A Transformer-Based Reconfigurable Dual LC-Ring Structure for Multiband Programmable Frequency Generation

This letter presents a transformer-based dual LC-ring structure that enables both multiphase signal generation and dual-mode operation of a transformer's coupling polarity. An inner in-phase ring facilitates a dual-mode function to change mutual coupling polarity in transformers, and an outer multiphase ring implements programmable multiplications of 2× and 4× together with an N-push multiphase combiner. A prototype of the proposed frequency generator and multiplier was fully integrated in a 65-nm CMOS process, and experimentally verified to provide programmable multiplications, achieving wide frequency ranges of 26.1-37.4 GHz and 52-74.3 GHz.