the coefficient of the atmospheric profile model. Statistical regression is performed on the data N ₀ and N ₁ , N ₉ , G, and C of each month in each grid to obtain the The relational expression of N ₁ , N ₉ , G, C and N ₀ for each month, for each month N ₀ of each grid, according to get N ₁ , N ₉ , G, C and N ₀ for each month of each grid The corresponding N ₁ , N ₉ , G, C can be obtained from the relational formula, so as to obtain the practical atmospheric profile N(h);

(6) The relationship between the ground refractive index and the atmospheric model coefficient is built, and the result of step (5) is used to set up a database, which consists of longitude, latitude, altitude, month, N ₀ and N ₁ relational expression, N ₀ and N ₉ relational expression , the relationship between N ₀ and G, and the relationship between N ₀ and C. In practical applications, the atmospheric profile N(h) is obtained according to the ground atmospheric refractive index N ₀ .

It is further defined that the atmospheric refractive index measuring instrument is an 11GHz atmospheric refractive index measuring instrument, which is designed according to the principle that the resonant frequency of the microwave resonant cavity changes with the change of the atmospheric medium in the cavity, and its working frequency is f ₀ =11GHz, The working mode is TE ₀₁₁ , and the resonant cavity frequency is:

$\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}}\sqrt{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}{\mathrm{<span\; class="notranslate">\; l</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 1.64</span>}\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

In the formula, c is the speed of light in vacuum, n is the refractive index of the medium in the cavity, l is the length of the cavity, and R is the radius of the cavity. When the resonant cavity is filled with atmospheric medium, the resonant frequency in the cavity is not equal to the vacuum The resonant frequency in the resonant cavity, but there is a certain frequency difference △f=f ₀ -f, so that the refractive index N of the atmosphere in the resonant cavity can be obtained as:

$\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; f</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; 10</span>}}^{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; \&ap;</span>\frac{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; f</span>}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; 10</span>}}^{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

The relationship between the atmospheric refractive index n and the atmospheric refractive index N is

n=1+N×10 ^-6 (5)

In fact, the measurement of the atmospheric refractive index or refractive index is mainly to measure the variation of the resonant frequency of the resonant cavity. The specific measurement process is:

(1) The 500KHz crystal oscillator provides two signals, one is input to the phase detector to provide a reference standard signal, and the other is input to a 100MHz voltage-controlled oscillator VCO to provide a modulation signal;

(2) The 100MHz voltage-controlled oscillator VCO provides two signals, one is input to the mixer, and the other is multiplied to generate an 11GHz signal in the frequency synthesizer;

(3) The 11GHz frequency synthesizer signal is attenuated and filtered to send the signal to the circulator, and the circulator sends the signal to the microwave resonator after the impedance adjustment of the branch adjuster;

(4) The circulator transmits the signal reflected by the cavity to the detector for detection, and the detector takes out the intermediate frequency signal with refractive index information from the high frequency signal reflected by the cavity;

(5) The phase detector compares the intermediate frequency signal with the refractive index information with the intermediate frequency signal generated by the 500KHz crystal oscillator, and the phase comparison result is a voltage signal, which is used to control the oscillation frequency of the 100MHz voltage-controlled oscillator VCO;

(6) The mixer mixes and amplifies the output frequency of the 100MHz voltage-controlled oscillator VCO and the frequency generated by the 100MHz crystal oscillator, and the obtained difference frequency signal △f contains atmospheric refractive index information, which can be calculated by using formula (4) The voltage signal representing the atmospheric refractive index N;

(7) Gather the voltage signal of N to obtain atmospheric refractive index N data through A/D, and then send it to a computer for storage and processing;

Among them, steps (2) to (5) are a main measurement circuit of a phase-locked circuit ring type, which locks the change of the resonant frequency of the resonant cavity caused by the change of the atmospheric refractive index in the cavity, and then performs a measurement with the high-precision 100MHz crystal oscillator signal After frequency difference, the magnitude of the atmospheric refractive index is obtained.

