Isolation Enhancement in Series-Fed Antenna Array With Decoupled Branch for Automotive Radars

In this paper, a new decoupled branch for decoupling between microstrip antenna arrays of an automotive millimeter-wave radar is proposed. The decoupled branch is made up of a group of U-shaped strips. Due to the decoupled branch, additional coupling is generated between the microstrip arrays to cancel part of the original coupling. Thus, the isolation between can be improved. It is shown that the isolation of the arrays is improved by 10 to 15 dB over the band of 76-78 GHz with little effect on the impedance matching of the arrays. Besides, the decoupled branch also slightly expands the beamwidth to help improve the coverage in a horizontal plane.