Title: Accurate Design of Higher-Performance Bandpass Filters Using Multi-Mode Dielectric Resonators for Wireless Communication Base Stations
Zhewang Ma
Saitama University, Saitama, Japan
In recent years, the rapid development of modern wireless communication technologies has imposed more severe requirements on the RF/microwave components and circuits. High-performance dielectric resonator (DR) bandpass filters (BPFs) have become essential components in many RF/microwave systems and have been receiving continuous attentions due to their many distinctive advantages like low loss, small size, light weight, and temperature-stable property.
There have been a large number of papers on DR BPFs. The initially reported BPFs using single-mode DRs are relatively simple in configuration and easy to design. Later, multi-mode DRs, like dual-mode and triple-mode DRs are preferred because they can further reduce both the size and weight of BPFs. However, due to the complicated field distributions in the multi-mode DRs, it is quite difficult to make it clear the mechanisms of inter-resonance couplings between DRs. Precise controls of the inter-resonance couplings, including their signs and strengths, are not accomplished, and the transmission zeros (TZs), which are needed for realizing compact and high-performance BPFs, could not be obtained at desired frequencies. Therefore, accurate design of BPFs using multi-mode DRs, particularly high-order DR BPFs, is still a challenging work.
This invited paper reviews our recent works on the accurate design of high-performance BPFs using multi-mode DRs for future applications in wireless communication base stations. It includes three parts. In Part I, a precise design method of high-order BPFs with complicated coupling topologies is developed, and an example design of an 11-pole TM010 DR BPF is provided. In Part II, novel combined coaxial and dual-mode DR BPFs are precisely designed with fully controllable TZs, and symmetrical or asymmetrical filter responses are realized with excellent satisfactions of design specifications. In Part III, a novel compact high-performance 11-pole BPF is developed by using two triple-mode DRs and five coaxial TEM-mode resonators. The designed 11-pole DR BPF provides the advantages of reduced size and weight, low-profile, high frequency selectivity, fully controllable bandwidth and TZs, and excellent spurious performance. All the design of the multi-mode DR BPFs meet the design specifications quite well, and are approved well by measured responses which agree excellently with their theoretical predictions.
