Tri-section Stepped Impedance Resonators Research Articles

A Highly Compact Sext-band Bandpass Filter with Simple Structure and Wide Bandwidth

A highly compact sext-band bandpass filter (BPF) is investigated in this paper, which adopts quad-section stepped impedance resonators (SIRs) along with a series of multiple open stubs. This quad-section SIRs are constructed by tri-section SIR loaded L-shaped resonator. To achieve compact size, the filter utilizes tri-section SIR and is embedded in the double L-shaped resonators. Aseries of multiple open stubs are introduced to improve fractional bandwidth and the return loss. A sext-band BPF centering at 1.12, 2,12, 2,78, 5,59, 6.59 and 8.97 GHz has been designed and fabricated. This highly compact sext-band with wide bandwidth and simple structure is constructed on Rogers 4350 with a dielectric constant of 3.66 and a height of 0.508mm. The overall size of the fabricated filter is 0.15λ g × 0.16λ g . Good agreements are observed between the simulated and measured results.

Compact dual‐band bandpass filter with flexible passband frequencies and sharp skirt using cross coupling and mixed magnetic and electric coupling

This paper presents the design of a compact dual-band bandpass filter (DB-BPF) with flexible passband frequencies and sharp skirt. A pair of stub loaded stepped-impedance resonators (SL-SIRs) together with two different tri-section stepped-impedance resonators (TS-SIRs) constitute this DB-BPF. The low impedance sections of two SL-SIRs and one TS-SIR are realized by ring structure, on the one hand to acquire two independent resonant modes of SL-SIRs, and on the other hand to let the harmonic mode of TS-SIR be away from the upper passband. The cross coupling, the canceling effect of mixed electric and magnetic coupling (MEMC), and the virtual ground introduce the TZs, resulting in the sharp skirt property of proposed DB-BPF. Step-to-step design process is given to guide the DB-BPF design. As an example, a 0.9 / 1.8 GHz DB-BPF is designed and fabricated. The fabricated sharp skirts DB-BPF has a compact size of 0.079λg × 0.193λg, low passband loss of 0.84 / 0.98 dB and high band-to-band rejection of better than 40.6 dB.

Compact microstrip bandpass filter with sharp roll-off and broad stopband using modified 0° feed structure

A compact microstrip bandpass filter (BPF) with sharp roll-off skirt and broad stopband, consisting of the proposed modified 0° feed structure and the shorted stub-loaded tri-section stepped impedance resonator (SSLTSIR), is presented. The first two high-order parasitic resonant frequencies of the conventional 0° feed structure can be suppressed when a pair of open-circuited SIRs is loaded on its upper transmission path. Thus, the proposed modified 0° feed structure with broad stopband response is realized. Moreover, the theoretical analysis and numerical investigations are carried out. Furthermore, by embedding the SSLTSIR into the proposed modified 0° feed structure, a BPF with sharp roll-off skirt and broad upper stopband is achieved. A demonstrated BPF is fabricated and measured, and its measured results agree well with the simulated ones.

Compact UWB bandpass filter with dual-notch bands using asymmetric tri-section stepped impedance resonator

In this study, a novel high selective UWB band pass filter (BPF) with dual notch band is presented. UWB BPF is realized using stub-loaded multiple-mode resonator (MMR). The MMR is constructed by loading a quintuple mode open stub at the centre in an asymmetric tri-section stepped impedance resonator (ATSSIR). Five modes, including two odd modes and three even modes, placed within UWB band. Two transmission zeros generated by the fractal stub improve the passband selectivity greatly. Two half wavelength long fractal Hilbert resonators are embedded near I/O line to achieve notch bands at 5.1 and 5.9 GHz. Aperture-backed interdigital coupled-lines are implemented to improve the coupling. The proposed prototype is fabricated and tested. The measured insertion loss is observed to be within 1.5 dB over the passband. By virtue of two transmission zeros (TZs), on either side of the passband, at 5.1 and 5.9 GHz, respectively, the passband selectivity is achieved with measured roll-off factor at around 34 dB/octave. The out-of-band rejection of the filter is greater than 22 dB up to 18 GHz. The simulated results are in good agreement with the measured responses.

Tri‐section stepped‐impedance resonator filter with controllable mixed electric and magnetic cross‐coupling

A novel tri-section stepped-impedance resonator (SIR) filter with controllable mixed electric and magnetic cross coupling is proposed. Two quarter-wavelength shorted-end SIRs and one half-wavelength SIR are used to realise tri-section topology. The electric and magnetic couplings in mixed cross coupling can be controlled by the inter-digital capacitor structure and the gap between shorted lines, respectively. Then, additional transmission zeros can be obtained for better frequency selectivity and high rejected level in stopband. One filter sample is designed and fabricated with single-layer PCB. Good agreements are achieved between the measured and simulated S -parameters.

