Stub-loaded Stepped-impedance Resonators Research Articles

A Lowpass Filter With Compact Size and Sharp Roll-Off

In this letter, a lowpass filter (LPF) is proposed based on a modified complementary split-ring resonator (CSRR) which can be considered as a traditional rectangular CSRR attached with two $C$ -shaped structures, and a composite resonator composed of a simple uniform line with four stub-loaded stepped impedance resonators (SLSIRs) connected at the four corners. The LPF was designed using the first two resonant points produced by the composite resonator, and operating mechanisms are investigated based on its equivalent models. The LPF was fabricated and measured. The measured results are in good agreement with the full-wave simulated results, showing the merits of compact size and sharp roll-off.

Compact triple-passband bandpass filter based on new modified stepped impedance resonators

This study proposed a triple-passband bandpass filter with compact size, low loss and high passband selectivity. The filter includes two coupled stepped impedance resonators (SIRs) and two embedded stub-loaded stepped impedance resonators (SL-SIRs), connected with coupling scheme at the symmetric plane of the filter. The filter is designed to have triple-passband at 2.4, 3.5 and 5.2GHz for worldwide interoperability for microwave access (WiMAX) applications. By properly tuning the impedance ratio and physical length ratio of the SL-SIRs, the three passbands can be easily determined, at the same time, achieving the high passband selectivity and wide stopband. Besides, the transmission zeros near passband edges of each passband are generated by the proposed filter with cross-coupling structure. The measured results are in good agreement with the full-wave electromagnetic (EM) simulation results.

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.

Balanced dual‐band BPF with intrinsic common‐mode suppression on double‐layer substrate

A balanced dual-band bandpass filter (BPF) with enhanced common-mode (CM) suppression is proposed. The dual-band differential-mode (DM) bandpass response is obtained using a double-layer substrate. The stub-loaded stepped-impedance resonators are used both in the top and the bottom layers to constitute a dual-band BPF with two controllable passbands. The slotline portion in the middle layer is excited under DM operation. Moreover, the even-symmetrical field along the slotline is highly attenuated under CM excitation, thus achieving excellent CM suppression over the desired DM passbands. To verify the proposed concept, a balanced dual-band BPF, operating at 1.9 and 2.8 GHz, is designed and fabricated, and the simulated and measured results are in good agreement.

Compact tri‐band bandpass filter with stub‐loaded stepped‐impedance resonator

A compact microstrip tri-band bandpass filter (BPF) based on two open stub-loaded multimode λ/4 stepped-impedance resonators (SIRs) with two separate coupling paths is investigated. A source–load coupling configuration is arranged to produce several extra transmission zeros for realising high-isolation performance. The centre frequencies of three passbands can be controlled by tuning the dimensions of two high impedance lines of the proposed open stub-loaded SIRs. The bandwidth of the three passbands could be conventionally controlled by adjusting the coupling strength of two coupling paths. The prototype of the BPF achieved insertion losses of 0.46, 1.05 and 1.4 dB at 0.82, 1.67 and 2.17 GHz, respectively. The measured results are in good agreement with electromagnetic simulation. The circuit only occupies 0.126λ g × 0.108λ g, where λ g is the guided wavelength at a lower passband centre frequency.

Tri-band superconducting filter using stub-loaded stepped-impedance resonators

A stub-loaded stepped-impedance resonator (SLSIR) with three resonant modes is proposed to design a tri-band bandpass filter (BPF). The couplings between adjacent resonators at different resonant modes can be controlled independently by properly selecting the geometric parameters of the resonator. A dual-feeding structure is used to realize the required external couplings of the three passbands simultaneously. A fourth-order tri-band BPF with the passbands centered at 1.73, 2.40 and 3.45GHz, respectively, is successfully designed and fabricated with superconducting thin films. The measured results exhibit high performance and agree well with the simulated ones.

Miniaturized Close Dual-Band Bandpass Filter Based on Short Stub-Loaded Stepped-Impedance Resonators

Based on a short stub-loaded stepped-impedance resonator, a novel compact microstrip bandpass filter with controllable passband center frequencies is presented. To obtain dual-passband characteristics, dual-mode short stub-loaded stepped-impedance resonator and novel quad-pole-splitting techniques are investigated. The single passband is split into two with a notch when two resonators are employed, and dual passbands of a close band could be realized. It was found that the filter exhibits two desirable close passbands, an adjustable fractional bandwidth, and wide upper-stopband response. Moreover, the compact size of the proposed structure can be achieved. Good agreement between the measured and simulated results is shown.

A High-Selectivity Tunable Dual-Band Bandpass Filter Using Stub-Loaded Stepped-Impedance Resonators

A novel varactor tunable dual-band bandpass filter (BPF) using stub-loaded stepped-impedance resonators is proposed in this letter. Compared with the traditional tunable filters, the source-load coupling and T-shape stub-loaded lines are employed in this design. The proposed BPF architecture has the advantages of high selectivity and less control voltages. In the overall tuning range, the proposed filter is designed with 5–6 transmission zeros and more than 30 dB rejection between the two passbands. Meanwhile, only one control voltage is needed for each passband. A prototype of this filter is fabricated and measured. The measurement results show great agreement with simulated results, which show that the first passband can be tuned in a frequency range from 0.8 to 1.02 GHz, and the second passband varies from 2.02 to 2.48 GHz.

