Dual-mode double-ring resonators for microstrip band-pass-filter applications

A novel design of a dual-mode resonator with a double-ring structure for band-pass filter applications is presented in this paper. Conventionally, dual-mode ring resonators are used to obtain band-pass filters. Based on voltage/current couplings, a dual-mode double-ring resonator was recently constructed to improve the responses of the conventional dual-mode ring resonator. In order to obtain a low insertion loss, a wide band and higher rejection, three filters using a dual-mode double-ring resonator are designed for 2.4 GHz ISM band applications.