It is further defined that the control and data processor is used to complete the input of radar geographic location and date, ground atmospheric refractivity and radar measurement positioning parameters, data exchange of profile models in the atmospheric profile database, radar measurement after correction of radio wave refraction error The output of parameters, the display and storage of refraction errors, and the calculation and correction of radio wave refraction errors, the specific steps are:

(1) Collect and control the geographic location and date data input to the GPS receiver;

(2) collect and control the surface atmospheric refractivity data n ₀ that is input into the atmospheric refractometer;

(3) Collect and control radar measurement data distance and elevation angle;

(4) select the atmospheric profile model in the atmospheric profile database according to the data of step (1);

(5) obtain the atmospheric profile n(h) according to the atmospheric profile model in the step (3) and the ground atmospheric refractive index in the step (2);

(6) Calculate the radio wave refraction error. According to the initial elevation angle θ ₀ measured by the radar, use the Senell theorem to calculate the ray refraction elevation angle θ(h) at any height of the radio wave ray, namely

$\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; cos</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; cos\&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

In the formula, θ(h) is the refracted elevation angle of radio waves at any height, rad; _θ0 is the elevation angle measured by the radar, rad; a is the average radius of the earth, a≈6370km; _h0 is the altitude of the radar antenna, km ; n(h) is the atmospheric refractive index at any height h,

Divide the radio wave rays into m sections, each section corresponds to a height of △h _i , i=1,2,3,...k, use the difference method to obtain the distance error △R _i and the geocentric angle of each section, namely The angle error between the center of the earth to the target and the center of the earth to the radar and the refraction angle error △θ _i on the radio wave ray, namely

In the formula, the refractive index gradient of each segment Obtained from the atmospheric profile n(h) in step (5),

Use the iterative method to obtain the corresponding parameters on the i+1 section of the radio wave ray, and the iterative formula is

According to the requirements of radar measurement accuracy, it is assumed that the accuracy of the distance error is δ, and when |R _i+1 -R _e |<δ, the iteration ends, and _Re is the distance parameter measured by the radar, km,

In order to reduce the iteration time, △h _i adopts variable step size, and the first iteration takes when , change the step size to The next iteration distance from Start to calculate, and so on, until transform p times, the step size is less than δ, appear When the iteration ends, the relevant parameters are obtained as

The calculation of refraction error, distance refraction error ΔR and elevation angle refraction error ε are respectively

$\left\{\begin{array}{c}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\\ \mathrm{<span\; class="notranslate">\; \&epsiv;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; )</span>$

In the formula, R _e , θ ₀ are the apparent distance and apparent elevation angle measured by the radar, respectively, R ₀ , α ₀ are the real distance and true elevation angle from the radar to the target obtained through geometric calculation, respectively,

(7) Correction of radar wave refraction error, after step (6), the corrected radar positioning parameters are

$\left\{\begin{array}{c}\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}\\ \mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\end{array}\right.$

(8) Send the correction result of step (7) to the radar processing unit for positioning calculation, and obtain the precise position of the target.

The refraction error correction method of the present invention is simple, with small amount of calculation, short time, high precision, high degree of automation and easy implementation, and can realize the online correction function of electric wave refraction error for radar high-precision positioning. During the operation of the present invention, only relevant The components are embedded in the radar measurement transmission signal line without changing all the hardware structures and processing methods in the radar system. By correcting the refraction error of the radar measurement parameters, 95% of the atmospheric refraction error is eliminated, thereby improving the positioning accuracy of the radar. .

Description of drawings

Figure 1 is a flow chart of the establishment of the atmospheric profile database;

Figure 2 is a measurement schematic diagram of the 11GHz atmospheric refractometer;

Fig. 3 is a block diagram of the control and data processor;

Fig. 4 is a module composition diagram of an online correction device for low-angle radar electric wave refraction error.

Detailed ways

The above-mentioned content of the present invention will be further described in detail through the following examples, but it should not be understood that the scope of the above-mentioned subject of the present invention is limited to the following examples. All technologies realized based on the above content of the present invention belong to the scope of the present invention.

