An N-way transformer based Wilkinson power divider in CMOS

This paper presents a transformer based N-way Wilkinson power divider. The λ/4 transmission lines in a conventional N-way Wilkinson divider are replaced by a fully symmetric N-coil transformer. The proposed design features low insertion loss as well as good input/output matching in an ultracompact chip area. By adding cancellation capacitors, excellent isolation is achieved between any two output ports. Through evenodd mode analysis, the closed-form design equations are derived and presented. As a proof-of-concept demonstration, a four-way transformer based Wilkinson power divider is implemented at 4.60GHz in a standard 130nm bulk CMOS process. The measurement results demonstrate 1.10dB insertion loss, <−15.0dB input/output matching, >17.0dB isolation, and 20.9% bandwidth, advancing the state-of-the-art performance of fully integrated Wilkinson power dividers.