Influence of Antenna Pattern on Synthetic Aperture Radar Resolution for NDE Applications
Chao Liu, Mohammad Tayeb Al Qaseer, Reza Zoughi
Abstract
The effect of antenna gain pattern on synthetic aperture radar (SAR) imaging is analyzed in this article. In prior investigations, only the effect of antenna half-power beamwidth (HPBW) on the resultant image spatial resolutions were described using approximations that are valid only at very large distances or at small distances with relatively wide HPBW. This article illustrates that this approximation is not valid in the near-field of the synthetic array when the antenna used is highly directive. In this article, the effect of the entire antenna (gain) pattern, instead of just assuming a constant pattern within the HPBW, on SAR image spatial resolutions (both range and cross-range) is demonstrated. Additionally, the effect of approximations which are necessary for implementing fast Fourier transform (FFT)-based algorithms (e.g., ω-k SAR algorithm) on the image resolutions are also studied. The concept of effective synthetic aperture length is introduced and corresponding empirical formulas are derived. Subsequently, this effective aperture length is used to calculate the image spatial resolutions. Finally, representative measurements were performed to verify the simulation results.