Microstrip Dual-Mode Bandpass Filter with Ultra-Broad Stopband Using Aperture-Backed Stepped-Impedance Ring Resonator

Hang WANG  Lei ZHU  

IEICE TRANSACTIONS on Electronics   Vol.E88-C   No.11   pp.2166-2168
Publication Date: 2005/11/01
Online ISSN: 
DOI: 10.1093/ietele/e88-c.11.2166
Print ISSN: 0916-8516
Type of Manuscript: LETTER
Category: Microwaves, Millimeter-Waves
stepped impedance resonator,  dual-mode bandpass filter,  backside aperture,  ultra-broad stopband,  

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A novel microstrip dual-mode bandpass filter with ultra-broad stopband is proposed using the aperture-backed stepped-impedance ring resonator (SIRR). This SIRR consists of low-impedance strips in the four bended corners and high-impedance strips in the four straight sides. With the cross-shaped aperture placed on the ground underneath the SIRR, the upper stopband is significantly broadened. In particular, the 2nd resonant frequency of this proposed SIRR is confirmed to exceed the four times of its 1st counterpart. The dual-mode filter with the passband of 7.5% at 1.59 GHz is then designed and implemented, demonstrating the measured stopband of 1.70-5.80 GHz and size reduction of 56.0%.