Compact Dual-band Bandstop Filter Research Articles

A novel compact dual-band bandstop filter with enhanced rejection bands

A novel compact dual-band bandstop filter with enhanced rejection bands

Compact dual-band bandstop filter based on coupled open-ended Hilbert resonators

ABSTRACTIn this paper, the design procedure of a compact dual-band bandstop filter (DBBSF) based on coupled open-ended Hilbert lines is proposed. The proposed filter topology consists of two pairs of coupled open-ended lines bended in the shape of the Hilbert fractal curves and a stepped-impedance line section (SIS). In that manner, tree transmission paths are crated allowing the independent control of filter characteristic in both bands. To obtain appropriate coupling between resonators, and the independent control of the center frequencies and in-band characteristics of the filter, the SIS is introduced as matching section. Design rules are derived using lossless transmission line model and even/odd analysis. To validate the design concept, two compact DBBSFs have been designed, fabricated, and measured. The proposed filters exhibit excellent in-band characteristics, high selectivity, and small dimensions.

Compact dual-band bandstop filter using folded resonator

A compact dual-band bandstop filter composed of main transmission line and four folded resonators is presented. Through analyzing the structure of folded resonator, it is found that the main transmission line connected with two proposed folded resonators exhibits the characteristic of band-rejection. Simulated results show that the center frequency of stopband is 2.72 GHz. Then, through adding another pair of folded resonator; a compact dual-band bandstop filter is achieved. Simulated results demonstrate that transmission poles are induced to have better selectivity. Additionally, in order to explain the mechanism of proposed structure, the LC equivalent circuit, analysis of parametric effect and surface current distributions are given. Due to the folded structure, the filter dimensions are reduced and the adjustable stopband is another feature. By virtue of optimization, proposed structure is fabricated. Measured results agree well with the simulation.

A compact dual-band bandstop filter having one spurline and two embedded open stubs

A compact dual-band microstrip bandstop filter (BSF) is presented. It combines a conventional open-stub BSF, a spurline, and two embedded open stubs. This BSF is simulated and fabricated. It generates two stopbands around 2.0GHz and 3.0GHz without increasing circuit size, compared with the conventional BSF.

Sharp-rejection dual-band bandstop filter based on signal interaction with three paths

A sharp-rejection dual-band bandstop filter using transversal signal-interaction with three paths, consisting of a transmission line path and two coupled paths, is proposed. By tuning the coupling coefficient and odd-mode impedance of the coupled lines, the center frequency ratio and bandwidth can be controlled, respectively, and the transmission line impedance is used to allocate the transmission poles to sharp the attenuation rate. A compact dual-band bandstop filter prototype is designed and fabricated. The simulation and measurement results agree well. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:657–660, 2015

New compact dual-band bandstop filter

This article introduces a compact single pole dual-band bandstop filter using capacitors loaded open rectangular DGS slot. A parametric study is reported to pull down lower and upper frequency bands of the unloaded DGS slot in the range of needed stopbands with the help of the loading capacitors. A systematic design process is reported to design a dual-band bandstop filter to suppress 2.4 GHz and 5.2 bands, with bandwidths 0.15/0.25 GHz, by 36 dB and 25 dB respectively. The passband between the two stop-bands has 0.2 dB insertion loss. A circuit model of dual-band bandstop filter is also presented.

Microwave dual-band bandstop filter with improved spurious resonance behavior

A design technique to improve the spurious resonance behavior of dual-band bandstop filters is presented. A compact dual-band bandstop filter with two stop bands that can be controlled independently with improved passband frequency response is designed. The operational bandwidth of the proposed compact dual-band bandstop filter is increased by pushing the first spurious resonance from being about twice the resonance frequency to more than three times the resonance frequency. Stepped impedance open loop resonators with substantially increased outer-edge width are used to improve the spurious resonance response. Both simulation and measured results are presented and good agreement is obtained between the results. The fabricated filter exhibits dual operating frequencies at 1460 MHz and 2640 MHz with 5.5% and 5% stopband fractional bandwidths, respectively. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 23: 627–633, 2013.

A compact dual-band band-stop filter with high performance and controllable response

A fourth-order dual-band microstrip band-stop filter is proposed in this paper. Folded stepped impedance resonators are implemented as well as capacitive gap and inductive grounded via, thus the dual-band performance can be obtained in merely one resonator. Besides its compact size, simplicity, and good spurious band suppression, the filter also features its excellent mid-band rejection and skirt characteristic which is achieved by four reflection zeros adjacent to the dual resonating frequencies. Controllable response of filter is realized by tuning of gap capacity and via inductance, and the theory is verified by both simulation and experimental results that agree well with each other.

A compact dual-band bandstop filter with defected microstrip slot

To investigate a compact dual-band bandstop filter (DBBSF), a defected microstrip structure is proposed in this paper. The filter is composed of a spur-line structure and a rectangle slot. Resonant frequencies and the bandwidths of the filter can be adjusted by changing the length of the slot. The frequencies of designed DBBSF are operated at 2.12 and 2.9 GHz. A fabricated sample has been tested to verify our design. Measured and simulated results are in good agreement. The proposed filter is much more efficient than other similar structures.

Compact dual-band open-stub bandstop filter with suppression of spurious passbands

In this article, by replacing the series quarter-wavelength connecting line of conventional open-stub bandstop filter (BSF) with the equivalent P-shaped line, a compact dual-band BSF is proposed and designed. Furthermore, it suppresses a lot of spurious passbands of the open-stub BSF. Design equations of P-shaped line are achieved by ABCD matrixes. To validate the design concept, two full-wave electromagnetic simulators are used and the proposed filter is fabricated. The simulate results are in excellent agreement with measurement results. The circuit area of the dual-band BSF is only 50% of the conventional open-stub BSF.

Microstrip dual-band bandstop filter of defected ground structure and stepped impedance resonators

This article presents a compact microstrip dual-band bandstop filter (BSF), in which one λg/4 defected ground structure (DGS) pair is utilised to realise one stopband while two stepped impedance resonators (SIRs) help obtain another stopband and suppress the spurious harmonics. The design strategies and the equivalent circuits are introduced in detail. The measured results indicate 43.8% and 18.7% fractional bandwidth in the two stopbands (2.4 GHZ and 5.2 GHz) respectively, and the return loss is greater than 15 dB in the whole passband. In addition, size reduction can be conveniently achieved by adjusting the length of the SIRs and DGS.

Compact Dual-Band Bandstop Filters Using Stepped-Impedance Resonators

This work presents a compact dual-band bandstop filter (DBBSF) that features two controllable stopbands at desired frequencies. Stepped-impedance resonators are utilized to realize the dual-stopband characteristics, and reduce size. The synthesis method is developed. An experimental circuit is fabricated and evaluated to validate the design concept. Measurements correlate well with the simulation results, and the size is 12.6% less than that of a standard DBBSF.