RADAR-IMAGING OF A SCENE IN THE FAR-FIELD OF A ONE-OR TWO-DIMENSIONAL RADAR ARRAY

• US 20110140954A1
• Filed: 05/04/2009
• Published: 06/16/2011
• Est. Priority Date: 05/15/2008
• Status: Active Grant

• Current Assignee: European Community
• Original Assignee: European Community
• Inventors: Fortuny-Guasch, Joaquim
• Granted Patent: US 8,466,834 B2
• Time in Patent Office: Days
• US Class Current: 342/179
• CPC Class Codes: G01S 13/32 using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
• CPC Class Codes: G01S 13/9011 with frequency domain processing of the SAR signals in azimuth G01S13/9005 takes precedence
• CPC Class Codes: G01S 13/9023 combined with interferometric techniques

Abstract

A method of radar-imaging a scene in the far-field of a one-dimensional radar array, comprises providing an array of backscatter data D(f_m, x′n) of the scene, these backscatter data being associated to a plurality of positions x′_n, n=0 . . . N−1, N>1, that are regularly spaced along an axis of the radar array. The backscatter data for each radar array position x′n are sampled in frequency domain, at different frequencies f_m, m=0 . . . M−1, M>1, defined by f_m=f_c−B/2+m−Δf, where f_c represents the center frequency, B the bandwidth and Δf the frequency step of the sampling. A radar reflectivity image 1(α_m′, β_n′) is computed in a pseudo-polar coordinate system based upon the formula (2) with formula (3) where j represents the imaginary unit, formula (A) is the baseband frequency, FFT2D denotes the 2D Fast Fourier Transform operator, α_m′, m′=0 . . . M−1, and β_n′, n′=0 . . . N−1 represent a regular grid in the pseudo-polar coordinate system, and P_max is chosen >0 depending on a predefined accuracy to be achieved. A corresponding method of radar-imaging a scene in the far-field of a two-dimensional radar array is also proposed.

$\begin{array}{cc}I\left({\alpha }_{m^{\prime }},{\beta }_{n^{\prime }}\right)=\sum _{p=0}^{P_{\max }}I_p\left({\alpha }_{m^{\prime }},{\beta }_{n^{\prime }}\right),& \mathrm{Formula}\left(2\right)\\ I\left({\alpha }_{m^{\prime }},{\beta }_{n^{\prime }}\right)={\frac{1}{p!}\left[\frac{-j2{\mathrm{\pi \beta }}_{n^{\prime }}}{f_c}\right]}^p\mathrm{FFT}2D\left[D\left(f_m,x_n^{\prime }\right){\left({\hat{f}}_m,x_n^{\prime }\right)}^p\right],& \mathrm{Formula}\left(3\right)\\ {\hat{f}}_m=-B/2+m·\Delta f& \mathrm{Formula}\left(A\right)\end{array}$

Claims

1-14. -14. (canceled)

15. Method of radar-imaging a scene in a far-field of a one-dimensional radar array, comprising

providing an array of backscatter data of said scene, said backscatter data being herein denoted by D(f_m, x′

_n),

said backscatter data being associated to a plurality of radar array positions, herein denoted by x′

_n, n=0 . . . N−

1, N>

1, regularly spaced along an axis of said radar array;

the backscatter data being sampled, for each radar array position x′

_n, at different frequencies, herein denoted by f_m, m=0 . . . M−

1, M>

1, defined by f_m=f_c−

B/2+m·

Δ

f, where f_c represents a center frequency, B a bandwidth and Δ

f a frequency step;

computing a radar reflectivity image, herein denoted by I(α

_m′

, β

_n′

), in a pseudo-polar coordinate system, in which coordinates of a point of said scene are expressible by equations;

16. The method as claimed in claim 15, wherein said radar array positions are defined by x′

_n=−

L_x/2+n·

Δ

x′

, where L_x represents a length of the radar array and Δ

x′

a spacing between said radar array positions.

17. The method as claimed in claim 15, wherein P_max is chosen depending on a ratio of radar array length to range resolution.

18. The method as claimed in claim 15, wherein said radar reflectivity image in said pseudo-polar coordinate system is mapped into at least one of a polar coordinate system and a Cartesian coordinate system.

19. The method as claimed in claim 15, wherein at least one of a coherence image and a 2D-phase interferogram is computed based upon said radar reflectivity image in said pseudo-polar coordinate system.

20. The method as claimed in claim 19, wherein said at least one of a coherence image and a 2D-phase interferogram is mapped into at least one of a polar coordinate system and a Cartesian coordinate system.

27. The method as claimed in claim 15, wherein said reflectivity image is computed in or nearly in real time.

29. A computer program product for controlling a data processing apparatus, comprising instructions causing said data processing apparatus to carry out the method as claimed in claim 15, when executed on said data processing apparatus.

21. Method of radar-imaging a scene in a far-field of a two-dimensional radar array, comprising

providing an array of backscatter data of said scene, said backscatter data being herein denoted by D(f_m, x′

_n, y′

_k),

said backscatter data being associated to a plurality of radar array positions, herein denoted by (x′

_n,y′

_k) n=0 . . . N−

1, N>

1, k=0 . . . K−

1, K>

1, regularly spaced along a first and a second axis of said radar array;

the backscatter data being sampled, for each radar array position (x′

_n,y′

_k) at different frequencies, herein denoted by f_m, m=0 . . . M−

1, M>

1, defined by f_m=f_c−

B/2+m·

Δ

f, where f_c represents a center frequency, B a bandwidth and Δ

f a frequency step;

computing a radar reflectivity image, herein denoted by I(α

_m′

, β

_n′

, γ

_k′

), in a pseudo-spherical coordinate system, in which coordinates of a point of said scene are expressible by equations;

22. The method as claimed in claim 21, wherein said radar array positions are defined by x′

_n=−

L_x/2+n·

Δ

x′

along said first axis, where L_x represents a length of the radar array along said first axis and Δ

x′

a spacing between said radar array positions along said first axis, and by y′

_k=−

L_y/2+k·

Δ

y′

along said second axis, where L_y represents a length of the radar array along said second axis and Δ

y′

a spacing between said radar array positions along said second axis.

23. The method as claimed in claim 21, wherein P_max is chosen depending on ratios of radar array lengths along said first and said second axis to range resolution.

24. The method as claimed in claim 21, wherein said radar reflectivity image in said pseudo-spherical coordinate system is mapped into at least one of a spherical coordinate system and a Cartesian coordinate system.

25. The method as claimed in claim 21, wherein at least one of a coherence image and a 3D-phase interferogram is computed based upon said radar reflectivity image in said pseudo-spherical coordinate system.

26. The method as claimed in claim 25, wherein said at least one of a coherence image and a 3D-phase interferogram is mapped into at least one of a spherical coordinate system and a Cartesian coordinate system.

28. The method as claimed in claim 21, wherein said reflectivity image is computed in or nearly in real time.

30. A computer program product for controlling a data processing apparatus, comprising instructions causing said data processing apparatus to carry out the method as claimed in claim 21, when executed on said data processing apparatus.