CN103729485A - Broadband radar coherent clutter simulation method based on DEM data - Google Patents

Abstract

The invention belongs to the technical field of radar simulation, and particularly relates to a broadband radar coherent clutter simulation method based on DEM data. The broadband radar coherent clutter simulation method comprises the following steps that firstly, simulation parameters are loaded; secondly, data of a nth flight path point are read; thirdly, the radar platform position and the sum beam irradiation direction are determined; fourthly, the radar irradiation area is determined through an antenna pattern; fifthly, a ground scattering unit is divided in the azimuth direction and the pitching direction at intervals with dtheta and dphi serving as the pitching angle and the azimuth angle respectively, and the area of the scattering unit is calculated; sixthly, the voltage power and amplitude of an echo of the scattering unit are calculated according to the radar equation; seventhly, an echo voltage signal of the scattering unit is calculated according to the obtained clutter amplitude and the characteristics of an LFM signal; eighthly, the position of the echo of the scattering unit in radar echo data is calculated; ninthly, coherent combination is carried out on the echo voltage signal of the scattering unit; tenthly, whether n is smaller than N or not is judged, if yes, simulation is finished, or otherwise, the second step is repeatedly executed. Complex electromagnetic scattering calculation is not carried out under the situation that ground up and down changes are taken into consideration.

Description

A kind of wideband radar coherent clutter emulation mode based on dem data

Technical field

The invention belongs to radar simulation technical field, be specifically related to a kind of wideband radar coherent clutter emulation mode based on dem data.

Background technology

Radar system is usually operated in certain ground environment, from the radar return on ground, enters receiver together with echo signal and noise etc., forms the clutter that disturbs radar detection performance.Along with improving constantly of modern radar sensitivity and precision, it is also increasing that radar system is subject to the impact of ground clutter environment.Carry out the optimal design of radar system, must understand and grasp the interaction of electromagnetic wave and clutter environment in depth.

Modern radar system generally adopts linear frequency modulation (LFM) signal in broadband to improve distance to resolution characteristic, adopt directional antenna that LFM signal is launched, LFM signal and ground target and environment are had an effect, reflected signal is received by radar receiver, through pulse compression, obtains one dimension High Range Resolution.During reception, need to carry out I road and sample in Q road to echoed signal simultaneously, obtain coherence data.

Existing radar clutter simulation method is mainly divided into two classes, and a class is the analogy method based on signal processing, does not consider the fluctuations on ground; Another kind of is method based on electromagnetism Scattering Calculation, but calculated amount is very large.

Summary of the invention

The object of the present invention is to provide a kind of wideband radar coherent clutter emulation mode based on dem data, considering under surface irregularity situation of change, do not carry out complicated electromagnetism Scattering Calculation, radar echo signal that can the extensive 3 D complex scene of Fast simulation, can provide effective support for radar system design and signal processing algorithm research.

For achieving the above object, the technical solution used in the present invention is:

A wideband radar coherent clutter emulation mode based on dem data, the method comprises the steps:

Step 1: be written into simulation parameter, comprise Texas tower motion flight path, speed, controlling antenna wave beam to point, ground grid dem data, and the wavelength of radar, pulsewidth, bandwidth, operating distance and antenna radiation pattern;

Step 2: the data of reading in n track points;

Step 3: determine Texas tower position and wave beam direction of illumination;

Step 4: in conjunction with antenna radiation pattern, determine the irradiation area of radar;

Step 5: with d θ and

be respectively the angle of pitch and azimuthal angle intervals along orientation to pitching to carrying out ground scatter dividing elements, the area of scattering unit is

Wherein, θ and

represent respectively the angle of pitch and position angle under spherical coordinate system, r represents the distance of radar to scattering unit;

Step 6: according to radar equation, echo voltage power and the amplitude of computing unit:

$P_r=\frac{P_r{G}^2\left(\mathrm{\θ}\right){\mathrm{\λ}}^2\mathrm{\σ}}{{\left(4\mathrm{\π}\right)}^3{r}^4}---\left(2\right)$

$A_i=\sqrt{P_r}---\left(3\right)$

Wherein: P _trepresent radar emission power, the W of unit; G (θ) is illustrated in the antenna gain of surface units direction; λ represents radar operation wavelength, the m of unit; σ represents that the scattering cross-section of surface units is long-pending; The surface units that represents r arrives the distance of radar, the m of unit;

