Design of an Ultra-Compact and Broadband C–X -Band Wilkinson Power Divider/Combiner in 65-nm CMOS Technology

This article presents an ultra-compact and broadband Wilkinson power divider/combiner (WPDC) designed for large-scale phased arrays. To minimize the chip area, a shortened transmission line (T-line) topology using a metal-stacked inductor is introduced into the two stages. Furthermore, to address the isolation bandwidth (BW) limitations, two sections of shortened T-lines are adopted and innovatively implemented within a single inductor footprint by utilizing a magnetic coupling self-canceling technique. Detailed analysis and design flow of the proposed network synthesis are provided, demonstrating a 67% area reduction. Moreover, a novel shielding topology is employed to simultaneously enhance isolation between combiners and ensure amplitude/phase uniformity across distribution branches. To verify the proposed technique, a C–X-band WPDC, consisting of two 1:4 power combining units dedicated to intermediate frequency (IF) and local oscillator (LO) bands, respectively, is fabricated in a 65-nm bulk CMOS process. The prototype exhibits a measured insertion loss (IL) of within 3.2/3.4 dB and isolation exceeding 24.9/26.0 dB across the IF (6–10 GHz)/LO (8–12GHz) band. Notably, isolation greater than 60 dB is attained between IF and LO crossover networks, which is validated in antenna-in-package (AiP) measurements. This design features an ultra-compact core area, a highly competitive fractional isolation BW, and an outstanding branch isolation among state-of-the-art reported works, rendering it well-suited for area-constrained large-scale and multibeam phased-array systems.