  This paper proposes a novel solution to address the leakage from the
transmitter (TX) to the receiver (RX) in frequency-modulated continuous-wave
(FMCW) radars. The proposed scheme replicates the leakage using an in-phase and
quadrature mixer (IQ-mixer) and performs leakage cancellation in the
radio-frequency (RF) domain. This approach utilizes a Wilkinson power combiner
after the RX antenna to subtract the replicated leakage signal from the
received signal, ensuring that only the true target signal reaches the
low-noise amplifier (LNA). This scheme enhances the dynamic range and the
receiver's ability to discern proximate targets from previously
indistinguishable low beat-frequency clutter. In addition, the proposed
technique incorporates a second IQ-mixer based complex modulator in the
transmitter to tune the leakage beat frequency. This allows for accurate
estimation of the leakage amplitude and phase without additional hardware.
Simulation results show more than 20 dB of leakage cancellation.
