Asymmetric Stepped-impedance Resonators Research Articles

Design of multi‐standard single/tri/quint‐wideband asymmetric stepped‐impedance resonator filters with adjustable TZs

This study presents an original asymmetric stepped-impedance resonator filter combined with meander coupled-line structures and enabling the realisation of finite transmission zeros (TZs) and the implementation of multi-band bandpass filters. The meander coupled sections (MCSs) tune the TZs and resonant frequencies: with higher-order spurious frequencies cancelled by the TZs, a single wideband with wide stopband from 1.18 to 1.84 GHz is possible. Furthermore, by positioning the finite TZs between the high-order spurious frequencies and adjusting the coupling strength between resonators, a quint-wideband filter can be realised, with centre frequencies of 1.19, 4.29, 5.43, 6.97, 9.9 GHz and fractional bandwidths of 31.9, 15.4, 15.8, 4.3, 39.2%, respectively. More importantly, two filters with single/quad-wideband performance can be realised by tuning the parameters of the MCS, and therefore they can be designed separately by using only one original structure. The triple-wideband filter is realised with the help of the asymmetric parallel uncoupled microstrip section. These filter structures enjoy the advantage of single/multi-band versatility, structure reusability and simplicity. The good in-band and out-of-band performance, low loss and simple structure of the proposed single/tri/quint-wideband filters make them very promising for applications in future multi-standard wireless communication.

Novel Tri-Band High-Temperature Superconducting Bandpass Filters Using Asymmetric Shunted-Line Stepped-Impedance Resonator (SLSIR)

In this paper, a tri-band high-temperature superconducting (HTS) bandpass filter (BPF) is proposed with a pair of asymmetric shunted-line stepped impedance resonators (SLSIRs). Compared with the conventional SIRs, the proposed asymmetric SLSIR has more degrees of freedom in controlling multi-mode operating characteristics. Moreover, design graphs for the relationship of electric characteristic parameters and the resonant frequency ratio are built and applied to multiband device design. For demonstration, a two-order tri-band HTS BPF is well designed with center frequencies of 1.575/2.4/3.5 GHz. The external quality factor and the coupling coefficient have also been analyzed to satisfy the bandwidth of the BPF. The designed filter is fabricated on the YBCO superconducting material and measured under superconducting conditions (at the temperature of 77 K). The measurement results are in good agreement with the simulation results, indicating that the insertion loss of the three passbands is about 0.1 dB, showing the advantage of in-band insertion loss.

Compact Balanced Bandpass Filter Design Using Asymmetric SIR Pairs and Spoof Surface Plasmon Polariton Feeding Structure

This letter demonstrates a design of a compact balanced bandpass filter (BPF) with stopband extension and common-mode (CM) suppression using asymmetric stepped-impedance resonator (SIR) pairs and a spoof surface plasmon polariton (SPP) feeding structure. The configuration of balanced SIR pairs is analyzed theoretically to obtain a wide stopband response and intrinsic CM suppression within differential-mode passband. Moreover, a novel SPP feeding structure is adopted as a low-pass filter and impedance matching section for enhancing filter transmission responses. Finally, a balanced BPF operating at 0.85 GHz with the SPP feeding structure is designed and fabricated to verify the design method.

Dual-band bandpass filters with multiple transmission zeros using λ/4 stepped-impedance resonators

Two novel dual-band microstrip bandpass filters (BPFs) with multiple transmission zeros are proposed in this article. The dual-band BPFs with second-order bandpass responses are due to two λ/4 stepped-impedance resonators (SIRs). Two passbands (center frequency ratio f s/f0 is 2.36) are realized based on the asymmetric SIRs. The transmission zeros near the passbands can be adjusted conveniently using the stopband transmission characteristic of the open/shorted coupled lines. Two planar microstrip dual-band BPFs (ε r = 2.65, h = 0.5 mm) with four and six transmission zeros are designed and fabricated. High selectivity and good in-band performances can be achieved in the proposed filters.

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.

Design of New Eight-Channel Diplexer for Multiband Wireless Communication System

In this paper, we proposed a new eight-channel diplexer (1.575/2.4/3.5/5.2 and 1.8/2.6/4.2/5.7 GHz) with a simple source-load input/output structure containing four pairs of coupled asymmetric stepped-impedance resonators (SIRs) in a compact circuit size. By tuning the impedance ratio and the length ratio of the asymmetric SIRs, each resonant mode can be easily determined, and the diplexer with close quad-passbands (quad-channels) can be implemented. The new eight-channel diplexer for multiband wireless communication systems including of global positioning system, global system for mobile communications, Wi-Fi, and 5G mid-band.

