Research on the impact of transceiver isolation of GB-SAR on imaging quality

Ground-Based Synthetic Aperture Radar (GB-SAR) systems frequently suffer from insufficient transceiver isolation due to their compact architecture. This insufficiency leads to transmitted signal leakage into the receiving channel, generating third-order intermodulation distortion (IM3). Consequently, the imaging signal to noise ratio (SNR) is degraded and artifacts in the range direction are introduced. Utilizing an independently developed Ku-band GB-SAR system termed S-SAR M, this study explores the influence mechanism of transceiver isolation on imaging quality through dynamic adjustment of antenna spatial parameters. It identifies a system-specific critical isolation threshold and an optimal design range, thereby offering a theoretical basis and practical guidelines for hardware optimization of GB-SAR systems. The isolation model is quantitatively calibrated against the measured horn radiation pattern and antenna geometry with a root-mean-square error of 1.8 dB, and the critical threshold is derived analytically from receiver nonlinearity parameters through the third-order input intercept point (IIP3). The results indicate that antenna angle is the dominant factor for isolation improvement, with an average enhancement of 56.3 percent achieved as the angle increases from 0 to 60 degrees. Antenna separation exhibits a synergistic effect on isolation at larger angles. A critical isolation threshold of 74 dB is established to suppress range artifacts induced by IM3 in the S-SAR M system; below this threshold, artifacts consistently occur. Moreover, a tri-segmented nonlinear relationship between isolation and SNR is observed, with an optimal balance region located between 74 dB and 80 dB where the peak SNR is maintained. One-way analysis of variance delivers a result with p less than 0.001 and confirms the significance of these trends. A quantitative artifact-to-background energy ratio further corroborates the visual artifact classification. These findings offer important insights for enhancing the performance of GB-SAR systems. It should be noted that the reported numerical thresholds are specific to the S-SAR M hardware configuration; a normalized isolation-margin framework is therefore provided to transfer the methodology, with platform-specific calibration, to GB-SAR systems using other frequency bands or receiver architectures.