CN102967861A - Terrain observation by progressive scans synthetic aperture radar (TOPSAR) system parameter engineering design method - Google Patents

Abstract

The invention provides a TOPSAR system parameter engineering design method. The technical scheme includes that satellite parameters, radar parameters and wave position parameters are known, and on the premise that images of the whole swath are continuous and uniform, system parameters applicable to engineering design are designed according to quantitative relations of design indexes and parameters of a system to be designed. Parameters of the TOPSAR system to be designed comprise the azimuth processing angle, the azimuth resolution ratio, the scanning speed, working time of all sub-swathes and the scanning period. By the aid of the method, all sub-swathes are consistent in the azimuth resolution ratio in design results, and the central azimuth ambiguity, the azimuth ambiguity deterioration, the noise equivalent sigma zero (NESZ) deterioration and azimuth overlapping ratios of all sub-swathes meet index requirements. By the aid of TOPSAR system parameters designed by the method, images of the whole swath are continuous and uniform during TOPSAR operation.

Description

TOPSAR systematic parameter engineering design method

Technical field

The invention belongs to the interleaving techniques field of space flight and microwave remote sensing, be particularly related to a kind of for satellite-borne SAR (Synthetic Aperture Radar, synthetic-aperture radar) new mode of operation---TOPSAR(Terrain Observation by Progressive scans Synthetic Aperture Radar, the orientation is to the electric scanning synthetic-aperture radar) the systematic parameter engineering design method.

Background technology

Scan pattern is the important process pattern that satellite-borne SAR is realized wide swath, and traditional scan pattern can be subject to the impact of scallop effect because the orientation is inhomogeneous to antenna weighting, and the scallop effect is compensated relatively difficulty, has limited the application of traditional scan pattern.TOPSAR is a kind of brand-new mode of operation of satellite-borne SAR, and this pattern is by antenna upwards scanning in the orientation, has solved the problems such as scallop effect of traditional scan pattern system.This mode of operation proposed from 2006, Success in Experiment on TerraSAR-X, and resulting image is almost complete absence of the scallop effect.It is reported that this mode of operation also will be designed for the up-to-date SAR satellite Sentinel-1 of European Space Agency.

At present, the research of TOPSAR mainly concentrated on the image processing method aspect.Not yet there is data to propose the systematic parameter engineering design method.

Summary of the invention

The objective of the invention is: propose to be suitable for the TOPSAR systematic parameter engineering design method of engineering design, be applied to the TOPSAR System Parameter Design.

The thinking of technical solution of the present invention is: known satellite parameter, radar parameter, ripple position parameter, at the image that satisfies whole mapping band continuously and uniformly under the prerequisite, according to the quantitative relationship between design objective and the systematic parameter to be designed, propose to be suitable for the System Parameter Design method of engineering design.TOPSAR systematic parameter to be designed comprises working time and the scan period of orientation processing angle, azimuthal resolution, sweep speed, each sub-swaths.The image of whole mapping band refers to continuously and evenly: (1) each sub-swaths has consistent azimuthal resolution; (2) each sub-swaths has consistent azimuth ambiguity performance; (3) to guarantee in the orientation to continuous imaging.

Technical solution of the present invention is:

Known satellite parameter and radar parameter: satellite velocities V _s, satellite-borne SAR signal wavelength lambda, wave beam T switching time _G, the antenna scanning angle is

The time corresponding round trip antenna radiation pattern function

Antenna beam 3dB width θ _03dB

Known ripple position parameter: pulse repetition rate

Wave beam footprint speed The center oblique distance Subscript i represents i sub-swaths, i=1 ~ N _s, N _sBe the sub-swaths number.

Requirement of system design: each sub-swaths has consistent azimuthal resolution, and the center hold blur level of each sub-swaths must be less than or equal to AASR ₀, the scanning angle of each sub-swaths must less than or equal to The azimuth ambiguity degree of each sub-swaths worsens must be less than or equal to AASR _Det0, the NESZ(Noise Equivalent Sigma Zero of each sub-swaths, equivalent noise figure) and worsening must be less than or equal to NESZ _Det0, the orientation is not less than e to Duplication.

