Novel Bandwidth-Agile Bandpass Filter using Defected Ground Structure

Abstract

A novel microstrip bandpass filter (BPF) with tunable passband width using defected ground structure (DGS) is proposed. In this DGS, a pair of slotted radial stubs that can be equivalent to a capacitor and an inductor in parallel are incorporated to realize an attenuation pole (AP) in the higher stopband of the proposed BPF without increasing the circuit size, and the equivalent circuit of the BPF is also given. By properly adding varactor diodes into the slotted stubs to tune the equivalent capacitance of the stubs, the corresponding AP can be shifted, and then the passband width of the BPF can be accordingly tuned, leading to a bandwidth-agile BPF.