A micromachined wide-band suspended-line coupler at 24GHz for vehicle radar applications

Directional couplers have extensive applications in microwave circuits such as beamforming networks. Recently there has been growing scientific and commercial interest in microwave components for anti-crash and pre-crash systems in cars centered at 24 GHz. In this paper a novel suspended transmission-line 3 dB coupler at 24 GHz is presented. This circuit has been micromachined on a glass-quartz substrate and BCB layers have been used to suspend the transmission lines of the coupler. In this paper simulated and experimental results are presented and the fabrication method described.