Triband High-Temperature Superconducting Bandpass Filters Using Multimode Resonators

In this paper, a simple multimode resonator (MMR) is proposed to design a compact triband high-temperature superconducting (HTS) bandpass filter (BPF). The MMR is constructed with three transmission line sections with different characteristic impedance, named asymmetric trisection stepped-impedance resonator (TSIR). Asymmetric TSIR can produce three controllable resonant modes, and its resonant characteristics are analyzed based on the transmission line theory. Meanwhile, some graphs for the relationship of size parameters and ratio of resonances are built for design conveniently. For demonstration, a second-order triband HTS BPF that centered at 1.5/3.5/5.8 GHz is well designed. The filters are fabricated on a 0.5-mm-thick MgO wafer with double-sided YBCO thin films and measured at the temperature of 77 K. Measured results agree well with the simulated ones and show that the insertion losses in all passbands are less than 0.16 dB, which exhibit superiority in midband insertion loss.

Analysis of the Total Electrical Length Extremum of TSSIR Using Lagrange Multipliers Method

A systematic approach to determine the extreme value of total electrical length for trisection stepped impedance resonator (TSSIR) is proposed in this paper. It utilizes the Lagrange multipliers method to search the extremum condition. Result demonstrates that the maximum resonator length of TSSIR is limited to triple that of the corresponding uniform impedance resonator (UIR). Spurious resonant frequency of λ/2 TSSIR is mainly analysized under the extremum condition (θ1≠θ2≠θ3). Through comparison between the proposed approach and previously assumed condition (θ1=θ2=θ3), the staircase discontinuity of transmission line can be reduced using the paper theory to achieve same harmonic ratio. Last, a simulated example is presented to verify correctness of the method. This paper aims to provide a theoretical basis and general guideline for the filter design using TSSIR.

Dual-band bandpass filter with controllable center frequency and bandwidth using short stub-loaded SIR and tri-section SIR

A novel compact dual-band bandpass filter (BPF) based on short stub-loaded stepped impedance resonator (SSL-SIR) and a pair of tri-section stepped impedance resonator (T-SIR) is presented. The dual-band BPF can be divided into two sub filters. The upper sub filter creates the first passband centered at 2.4GHz, and the lower sub filter generates the second passband centered at 3.5GHz. The two passbands can be controlled separately and have almost no mutual influence between each other. The structure of the filter is miniaturized and a wide stopband performance is also achieved by introducing SIR. The simulated and measured results are both presented and show good agreement.

A miniaturized quad‐band bandstop filter with high selectivity based on shunt‐connected, T‐shaped stub‐loaded, stepped‐impedance resonators

ABSTRACTThis letter presents a microstrip quad‐band bandstop filter (QBBSF) with a miniaturized size and high selectivity. The structure of the proposed QBBSF consists of two‐folded, shunt‐connected trisection stepped‐impedance resonators (TSSIRs). One of these TSSIRs, which operates on the second and fourth central frequencies, has been embedded inside another TSSIR operating at the first and third central frequencies of the proposed QBBSF. Characterized by equivalent circuit analysis and full‐wave EM simulations, each TSSIR has been miniaturized by a T‐shaped stub load. The main advantage of the proposed QBBSF lies in its central frequencies, which can be adjusted conveniently within a wide range by varying parameters of TSSIRs, the positions, and dimensions of the stub loads. A protocol QBBSF with a compact size of 0.0115 λg2 operating at central frequencies of 1.90, 3.32, 5.77, and 6.75 GHz was designed, simulated, and fabricated to verify the proposed method. The measured minimum stop band return loss of 21.4 dB and maximum pass band insertion loss of 0.66 dB indicated the excellent in‐band and out of band selectivity of the proposed QBBSF. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1129–1132, 2015

Compact Tri-Band Bandpass Filter Using Open Stub Loaded Tri-Section $\lambda /4$ Stepped Impedance Resonator

A modified tri-mode λ/4 stepped impedance resonator (SIR) is proposed, in which a shunt open stub is loaded in the conventional λ/4 tri-section SIR. The resonant frequencies and frequency ratios can be properly controlled by adjusting the loaded open stub. A compact second-order tri-band bandpass filter (BPF) based on two coupled proposed open stub loaded λ/4 tri-section SIR is presented. A pair of transmission zeros (TZs) are generated at the lower and upper stopband of each passband for high selectivity and excellent band-to-band isolation. A tri-band BPF with the central frequencies of 1.92, 3.50, 5.75 GHz, and respective fractional bandwidths of 5.4%, 4.0%, and 2.4% is designed and fabricated. Measured results show good agreement with simulations. Moreover, the circuit only occupies 0.09 λg ×0.10 λg.

