Wideband Leakage Cancellation Network for Monostatic Continuous-Wave Radars

For a monostatic stepped-frequency continuous-wave (SFCW) radar operating from 2 GHz to 4 GHz, a wideband passive leakage cancellation network using two circulators and a wideband 180-degree power combiner has been developed. Two similar circulators are utilized to provide two identical leakage signals and then leakage is canceled when both leakage signals are combined by a 180-degree power combiner. The wideband 180-degree power combiner has been implemented using parallel-strip lines. This proposed leakage canceller provides more than 33 dB cancellation over 2 GHz bandwidth, has 27.7 dB cancellation depth, does not require exhaustive adjustments, and is suitable for monostatic radar operation. The successful realtime monitoring of the subject using this monostatic radar indicates that the proposed leakage canceller can be utilized in a monostatic CW radar with a wideband antenna.