A tri‐band bandpass filter using stub‐loaded SIRS with controllable bandwidths

ABSTRACTIn this article, we present a tri‐band bandpass filter (BPF) based on a stub‐loaded stepped‐impedance resonator (SIR). The proposed resonator has the compact size based on a short‐circuited SIR as well as the controllability of three resonant frequencies by adjusting impedance ratios. Bandwidths for the first and second passbands can be independently controlled using two coupling paths between resonators, while the third bandwidth can be designed by adjusting dimensions of an open‐stub loaded to the resonator. Two‐pole tri‐band BPF is designed and tested at center frequencies of 1.575, 2.4, and 3.5 GHz with fractional bandwidths of 10%, 6%, and 4%, respectively. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2907–2910, 2014

Compact six‐band triplexer using stub‐loaded stepped impedance resonators

A novel six-band triplexer based on short- and open-ended stub-loaded stepped impedance resonators (SLSIRs) is presented. The stub added at the centre of the SIR introduces a flexible even mode close to the first odd mode, realising a dual-band response with nearby passbands and a wide stop band. Three second-order dual-band channels combined with a common T-shaped SIR feed line form a six-band triplexer with compact size, low insertion loss and high isolation. A practical six-band triplexer operating at 1.9/2.4, 3.5/4.2 and 5.2/5.8 GHz is designed and realised based on the proposed multi-band multiplexer coupling scheme.

Design of multi-layered bandpass filter with independently controllable triple-passband response

In this paper, a new multi-layered triple-passband bandpass filter using embedded and stub-loaded stepped impedance resonators (SIRs) is proposed. The filter is designed to have triple-passband at 1.8, 2.4, and 3.5 GHz. The 1st and 2nd passbands (1.8/2.4 GHz) are simultaneously generated by controlling the impedance and length ratios of the embedded SIRs (on top layer). The 3rd passband (3.5 GHz) is generated by using the stub-loaded SIR (on bottom layer). Using the embedded SIR, the even modes can be tuned within very wide frequency range and without affecting the odd modes. Therefore, the design of multi-band filters with very close passbands can be easily achieved and having a high isolation between the passbands. The filter can provide the multi-path propagation to enhance the frequency response and achieving the compact circuit size. The measured results are in good agreement with the full-wave electromagnetic simulation results.

Balanced dual-band bandpass filter using stub-loaded stepped-impedance resonators

A balanced dual-band bandpass filter (BPF) based on stub-loaded stepped-impedance resonators (SIRs) is proposed in this paper. With the aid of the two open stubs loaded to the SIR symmetrically, the employed stub-loaded SIR possesses more design freedom for controlling differential-mode fundamental resonant frequency and second harmonic, as well as the ratio between them in the design of the proposed BPF. In addition, as the loaded stubs’ length increases, both fundamental resonant frequency and second harmonic can be shifted down, implying that the size reduction in this design is achieved. Finally, a two-order balanced dual-band BPF is designed and fabricated for demonstration, and the simulated and measured results are presented, showing good agreement. In addition, the centrally loaded resistor is added and optimized to achieve high common-mode suppression, especially in the two differential-mode passbands.

Tri-band Microstrip Bandpass Filter Using Dual-Mode Stepped-Impedance Resonator

This letter presents a compact dual-mode tri-band bandpass filter by using a short-circuited stub-loaded stepped-impedance resonator (SIR) and a short-circuited stub-loaded uniform impedance resonator. Also, a hairpin SIR geometry is introduced to miniature the size of this filter while maintaining excellent performance. The use of a short-circuited stub at the central point of the hairpin SIR can generate two resonant modes in two passbands. Its equivalent circuit structure is analyzed by using the even-odd mode theory. For demonstration purposes, a tri-band filter for the applications of the Global Positioning System at 1.57 GHz, Worldwide Interoperability for Microwave Access at 3.5 GHz, and wireless local area networks at 5.2 GHz is designed, fabricated, and measured.

Tri-band Microstrip Bandpass Filter Using Dual-Mode Stepped-Impedance Resonator

This letter presents a compact dual-mode tri-band bandpass filter by using a short-circuited stub-loaded stepped-impedance resonator (SIR) and a short-circuited stub-loaded uniform impedance resonator. Also, a hairpin SIR geometry is introduced to miniature the size of this filter while maintaining excellent performance. The use of a short-circuited stub at the central point of the hairpin SIR can generate two resonant modes in two passbands. Its equivalent circuit structure is analyzed by using the even-odd mode theory. For demonstration purposes, a tri-band filter for the applications of the Global Positioning System at 1.57 GHz, Worldwide Interoperability for Microwave Access at 3.5 GHz, and wireless local area networks at 5.2 GHz is designed, fabricated, and measured.