High-temperature superconducting filter using self-embedding asymmetric stepped impedance resonator with wide stopband performance and miniaturized size**Project supported by the National Natural Science Foundation of China (Grant No. 61371009) and the National High Technology Research and Development Program of China (Grant No. 2014AA032703).

In this study, a novel self-embedding asymmetric stepped impedance resonator (SE-ASIR) topology is proposed. By embedding asymmetric stepped impedance resonators in themselves, circuit sizes of ASIRs can be reduced effectively, while the ability to control spurious modes of ASIRs remains. Therefore, SE-ASIRs are suitable for being used to design filters with wide stopbands and miniaturized sizes. Furthermore, the construction process of the SE-ASIR is described in detail, and an equivalent model of the SE-ASIR is proposed. For demonstration, a high-temperature superconducting bandpass filter centered at 1112 MHz is designed and fabricated. The measured result agrees well with the simulation result and shows that the out-of-band rejection is better than 60 dB up to 4088 MHz, which is about 3.7 times the center frequency. The filter circuit size is 31 mm × 13 mm or , where is the guided wavelength at 1112 MHz.

Microwave Microstrip Six-Channel Triplexer and Eight-Channel Quadruplexer

This paper presents two microstrip multiband multiplexers using distributed coupling technique. The proposed multiband multiplexers consist of a distributed coupling feeding line, asymmetric stepped-impedance resonators, and output feeding lines. Each pair of resonators controls a respective bandpass channel for good design freedom. By using distributed coupling technique, there is no extra matching network required in the multiplexers. In order to obtain a wide stopband, asymmetric stepped-impedance resonators and asymmetric feeding lines are employed. The operation frequencies of the first multiband multiplexer are at 1, 1.3, 1.6, 1.9, 2.2, and 2.5 GHz, and the second one operates at 1, 1.3, 1.6, 1.9, 2.2, 2.5, 2.8, and 3.1 GHz. The stopband rejection level is better than 20 dB up to 4.6 times the lowest operation frequency. The proposed design concept is validated with the two fabricated multiband multiplexers. The measurements show good agreement with simulations.

A Novel of Dual-Band Bandpass Filter Employing Coupled Stepped Impedance Resonator and U-Shaped Defected Microstrip Structure (DMS)

This paper presents the integration between a pair of coupled asymmetric stepped impedance resonators (SIRs) and U-shaped Defected Microstrip Structure (DMS) in producing of dual-band bandpass filter (BPF). In this study, as the DMS were integrated with SIR bandpass filter, the low loss, high attenuation and good selectivity between dual-bandpass were produced. The DMS was designed at resonant frequency of 3 GHz with the attenuation is better than 60 dB. The measured results show two bandpasses centered at 2.50 GHz and 3.50 GHz with the fractional bandwidth of 16% and 18.3%, respectively. Meanwhile, the return and insertion losses are greater than 15dB and 1dB, respectively. Additionally, the proposed filter is designed with 3 transmission zeroes with the attenuation level more than 50dB. The simulated and measured results are both presented and show a good agreement. This filter is very useful in modern wireless communication and many applications.

A bandpass filter using asymmetric stepped-impedance resonators and symmetric T-shape interdigital capacitor structures with wide out-of-band rejection

In this study, a novel stepped impedance resonator (SIR) is proposed. This SIR is composed of two stepped impedance transmission-lines and an interdigital capacitor structure. The proposed resonator has a high ratio of the first spurious frequency fs to the fundamental frequency f0 and is suitable to design wide stopband filters. An equivalent model is used to analyze the resonant properties of the resonator. The design guidelines of the proposed resonator are summarized. Moreover, the coupling properties of the resonator are simulated and analyzed. Finally, a small high-temperature superconducting bandpass filter is designed and fabricated using the proposed SIRs. The stopband of the filter is extended up to 4.0 f0 and 3.5 f0 with 30 and 60 dB out-of-band rejection levels, respectively.