The process of establishing the atmospheric profile database is shown in Figure 1. my country's complex geographical environment has caused complex and changeable atmospheric environments, so the parameters in the atmospheric refractivity model vary greatly from place to place, and it is necessary to establish atmospheric profiles for each region. According to the characteristics of atmospheric changes, the relationship between the coefficients in each regional atmospheric model and the surface atmospheric refractivity can be established. In practical applications, the coefficients in the atmospheric model can be obtained from the ground refractive index in each area, so as to obtain a practical atmospheric profile. The specific establishment method includes the following steps:

(1) According to the geographic location of commonly used radars in my country and the changing characteristics of the radio meteorological environment, the grid technology is used to divide the area. In the range of 700 to 1350 east longitude, it is divided by 10 intervals, and in the range of north latitude 150 to 550, it is divided by 0.10 intervals, and the number of grids established after division is 26,000.

(2) Determine the measured atmospheric profile in each grid. According to the current location of the existing atmospheric profile detection stations in my country, the atmospheric measured profile data of the corresponding grid within 20 years are found from the detection data of the national atmospheric detection stations (two sets of data per day, each station has a total of 14600 sets). If there is measured data in the grid, the data in the grid is the measured atmospheric profile data; if there is no measured atmospheric profile data in the grid, according to the measured atmospheric profile data in the adjacent four grids, the Lagrang The daily interpolation formula obtains the atmospheric profile in the grid, and finally makes each grid have 20 years of measured data of the atmospheric profile.

(3) Determine the atmospheric model. By comparing various atmospheric models, the high-precision atmospheric profile segmentation model is finally selected, namely

$\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; G</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>& {\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; \&le;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; m</span>}\\ {\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; \&lsqb;</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span>& <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; 9</span>}\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; m</span>}\\ {\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 9</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; \&lsqb;</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 9</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span>& \mathrm{<span\; class="notranslate">\; 9</span>}\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 60</span>}\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; m</span>}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula, h ₀ is the ground altitude, km; N ₀ is the ground atmospheric refraction index; G is the refraction index gradient from the ground to a height of 1 km, 1/km; N ₁ is the atmospheric refraction index at a ground height of 1 km; N ₉ is Atmospheric refraction index at an altitude of _9km ; c is the attenuation coefficient of the atmosphere from 1km to 9km above sea level, 1/km; c9 is the attenuation coefficient of the atmosphere above 9km above sea level, 1/km.

(4) Calculation of atmospheric model coefficients in each grid. Use formula (2) to calculate the corresponding coefficients G and C for each detection data in each grid, namely

$\left\{\begin{array}{c}\mathrm{<span\; class="notranslate">\; G</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\\ \mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{<span\; class="notranslate">\; \&Sigma;</span>}}\frac{{\mathrm{<span\; class="notranslate">\; ln</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; ln</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

In the formula, N ₁ is obtained by interpolating the measured detection data, N _i is the atmospheric refraction index at each height h _i within the range of 1 km from the ground to 9 km above sea level, and m is the number of atmospheric refraction index detection data in this range.

The N ₉ in each detection data is also obtained by interpolation from the actual detection data, and the C ₉ has little change across the country, so the national annual average value of 0.1434 is adopted. In this way, a set of N ₀ , N ₁ , N ₉ , G, and C data can be obtained from each actual measurement of the atmospheric profile of each grid, and these data are substituted into (1) to obtain the atmospheric profile model of the actual detection data.

(5) Statistics of the relationship between the ground refraction index N ₀ of each grid and the coefficient of the atmospheric profile model. Perform statistical regression on the data N ₀ and N ₁ , N ₉ , G, and C of each month in each grid to obtain the relationship between N ₁ , N ₉ , G, C and N ₀ in each month of each grid. In this way, as long as there is N ₀ for each month of each grid, the corresponding N ₁ , N ₉ , G, and C can be obtained according to this relational formula, so as to obtain the practical atmospheric profile N(h).

