An Ultra-Compact and Broadband C—X-Band Wilkinson Power Divider/Combiner Using a Folded Two-Section Mechanism in 65-nm Bulk CMOS Technology

This paper presents an ultra-compact and broadband $C-X$-band Wilkinson power divider/combiner comprised of two power combining 1:4 units, respectively for IF and LO frequency. To overcome the isolation bandwidth constraints, two sections of $\lambda / 4$ transmission lines are employed and innovatively realized within one inductor footprint by using a magnetic coupling self-canceling technique. A novel shielding topology is adopted to achieve IF/LO isolation enhancement and amplitude/phase uniformity simultaneously. The prototype is implemented with core sizes of $0.069 / 0.059 \text{mm}^{2}$ for IF/LO networks, respectively. Measurement results show insertion loss within 3.2/3.4 dB, isolation greater than $24.9 / 26.0 \text{dB}$ across IF ($6-10 \text{GHz}$)/LO ($8-12 \text{GHz}$) frequency range, and over 60-dB isolation between IF and LO crossover branches. To the best of our knowledge, this design achieves the most compact normalized core size, competitive fractional isolation bandwidth, and the highest branch isolation among the published works.