Compact tri-band bandpass filter using asymmetric stub-loaded stepped-impedance resonator with multiple transmission zeros

In this paper, a tri-band bandpass filter (BPF) using asymmetric stub-loaded stepped-impedance resonator (SL-SIR) is presented. The asymmetric characteristic of SL-SIR broadens degrees of freedom for three controllable modes design. Also, the coupling coefficients (Mij) and the external quality factors (Qei) at each passband of the filter can be independently adjusted by the proposed mixed-type feedline structure. Besides, multi-transmission zeros are produced to improve the isolation and selectivity of the passbands. Finally, a tri-band BPF is operated at 1.9 GHz (time division long term evolution – TD-LTE band), 3.2 GHz (worldwide interoperability for microwave access – WiMAX band), and 5.8 GHz (wireless local area networks – WLAN band) and their insertion loss are 1.03, 0.94, and 1.27 dB, respectively. The measured results of the fabricated tri-band BPF exhibit good agreement with simulated results.

Design of compact and miniaturize asymmetric SIR-DRA filter-antenna subsystem

The proposed work presents a compact filter–antenna subsystem design using asymmetric stepped impedance resonator filter and cylindrical dielectric resonator antenna. A cylindrical dielectric resonator antenna is excited from stepped impedance resonator through slot. The DRA is excited for HEM11 mode. Rather than utilizing customary 50 Ω interfaces, some intermediate impedance between filter and antenna is optimized to get the desired results. The assembly of both filter and antenna into one module leads to compactness in the RF front-end. The designed filter antenna subsystem has efficiency of 93%.

Compact Dual-Band HTS Bandpass Filter Using Spirally Asymmetric Stepped-Impedance Resonators

In this paper, a compact dual-band high-temperature superconducting (HTS) bandpass filter (BPF) is constructed by spirally asymmetric stepped-impedance resonators (SIRs) and a pair of parallel-coupled feed lines. The resonant characteristics of spirally asymmetric SIRs with one step discontinuity are investigated in the dual-band BPF design. Owing to its intrinsic characteristics and the multipath propagation effect, multiple transmission zeros are created to improve the selectivity of the passband and the rejection level of stopband. For demonstration purposes, a compact HTS filter operating at 2.4/5.8 GHz for wireless local area networks is fabricated. Measured insertion losses at each passband are 0.12 and 0.18 dB, respectively. A good agreement between the measurements and the simulations is observed, which verifies the circuit design methodology. Finally, the temperature dependence and the input-power dependence of microwave nonlinear properties of the dual-band HTS filter at each passband are also measured and analyzed. Measured results have a good agreement with simulations.

Compact microstrip diplexer using new design of triangular open loop resonator for 4G wireless communication systems

A compact microstrip diplexer for 4G wireless communication systems is proposed in this paper. This diplexer consists of two bandpass filters based on the triangular open loop asymmetric stepped impedance resonator in order to have a small size as well as simple structure. The T-shaped open stub is used for attenuating the undesired modes. Attenuation level for the proposed diplexer is less than 21dB in the range of 0–10GHz owing to using this T-shaped open stub. The center frequency of each filter can easily change in the range of 20MHz through varying the gap length of the resonator without any changes in the whole structure of the diplexer. The result of this is the stability of other parameters like insertion loss, return loss and isolation. This diplexer has a narrow band frequency response that makes it suitable for modern wireless communication systems. Finally, the diplexer is fabricated at 2.30 and 2.55GHz and measurements demonstrate a good agreement between simulated and fabricated diplexer.

Dual‐band BPF design using ASIR structures with a dumbbell‐shaped notch

ABSTRACTPresented is a miniaturized microstrip dual‐band bandpass filter (BPF). An asymmetric stepped impedance resonator (ASIR) is employed with a dumbbell‐shaped notch. Compared with the conventional stepped impedance resonator (CSIR) and the multiple‐mode resonator (MMR), the ASIR utilizes the first two modes to produce a wider lower passband, while the third mode produces an upper passband. The input and output ports of the ASIR are connected with interdigital capacitive‐coupled lines. The measured data of the fabricated filter demonstrates a very good agreement to those simulated with a steep upper‐stopband suppression. The filter simultaneously operates at 13.88 and 24.75 GHz, respectively, with the corresponding fractional bandwidths of 29.4% and 7.1%. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:532–535, 2016

Coplanar waveguides loaded with symmetric and asymmetric multisection stepped impedance resonators: Modeling and potential applications

