Range‐resolution improvement for spaceborne/airborne bistatic synthetic aperture radar using stepped‐frequency chirp trains

Abstract

In this paper, a stepped-frequency spaceborne/airborne bistatic synthetic aperture radar (SFSA-BiSAR) configuration is proposed to show to improve the range resolution of BiSAR. First, the geometry and the signal model of SFSA-BiSAR are formulated, and then an analytical bistatic point target reference spectrum (BPTRS) is derived. Second, based on the developed BPTRS, two imaging algorithms called combination-before-focusing algorithm (CBFA) and combination-after-focusing algorithm (CAFA) are proposed to obtain BiSAR images with improved range resolution. CBFA uses sub-band combination to obtain synthetic BPTRS, and then uses a new bistatic frequencydomain algorithm (BFDA) to obtain the improved BiSAR image, whereas CAFA first uses the BFDA to focus all the subpulses, and then uses sub-image combination to obtain the improved BiSAR image. Both of the two algorithms can focus the SFSA-BiSAR signal well and comparison simulations are performed to verify the authors' conclusion. Computation loads are also calculated to compare the two algorithms and show that CAFA uses less floating-point operations than CBFA. Besides, some important parameters of SFSA-BiSAR are analysed both theoretically and numerically to provide a reference for system design.

Azimuth Resolution Improvement and Target Parameters Inversion for Distributed Shipborne High Frequency Hybrid Sky-Surface Wave Radar

“…There have been similar studies to increase the resolution through spectral synthesis for spaceborne and airborne distributed SAR systems operating in the microwave band. Among these works, the images acquired with slightly different viewing angles are coherently combined to increase the range bandwidth based on the spectral shift principle, and thus, the range resolution of a distributed SAR is improved [28][29][30][31][32][33][34][35]. This paper draws on the core idea of range resolution improvement algorithms of spaceborne and airborne SAR images and focuses on improving the azimuth resolution of the distributed shipborne HFHSSWR system by spectral synthesis.…”

Inverse second‐order polynomial time–frequency transform‐based detection of moving targets in the stepped‐frequency radars

“…This technique is still utilised [11] and its applications are not limited to GPR. Phased array radars with active beam forming [12], synthetic aperture radars (SARs) and inverse SAR [13,14] are some of the applications of this waveform.…”