Compensation Method for a Wideband Signal’s Squint Problem of an AESA SAR System Using a Cross-Range-Variant Antenna Gain Equalizer

In order to obtain a high-resolution image, a wideband signal is required in a synthetic aperture radar (SAR). However, in an active electronically steered array (AESA) SAR, consideration of the beam squint problem is indispensable especially when a forward directed AESA operates in a squint spotlight SAR mode. In this paper, we present an accurate compensation method for the squint problem without added hardware, such as true time delays. To clarify the beam squint effect, an antenna gain radiated to point targets located on the ground was derived and we confirmed that the antenna gain for the targets placed on the same cross-range axis has similar tendency within 1.5-dB difference. Based on the results, we proposed a cross-range-variant antenna gain equalizer. Through test simulations, we confirmed that the suggested method effectively compensated for the degraded resolution performance of about 14% for the AESA SAR.