A 240 GHz circular polarized FMCW radar based on a SiGe transceiver with a lens-integrated on-chip antenna

A 240 GHz monostatic circular polarized SiGe FMCW radar system based on a transceiver chip with a single on-chip antenna is presented. The radar transceiver front-end is implemented in a low-cost 0.13-μm SiGe HBT technology version with cutoff frequencies f_T/f_max of 300/450 GHz. The transmit block comprises a wideband x16 frequency multiplier chain, a 3-stage PA, while the receive block consists of an LNA, a fundamental quadrature down-conversion mixer, and a 3-stage PA to drive the mixer. A differential branch line coupler, and a differential dual polarized on-chip antenna complete the transceiver architecture. All building blocks are implemented fully differential. The use of a single antenna in the circular polarized radar transceiver leads to compact size and high sensitivity. The measured peak radiated power from the Si-lens equipped radar module is +3 dBm (EIRP) at 236 GHz. The operational bandwidth of the radar transceiver is 60 GHz around the center frequency of 240 GHz. After system calibration a range resolution of 3.65 mm is achieved, which is only 21% above the theoretical limit.