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

Abstract

The invention discloses a method for on-line correcting low-angle radar electric wave refraction error. When a radar measures a target, radar measured parameter distance and angle are used to obtain radar positioning parameters with atmosphere refraction errors eliminated through a device formed by a GPS receiver, a ground atmospheric refractivity measuring instrument, an atmosphere profile database, a control and data processor and related interface circuits. The parameters are used for positioning a target, and the radar positioning precision is improved. The refraction error correction method is simple, and low in computation burden, short in time, high in precision, high in automation level and easy for realization. The method realizes on-line correcting radar electric wave refraction error in a high-precision way.

Description

A kind of low angle radar wave refraction error on-line amending method

Technical field

The invention belongs to radar measurement errors modification method technical field, be specifically related to a kind of low angle radar wave refraction error on-line amending method.

Background technology

The measurement and positioning precision improving radar is the necessary condition of the applications such as navigation, satellite and observing and controlling.Along with the raising of the precision of electronic devices and components own and the optimization of Correlation method for data processing method of composition radar system, the refraction error of radio (light) wave that atmospheric environment causes has become the principal element that restriction radar measurement accuracy improves further.

During radar detection aerial target, electric wave will pass through air (comprising troposphere and ionosphere) environment.Produce refraction effect when the unevenness of atmospheric environment makes electric wave propagate in an atmosphere, electric wave ray is along curve instead of linearly propagate, and velocity of propagation is less than the light velocity, makes radargrammetry parameter produce refraction error, and then affects radar fix precision.Radar fix precision to be improved further, must refraction error of radio (light) wave correction be carried out.Because the horizontal unevenness of air is very little, therefore refraction error only considers distance error and elevation angle error, and does not need to consider azimuth angle error.At present, most scholar utilizes actual measurement atmospheric environmental parameters, the ray tracing method based on integrated form is adopted to carry out calculating and the correction of refraction error of radio (light) wave, because the method needs to measure atmospheric environmental parameters and integral operation, the processing time needed is very long, therefore it is only applicable to the radar system of target range and Experimental Base, and is not suitable in practical application the radar system needing online (in real time) to carry out refraction error of radio (light) wave correction.

Current existing refraction error of radio (light) wave real-time correcting method mainly contains two classes, one class utilizes microwave radiometer instrumentation radar electric wave ray through the thermonoise of atmospheric environment, utilize Marko (Marcor) technology to obtain the relation of thermonoise and refraction error, and then carry out Refraction error correcting.But this method one to carry out distance Refraction error correcting, and can not carry out the correction of angle refraction error, corrected parameter is imperfect; Two is refraction error margins of error just from radar to unlimited distance that it obtains, and be not the margin of error between radar to target, extent of amendment is greater than actual electric wave by interval, expands the margin of error.Another kind of is carry out idealized approximate simplification revised law to some parameter, and it not only needs to carry out a large amount of Primary Stage Data statistical works, and it is lower to revise precision, can only be applicable to the radar system of the type area participating in statistics.

In order to meet the refraction error of radio (light) wave on-line amending of the radar system in practical application, improving radar fix precision further, being necessary a kind of low angle of research and development radar wave refraction error on-line amending method.

Summary of the invention

The technical matters that the present invention solves there is provided a kind of low angle radar wave refraction error on-line amending method, when radar is measured target, the radar fix parameter of Atmospheric Refraction Error that radargrammetry parameter (Distance geometry angle) is eliminated by the device be made up of GPS, terrestrial refraction rate measuring instrument, atmospheric profile database, control and data processor and concerned interface circuit etc., carry out the location of target by this parameter, improve the positioning precision of radar.

The present invention adopts following technical scheme for solving the problems of the technologies described above, a kind of 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.

Further restriction, 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

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

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

$\left\{\begin{array}{c}G=N_1-N_0\\ C=\frac{1}{m}\underset{i=1}{\overset{m}{\&Sigma;}}\frac{{\mathrm{lnN}}_1-{\mathrm{lnN}}_i}{h_1-1}\end{array}\right.---\left(2\right)$

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).

Further restriction, described air index measuring instrument is 11GHz air index measuring instrument, and 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 △ 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)

In fact, 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 △ 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.

Further restriction, 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 △ h _i, i=1,2,3 ... k, adopts method of difference to obtain the distance error △ 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, △ 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 △ 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

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

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

Refraction error correcting method of the present invention is simple, operand is little, time is shorter, precision is higher, automaticity high and be easy to realize, the refraction error of radio (light) wave on-line amending function of radar hi-Fix can be realized, only associated components is embedded in radargrammetry transmission signal line in operational process of the present invention, and all hardware structure of not changing in radar system and disposal route, by the Refraction error correcting to radargrammetry parameter, eliminate the Atmospheric Refraction Error of 95%, and then improve the positioning precision of radar.

Accompanying drawing explanation

Fig. 1 is atmospheric profile Database process flow diagram;

Fig. 2 is 11GHz air index measuring instrument measuring principle figure;

Fig. 3 controls the module composition diagram with data processor;

Fig. 4 is the module composition diagram of low angle radar wave refraction error on-line amending device.

Embodiment

By the following examples foregoing of the present invention is described in further details, but this should be interpreted as that the scope of the above-mentioned theme of the present invention is only limitted to following embodiment.All technology realized based on foregoing of the present invention all belong to scope of the present invention.

