Small Dual Narrowband BPF with Ultra-Rejection Band Using Grounded Stepped-Impedance Resonator

Abstract

A simple technique, to design a dual narrowband bandpass filter with wide stopband performance, is introduced in this article based on a grounded stepped-impedance resonator (GSIR). The GSIR is a multi-behavior resonator. Following the even–odd analysis, the proposed GSIR is first analyzed to generate the specified center frequencies of the proposed passbands. Next, two ring-shaped stubs are electrically coupled to the low impedance part of the GSIR, using coupling space (s) and direct connection to the input/output ports to determine the filtering response. Finally, an experimental filter for 2.4 GHz wireless local area network and 3.5 GHz worldwide interoperability for microwave access (WiMAX) applications is constructed. The filtering characteristic performances of the simulation and measurement results are compared and discussed. Consequently, two narrow bandwidths, 40 MHZ at 2.4 GHz and 60 MHz at 3.5 GHz, are generated with ultra-high frequency suppression above 20 GHz. The surface area of the designed filter is about 56 mm2 terminating the feeding ports.