Stepped Impedance Resonators Research Articles

Design of a novel compact highly selective wideband bandstop RF filter using dual path lossy resonator for next generation applications.

This article presents the design of a wideband bandstop RF filter intending to improve selectivity and compactness. Conventional bandstop filter topology with finite unloaded quality factor produces degraded bandstop filter performance due to dissipation loss. In the proposed filter design, a novel dual path Capacitive Coupled Step Impedance Resonator (CCSIR) structure is used to obtain an infinite stopband attenuation. A uniform impedance resonator is used in Path 1, whereas Path 2 contains a resonator that is twice coupled to the transmission lines. The electrical length of both paths is chosen to be out of phase, resulting in a high rejection level at higher frequencies. It has been analyzed that the selectivity can be improved by increasing the order of the dual coupled step impedance resonator. The proposed design produces a wideband BSF centered at 5.25 GHz with a high rejection level of 104.3 dB and fractional bandwidth of 58.5%. The results have demonstrated that the resonant frequencies are regulated by varying the electrical length of CCSIR. Moreover, it has been realized that out of phase signal cancellation due to the dual path is involved in producing the finite frequency transmission poles, which further enhances the filter selectivity. However, the same electrical performance can only be achieved from coaxial cavities and waveguides due to the high-quality factor. The proposed topology is fabricated and measured on a high-frequency microstrip substrate having a low-quality factor with a compact output and better electrical performance compared to coaxial cavities or waveguides. Due to its high electrical performance and small size, the proposed BSF is appropriate for 4G and 5G (FR1) applications. The measurement shows good concurrence with the full-wave EM simulated results. The fabricated prototype of third order BSF has a compact size of (0.7 × 0.77)λg at 5.25 GHz.

A new compact, wide bandwidth dual‐passband microstrip filter based on dual‐mode stepped‐impedance‐resonators

In this article, a new compact, wide bandwidth dual-band bandpass filter (DB-BPF) with four transmission zeros (TZs) is proposed. A dual-path configuration is realized by cascading different dual-mode resonators. The novel dual-mode resonators are based on stepped impedance resonators (SIRs) that generate the TZs owing to their intrinsic characteristics. The proposed DB-BPF can fulfill simultaneous independent control of the external and internal-resonator coupling. The design procedure based on the cascaded dual-mode resonators and frequency transformation is also introduced. The surface current distributions are simulated to verify the performance of the proposed filter. The measured results show 2.14/4.33 GHz DB-BPF with 3-dB fractional bandwidth (FBW) of 0.27/0.15, respectively, which is suitable for WLAN applications. The return and insertion losses of the passband are better than 15/15-dB and less than 0.8/1.3-dB, respectively. The overall physical size of the fabricated DB-BPF is 20.4 mm × 20.4 mm, equivalent to 0.23λg × 0.23λg, where λg is the guided wavelength at 2.14 GHz. The simulation results are in good agreement with the measurement results.

Wideband filtering waveguide antenna based on the stepped impedance resonator

A wideband filtering waveguide antenna is proposed. The stepped impedance waveguide resonator is used to obtain three resonance modes, widening the bandwidth from 1.9 to 5 GHz. Besides, the antenna integrates a band-stop filter, which consists of four rectangular resonant cavities, without increasing the lateral and vertical dimensions of the entire antenna. The integrated filter effectively suppresses the antenna gain near 16 GHz, which is outside the working band. Additionally, groove resonance is used to increase the gain of antenna by 4 dB, and two pair of grooves which resonant at different frequencies are employed to increase the bandwidth of realised gain. Finally, a prototype has been developed, the measured relative impedance bandwidth (|S11| < −10 dB) of the proposed antenna is 49.6% at the centre frequency of 11 GHz, and the 3 dB gain bandwidth is 5.1 GHz.

Modelization Methodology for the Quality Factor of Quarter-Wavelength n-Section Coaxial Stepped Impedance Resonators

This paper proposes a method to develop an analytical model and/or numerical resolution of the quality factor of quarter-wavelength n-section coaxial stepped impedance resonators (SIRs). The topology is based on cascaded coaxial sections nested within each other. Thanks to the SIR effect, this type of geometrical arrangement offers practical degrees of freedom to modulate the size of the resonator in both longitudinal and transverse dimensions. Moreover, in an air-filled configuration, it provides interesting quality factor, although this depends on its shape factor at any given frequency. In this paper, we show the added value of using an analytical model or numerical resolution for the quality factor, to be able to optimize the topology. To demonstrate the advantages of this model and the numerical method, comparisons of two- and three-section coaxial SIRs at two different frequencies are proposed and discussed. To validate the analytical model and numerical resolution, the values are compared with ones obtained in eigenmodes <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ANSYS HFSS</i> with electromagnetic simulation tool.

