DOUBLE-LAYERED QUAD-BAND BANDPASS FILTER FOR MULTI-BAND WIRELESS SYSTEMS

摘要

A compact double-layered quad-band (DLQB) bandpass filter (BPF) is presented to provide four passbands at the desired frequencies with efficient out-of-band suppression. The designed filter is verified by pattern implementation on two FR4 boards. The proposed DLQB-BPF consists of two L-shaped resonators on the first layer and two symmetrically-coupled stepped-impedance resonators (SIRs) on the second layer. The bottom of the second layer is ground plane. There are seven transmission zeros generated to perform quad-band characteristics at 1.57 GHz, 2.45 GHz, 3.6 GHz, and 5.8 GHz. An equivalent circuit model is constructed by analyzing the symmetry property of the proposed filter. A good agreement between the simulated and measured results is observed.