A Fully Differential Hybrid Coupler for Automotive Radar Applications

In this paper, a fully differential hybrid coupler manufactured in a 130 nm SiGe technology is proposed. The designed coupler offers a phase error below 3o and an amplitude imbalance below 2 dB in the bandwidth of interest between 70 GHz and 90 GHz. Furthermore, a method to characterize the proposed coupler with a four-port vector network analyzer is presented. In addition, a transmitter circuit containing a quadrature modulator using the proposed coupler has been designed. Thereby an image suppression ratio of more than 30 dB has been achieved.