New wideband integrated miniature branchline coupler for beamforming applications

In this paper, we present a new wideband miniature branchline coupler as a key element to be integrated for 60 GHz beamforming networks in phased arrays. Theory and equations as well as a first proof-of-concept at 2.2 GHz are presented. A 25% matching bandwidth (−10 dB), ± 1 dB amplitude imbalance and ± 2° phase imbalance are measured with a reduced footprint. Then, the same coupler topology is optimized at 60 GHz in a BiCMOS9MW and IPD technology, both from ST Microelectronics. Its implementation on both technologies is discussed and compared to state-of-the art recently published couplers operating at 60 GHz.