(6) Build a database for the relationship between ground refractivity and atmospheric model coefficients. Utilize the result of step (5) to set up database, it is by longitude, latitude, altitude, month, N ₀ and N ₁ relational expression, N ₀ and N ₉ relational expression, N ₀ and G relational expression, N ₀ and C relational expression composition. In practical application, as long as the surface atmospheric refractive index N ₀ is given, the atmospheric profile N(h) can be obtained.

The schematic diagram of the 11GHz atmospheric refractivity measuring instrument is shown in Figure 2. The Atmospheric Refractive Index Measuring Instrument is designed according to the principle that the resonant frequency of the microwave cavity changes with the change of the atmospheric medium in the cavity. Its working frequency is f ₀ =11GHz, and its working mode is TE ₀₁₁ . The resonator frequency is:

$\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}}\sqrt{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}{\mathrm{<span\; class="notranslate">\; l</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 1.64</span>}\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

In the formula, c is the speed of light in vacuum, n is the refractive index of the medium in the cavity, l is the length of the cavity, and R is the radius of the cavity.

When the resonant cavity is filled with atmospheric medium, the resonant frequency in the cavity is not equal to the resonant frequency in vacuum, but there is a certain frequency difference △f=f ₀ -f, so the refractive index N of the atmosphere in the resonant cavity can be obtained as

$\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; f</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; 10</span>}}^{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; \&ap;</span>\frac{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; f</span>}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; 10</span>}}^{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Here, the relationship between the atmospheric refractive index n and the atmospheric refractive index N is

n=1+N×10 ⁻⁶ (5) Actually, the measurement of the atmospheric refractive index or refractive index is mainly to measure the variation of the resonant frequency of the resonant cavity.

In Figure 2, the specific working process of the atmospheric refractometer is as follows:

(1) The 500KHz crystal oscillator provides two signals, one is input to the phase detector to provide a reference standard signal, and the other is input to a 100MHz VCO (voltage controlled oscillator) to provide a modulation signal;

(2) The 100MHz VCO provides two signals, one is input to the mixer, and the other is multiplied to generate an 11GHz signal in the frequency synthesizer;

(3) The 11GHz frequency synthesizer signal is attenuated and filtered to send the signal to the circulator, and the circulator sends the signal to the microwave resonator after the impedance adjustment of the branch adjuster;

(4) The circulator transmits the signal reflected by the cavity to the detector for detection, and the detector takes out the intermediate frequency signal with refractive index information from the high frequency signal reflected by the cavity;

(5) The phase detector compares the intermediate frequency signal with the refractive index information with the intermediate frequency signal generated by the 500KHz crystal oscillator, and the phase comparison result is a voltage signal, which is used to control the oscillation frequency of the 100MHz VCO;

(6) The mixer mixes and amplifies the 100MHz VCO output frequency and the frequency generated by the 100MHz crystal oscillator, and the obtained difference frequency signal △f contains atmospheric refractive index information, and the representative atmospheric refractive index in the cavity can be calculated using formula (4) N voltage signal;

(7) The voltage signal of N is collected by A/D to obtain the atmospheric refractive index N data, and then sent to the computer for storage and processing.

As a further illustration, steps (2) to (5) are a phase-locked circuit ring-type main measurement circuit, which locks the change in the resonant frequency of the resonant cavity caused by the change in the refractive index of the atmosphere in the cavity, and then compares it with the high-precision 100MHz The value of the atmospheric refraction index is obtained after the crystal oscillator signal is frequency-differenced.

The composition of the control and data processor is shown in Figure 3. The control and data processor mainly complete the input of radar geographic location and date, surface atmospheric refractivity and radar measurement positioning parameters, data exchange of profile models in the atmospheric profile database, display of radar measurement parameters and refraction errors after correction of radio wave refraction errors , stored output control, and the calculation and correction of radio wave refraction errors. The specific steps are:

(1) Collect and control the geographic location and date data input to the GPS receiver;

(2) collect and control the surface atmospheric refractivity data n ₀ that is input into the atmospheric refractometer;

(3) Acquisition and control of radar measurement data (distance and elevation);

(4) select the atmospheric profile model in the atmospheric profile database according to the data of step (1);

(5) obtain the atmospheric profile n(h) according to the atmospheric profile model in the step (3) and the ground atmospheric refractive index in the step (2);

(6) Calculate the radio wave refraction error.

