Design of Wide Stopband Narrow-Band BPFs Exhibiting Harmonic Suppression

Abstract

This paper presents narrow-band bandpass filters with wide stopband for WLAN and WiMAX systems. First, open-stub and T-shaped resonators were used to design a filter (F1) with the center frequency 2.4 GHz. In order to examine the architectures of the proposed resonators, their frequency responses were compared to the response of an LC model. Next, Defected Ground Structure (DGS) was utilized to achieve a wide stopband within the frequency response of F1. Then, the structure of F1 (without using DGS) only with some changes in the dimensions of the resonators was employed to design the narrow-band filters F2 and F3 with the center frequencies 3.7 GHz and 5.1 GHz, respectively. Advantages of these filters include simplicity, architectural symmetry, tenability for applications at other frequency, and proper bandwidth. The filters also provide optimal return loss and insertion loss.