A Transformer-Based Reconfigurable Dual <italic>LC</italic>-Ring Structure for Multiband Programmable Frequency Generation

Abstract

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\times $ and $4\times $ 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.