Ultra‐High Isolation Decoupling and Matching Network for mmWave Antennas in Near‐Range FMCW Radars

ABSTRACT A decoupling and matching network (DMN) based on substrate integrated coaxial line technique is proposed to suppress the mutual coupling between a pair of transmitting and receiving antennas operating at 35 GHz. The distorted radiation patterns, typically observed in closely spaced antennas, were improved by introducing carefully designed coupled transformers between antenna feedlines and DMN. The resultant two antennas in the transmitter and receiver produced overlapped patterns to meet radar detection requirements. In this work, a pair of 35 GHz patch antennas with an edge‐to‐edge gap of mere 0.2 mm was prototyped. The measured 30 dB isolation bandwidth reaches 160 MHz, allowing detection of a target with a weak radar cross section of −14 dBsm at a range of 2 m. The achieved pattern beam shifts by from the boresight, with a beamwidth overlap of .