Atmospheric profile Database flow process as shown in Figure 1.The geographical environment of China's complexity causes the complicated and changeable of atmospheric environment, and the parameter various places difference therefore in air index pattern is comparatively large, needs the atmospheric profile setting up each region.The relation of coefficient and terrestrial refraction rate in each Regional atmospheric model can be set up according to Atmosphere changes feature.Each region can be obtained the coefficient in atmospherical model by terrestrial refraction rate in actual applications, thus obtains practical atmospheric profile.Concrete method for building up comprises the 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 in north latitude 150 to 550 scope by 0.10 interval, 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, from the detection data at national atmospheric exploration station, find out air measured section data in corresponding grid 20 years (every day two groups of data, each station has 14600 groups).If have measured data in grid, then the data 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, utilize Lagrange's interpolation formula to try to achieve atmospheric profile in this grid, finally make the atmospheric profile measured data having 20 years in each grid.

(3) atmospherical model is determined.By contrasting various atmospherical model, finally select high-precision atmospheric profile segmented model, namely

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

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; 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.To in each grid each time detection data utilize (2) formula to calculate corresponding coefficient G and C, namely

$\left\{\begin{array}{c}G=N_1-N_0\\ C=\frac{1}{m}\underset{i=1}{\overset{m}{\&Sigma;}}\frac{{\mathrm{lnN}}_1-{\mathrm{lnN}}_i}{h_1-1}\end{array}\right.---\left(2\right)$

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.

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.Survey atmospheric profile each time by each grid like this and just can obtain one group of N 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.As long as each month have N like this to each grid ₀just can obtain corresponding N according to this relational expression ₁, N ₉, G, C, thus obtain practical atmospheric profile N (h).

(6) terrestrial refraction rate and atmospherical model Relationship of Coefficients build storehouse.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, as long as provide terrestrial refraction index N ₀, just can obtain atmospheric profile N (h).

11GHz air index measuring instrument schematic diagram as shown in Figure 2.Air index measuring instrument be according to the resonance frequency of microwave cavity with atmospheric medium change in chamber the principle of change and designing.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.

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 △ f=f ₀-f, thus the refraction index N that can obtain air in resonator cavity is

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

Here, the pass of air index n and atmospheric refraction index N is

N=1+N × 10 ^-6(5) in fact, the variable quantity of the resonance frequency of resonator cavity is mainly measured in the measurement of atmospheric refraction index or refractive index.

In fig. 2, the specific works process of air index measuring instrument 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 100MHzVCO (voltage controlled oscillator) and provides modulation signal for it;

(2) 100MHzVCO 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 100MHzVCO;

(6) frequency that 100MHzVCO output frequency and 100MHz crystal oscillator produce is carried out mixing and amplification by frequency mixer, the difference frequency signal △ 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.

As further instruction, 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.

Control to form as shown in Figure 3 with data processor.Control mainly to complete with data processor 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 display of the revised radargrammetry parameter of refraction error of radio (light) wave, refraction error, storage controls, and the calculating of 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 control radar measurement data (the 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 △ h _i, i=1,2,3 ... k, adopts method of difference to obtain the distance error △ R of each section _i, geocentric angle (the earth's core is to the angle between target and the earth's core to radar) error 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

According to the requirement (supposing that the precision of distance error is δ) of radar measurement accuracy, when | R _i+1-R _e| during < δ, iteration terminates, R _efor the distance parameter (apparent range) of radargrammetry, km.

In order to reduce iteration time, △ 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 △ 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.

By comparatively validate, adopt finite-difference iterative method to carry out radar wave Refraction error correcting, working time is less than 6% of common integral method, and precision is slightly less than integration method.

Radar wave refraction error on-line amending schematic diagram of device as shown in Figure 4.In Fig. 1, GPS can obtain geographic position residing for radar antenna (longitude, latitude and height above sea level height) and date (month), the atmospheric refraction index pattern in region and month when determining that radar works by these parameters from atmospheric profile database.The terrestrial refraction rate at radar place is obtained by the measurement of 11GHz air index measuring instrument, utilizing the relation of correlation parameter and terrestrial refraction rate in air index model in atmospheric profile database to obtain only containing the practical atmospheric profile of unknown number h (highly), using when refraction error of radio (light) wave calculates for carrying out.Control to carry out refraction error calculating with data processor according to the radar measured data of known atmospheric profile and input, then Refraction error correcting is carried out to radargrammetry parameter, finally revised radar parameter is sent to radar processing unit and positions.Have employed due to during location the parameter eliminating refraction error, therefore achieve the function improving radar fix precision.

In sum, compare with general online Refraction error correcting method with the integration method of electric wave ray tracing, modification method of the present invention and device not only can automatically be measured and carry out refraction error of radio (light) wave correction by atmospheric refraction index, and the operation time needed is very little, the Atmospheric Refraction Error of 95% can be revised, meet the function of the online Refraction error correcting of radar, improve the positioning precision of radar further.

Embodiment above describes ultimate principle of the present invention, principal character and advantage; the technician of the industry should understand; the present invention is not restricted to the described embodiments; what describe in above-described embodiment and instructions just illustrates principle of the present invention; under the scope not departing from the principle of the invention; the present invention also has various changes and modifications, and these changes and improvements all fall in the scope of protection of the 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.