The Latest Development of Tunable Microwave Filters

Abstract

There have been many types of filters for various communication implications such as surface acoustic wave (SAW) filters, bulk wave (BAW) filters, transmission line filters, cavity filters, substrate integrated waveguide (SIW) filters, etc. As the radio frequency (RF) front end continues to develop, bandpass filters (BPFs) with excellent frequency response and tunability are becoming more and more competitive. In this chapter, three different types are reported, including On-chip-based TBPF, microstrip-based TBPF, and SIW-based TBPF, and some of them are theoretically analyzed carefully. Filters with frequency tuning, bandwidth tuning, and transmission zeros tuning are shown comprehensively. In addition, the limitations and future trends of tunable microwave filters are objectively expounded.