Fast Factorized Backprojection Algorithm for UWB Bistatic SAR Image Reconstruction

Transcription

1 Fast Factorized Bacprojection Agorithm for UWB Bistatic SA Image econstruction Viet Vu Thomas Sjögren and Mats Pettersson Beinge Institute of Technoogy Karsrona Sweden.

2 Outine Motivation Contribution Deveopment from GBP to BiFFBP From monostatic GBP to bistatic GBP Bistatic FBP deveopment on bistatic GBP From bistatic FBP to bistatic FFBP Simuation esuts and Evauation Concusion

3 Motivation Agorithms for NB bistatic SA Frequency-domain: ange Dopper (D) ange Migration (M) Chirp Scaing (CS). Time-domain: Goba Bacprojection appied to bistatic cases (BiGBP). Agorithms for UWB monostatic SA Frequency-domain: not recommended []. Time-domain: GBP Fast Bacprojection (FBP) Fast Factorized Bacprojection (FFBP). [] V. T. Vu et. a. A comparison between fast factorized bacprojection and frequency-domain agorithms in UWB ow frequency SA in Proc. IEEE IGASS 008 Boston MA Ju. 008 pp

4 Motivation (cont.) Agorithms for UWB bistatic SA BiGBP: Avaibiabe in principa. equire huge computationa burden. BiFBP: Shown to wor with UWB bistatic SA data []. equire ow computationa cost. BiFFBP: Need to be investigated. Supposed to require even ower computationa cost. [] V. T. Vu et. a. Fast bacprojection agorithm for UWB bistatic SA in Proc. IEEE adarcon 0 Kansas City MO May 0 pp

5 Contribution BiFFBP a fast time-domain agorithm Aim at UWB bistatic SA systems but avaiabe for NB bistatic SA systems. Inherit time-domain characteristics such as unimited scene size oca processing motion compensation and so on. Tested with different bistatic configurations and shown to be not imited by any bistatic configuration. Low computationa cost.

6 From GBP to BiGBP GBP econstructed either on a sant-range pane or ground pane. Time-domain characteristics. Spherica mapping. Huge computationa burden. h ti x c m rn g vpt ti dt

7 From GBP to BiGBP (cont.) BiGBP econstructed ony on a ground pane. Time-domain chracteristics. Eipsoida mapping. No imitation of bistatic configuration. Aso huge computationa burden. h ti x m rn gvtt vrtc ti dt

8 BiFBP Deveopment on BiGBP BiFBP econstructed ony on a ground pane. Time-domain chracteristics. Eipsoida mapping. No imitation of bistatic configuration. Two processing stages: Beam forming. Loca bacprojection Low computationa cost.

9 BiFBP Deveopment on BiGBP (cont.) Beam forming from radar echoes Linear superpositions of radar echoes. eferences for superposition are centers of b v t t ts t ts t Transmitter subaperture eceiver subaperture Subimage. v g r t c t v t v r t c dt

10 BiFBP Deveopment on BiGBP (cont.) Loca bacprojection from formed beam Over eipsoida mapping. Foci determined by centers of subapertures. Major axis defined by ine connecting foci. L c r t n m t v v t b y x h

11 From BiFBP to BiFFBP BiFFBP econstructed ony on a ground pane. Time-domain chracteristics. Eipsoida mapping. No imitation of bistatic configuration. More than two processing stages: Firtst beam forming.... Fina beam forming Loca bacprojection Lower computationa cost than BiFBP.

12 From BiFBP to BiFFBP (cont.) Beam forming from beam previousy formed Linear superpositions of beam formed in previous stage. econstructed ony on a ground pane. eferences for superposition are centers of New (onger) transmitter subaperture New (onger) receiver subaperture New (smaer) subimage. L L L L c c c c t b t b

13 From BiFBP to BiFFBP (cont.) Mathematica expression for BiFFBP with two beam forming stages dt t v v t g y x h s s t t t t c c c r t K K K K K L L L L L n m c

14 Simuations and Evauation Simuation parameters Parameter CAABAS-II (transmitter) LOA (receiver) The maximum frequency 8 MHz The minimum frequency MHz Patform speed v p 6 m/s 30 m/s Aperture step m m Aperture ength 3840 m 3950 m Fight atitude 3700 m 900 m Minimum range r m 3000 m PF 37 Hz Bistatic ange 0 0 /0 0 /60 0

15 Simuations and Evauation (cont.) Simuated ground scene Series of point-ie scaterers. Equay spaced. The same radar cross sections (CS). No noise added.

16 Simuations and Evauation (cont.) Considered bisatic configurations Quasi-monostatic: transmitter and receiver are mounted on a singe patform. Azimuth-invariant: transmitter and receiver are mounted on two different patforms whose fight tracs are parae. Genera bistatic: transmitter and receiver are mounted on two different patforms whose fight tracs are arbitrary e.g

17 Simuations and Evauation (cont.) Quasi-monostatic: Wor. Simiar monostatic

18 Simuations and Evauation (cont.) Azimuth-invariant: Wor. Beter resoution.

19 Simuations and Evauation (cont.) Genera bistatic: Wor. Famiiar features

20 Simuations and Evauation (cont.) Compared to BiGBP

21 Simuations and Evauation (cont.) Comparison between BiGBP and Phase error due to approximations in BiFFBP is observed.

22 Phase Error Cacuation Phase error equation [3] Cacuate the phase error generated by approximations in BiFFBP. Seect subimage and subaperture size. Minimize phase error. [3] V. T. Vu et. a. Phase error cacuation for fast time-domain bistatic SA agorithms in Proc. IEEE Trans. Aerosp. Eectron. Syst. submitted for pubication.

23 Concusion Propose an agorithm BiFFBP. Derive BiFFBP anayticay. Test BiFFBP with simuated UWB bistatic SA data. Test BiFFBP with different bistatic configurations. Compare with BiGBP.

24 Thans for your attention!