A 2.9–8.4-GHz Reconfigurable 90° Coupler With Compact Size in 0.13-μm SiGe BiCMOS

This article proposes a reconfigurable 90° coupler with an ultrawide bandwidth (97%) and an ultracompact chip size. To provide a cost-effective solution that simultaneously achieves broadband high performance and on-chip integration, this design incorporates a 3-bit switch array into a spiral 90° stacked coupler. Fabricated using 0.13-
$\mu \text{m}$
SiGe BiCMOS technology, the proposed coupler demonstrates measured amplitude and phase errors within ±1 dB and ±10° over the 2.9–8.4-GHz reconfigurable frequency band while occupying only a core size of 0.16 mm2. The return loss at all the ports in the band of interest exceeds 13 dB, and the isolation exceeds 19 dB. This coupler offers a practical solution for integrating high-performance 90° couplers into the intermediate frequency (IF) section of broadband/multiband millimeter-wave (mmWave) transceivers.