The first step: orientation processing angle design

To i sub-swaths, carry out following processing:

Order

${\mathrm{\θ}}_{0_j}^{\left(i\right)}=2\arcsin \left(\frac{{\mathrm{\λf}}_p^{\left(i\right)}}{{4V}_s}\right)\frac{j}{N_j},$ j＝1,2,3,…,N _j (1)

Wherein, N _jBe a positive integer, relevant with the orientation processing angle precision of needs.In general, N _jLarger, orientation processing angle computational accuracy is higher.To each

Calculate doppler bandwidth with following formula

$B_{a_j}^{\left(i\right)}=\frac{{4V}_s}{\mathrm{\λ}}\sin \left(\frac{{\mathrm{\θ}}_{0_j}^{\left(i\right)}}{2}\right)---\left(2\right)$

Calculate corresponding center hold blur level with following formula again

Wherein,

It is right to represent

It is squared,

Be the round trip antenna radiation pattern

When

The time function.Be calculated as follows orientation processing angle θ _0amb

$j_{0\mathrm{amb}}^{\left(i\right)}=\underset{{\mathrm{AASR}}_{c,j}^{\left(i\right)}\≤{\mathrm{AASR}}_0}{\max }\left(j\right)$ (4)

${\mathrm{\θ}}_{0\mathrm{amb}}^{\left(i\right)}={\mathrm{\θ}}_{0_{j_{0\mathrm{amb}}^{\left(i\right)}}}^{\left(i\right)}$

Then, final orientation processing angle

And doppler bandwidth

For:

${\mathrm{\θ}}_0^{\left(i\right)}=\min \{{\mathrm{\θ}}_{0\mathrm{amb}}^{\left(i\right)},{\mathrm{\θ}}_{03\mathrm{db}}\}---\left(5\right)$

$B_a^{\left(i\right)}=\frac{{4V}_s}{\mathrm{\λ}}\sin \left(\frac{{\mathrm{\θ}}_0^{\left(i\right)}}{2}\right)---\left(6\right)$

Second step, the azimuthal resolution design

Order

${\mathrm{\ρ}}_{a_k}^{\′}=\underset{i=1}{\overset{N_s}{\mathrm{\Σ}}}\frac{\mathrm{\λ}}{{2\mathrm{\θ}}_0^{\left(i\right)}}\frac{V_g^{\left(i\right)}}{V_s}(1+\frac{k}{N_k}),$ k＝1,2,3,…,N _k (7)

Wherein, N _kBe positive integer, relevant with the azimuthal resolution precision of needs.In general, N _kLarger, the azimuthal resolution precision is higher.To each

Carry out following processing:

At first, calculate:

I=1,2,3 ..., N _s(8)

Solve linear equations again:

i＝1,2,3,…,N _s (9)

Can obtain each sub-swaths working time

With scan period T _k

Then, calculate the maximum scan angle that needs with following formula

And corresponding centre frequency

Calculating corresponding azimuth ambiguity degree according to following formula again worsens

And calculate corresponding NESZ with following formula and worsen

At last, be calculated as follows azimuthal resolution ρ _a:

${\mathrm{\ρ}}_a={\mathrm{\ρ}}_{a_{k_{{\mathrm{\ρ}}_a}}}^{\′}$

The 3rd step: timing Design

At first obtain sweep speed according to following formula

Then take off the group that establishes an equation:

i＝1,2,3,…,N _s(16)

Can try to achieve each sub-swaths working time

With scan period T.

