Novel quad‐band filter with high frequency ratio and controllable bandwidths using SLHSIRs and SLQSIRs

Abstract

applied to replace each single-band section of the conventional branch-line coupler. The proposed multiband transmission line consists of Pi-type line with open-and short-ended stubs. The Pi-type line supports the dual-band operation at first two working frequencies, while the open-and short-ended stubs are tapped at the center of the Pi-type line to realize the operation at the third working frequency. To prove the design concept, a multiband branch-line coupler operating at 1/2.5/4.5GHz is designed and tested. Both the simulated and measured results have verified the design theory.

A compact quad‐band bandpass filter with separate signal paths

“…The resonance of the DRA is combined with that of the feeding structure, making the required frequency band covered. Wideband DRAs taking advantage of this kind of hybrid structures have been reported in designs [3][4][5][6].…”

“…(3) Using water as DR, flexible feeding structures (such as folded feeding probe in this article) can be easily tuned and experimented inside the water that is difficult for conventional ceramic dielectric materials [7,8]. (4) Due to the transparency of water, the proposed water antenna is almost optically transparent. The detailed dimensions are presented, and good results are obtained.…”

“…However, when compared with dual-band filters, there are relative little public reports about quad-band filters in literatures. In references [1][2][3][4], two dual-band filters with different center frequencies are combined in parallel with common input/ output ports to form quad-band filter. Two electric-coupling quad-mode resonators are used to realize the quad-band filter [5][6][7].…”

A Very Compact Quintuple Band Bandpass Filter Using Multimode Stub Loaded Resonator

“…Assembled resonators technique is used to implement quad-band bandpass filter in [19], and quad mode stub loaded resonator is utilized to get quad-band bandpass filter in [20], but the presented designs have complex structures with large circuit size and narrow passbands. Another novel technique using stub loaded half wave SIRs and stub loaded quarter wave SIRs is employed to get the quad-band spectrum in [21]. The main purpose of the technique was to control the bandwidths.…”

A miniature hext‐band bandpass microstrip filter using stepped‐impedance spiral resonators

“…These MBPFs should be characterized by compactness, low‐cost fabrication process, suppressed spurious responses, low insertion loss in sub‐bands, high selectivity, less complexity in designs, and having a sufficient number of sub‐bands specified for various wireless standards. In the literature, intensive research efforts by the scientific community have focused, to achieve numerous design and analysis techniques, to realize MBPFs, having aforementioned characteristics, including dual‐, triple‐, and quad‐bands . However, comparatively, a limited research work has been conducted to date to achieve quint‐ and hext‐band filters and beyond.…”