The design of wideband leakage canceller for FMCW radars

The Frequency Modulated Continuous Wave (FMCW) radar is widely applied in various fields such as military, transportation, and aviation. However, in an FMCW radar system that uses a single antenna for both transmission and reception, leakage signals from the transmitter can enter the receiver due to the imperfect isolation of the circulator and the impedance mismatch of the antenna. This issue can degrade system performance, distort the reflected signal from the target, and affect the detection capability of small targets in the close range. This paper proposes an effective wideband leakage cancellation method utilizing an RF-domain canceller structure combined with a discrete phase control mechanism for narrow sub-bands. The system is designed to automatically adjust the phase shift to effectively cancel the leakage signal across the entire frequency band. Simulation results on ADS Keysight software demonstrate that the proposed leakage canceller achieves over 40 dB cancellation within a 500 MHz bandwidth, which is 4.5 times higher than the conventional method.