A compact dual‐band bandpass filter with high design flexibility using fully isolated coupling paths

Abstract

A second‐order dual‐band bandpass filter using two outer folding open‐loop resonators and two embedded anchor‐shaped stepped impedance resonators is presented in this letter. The proposed scheme provides sufficient isolation between the two specific passbands, thus each passband can be individually turned. Electric couplings are adopted among the four resonators. By adjusting the spacing of resonators, the electric coupling of two different coupling feeding paths can be independently controlled, which allows flexible control of each bandwidth. The embedded structure which is introduced can further miniaturize the dimensions of the overall structure. In addition, the proposed filter has three transmission zeros at each passband, which exhibit high skirt selectivity. Good agreement between the simulated and measured results validates the correctness of the proposed design approach and shows that the two central frequencies of the fabricated filter are located at 2.5 and 5.1 GHz as desired, with 3 dB fractional bandwidths of 13.8 and 13.6%, respectively. The measured return losses are greater than 18.5 dB, while insertion losses are less than 0.9 dB in each of the two passbands. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:642–646, 2014

Very compact differential transformer-type bandpass filter with mixed coupled topology using integrated passive device technology

“…Several conventional technologies, such as printed circuit boards and low-temperature co-fired ceramic technology, cannot meet the requirements for this continuing trend [1,2]. Along with the advent of integrated passive device (IPD) technology, the above-mentioned issues were skillfully conquered, and IPD technology offered compatibility with active devices to make an essential system in both a package and a system on chip [3][4][5][6].…”

Dual‐/triple‐wideband microstrip bandpass filter using independent triple‐mode stub‐loaded resonator

“…Bandpass filters (BPFs) are indispensable components in the radio frequency front ends of both transmitters and receivers . With the fast development of novel wireless communication technology, multi‐band microstrip BPFs have become increasingly important for integrating more than one communication modes into a single system, where different frequency bands satisfy the requirement for different standards . Consider the triple‐band BPF as an example; by using half‐wavelength or quarter‐wavelength resonators, there are many different design topologies that have been introduced and reported for the design of a triple‐band BPF.…”

A novel miniature dual‐band bandpass filter based on the first and second resonances for 2.4/5.2 GHz WLAN application

“…In , Hsu used two capacitance loaded square loop resonators. In , Li used two outer folding open‐loop resonators and two embedded anchor‐shaped stepped‐impedance resonators (SIRs) to achieve a second‐order dual‐band bandpass filter. In , Yang used a modified coupling between two input/output microstrip lines and a pair of SIRs to realize a dual‐band bandpass filter.…”