A Dual-Band Bandpass Filter Using Coupled Semi-circular Stepped Impedance Resonators with Sharp Roll-off and Wide Stopband

In this paper, a dual-band bandpass filter using three-pole Chebyshev filter based on the semi-circular tri-section stepped impedance resonators (SIRs) loaded by trapezoidal stub is presented. The first passband is adjusted by the proper ratios of the tri-section SIR. By optimizing the resonator and inserting the trapezoidal stub, undesirable response is suppressed and the second passband is adjusted at the desired frequency. The proposed filter has low insertion losses, high return losses, good 3 dB bandwidths and sharp roll-off rates in two passbands and wide and high rejection in the stopband. There is a good agreement between the simulated and measured results.

COMPACT TRI-BAND BANDPASS FILTER FOR WLAN AND WIMAX USING TRI-SECTION STEPPED-IMPEDANCE RESONATORS

In this paper, a compact tri-band microstrip bandpass fllter (BPF) using tri-section stepped- impedance resonators (TSSIRs) with open stub line and zero-degree feed line is presented. Three tunable passbands are achieved by changing the ratio of impedance. By adding the open stub line, the frequency responses of tri-band at 2.4GHz/3.5GHz/5.2GHz can be obtained precisely. With a proper length of the cone-shaped zero-degree feed structure, we can obtain transmission zeros in stopbands and better return loss in passbands. The proposed tri-band BPF has high selectivity and is simple in fabrication.

Microstrip triband bandstop filter with sharp stop band skirts and independently controllable second stop band response.

This paper presents a compact planar triband bandstop filter (TBBSF) with compact size and high selectivity. The structure of the filter incorporates two folded trisection stepped-impedance resonators (TSSIRs). One of these resonators is designed to operate at the first and third center frequencies and the other resonator is designed to operate at the second center frequency of the proposed filter. To achieve a compact size filter, alternating impedance lines of the resonators are folded widthwise and also one resonator is embedded within another. Theoretical analysis and design procedures are described, including the synthesis equations for each resonator. The main advantage of the proposed method is that the filter provides flexibility to tune the second center frequency and control the corresponding bandwidth without changing the first and third stop band response. Additionally, several reflection zeros (RZs) are introduced in the pass band to improve its flatness. To demonstrate the feasibility of the proposed design method, both the first and second order TBBSFs were designed, simulated, and fabricated, with center frequencies of 1.92 GHz, 3.55 GHz, and 5.5 GHz.

Tri‐band bandpass filters using modified tri‐section stepped impedance resonator with improved selectivity and wide upper stopband

This study presents tri-band bandpass filters using two variant designs based on tri-section stepped impedance resonators (SIR) to achieve passband selectivity. The passbands are centred about 2.4, 3.5 and 5.5 GHz, respectively. The first design pertains to an asymmetric stepped impedance stub-loaded tri-section SIR and the second one consists of embedded SIR. Both the techniques contribute in improving the selectivity by inserting transmission zero between first passband and second passband. With a simple extension of one of the input/output coupling feed lines transmission zeros are inserted between second and third passband. The filter exhibits a wide stopband till 10 GHz because of, cascading with the feed line, a low-pass filter with upper cutoff at 6.4 GHz. The passband insertion loss is within 2 dB. The group delay excursion for both the developed filters for the three passband suggests linearity of phase. Fabricated prototypes for both the variants are realised with simulated and measured results in good agreement.

Developing single‐layer ultra‐wideband band‐pass filter with multiple (triple and quadruple) notches

New ultra-wideband (UWB) band-pass filters (BPFs) with multiple (triple and quadruple) notches are proposed. A systematic approach is demonstrated to establish one to four or more notch-bands within the passband of a UWB BPF on a single-layer substrate using μ-strip technology, while avoiding the use of any via-holes. The proposed filters are based on parallel integration of gap-coupled microstrip resonators (GCMR) and two tri-section stepped-impedance resonators (TSSIR) to generate multiple notches. Two notches are produced by the use of TSSIR fundamental and first spurious resonance frequencies and the third and fourth notches are introduced by developing transmission zeros using additional integrated GCMR. Two samples of triple and quadruple notch-band UWB filters are fabricated and tested. In comparison to the previous triple single-layer notch-band BPFs with via-holes, the proposed single-layer triple notch BPF offers a size reduction of around 52%. The authors have also expanded the concept and designed a new quadruple notch-band UWB BPF. The proposed filter uses only a single layer and can be easily mass-produced with low cost.

