A Variable PRF Imaging Method for High Squint Diving Sar

Abstract

Abstract-The high squint diving SAR is widely used to provide the information in advance. Large squint angle deduces the deeper coupling of range and azimuth of SAR echoes which makes SAR imaging more difficult. Especially, the large range migration of the deep couple heavily burdens the imaging processing time and storage units. The diving motion of platform worsens the situation. This paper proposes the varied azimuth sample frequency (Pulse Repeat Frequency, PRF) to implement the high squint diving SAR imaging. Based on the signal model of the diving squint SAR, it is analyzed that the range walk is the prominent component of range migration in the high squint SAR. The varied PRF imaging method dramatically decreases the range walk of echoes by shifting the beginning position of transmitted pulses and received echoes and the shift is implemented by the PRF variation. Then the range migration is decreased and the couple of range and azimuth of SAR echoes is reduced. The PRF variation law is deduced and the applicable condition of varied PRF is presented. The simulation results show that the variable PRF method is efficient to reduce range walk of echoes. Comparison to the traditional constant PRF, the novel variable PRF method for high squint needs less storage and less time expense, which is helpful to real time SAR imaging. The non-uniform FFT can be used for the azimuth compressing of the variable PRF SAR. It will simplify the implementation of the variable PRF SAR imaging.

An Improved Range-Doppler Algorithm for Sar Imaging at High Squint Angles

“…The Doppler spectrum in a SAR scenario at a high squint angle becomes very oblique, demanding a higher pulse repetition frequency (PRF) and possibly resulting in a folded spectrum in the Dopplerfrequency domain [6][7][8]. The folded-spectrum problem can be solved by increasing the PRF [6,7], which is equivalent to reducing the azimuth sampling interval.…”

“…The folded-spectrum problem can be solved by increasing the PRF [6,7], which is equivalent to reducing the azimuth sampling interval. As a result, the received signals are recorded at more azimuth positions, increasing the computational load and memory size.…”

“…In [7], a variable PRF was proposed to implement high-squint SAR imaging, which dramatically decreased the range walk of returned signals by shifting the transmitted pulses and the received echoes. In [8], a high-order phase correction approach (HPCA) was combined with the SPECAN method to focus high-squint SAR images reconstructed with small-aperture data.…”

Sparse Autofocus Recovery for Under-Sampled Linear Array Sar 3-D Imaging

“…Exploiting high resolution 3-D images, LASAR can provide more details in target recognition and decision-making tasks than conventional twodimensional (2-D) SAR. In addition, unlike classical SAR structures limited by the side-looking configuration [6,7], LASAR can work in flexible mode, e.g., forward-looking and down-looking, make it very suitable for the reconnaissance and surveying applications in complex terrains. With the linear array antenna (LAA), LASAR extends the synthetic aperture principle into the cross-track direction (the third dimension) for 3-D imaging.…”

A New Conical-Trajectory Polar Format Algorithm for Spotlight Bistatic Sar

“…PFA can be employed for spotlight mode either in monostatic or bistatic geometry [1,[10][11][12][13]. However, in the classic lineartrajectory PFA, the range processing (either sinc-interpolation or chirp-z transformation) introduces heavy computational load, which limits the image formation speed and its real-time applications.…”