Analog phase‐locked loop‐based multistage interference cancellation in passive radar systems

Abstract Passive radar systems are highly sensitive to direct signal interference (DSI) that can obscure weak target echoes and considerably degrade detection performance. Effective suppression of DSI before Doppler‐domain processing is essential for improving radar's dynamic range and extending its detection capability. This study proposes a novel interference attenuation technique based on a generalized phase‐locked loop (PLL) architecture for analog‐domain DSI mitigation. The proposed method provides independent control of the amplitude and phase of the reference and surveillance signal paths, enabling interference attenuation of up to 50 dB and substantially outperforming conventional analog cancellation methods. Comprehensive simulations and prototype‐circuit measurements validate the effectiveness of the proposed approach to substantially reduce interference, thereby improving target visibility and radar's dynamic range. The proposed architecture offers a simple, adaptive, and hardware‐efficient solution that reduces the computational burden of subsequent digital signal processing.