Quasistatic Resonators Based Triple-Mode Notched Microstrip Bandpass Filter

Abstract

This article discusses new approach for design and development of triple-mode notched microstrip bandpass filter based on quasistatic resonators (QR). The proposed approach is composed of two quasistatic resonant elements; Horizontal Plane Split Ring Resonator (HP-SRR), Vertical Plane Split Ring Resonator (VP-SRR) and a single Asymmetric Step Impedance Resonator (A-SIR)with parallel coupled feed structure. An additional attenuation pole realized by VP-SRR in desired passband tunes the dual-mode response to triple mode and enhances the 3dB bandwidth without changing the dimensions of basic the filter cell. The HP-SRR realizes a notch at WiMAX band (IEEE 802.11a lower band) in the desired passband. Further by changing the impedance of VP-SRR and HP-SRR both the location of additional attenuation pole frequency and notch band can be controlled. The proposed approach eliminates conventional method of realizing notch in the desired passband using vias and defective ground structures which have practical difficulties in realization and also the proposed approach results in compact notched wideband filter design.