ABSTRACTThis article is focused on the analysis and modeling of coplanar waveguide (CPW) transmission lines loaded with multisection stepped impedance resonators (MS‐SIRs), transversely etched on the back substrate side. The considered structure consists of a CPW loaded with a 5‐section SIR (5S‐SIR) with wide (capacitive) central and external sections cascaded with narrow (inductive) sections. The general case of a 5S‐SIR with arbitrary lengths and widths of the different sections is considered. The structure is described by a pair of inductively coupled grounded series resonators coupled to the line through the capacitance of the central 5S‐SIR section. If the structure is symmetric, the transmission coefficient exhibits a single transmission zero. Hence, these structures can be used as notch filters exhibiting wide bandwidths, provided the inductance of the 5S‐SIR can be made small, and the capacitance can be enhanced by virtue of the broadside coupling. However, if symmetry is broken, two notches separated a distance that depends on the level of asymmetry and inductive coupling appear. Therefore, these structures are also useful for the implementation of differential sensors and comparators. The proposed model is validated through parameter extraction and experiment, and a proof‐of‐concept of a comparator is reported. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:722–726, 2016

High-Temperature Superconducting Bandpass Filter Using Asymmetric Stepped-Impedance Resonators With Wide-Stopband Performance

This paper presents a wide-stopband high-temperature superconducting (HTS) bandpass filter (BPF). The filter is implemented by the asymmetric stepped-impedance resonators (SIRs) with only one step discontinuity, which leads to low loss and compact size. With varied characteristic impedance ratios and length ratios, the diversity of asymmetric SIR has been studied, and the spurious resonant-mode responses are discussed. Adopting different asymmetric SIR units operated at the same fundamental frequency $f_{0}$ (2.4 GHz), its wide upper stopband can be realized by dispersing the higher order spurious resonant modes of these resonators. Furthermore, a modified input/output (I/O) feedline structure has been utilized to enhance the stopband performance. Finally, a fourth-order HTS BPF for wireless application is designed and fabricated on a MgO wafer with double-sided YBCO films. The filter measurement shows excellent performance with 0.05-dB minimum insertion loss and better than −20-dB rejection level in the stopband up to 10.46 GHz (about 4.4 $f_{0}$ ). In addition, the size of the HTS filter is 12.45 mm $\times$ 23 mm (i.e., 0.256 $\lambda_g$ by 0.472 $\lambda_g$ , where $\lambda_g$ is the guided wavelength at the center frequency).

A triband bandpass filter with low loss and high band selectivity using the split‐end asymmetric stepped impedance resonators

ABSTRACTIn this article, a triband bandpass filter for the applications of global system for mobile communications at 1.8 GHz, WiMAX at 3.5 GHz, and WLAN at 5.2 GHz with low insertion loss and high selectivity is presented. First, the triband passband responses are designed by tuning the length ratio (u) and impedance ratio (R) of asymmetric stepped impedance resonators (SIRs). Second, the band performances are improved by carefully arranging the coupling structure of the SIR. In this design, the split‐end asymmetric SIRs are used to provide desired triband performances. Due to the four transmission zeros near the passband edge, the band selectivity of the proposed filter is much improved. The filter was fabricated and the measured results have a good agreement with the full‐wave simulated results. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1427–1430, 2014

DESIGN OF A COMPACT AND HIGH SELECTIVITY TRI-BAND BANDPASS FILTER USING ASYMMETRIC STEPPED-IMPEDANCE RESONATORS (SIRS)

In this article, a compact tri-band microstrip bandpass fllter (BPF) using asymmetric stepped-impedance resonators (SIRs) is proposed. Only one set of asymmetric SIRs are used in designing this fllter to achieve triple passband response with high selectivity and band-to-band isolation level. By properly selecting the impedance and electrical length ratios of the asymmetric SIRs, the tri-band BPF is designed. By using a cross-coupled conflguration and 0 - feed structure, high selectivity frequency responses with six transmission zeros are achieved. The three bands of the proposed tri-band fllter are located at 1.57/3.9/7GHz, respectively, and the circuit size is much smaller in comparison with previous works using the same substrate. Measured results are in good agreement with electromagnetic (EM) simulation.

Wide-Stopband Bandpass Filters Using Asymmetric Stepped-Impedance Resonators

This letter presents novel bandpass filters (BPFs) with a wide stopband using asymmetric stepped-impedance resonators (SIRs). An uncoupled section located within conventional coupled lines functions as a means of achieving additional transmission zeros between each existing zeros, created by the conventional coupled lines. Designing two types of resonators, which have the same fundamental resonant frequency f1 with different spurious harmonic resonances, results in extending the stopband bandwidth with the better suppression level. Embedded inserted feeder structure is also designed to create supplementary transmission zeros at about 9.0 and 13.0 GHz. Measured results of the proposed filter show the suppression level of -23.7 dB up to 10.6f1 with the FBW of 8.9%.