According to the initial elevation angle θ ₀ measured by the radar, the ray refraction elevation angle θ(h) at any height of the radio wave ray is calculated by using the Senell theorem, namely

$\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; cos</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; cos\&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

In the formula, θ(h) is the refracted elevation angle of radio waves at any height, rad; _θ0 is the elevation angle measured by the radar, rad; a is the average radius of the earth, a≈6370km; _h0 is the altitude of the radar antenna, km ; n(h) is the atmospheric refractive index at any height h.

Divide the radio wave rays into m sections, each section corresponds to a height of △h _i , i=1,2,3,...k, use the difference method to obtain the distance error △R _i and the geocentric angle ( The angle between the center of the earth to the target and the center of the earth to the radar) error and the refraction angle error △θ _i on the radio wave ray, namely

In the formula, the refractive index gradient of each segment Obtained from the atmospheric profile n(h) in step (5).

Use the iterative method to obtain the corresponding parameters on the i+1 section of the radio wave ray, and the iterative formula is

According to the requirements of radar measurement accuracy (assuming that the accuracy of distance error is δ), the iteration ends when |R _i+1 -R _e |<δ, and _Re is the distance parameter measured by radar (apparent distance), km.

In order to reduce the iteration time, △h _i adopts variable step size, and the first iteration takes when , change the step size to The next iteration distance from Start to calculate, and so on, until transform p times, the step size is less than δ, appear When the iteration ends, the relevant parameters are obtained as

Calculation of refraction error. The distance refraction error △R and the elevation angle refraction error ε are respectively

$\left\{\begin{array}{c}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\\ \mathrm{<span\; class="notranslate">\; \&epsiv;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; )</span>$

In the formula, R _e , θ ₀ are the apparent distance and apparent elevation angle measured by the radar, respectively, and R ₀ , α ₀ are the real distance and true elevation angle from the radar to the target obtained through geometric calculation, respectively.

(7) Correction of radar wave refraction error. After step (6), the corrected radar positioning parameters are

$\left\{\begin{array}{c}\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}\\ \mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 12</span>}<span\; class="notranslate">\; )</span>$

(8) Send the correction result of step (7) to the radar processing unit for positioning calculation, and obtain the precise position of the target.

Through comparison and verification, the differential iterative method is used to correct the radar wave refraction error, the running time is less than 6% of the commonly used integral method, and the accuracy is slightly lower than the integral method.

The schematic diagram of the radar wave refraction error online correction device is shown in Figure 4. In Figure 1, the GPS receiver can obtain the geographic location (longitude, latitude, and altitude) and the working date (month) of the radar antenna, and these parameters can determine the atmospheric refraction of the area and month where the radar is working from the atmospheric profile database. Exponential mode. The ground refractivity at the radar is measured by the 11GHz atmospheric refractivity measuring instrument, and the practical atmospheric profile containing only the unknown h (height) is obtained by using the relationship between the relevant parameters in the atmospheric refractivity model in the atmospheric profile database and the ground atmospheric refractivity. It is used when calculating the radio wave refraction error. The control and data processor calculates the refraction error based on the known atmospheric profile and the input radar measurement data, then corrects the refraction error of the radar measurement parameters, and finally sends the corrected radar parameters to the radar processing unit for positioning. The function of improving the positioning accuracy of the radar is realized because the parameters to eliminate the refraction error are adopted in the positioning.

In summary, compared with the integration method of radio wave ray tracing and the general online refraction error correction method, the correction method and device of the present invention can not only automatically measure the atmospheric refractive index and perform radio wave refraction error correction, but also require less computing time It is very small and can correct 95% of the atmospheric refraction error, which satisfies the function of radar online refraction error correction and further improves the positioning accuracy of the radar.

