77-GHz Active Quasi-Circulator based Monostatic Radar with LO Feed-Through Functionality

A modified QC based transceiver system is presented with focus on the enhancement of system efficiency. In common TX/RX separation units for W-band automotive radars, half of the transmit power is terminated due to the structure. We present a solution, which reuses this terminated power as LO signal for the down-conversion. Thus, a separate LO path for the down-conversion mixer can be omitted, which shrinks the foot print of the system and improves the overall system efficiency. In the previous design, half of the transmit power is terminated in a W-band impedance tuner, which acts as TX/RX leakage canceler. This impedance tuner is modified on circuit level to migrate the LO feed-through functionality. Based on on-wafer measurements, it can be shown, that the proposed modification doesn't degrade the performance of the QC according TX/RX isolation and noise figure as well as the overall radar system performance.