A compact reconfigurable microstrip dual-band filter using varactor-tuned stub-loaded stepped-impedance resonators

A new varactor-tuned microstrip dual-band band-pass filter (BPF) based on the tri-mode stub-loaded stepped-impedance resonators (SL-SIRs) is investigated. By employing the dual coupling paths, the two passbands can then be fully controlled and designed independently. Meanwhile, a third-order bandpass response can be realized by properly incorporating the first three resonator modes of a tri-mode SL-SIR at adjacent frequencies into the passband. Thus, the third-order dual-band BPF can be designed with only two resonators, resulting in an extremely small size. In addition, for the electronic tuning, three varactors are loaded onto the open-ends of each resonator and, thus, the passband frequency can be changed by properly tuning the first three resonant modes of the SL-SIR. For the demonstration, a compact reconfigurable dual-band BPF with a size of 0.19 λ0 by 0.04 λ0 has been designed and fabricated. Good agreement is also achieved between simulation and measurement.

NOVEL DESIGN OF A COMPACT TRIPLE-BAND BANDPASS FILTER USING SHORT STUB-LOADED SIRS AND EMBEDDED SIRS STRUCTURE

A novel compact planar triple-band bandpass fllter using two sets of short stub-loaded stepped impedance resonators (SSLSIRs) and a pair of embedded stepped impedance resonators (ESIRs) has been proposed. The SSLSIRs can adjust the bandwidths of the corresponding passbands over a wide range, and the ESIRs employing non 0 - -feed coupled structure with mixed electric and magnetic coupling can obtain an extra transmission zero. The embedded resonators structure can further miniaturize the dimensions of the whole triple-band fllter. The operating frequencies of the SSLSIRs and ESIRs are designed for the applications of the WLAN (2.45/5.2GHz) and WiMAX (3.5GHz) systems, respectively. The simulated and measured results are both presented and show good agreement.

Design of tri-band microstrip BPF using SLR and quarter-wavelength SIR

A tri-band microstrip bandpass filter (BPF) with compact size and high selectivity is presented by using the stub-loaded resonator (SLR) and quarter-wavelength stepped-impedance resonator (SIR). The quarter-wavelength SIR is designed for the first and third passband and the SLR mainly controls second passband performance, so three passband frequencies can be flexibly tuned. Because of the intrinsic characteristics of the resonators and source-load coupling, multiple transmission zeros can be created to improve the selectivity. Finally, a tri-band BPF prototype located at 0.98 GHz (FRID application), 3.6 GHz (Wimax application), and 5.8 GHz (WLAN application) is designed. Measurement results agree well with the full-wave EM simulated results. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:212–215, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27247

Compact wide-stopband microstrip bandpass filter-based on stub-loaded stepped-impedance resonators

This study presents compact wide-stopband microstrip bandpass filters using stub-loaded stepped-impedance resonators. The resonators consist of three stepped-impedance sections. By adjusting the parameters of the resonators, one can control the frequencies of the resonant modes as well as the frequency of the transmission zero. When the transmission zero frequency is close to the spurious resonant mode frequencies, one can have a wide-stopband bandpass filter without external filtering circuits or increasing the resonator number for suppressing the spurious passbands. To validate the design concept, three dual-band bandpass filters and one wideband bandpass filter are designed, fabricated and tested.

Design of high selectivity tri-band bandpass filter with wide upper stopband

This article presents a dual-plane structure high selectivity tri-band bandpass filter (BPF) which consists of a pair of T-shaped microstrip feed lines with capacitive source-load coupling as well as spur lines embedded, and three resonators, i.e., a dual-mode stub-loaded stepped impedance resonator and two nested dual-mode defected ground structure resonators. Using the intrinsic characteristics of the resonators and feed lines, nine transmission zeros near the passband edges and in the stopband can be generated to achieve high selectivity. An experimental tri-band BPF located at 2.4/5.7 GHz [wireless local area networks (WLAN) application] and 3.5 GHz [worldwide interoperability for microwave access (WiMAX) application] has been simulated and fabricated. Good agreement between the simulated and measured results validates the design approach. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.

Miniaturized and high isolation microstrip diplexers based on the tri-mode stub-loaded stepped-impedance resonators

Compact size and high isolation microstrip diplexers designed with tri-mode stub-loaded stepped-impedance resonators (SL-SIRs) have been proposed. By adjusting the structural parameters of the proposed tri-mode SL-SIR, its first three resonant frequencies can be controlled. Thus, it can be utilized to implement a third-order bandpass filter with a transmission zero at the upper side of the passband edge when these resonant frequencies are suitably assigned. In addition, by utilizing multiple coupling paths with a common input coupled-line section, the two passbands of the diplexer can then be fully controlled and, thus, the design is flexible so as to independently realize different channels. For our demonstration, a third-order bandpass diplexer formed by only two tri-mode resonators has been designed and fabricated. It is shown that the diplexer occupies an extremely small area, i.e. 0.14 by 0.12, while still keeping good isolation better than 40 dB for the two channels. Good agreement is also achieved between simulation and measurement.