The above embodiments have described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What are described in the above embodiments and description are only to illustrate the principles of the present invention. Without departing from the scope of the principle of the present invention, there will be various changes and improvements in the present invention, and these changes and improvements all fall within the protection scope of the present invention.

Claims (4)

1. one kind low angle radar wave refraction error on-line amending method, it is characterized in that comprising the following steps: (1) obtains geographic position and the work month of radar antenna by the GPS of radar antenna, and be transported to control with data processor by data-interface; (2) to control with data processor, according to the geographic position of radar and working month, look in atmospheric profile database and determine required Atmospheric models; (3) the terrestrial refraction rate of air index measuring instrument to radar place is measured, and terrestrial refraction rate measured value is transported to control with data processor by data-interface; (4) control to carry out parameter according to air index measured value to the Atmospheric models determined in step (2) with data processor to determine, obtain only containing the practical atmospheric profile of unknown number height h; (5) radargrammetry parameter is transported to by data-interface and controls with data processor; (6) in control with data processor, according to the atmospheric profile determined and radargrammetry parameter, utilize differential electrical wave refraction error correcting method to calculate refraction error of radio (light) wave, and radargrammetry parameter is carried out error correction, obtain correction result; (7) the localization process unit revised radargrammetry parameter being transported to again radar carries out target and accurately locates; (8) Radar Refraction error is carried out showing and storing.

2. low angle according to claim 1 radar wave refraction error on-line amending method, is characterized in that: the method for building up of described atmospheric profile database specifically comprises the following steps:

(1) geographic position and the meteorological environmental change feature of radio residing for China's common radar, adopt grid technique zoning, divide by 10 intervals in east longitude 700 to 1350 scope, divide by 0.10 interval in north latitude 150 to 550 scope, the grid number set up after dividing is 26000;

(2) the air measured section in each grid is determined, according to the position of the existing atmospheric profile acquisition station of current China, the air measured section data in corresponding grid 20 years are found out from the detection data at national atmospheric exploration station, every day two groups of data, each station has 14600 groups, if have measured data in grid, data then in this grid are actual measurement atmospheric profile data, if do not survey atmospheric profile data in grid, according to the actual measurement atmospheric profile data in adjacent four grids, Lagrange's interpolation formula is utilized to try to achieve atmospheric profile in this grid, finally make the atmospheric profile measured data having 20 years in each grid,

(3) determining atmospherical model, by contrasting various atmospherical model, finally selecting high-precision atmospheric profile segmented model, namely

$N\left(h\right)=\left\{\begin{array}{cc}{N}_0+G\left(h-h_0\right)& h_0\&le;h\&le;\left(h_0+1\right)km\\ N_1\exp \&lsqb;-c\left(h-h_0-1\right)\&rsqb;& \left(h_0+1\right)km<h\&le;9km\\ N_9\exp \&lsqb;-c_9\left(h-9\right)\&rsqb;& 9km<h<60km\end{array}\right.---\left(1\right)$

In formula, h ₀for elevation, km; N ₀for terrestrial refraction index; G is the refractive index gradient that 1km height is arrived on ground, 1/km; N ₁for the atmospheric refraction index on the 1km height of ground; Wherein N ₉for the atmospheric refraction index on height above sea level 9km height; C is the atmospheric attenuation coefficient of ground 1km to height above sea level 9km, 1/km; c ₉for the highly atmospheric attenuation coefficient of more than height above sea level 9km, 1/km;

(4) atmospherical model coefficient calculations in each grid, in each grid each time detection data utilize (2) formula to calculate corresponding coefficient G and C, namely

$\left\{\begin{array}{c}G=N_1-N_0\\ C=\frac{1}{m}\underset{i=1}{\overset{m}{\&Sigma;}}\frac{\ln N_1-\ln N_i}{h_1-1}\end{array}\right.---\left(2\right)$

