CPW-Fed Dual-Mode Double-Square-Ring Resonators for Quad-Band Filters

We propose the improved CPW-fed configurations with dual-mode double-square-ring resonators (DMDSRR) for quad-band applications. The resonant frequency equations of DMDSRR are introduced for simply designing quad-band bandpass filter (BPF). Resonant frequencies can be controlled by tuning the perimeter ratio of the square rings. To obtain lower insertion loss, higher out-of-band rejection level and wider bandwidth of quad-band, the improved CPW-fed and dual-mode perturbations are designed. The proposed filter is successfully simulated and measured. It can be applied to 0.95, 1.26, 1.89 and 2.29 GHz systems.

I. Introduction

The increasing demand for multi-band applications has required a single wireless transceiver to support multi-band operations. The multi-band BPFs play an important role in a multi-band transceiver, such as dual-band [1], tri-band [2]–[10] and quad-band [11] filters.