A wideband 240 GHz lens-integrated circularly polarized on-chip annular slot antenna for a FMCW radar transceiver module in SiGe technology

This paper reports on the design of a broadband lens-integrated differentially-driven circularly polarized annular slot on-chip antenna for a 240 GHz homodyne monostatic FMCW transceiver in a SiGe HBT technology. A complete antenna layout consists of the main radiating annular slot fed by a wideband differential quadrature coupler. The slot is excited by 2 pairs of orthogonal sectorial patch probes located 90° apart along the slot circumference, whereby the mutual coupling between them is exploited to extend the antenna operation bandwidth. The circularly-polarized antenna was simulated to provide an input match superior to -25 dB for 180-310 GHz with consistent radiation patterns. The antenna allows a frequency-unlimited high-efficiency operation of the FMCW transceiver module with a Tx/Rx isolation below -22 dB for 180-310 GHz, a peak radiated power of 4 dBm and in excess of -10 dBm for 214-268 GHz.