Tri-band bandpass filter using dual-mode resonators

Abstract

This letter presents a compact tri-band bandpass filter (BPF) with controllable bandwidths. The proposed filter employs dual-mode resonators, i.e., crossed open-short stub loaded resonators and tri-section stepped impedance resonators. The center frequencies and bandwidths of the three passbands can be conveniently controlled by tuning the dimensions of two resonators. Moreover, on each side of each passband, there is at least one transmission zero, resulting in high skirt selectivity. To validate the design and analysis, a prototype of tri-band BPF is fabricated. Good agreement can be found between the measured and simulated results. Index Terms-Tri-band bandpass filter, Crossed open-short stub loaded resonators, Stepped impedance resonators.

Design of microstrip tri-band bandpass filter using square ring loaded resonator

“…To reduce the overall size, embedded resonator was explored and developed. [3,4] Short-ended SIR, [5][6][7][8] can also be used to construct tri-band operation and more compact BPFs have been reported. [7,8] Other method, such as nested dual-mode defected ground structure resonators (DDGSRs) [9] and ring resonator, [10] are also developed for tri-band design.…”

“…Stepped impedance resonators (SIRs) are usually used to construct tri-band BPFs due to their controllable multiband behaviours. [1][2][3][4][5][6][7][8] Generally, at least two resonators are utilized to form a tri-band response, [1,2] thus leading to a large circuit size. To reduce the overall size, embedded resonator was explored and developed.…”

Novel Tri-Band Bandpass Filter With High Selectivity

“…Many design approaches have been published. They are divided into several categories: (1) tri-section stepped-impedance resonators (TSSIRs) [1][2][3], whose the centre frequencies of triple passbands depend on the impedance ratios when electric length (θ i ) of each section is equal, (2) stub loaded resonators (SLR), including single or multistub loaded resonators [4][5][6][7] and square ring loaded resonator (SRLR) [8], because stubs are used to control the passband and open stubs independently to produce transmission zeros, (3) transmission zeros to construct triple passbands or split a single passband to tri-band [9][10][11], (4) three single-band sub-filters with matching junctions [12], (5) combination of dual-mode resonator and half-wavelength resonator [13,14], (6) multilayer substrate technique, such as LTCC [15], (7) special structures, such as Hilbert-fork resonators [16]. However, it is difficult for many structures to tune centre frequencies, and the isolation between adjacent passbands needs to be improved.…”