Compact dual‐band bandpass filter with ultra‐wide upper‐stopband

Proposed is a compact dual-band bandpass filter (BPF) using stepped impedance resonators (SIRs). To improve the upper-stopband of the proposed filter, tri-section folded SIRs are used. By adjusting the impedance ratio and electronical length ratio of the tri-section SIR, the out-of-band of the filter can be improved. A 2.09/2.62 GHz dual-band experimental BPF has been designed and fabricated to demonstrate the proposed method. The measured results are in good agreement with the electromagnetic simulation. The spurious frequencies of the upper-stopband are suppressed below 20 dB from 2.79 to 22.13 GHz. The circuit only occupies 0.29 λg × 0.13 λg.

H-shaped SIR bandpass filter with dual and tri-band

Compact dual-band bandpass filter which meets IEEE 802.11 application requirements by using new H-shaped tri-section stepped-impedance resonator is proposed, and a tri-band bandpass filter which achieves insertion loss of 0.41, 0.66, and 1.65 dB at 2.5, 3.49, and 5.6 GHz, respectively, is also designed with two-path coupling. The new designs are demonstrated by experiment. The new filters have advantages of compact structures, low passband insertion losses, good frequency selectivity, and miniature circuit sizes. All these have prospect to be applied in future wireless communication systems. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1686–1688, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26888

Compact microstrip ultra-wideband double/single notch-band band-pass filter based on wave's cancellation theory

A novel approach with a new configuration is introduced to design an ultra-wideband (UWB) band-pass filter (BPF) that demonstrates double/single notch-bands using micro-strip transmission lines without using any via-hole. The proposed approach is established using two parallel stepped-impedance resonators (SIR) that provide two paths with different electrical lengths. The mechanism of realising notch-bands within the pass-band of the UWB BPF is developed based on the waves’ cancellation theory. To realise single or double notch-bands (DNBs) within the pass-band of a UWB BPF, the conventional tri-section stepped-impedance resonator (TSSIR) is adopted and its fundamental and first spurious resonance frequencies are chosen either to be suppressed or supported. New parallel dual-section T-shaped and TSSIRs are proposed, optimised and fabricated to provide single and DNBss, respectively. The proposed concept avoids using via holes, which is conventionally used in notch filters. In addition, a size reduction of about 75% is reported in comparison with the conventional BPF with a single notch-band accompanied by two transmission zeroes at the lower and upper stop-bands. Moreover, our proposed DNBs BPF demonstrates a comparable performance while being smaller in size (up to a 12.6% size reduction) to that of the latest UWB BPF design that used complicated and expensive multilayer liquid crystal polymer (LCP) technology.

계단형 임피던스 공진기를 이용한 소형화된 마이크로스트립 이중 대역 저지 필터

본 논문에서는 듀얼 밴드 대역저지 필터의 소형화 설계를 위한 새로운 구조를 제안한다. 본 구조는 전송 라인과 두 개의 병렬로 연결된 3단 계단형 임피던스 공진기로 구성되어 있다. 필터의 등가회로를 통한 이론적 분석과 설계 절차를 나타내었다. 공진조건으로부터 유도한 방정식으로부터 각 설계 변수에 대한 특성 결과를 그래프로 나타내어 설계의 편의성을 제공한다. 제안된 필터 구조의 장점은 설계의 소형화 가능성, 구현 가능한 공진 주파수의 비율이 넓은 점, 그리고 구현 가능한 임피던스의 선택이 자유롭다는 점이다. A novel circuit structure of dual-band bandstop filters is proposed in this paper. This structure comprises two shunt-connected tri-section stepped impedance resonators with a transmission line in between. Theoretical analysis from the equivalent circuit and design procedures are described. We represented graphs for filter design from the derived synthesis equations by resonance condition of circuits. Notably, advantages of the proposed filter structure are compact size in design, wide range of realizable resonance frequency ratio, and more realizable impedances.

Design of compact low pass filter with wide stop band using tri-section stepped impedance resonator

This paper reports the design of a compact low pass filter (LPF) with wide stop band region using tri-section stepped impedance resonators in microstrip medium. Experimental results of a low pass filter designed at 1 GHz have been compared against the analytical and EM simulation results for the validation of the design. Results are satisfactorily matching each other. The maximum insertion of the measured filter is 0.2 dB and minimum return loss is 13.5 dB over the pass band. The stop band rejection is better than 20 dB from 1.5 GHz to 4.2 GHz and hence wide stop band performance is achieved. Overall size of the filter is 30 mm × 20 mm × 0.78 mm which is 0.1 λ × 0.066 λ × 0.0026 λ at 1 GHz.