Airborne synthetic aperture radar (SAR) is vulnerable to continuous wave (CW) interference in complex electromagnetic environments, leading to significant degradation in imaging quality. Its susceptibility to front-door coupling electromagnetic effects is a critical concern.

This study aims to systematically investigate the impact patterns and physical mechanisms of single-frequency CW interference on airborne SAR imaging through equivalent injection experiments. It further seeks to establish a robust evaluation method for interference effects.

Equivalent injection testing was employed to simulate CW interference susceptibility. The interference effect was evaluated using a composite SAR image quality factor integrating the Pearson correlation coefficient (PCC), Structural Similarity Index (SSIM), and Peak Signal-to-Noise Ratio (PSNR). Detailed analysis of the radio frequency (RF) front-end response and Analog-to-Digital Converter (ADC) behavior under interference was conducted.

Significant interference effects were observed when the interfering frequency fell within the receiver's hardware passband (8.5−9.5 GHz) and the jammer-to-signal ratio (JSR) reached 15 dB. While the RF front-end exhibited no significant nonlinearity, the interference induced a nonlinear response specifically within the internal Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) of the ADC sampling chip. This nonlinearity generated additional DC components and harmonics, identified as the fundamental physical cause of characteristic interference stripes and overall SAR image quality degradation.

The generation of DC offsets and harmonic distortion within the ADC’s MOSFET circuitry is the root physical mechanism behind SAR image degradation under CW interference within the specified band and JSR threshold. This research provides a solid theoretical foundation for designing electromagnetic interference (EMI) countermeasures in airborne SAR systems, thereby enhancing their robustness and imaging capability in challenging complex electromagnetic environments.