A Fully Differential Ultra-Compact and High Isolation Transformer-Based Wilkinson Power Divider

An ultra-compact transformer-based differential power divider with low insertion loss and high isolation is presented in this paper. To achieve the impedance transforming and power combining, two differential transformers are connected in parallel in the proposed Wilkinson power divider. Shunt capacitors are added between the output ports for matching and isolation enhancement. Designed in 40nm CMOS technology, the proposed power divider occupies a core chip area of 396um×156um. Post-layout simulation results show that the power divider achieves an insertion loss (S21) of 1.37dB, an input return loss (S11) of 14dB, an output return loss (S22) of 21dB and a port-to-port isolation of 32dB at 28.5GHz.