Adopt the present invention desirable following technique effect:

The TOPSAR System Parameter Design method that is suitable for engineering design that the present invention proposes, the method adopt orientation processing angle design, and azimuthal resolution design and three steps of timing Design can design the TOPSAR systematic parameter.Can make each sub-swaths of design result that consistent azimuthal resolution is arranged, and the center hold blur level of each sub-swaths, the azimuth ambiguity degree worsens, and NESZ worsens and the orientation all satisfies index request to Duplication.The TOPSAR systematic parameter that the method for designing that proposes by the present invention designs can make the image of whole mapping band in the TOPSAR work continuously and evenly.

Description of drawings

Fig. 1 is TOPSAR System Parameter Design process flow diagram provided by the invention;

Fig. 2 is original optical scene;

Fig. 3 is satellite parametric reduction and radar parameter;

Fig. 4 is sub-swaths ripple position parameter;

Fig. 5 is the design objective requirement;

Fig. 6 is TOPSAR System Parameter Design result and to result's performance evaluation;

Fig. 7 is the TOPSAR imaging results.

Embodiment

Fig. 1 is TOPSAR System Parameter Design process flow diagram provided by the invention.Whole flow process was divided into for three steps.With ripple position parameter, satellite parametric reduction and radar parameter as input, the first step, orientation processing angle design requires to determine the orientation processing angle according to the center hold blur level; Second step, the azimuthal resolution design in certain azimuthal resolution scope, is analyzed the relation that azimuthal resolution and scanning angle, the deterioration of azimuth ambiguity degree and NESZ worsen, and selects according to demand the system performance of suitable resolution to satisfy the demand; In the 3rd step, timing Design according to the resolution of selecting, requires design sweep speed and working time parameter according to sequential, thus complete design.

Fig. 2 ~ Fig. 7 is the result who carries out emulation experiment.

Fig. 2 is original optical scene, with the Radar Cross Section of optics picture intensity as scene.

Fig. 3 is satellite parametric reduction and radar parameter, comprises 4 parameters of input needs.

Fig. 4 is sub-swaths ripple position parameter, comprises 6 groups of parameters of input needs.

Fig. 5 is the design objective requirement, comprises 5 indexs of input needs.

Fig. 6 is TOPSAR System Parameter Design result and to result's performance evaluation.Wherein, front 5 row are the TOPSAR System Parameter Design results that use System Parameter Design method of the present invention, and rear 5 row are the performance evaluations to design result.Utilize when of the present invention N _j=100, N _k=100, it is 16m all that design result makes the azimuthal resolution of each sub-swaths, satisfies index request, the center hold blur level of each sub-swaths is-and the 25dB(index request-25dB); The scanning angle of each sub-swaths is less than or equal to 0.42 ° (0.42 ° of index request), the azimuth ambiguity degree of each sub-swaths worsens less than or equal to 0.33dB(index request 0.5dB), the NESZ of each sub-swaths worsens less than or equal to 0.26dB(index request 0.5dB), and guaranteed that the orientation is to Duplication 10%(index request 10%), satisfy the design objective among Fig. 5, the validity of method for designing of the present invention has been described.

Fig. 7 is the space based radar analogue system through this development in laboratory, according to the input parameter of Fig. 3 ~ Fig. 4, and the result of the analogue echoes that the parameter of utilizing Fig. 6 to design realizes, imaging and sub-swaths splicing.Marked the imaging region in two cycles on the image of each sub-swaths and the first sub-swaths among the figure.The result is except having certain coherent spot effect in splicing, and image light and shade and former picture are consistent; The resolution of whole image is consistent, the orientation to have between the image in two cycles 10% overlapping, the correctness of design result of the present invention has been described.

