Guoqian Wang

Fast Factorized Backprojection Algorithm for One-Stationary Bistatic Spotlight Circular SAR Image Formation

In this paper, a fast factorized backprojection (FFBP) algorithm is proposed for the one-stationary bistatic spotlight circular synthetic aperture radar (OS-BSCSAR) data processing. This method represents the subimages on polar grids in the slant-range plane instead of the ground plane, which can be accurately referenced to the tracks of both transmitter and receiver. It can not only accurately accommodate the complicated circular track including the motion error, scene topographic information, large spatial variances and significant range-azimuth coupling of the echo data, but also improve the imaging efficiency compared with the backprojection (BP) algorithm. First, OS-BSCSAR imaging geometry is provided, and then the bistatic BP algorithm for the OS-BSCSAR imaging is derived to provide a basis for the proposed FFBP algorithm. Second, based on the subaperture imaging model, the polar grids for calculating the subimages are defined, and the sampling requirements for the polar grids are derived from the viewpoint of the bandwidth, which can offer the near-optimum tradeoff between the imaging quality and the imaging efficiency. Finally, implementation and computational burden of the proposed FFBP algorithm is discussed, and then the speed-up factor of the proposed FFBP algorithm with respect to the bistatic BP algorithm is derived. Experiment results are given to prove the correctness of the theory analysis and validity of the proposed FFBP algorithm.

Imaging experiment of low frequency ultrawideband bistatic SAR using fixed-receiver configuration

Low frequency ultrawideband (LF UWB) bistatic synthetic aperture radar (BSAR) is able to provide the high-resolution BSAR image and obtain more information of the scene. Here, an imaging experiment of the LF UWB BSAR using the fixed-receiver configuration is presented in the paper. In August 2015, based on the monostatic LF UWB SAR system, a LF UWB BSAR imaging experiment was carried out, and the then LF UWB BSAR raw data was collected. This BSAR system has a LF UWB SAR system as the moving transmitter and the other LF UWB radar system as a fixed-receiver. The aim was to investigate the imaging property of the LF UWB BSAR system. One pulse per second (1PPS) signal in combination with the global position system (GPS) disciplined 100MHz oscillator from the GPS receivers were used to implement the time and frequency synchronization in this BSAR system. LF UWB BSAR image was obtained using the fast factorized back projection (FFBP) algorithm integrated with the subaperture-based spectrum equilibrium method. The excellent results are shown to prove the validity of the imaging experiment of the LF UWB BSAR system.

Fast time domain imaging for Bistatic SAR including motion errors

In this paper, a fast time domain imaging for the bistatic synthetic aperture radar (BSAR) including the motion errors is presented. This method is called the fast factorized backprojection (FFBP) algorithm, which not only precisely handles the large spatial-variance, serious range-azimuth coupling and complicated motion errors, but also greatly improves the imaging efficiency compared with the backprojection (BP) algorithm. In addition, it requires the local beamforming from radar echoes as an intermediate processing in the slant range plane instead of the ground plane, which can be accurately referenced to tracks of the transmitter and receiver considering the platform altitudes. Moreover, it analyzes the bistatic range error considering motion errors to derive the requirement for selecting sizes of the subaperture and subimage, which can offer a near-optimum tradeoff between imaging precision and efficiency. Experiment results prove that the proposed method outperforms the BP algorithm in the terms of the efficiency improvement.

Imaging Experiment of Monostatic and Bistatic UWB SAR at UHF-band

Due to the intrinsic property, ultrahigh frequency ultrawideband (UHF UWB) synthetic aperture radar (SAR) has lately become of a particular interest to the SAR community. Monostatic and bistatic UHF UWB SAR has the well foliage penetrating ability, high-resolution imaging and providing the increased information. In 2015, the monostatic and bistatic UHF UWB SAR experiment has been conducted. In this experiment, the monostatic and bistatic data were collected simultaneously by operating the vehicle-based radar in the SAR mode, in conjunction with the stationary ground-based receiver. Bistatic and monostatic SAR images were obtained by the subaperture spectrum-equilibrium method integrated with a fast factorized back projection (FFBP) method. Experiment results prove the property of the monostatic and bistatic UHF UWB SAR.

Comparison of imaging properties between monostatic and bistatic circular SAR

Due to the intrinsic property and unique advantage, circular synthetic aperture radar (CSAR) has lately become of the particular interest to the SAR community. The differences of the imaging properties between the monostatic and bistatic CSAR are compared and analyzed in this paper. Specifically, the detailed comparison of the wavenumber and resolution of targets in the monostatic and bistatic CSAR imaging is carried out. First, imaging geometries of monostatic and bistatic CSAR systems are built, and the wavenumbers of the target echo data are derived. Then, based these wavenumbers, the resolutions of the monostatic and bistatic CSAR systems are discussed, which can provide a basis for comparing their imaging properties. Finally, experimental results are shown to prove correctness of the comparison and analysis of their imaging properties.