In formula, N ₁obtained by actual measurement detection data interpolation, N _ifor height h each within the scope of ground 1km to height above sea level 9km _ion atmospheric refraction index, m is the number of atmospheric refraction index detection data within the scope of this, the N each time in detection data ₉also obtained by actual measurement detection data interpolation, C ₉whole nation change is little, therefore adopts national annual mean 0.1434, surveys atmospheric profile each time like this obtain one group of N by each grid ₀, N ₁, N ₉, G, C data, these data are updated to the atmospheric profile model that (1) formula just obtains this actual detection data;

(5) each grid terrestrial refraction index N ₀add up with the relation of atmospheric profile model coefficient, to the data N in each month in each grid ₀with N ₁, N ₉, G, C carry out statistical regression, obtains each month N of each grid ₁, N ₉, G, C and N ₀relational expression, for each month N of each grid ₀again according to obtaining each month N of each grid ₁, N ₉, G, C and N ₀relational expression draw corresponding N ₁, N ₉, G, C, thus obtain practical atmospheric profile N (h);

(6) terrestrial refraction rate and atmospherical model Relationship of Coefficients build storehouse, and utilize the result building database of step (5), it is by longitude, latitude, sea level elevation, month, N ₀with N ₁relational expression, N ₀with N ₉relational expression, N ₀with G relational expression, N ₀form with C relational expression, in actual applications, according to ground atmospheric refraction index N ₀obtain atmospheric profile N (h).

3. low angle according to claim 1 radar wave refraction error on-line amending method, it is characterized in that: described air index measuring instrument is 11GHz air index measuring instrument, design according to the principle that the resonance frequency of microwave cavity changes with atmospheric medium change in chamber, its frequency of operation is f ₀=11GHz, mode of operation is TE ₀₁₁, resonator cavity frequency is:

$f=\frac{c}{n}\sqrt{\frac{1}{4l^2}+{\left(\frac{1}{1.64R}\right)}^2}---\left(3\right)$

In formula, c is the light velocity in vacuum, and n is the refractive index of medium in chamber, and l is the length of cavity, and R is the radius of cavity, and when being full of atmospheric medium in resonator cavity, the resonance frequency in chamber is not equal to the resonance frequency in vacuum, but there is certain difference on the frequency Δ f=f ₀-f, thus the refraction index N that can obtain air in resonator cavity is:

$N=\frac{\mathrm{\&Delta;}f}{f}\&times;{10}^6\&ap;\frac{\mathrm{\&Delta;}f}{f_0}\&times;{10}^6---\left(4\right)$

The pass of air index n and atmospheric refraction index N is

n＝1+N×10 ^-6(5)

The variable quantity of the resonance frequency of resonator cavity is mainly measured in the measurement of atmospheric refraction index or refractive index, and its concrete measuring process is:

(1) 500KHz crystal oscillator provides two paths of signals, and a road is input to phase detector and provides normative reference signal for it, and another road is input to 100MHz voltage controlled oscillator VCO and provides modulation signal for it;

(2) 100MHz voltage controlled oscillator VCO provides two paths of signals, and a road is input to frequency mixer, and another road generates 11GHz signal after frequency multiplication in frequency synthesizer;

(3) signal is delivered to circulator through decay, filtering by 11GHz frequency synthesizer signal, and signal is delivered to microwave cavity by circulator again after the impedance of detail tuner regulates;

(4) signal that cavity reflections is returned by circulator sends wave detector to and carries out detection, and the intermediate-freuqncy signal with refractive index information in the high-frequency signal that cavity reflections returns by wave detector is taken out;

(5) intermediate-freuqncy signal with refractive index information is carried out than phase with the intermediate-freuqncy signal that 500KHz crystal oscillator produces by phase detector, is a voltage signal than phase result, by the oscillation frequency of this voltage signal control 100MHz voltage controlled oscillator VCO;

(6) frequency that 100MHz voltage controlled oscillator VCO output frequency and 100MHz crystal oscillator produce is carried out mixing and amplification by frequency mixer, the difference frequency signal Δ f obtained contains air index information, and (4) formula of utilization can calculate the voltage signal of the representative atmospheric refraction index N in place's cavity;

(7) voltage signal of N is collected atmospheric refraction index N data through A/D, then deliver to computing machine and carry out Storage and Processing;

Wherein, step (2) to (5) is the main metering circuit of a phase lock circuitry ring type, atmospheric refraction index in cavity is changed the change locking of the resonant frequency caused by it, obtains the value of atmospheric refraction index after then carrying out difference frequency with high-precision 100MHz crystal oscillation signal.