Step 7: the clutter amplitude A obtaining according to step 6 _i, in conjunction with LFM characteristics of signals, be calculated as follows the echo voltage signal of scattering unit:

Wherein,

represent initial phase, k _rrepresent the modulation rate of LFM signal, f _drepresent Doppler frequency;

Step 8: calculate the position of scattering unit echo in radar return data

m _i＝(int){(r-R _start)/bin+0.5} （6）

Wherein, (int) expression rounding operation, R _startthe initial sampled distance that represents radar, bin represents the width of range gate;

Step 9: to the echo voltage signal of all scattering units, be concerned with synthetic, the echoed signal of n track points is:

$S_n\left(t\right)=\underset{i}{\mathrm{\Σ}}{S}_i\left(t\right)---\left(8\right)$

Step 10: judge that n < N(N represents that whole flight paths count) whether set up, if set up, emulation finishes so; Otherwise repeating step two.

In described step 6, the long-pending σ of the scattering cross-section of surface units calculates with following formula

σ＝σ ₀ds （4）

Wherein, σ ₀represent the backscattering coefficient on ground.

In described step 8, bin calculates according to following formula

bin＝c/2/f _s （7）

Wherein, c represents the light velocity, and value is 3 × 10 ⁸m/s; f _sfor A/D sampling rate; If r < is R _start, the echo of this unit, outside receiver window, can not be received, and can directly give up.

The obtained beneficial effect of the present invention is:

Wideband radar coherent clutter emulation mode based on dem data of the present invention, considering under surface irregularity situation of change, do not carry out complicated electromagnetism Scattering Calculation, radar echo signal that can the extensive 3 D complex scene of Fast simulation, can provide effective support for radar system design and signal processing algorithm research.

Fig. 2 has provided the Radar Clutter Signal simulation result of a typical environment, its I road and Q road signal have typical LFM signal intensity characteristic, Fig. 3 has provided and has carried out the result after pulse compression with frequency matching function, and after wherein narrower peak value fluctuations shows pulse compression, LFM signal is removed.

Accompanying drawing explanation

Fig. 1 is the wideband radar coherent clutter emulation mode process flow diagram based on dem data of the present invention;

Fig. 2 is the Radar Clutter Signal simulation result of typical environment;

Fig. 3 carries out the result after pulse compression with frequency matching function;

Fig. 4 is that surface units is divided geometric graph;

Fig. 5 is scatter echo stack schematic diagram.

Embodiment

Below in conjunction with the drawings and specific embodiments, the present invention is described in detail.

As shown in Figure 1, the wideband radar coherent clutter emulation mode based on dem data of the present invention comprises the steps:

Step 1: be written into simulation parameter, mainly comprise Texas tower motion flight path, speed, controlling antenna wave beam to point, ground grid dem data, and the wavelength of radar, pulsewidth, bandwidth, operating distance and antenna radiation pattern etc.;

Step 2: the data of reading in n track points;

Step 3: determine Texas tower position and wave beam direction of illumination;

Step 4: in conjunction with antenna radiation pattern, determine the irradiation area of radar;

Step 5: with d θ and

be respectively the angle of pitch and azimuthal angle intervals along orientation to pitching to carrying out ground scatter dividing elements, as shown in 4, the area of scattering unit is

Wherein, θ and

represent respectively the angle of pitch and position angle under spherical coordinate system, r represents the distance of radar to scattering unit;

Step 6: according to radar equation, echo voltage power and the amplitude of computing unit:

$P_r=\frac{P_r{G}^2\left(\mathrm{\&theta;}\right){\mathrm{\&lambda;}}^2\mathrm{\&sigma;}}{{\left(4\mathrm{\&pi;}\right)}^3{r}^4}---\left(2\right)$

$A_i=\sqrt{P_r}---\left(3\right)$

Wherein: P _trepresent radar emission power, the W of unit; G (θ) is illustrated in the antenna gain of surface units direction; λ represents radar operation wavelength, the m of unit; σ represents that the scattering cross-section of surface units is long-pending; The surface units that represents r arrives the distance of radar, the m of unit;

Wherein, the long-pending σ of the scattering cross-section of surface units calculates with following formula

σ＝σ ₀ds （4）

Wherein, σ ₀represent the backscattering coefficient on ground.

