Wide-Tuning CMOS Reconfigurable Bandpass Filter for RF and Microwave Circuits

The rapid development of modern wireless communication systems operating across multiple standards and frequency bands has intensified the need for reconfigurable RF and microwave front-end components. Among these, bandpass filters are essential for spectrum selectivity, interference suppression, and maintaining system linearity. This chapter provides a detailed overview of reconfigurable bandpass filter design in CMOS and hybrid technologies, emphasizing tuning techniques and integration challenges. It examines both passive and active approaches, including MEMS-based filters, acoustic-wave devices, piezoelectric LTCC implementations, and active topologies such as G_m-C, N-path, Q-enhanced LC, and active-inductor-based filters. Their tuning mechanisms, design trade-offs, and performance characteristics are thoroughly analyzed. The discussion highlights the advantages of active inductor-based designs in achieving compact size, wide tuning range, and high integration density while also addressing remaining challenges in noise and linearity for next-generation RF front-ends.