4. low angle according to claim 1 radar wave refraction error on-line amending method, it is characterized in that: described control and data processor are for completing the input of radar geographic position and date, terrestrial refraction rate and radargrammetry positional parameter, the exchanges data of the section model in atmospheric profile database, the output of the revised radargrammetry parameter of refraction error of radio (light) wave, the calculating of the display of refraction error and storage and refraction error of radio (light) wave and correction, its concrete steps are:

(1) to gather and the geographic position that obtains of control inputs GPS and date data;

(2) to gather and the terrestrial refraction rate data n that obtains of control inputs air index instrument ₀;

(3) collection and the control radar measurement data Distance geometry elevation angle;

(4) in atmospheric profile database, atmospheric profile model is selected according to the data of step (1);

(5) atmospheric profile n (h) is obtained according to the terrestrial refraction rate in the atmospheric profile model in step (3) and step (2);

(6) refraction error of radio (light) wave calculating is carried out, according to the initial elevation θ of radargrammetry ₀, utilize senell theorem to calculate ray diffraction elevation angle theta (h) at electric wave ray arbitrary height place, namely

$\mathrm{\&theta;}\left(h\right)={\cos }^{-1}\frac{n_0(a+h_0){\mathrm{cos\&theta;}}_0}{n\left(h\right)(a+h)}---\left(6\right)$

In formula, the refraction elevation angle of the electric wave ray that θ (h) is arbitrary height, rad; θ ₀for the elevation angle that radargrammetry is arrived, rad; A is earth mean radius, a ≈ 6370km; h ₀for the sea level elevation of radar antenna, km; N (h) is the air index at arbitrary height h place,

Electric wave ray is divided into m section, and each section of corresponding height is Δ h _i, i=1,2,3 ... k, adopts method of difference to obtain the distance error Δ R of each section _i, geocentric angle and the earth's core be to the angle error between target and the earth's core to radar with refraction angle error delta θ on electric wave ray _i, namely

In formula, the refractive index gradient of every section obtained by atmospheric profile n (h) in step (5),

Employing process of iteration tries to achieve the corresponding parameter on i+1 section electric wave ray, and iterative formula is

Precision according to the requirement hypothesis distance error of radar measurement accuracy is δ, when | R _i+1-R _e| during < δ, iteration terminates, R _efor the distance parameter of radargrammetry, km,

In order to reduce iteration time, Δ h _iadopt variable step, iteration is got for the first time when time, changing step-length is next iteration distance from start to calculate, by that analogy, until convert p time, step-length is less than δ, occurs time iteration terminate, thus obtain relevant parameters and be

The calculating of refraction error, distance refraction error Δ R and elevation angle refraction error ε is respectively

$\left\{\begin{array}{c}\mathrm{\&Delta;}R=R_e-R_0\\ \mathrm{\&epsiv;}={\mathrm{\&theta;}}_0-{\mathrm{\&alpha;}}_0\end{array}\right.---\left(10\right)$

In formula, R _e, θ ₀be respectively apparent range and the apparent elevation angle of radargrammetry, R ₀, α ₀be respectively the radar that calculates through geometry to the actual distance of target and the true elevation angle,

(7) radar wave Refraction error correcting, after step (6), obtain revised radar fix parameter is

$\left\{\begin{array}{c}R=\mathrm{\&Delta;}R+R_e\\ \mathrm{\&theta;}=\mathrm{\&epsiv;}+{\mathrm{\&theta;}}_0\end{array}\right.---\left(12\right)$

(8) correction result of step (7) is transported to radar processing unit and positions calculating, obtain the exact position of target.