Claims (1)

1. an orientation is characterized in that to electric scanning polarization sensitive synthetic aperture radar system parameter engineering method for designing, comprises the steps:

Known satellite parameter and radar parameter: satellite velocities V _s, satellite-borne synthetic aperture radar signal wavelength lambda, wave beam T switching time _G, the antenna scanning angle is

The time corresponding round trip antenna radiation pattern function Antenna beam 3dB width θ _03dB

Known ripple position parameter: pulse repetition rate Wave beam footprint speed

The center oblique distance Subscript i represents i sub-swaths, i=1 ~ N _s, N _sBe the sub-swaths number;

Requirement of system design: each sub-swaths has consistent azimuthal resolution, and the center hold blur level of each sub-swaths is less than or equal to AASR ₀, the scanning angle of each sub-swaths less than or equal to

The azimuth ambiguity degree of each sub-swaths worsens less than or equal to AAST _Det0, the equivalent noise figure NESZ of each sub-swaths worsens less than or equal to NESZ _Det0, the orientation is not less than e to Duplication;

The first step: orientation processing angle design

To i sub-swaths, carry out following processing:

Order

${\mathrm{\θ}}_{0_j}^{\left(i\right)}=2\arcsin \left(\frac{{\mathrm{\λf}}_p^{\left(i\right)}}{{4V}_s}\right)\frac{j}{N_j},$ j＝1,2,3,…,N _j

Wherein, N _jBe a positive integer, relevant with the orientation processing angle precision of needs, N _jLarger, orientation processing angle computational accuracy is higher; To each

Calculate doppler bandwidth with following formula

$B_{a_j}^{\left(i\right)}=\frac{{4V}_s}{\mathrm{\λ}}\sin \left(\frac{{\mathrm{\θ}}_{0_j}^{\left(i\right)}}{2}\right)$

Calculate corresponding center hold blur level with following formula again

Wherein,

It is right to represent It is squared, Be the round trip antenna radiation pattern

When

The time function; Be calculated as follows orientation processing angle θ _0amb

$j_{0\mathrm{amb}}^{\left(i\right)}=\underset{{\mathrm{AAST}}_{c,j}^{\left(i\right)}\≤{\mathrm{AASR}}_0}{\max }\left(j\right)$

${\mathrm{\θ}}_{0\mathrm{amb}}^{\left(i\right)}={\mathrm{\θ}}_{0_{j_{0\mathrm{amb}}^{\left(i\right)}}}^{\left(i\right)}$

Then, final orientation processing angle

And doppler bandwidth

For:

${\mathrm{\θ}}_0^{\left(i\right)}=\min \{{\mathrm{\θ}}_{0\mathrm{amb}}^{\left(i\right)},{\mathrm{\θ}}_{03\mathrm{dB}}\}$

$B_a^{\left(i\right)}=\frac{{4V}_s}{\mathrm{\λ}}\sin \left(\frac{{\mathrm{\θ}}_0^{\left(i\right)}}{2}\right)$

Second step, the azimuthal resolution design

Order

${\mathrm{\ρ}}_{a_k}^{\′}=\underset{i=1}{\overset{N_s}{\mathrm{\Σ}}}\frac{\mathrm{\λ}}{{2\mathrm{\θ}}_0^{\left(i\right)}}\frac{V_g^{\left(i\right)}}{V_s}(1+\frac{k}{N_k}),$ k＝1,2,3,…,N _k

Wherein, N _kBe positive integer, relevant with the azimuthal resolution precision of needs, N _kLarger, the azimuthal resolution precision is higher; To each

Carry out following processing:

At first, calculate:

i＝1,2,3,…,N _s

Solve linear equations again:

i＝1,2,3,…,N _s

Can obtain each sub-swaths working time

With scan period T _k

Then, calculate the maximum scan angle that needs with following formula

And corresponding centre frequency

Calculate again the azimuth ambiguity degree deterioration of each sub-swaths according to following formula

And the NESZ deterioration of calculating each sub-swaths with following formula

At last, be calculated as follows azimuthal resolution ρ _a:

${\mathrm{\ρ}}_a={\mathrm{\ρ}}_{a_{k_{{\mathrm{\ρ}}_a}}}^{\′}$

The 3rd step: timing Design

At first obtain sweep speed according to following formula

Then take off the group that establishes an equation:

i＝1,2,3,…,N _s

Can try to achieve each sub-swaths working time

With scan period T.

Images