A Fully Differential Ultra-Compact Broadband Transformer-Based Wilkinson Power Divider

This letter presents a fully differential and integrated transformer-based Wilkinson power divider with a broad bandwidth, low loss, high isolation, and an ultra-compact form factor. Two differential transformers connected in parallel serve as the impedance transforming and power combining network in the proposed Wilkinson power divider. Shunt capacitors are added between the output ports for matching and isolation enhancement. A proof-of-concept transformer-based Wilkinson power divider is designed at 60 GHz and implemented in a standard 130 nm SiGe BiCMOS process with the core chip area of 270 μm × 107 μm and the simulated 1 dB-magnitude fractional bandwidth of 64% at the 60 GHz center frequency. Measurement results of 4 independent samples demonstrate the passive loss of 1.32 dB at 62 GHz with standard deviation of 0.1 dB and the peak isolation of 28 dB at 65 GHz with magnitude and phase imbalance within 0.2 dB and 5°, respectively.