Improved Tx-to-Rx isolation with balanced radar front-end

This paper presents a balanced radar front-end MMIC to reduce Tx leakage at receiver. The radar front-end MMIC is composed of a differential cross-coupled oscillator, two differential amplifiers, two Lange couplers, and a Wilkinson combiner, which are implemented using low cost InGaP/GaAs HBT technology. The differential cross-coupled VCO shows the tuning range of 70 MHz from 22.767 GHz to 22.837 GHz. The peak output power is 0 dBm. The phase noise of VCO is -98.33 dBc/Hz at 1 MHz offset frequency. High Tx-to-Rx isolation of 50 dB is achieved in the balanced radar front-end. The additional cancellation due to balanced topology is expected to be 29.5 dB. The chip size is 2.25 x 1.75 mm(2).