Reflective-Type Phase Shifter Design with a Patch Antenna for a 250 GHz On-Chip Beamforming System

Abstract

This paper introduces a reflective-type phase shifter (RTPS) and a defected ground patch antenna design for configuring a 4-bit 250 GHz on-chip beamforming system using a SiGe HBT device. The patch antenna is designed to operate at 250 GHz, with a defected ground structure implemented to address the issue of narrow bandwidth. Four ground slots, each sized 50 x 121  m2, are fabricated, and measurement results show that the patch antenna operates within the 240-257 GHz band. The RTPS is designed using a 90o hybrid coupler and variable loads using varactors. The 90o hybrid coupler is made compact by overlapping two adjacent 50- quarter-wavelength lines and forming a slot on the ground plane. The varactor is based on a diode-connected SiGe HBT device, and its size is selected as the largest available 7.2 mm in length to maximize the capacitance variation with the bias input. Two RTPS unit cells are connected in series to achieve a 360o phase shift, and the measurement results demonstrate a 4-bit phase shift.