Triple-Band Composite Right/Left Handed Bandpass Filter Using a New Circular Inter-Digital Capacitor for Wireless Applications

Abstract

Abstract-In this paper, a compact triple-band bandpass filter based on composite right/left handed (CRLH) approach has been proposed. The zeroth order resonance (ZOR) frequency of the designed filter can be controlled effectively by varying the series parameters. A new circular interdigital capacitor is integrated to provide series capacitance. The number of passbands depends on number of rings of circular interdigital capacitor (C-IDC). In order to validate metamaterial behavior, a dispersion diagram has been plotted for the designed filter. The proposed filter offers measured 3 dB fractional bandwidth of 71% at 1.7 GHz, 24% at 2.9 GHz and 12% at 4.1 GHz as center frequencies. The designed filter will be suitable for different wireless applications such as global navigation satellite systems (1.559-1.610 GHz), GSM1800, indoor femtocells (2.5-2.7 GHz), air traffic surveillance (2.7-2.9 GHz) and fixed satellite services (3.8-4.2 GHz). The size of the proposed filter is 0.13λ 0 × 0.11λ 0 , where λ 0 is the free space wavelength at ZOR frequency of 1.7 GHz.

A centrosymmetric‐coupled tri‐band bandpass filter constituted by loaded bar and embedded S‐shaped resonator

“…LB introduces perturbation which causes the change of in‐band performances as well as the center frequencies of two passbands 20 . In this case, LBs connects center‐LBs (CLBs) and SRRs with the distance away from the port.…”

“…LB introduces perturbation which causes the change of inband performances as well as the center frequencies of two passbands. 20 In this case, LBs connects center-LBs (CLBs) and SRRs with the distance g 1 away from the port. Transmission paths of incentive signals from the input port to output port are perturbed hence leading to the location change of RMs in passband 2.…”

“…For coupling structures combined with perturbation, loaded stub, SIR, and other methodologies, such as metamaterial inspired or circular cross coupling constructions could also be adopted in multi‐band application design 16–20 . Response types can be switched through parallel or cascaded coupled lines for single‐band filter 21,22 .…”

“…For coupling structures combined with perturbation, loaded stub, SIR, and other methodologies, such as metamaterial inspired or circular cross coupling constructions could also be adopted in multi-band application design. [16][17][18][19][20] Response types can be switched through parallel or cascaded coupled lines for single-band filter. 21,22 With the meandered loop square resonator and internal coupling in SSR, the triple-band filter's central frequencies can be flexibly tuned.…”

Multi‐band bandpass filter based on direct‐connected T‐shaped stub‐loaded resonator

“…Bandpass filters (BPFs) have been extensively used in RF wireless systems. In recent years, with the rapid development of multi-band wireless communication systems, 1,2 increasing requirements for multi-band BPF [3][4][5][6][7][8] has attracted growing interests.…”