A novel planar tri-band bandpass filter using stub-loaded resonators

Abstract

This letter presents a novel planar tri-band bandpass filter (BPF) using a set of stepped-impedance resonators (SIRs) and a short-circuited stub-loaded uniform impedance resonator. The former is designed to operate at the first and third passbands and the latter at the second passband. Corresponding equivalent circuit is analyzed by using the even-odd mode theory. Skirt selectivity is obtained due to source-load coupling. For validation, a tri-band BPF with compact size is designed, fabricated, and measured, its center frequencies are located at 2.4, 3.5, 5.15 GHz. Measured results show good performance on insertion loss and return loss.

Design of Wideband/Dual-Wideband/Tri-Band BPF Based on a Penta-Mode Resonator

“…Up to now, a variety of topology structures and design methods have been studied. In [1][2][3][4][5], wideband BPFs are proposed, and dual-band BPFs are presented in [6][7][8], Moreover, in [9][10][11][12][13], tri-band BPFs are studied. Although these filters exhibit their merits, they also suffer from many drawbacks.…”

“…For example, the BPFs in [2,3,9] are not planar implementation, i.e., defected ground structure is employed in [2], while multilayer structure is utilized in [3] and [9], which makes the fabrication procedure more complex. Two or more resonators are utilized in the multiband BPFs proposed in [6,8,12,13], which leads to large circuit size. Besides, to the authors' knowledge, very few works about the resonating structure which can be utilized for both wideband and multiband BPFs are reported.…”

Design of triple-band bandpass filter using quad-mode stepped impedance resonator (SIR) with shorted stub

“…But, these design suffer from big circuit size. Stub-loaded resonators (SLR) [3,4], multi-mode stepped-impedance resonator (SIRs) [5,6] and stub-loaded SIRs [7,8] were proposed to realize the triple-band responses. Nevertheless, the bandwidth of each passband for these structures are difficult to be controlled independently.…”