Step 7: the clutter amplitude A obtaining according to step 6 _i, in conjunction with LFM characteristics of signals, be calculated as follows the echo voltage signal of scattering unit:

Wherein,

represent initial phase, kr represents the modulation rate of LFM signal, and fd represents Doppler frequency.

Step 8: calculate the position of scattering unit echo in radar return data

m _i＝(int){(r-R _start)/bin+0.5} （6）

Wherein, (int) expression rounding operation, R _startthe initial sampled distance that represents radar, bin represents the width of range gate, bin calculates according to following formula

bin＝c/2/f _s （7）

Wherein, c represents the light velocity, and value is 3 × 10 ⁸m/s; f _sfor A/D sampling rate; If r < is R _start, the echo of this unit, outside receiver window, can not be received, and can directly give up.

Step 9: to the echo voltage signal of all scattering units, be concerned with synthetic, the echoed signal of n track points is:

$S_n\left(t\right)=\underset{i}{\mathrm{\&Sigma;}}{S}_i\left(t\right)---\left(8\right)$

When relevant synthetic, note the scattering unit echo that calculates in the step 8 position in radar return data, as shown in Figure 5.

Step 10: judge that n < N(N represents that whole flight paths count) whether set up, if set up, emulation finishes so; Otherwise repeating step two.

Claims (3)

1. the wideband radar coherent clutter emulation mode based on dem data, is characterized in that:

The method comprises the steps:

Step 1: be written into simulation parameter, comprise Texas tower motion flight path, speed, controlling antenna wave beam to point, ground grid dem data, and the wavelength of radar, pulsewidth, bandwidth, operating distance and antenna radiation pattern;

Step 2: the data of reading in n track points;

Step 3: determine Texas tower position and wave beam direction of illumination;

Step 4: in conjunction with antenna radiation pattern, determine the irradiation area of radar;

Step 5: with d θ and be respectively the angle of pitch and azimuthal angle intervals along orientation to pitching to carrying out ground scatter dividing elements, the area of scattering unit is

Wherein, θ and

represent respectively the angle of pitch and position angle under spherical coordinate system, r represents the distance of radar to scattering unit;

Step 6: according to radar equation, echo voltage power and the amplitude of computing unit:

$P_r=\frac{P_r{G}^2\left(\mathrm{\&theta;}\right){\mathrm{\&lambda;}}^2\mathrm{\&sigma;}}{{\left(4\mathrm{\&pi;}\right)}^3{r}^4}---\left(2\right)$

$A_i=\sqrt{P_r}---\left(3\right)$

Wherein: P _trepresent radar emission power, the W of unit; G (θ) is illustrated in the antenna gain of surface units direction; λ represents radar operation wavelength, the m of unit; σ represents that the scattering cross-section of surface units is long-pending; The surface units that represents r arrives the distance of radar, the m of unit;

Step 7: the clutter amplitude A obtaining according to step 6 _i, in conjunction with LFM characteristics of signals, be calculated as follows the echo voltage signal of scattering unit:

Wherein,

represent initial phase, k _rrepresent the modulation rate of LFM signal, f _drepresent Doppler frequency;

Step 8: calculate the position of scattering unit echo in radar return data

m _i＝(int){(r-R _start)/bin+0.5} （6）

Wherein, (int) expression rounding operation, R _startthe initial sampled distance that represents radar, bin represents the width of range gate;

Step 9: to the echo voltage signal of all scattering units, be concerned with synthetic, the echoed signal of n track points is:

$S_n\left(t\right)=\underset{i}{\mathrm{\&Sigma;}}{S}_i\left(t\right)---\left(8\right)$

Step 10: judge that n < N(N represents that whole flight paths count) whether set up, if set up, emulation finishes so; Otherwise repeating step two.

2. a kind of wideband radar coherent clutter emulation mode based on dem data according to claim 1, is characterized in that: in described step 6, the long-pending σ of the scattering cross-section of surface units calculates with following formula

σ＝σ ₀ds （4）

Wherein, σ ₀represent the backscattering coefficient on ground.

3. a kind of wideband radar coherent clutter emulation mode based on dem data according to claim 1, is characterized in that: in described step 8, bin calculates according to following formula

bin＝c/2/f _s （7）

Wherein, c represents the light velocity, and value is 3 × 10 ⁸m/s; f _sfor A/D sampling rate; If r < is R _start, the echo of this unit, outside receiver window, can not be received, and can directly give up.

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