Dual-Narrowband/Wideband Filters Using Modified Coaxial Cavities With Large Frequency Ratios

This article presents two types of dual-narrowband/ wideband filters using modified coaxial cavities with large frequency ratios. The dual-narrowband/ wideband filters mean two dual-band bandpass filters, one of which is a dual-band wideband filter, and the other is a dual-band narrowband filter. The proposed coaxial resonator in the dual-narrowband filter consists of a pair of disk-loaded coaxial stepped impedance resonator (DLCSIR), which provides a large frequency ratio. The frequency ratio of the first two resonant modes of the DLCSIR can be precisely controlled by adjusting the impedance ratios and dimensions of the loading disk. By contrast, the proposed coaxial resonator in the dual-wideband filter is a rectangular coaxial stepped impedance resonator (RCSIR), which has the merits of miniaturized size, large frequency ratio, and convenience for strong coupling. Finally, two second-order dual-narrowband/ wideband filters with large frequency ratios were designed, fabricated, and measured. The exhibited dual-passband performance of the two filters verifies the proposed concept.

Varactor-tuned wideband band-pass filter for 5G NR frequency bands n77, n79 and 5G Wi-Fi

A wide-band band-pass filter (BPF) using coupled lines, rectangular stubs and Stepped-Impedance Resonators (SIRs) is presented in this paper. The proposed BPF operates over a large pass-band from 3.15 to 6.05 GHz covering 5G New Radio (NR) frequency Bands n77, n79 and 5G Wi-Fi, which includes the G band of US (3.3 to 4.2 GHz), 5G band of Japan (4.4 to 5 GHz) and 5G Wi-Fi (5.15 to 5.85 GHz). The presented filter has a maximum pass-band Insertion-Loss (IL) of 2 dB, a sharp roll-off rate and suppresses all the unwanted harmonics from 4.2 GHz up to 12 GHz with a 15 dB attenuation level. The performance of each section can be analyzed based on lumped-element circuit models. The electrical size of the BPF is 0.258 λg × 0.255 λg, where λg is the guided wavelength at the central frequency. The design accuracy is verified through implementing and testing the final BPF. The pass-band band-width can be controlled by adding the varactor diodes. A good relationship between the band-width and the varactor diodes are extracted by the curve fitting technique.

A dual‐band reconfigurable filtering antenna using PIN diodes for WiMAX and WLAN applications

The realization of a compact dual band reconfigurable filtering antenna is described for WiMAX and WLAN application through this communication. First and foremost, a dual band filter is offered employing four open ended half wavelength Stepped Impedance Resonators (SIRs) to resonate at 3.2 GHz and 5.35 GHz. PIN diodes have been connected to the edges of the innermost resonators to switch the operation from dual passband to two different single passbands and to all stop configuration. Multipath coupling helps to create transmission zeroes on either side of passband enriching the selectivity. In order to implement the filtering antenna, a compact monopole antenna is presented using two triangular radiating patches radiating at 3.2 GHz and 5.35 GHz. Finally, the filter and the antenna structures are combined to accomplish the proposed dual band reconfigurable filtering antenna. The results with reference to return loss and radiation pattern are provided and good performances are obtained. The suggested filtering antenna has the reflection coefficient lower than −16 dB for all the desired operating bands. As well, it offers gain of about 3.21 dBi and 5.08 dBi at the two radiating bands. The developed prototype is fabricated and measured to examine the anticipated and simulated results where a close agreement is established between them.

Sharp roll‐off triband microstrip bandpass filter with wide stopband for multiband wireless communication systems

Design of a novel triband bandpass filter is presented for wireless communications systems. The filter is based on inter-coupled stepped impedance resonators and inter-digitally coupled to the input/output ports. The configuration of the filter circuit consists of open-loop resonators that are electromagnetically coupled to each other using inverted T-shaped open stubs. The intrinsic characteristics of filter structure generates five transmission zeros that results in triband bandpass response exhibiting sharp selectivity, high inter-band isolation and a wide out of band rejection. Unlike other triband filters reported recently in literature the proposed single layer filter does not require any short-circuited plated through hole which can introduce fabrication complexity and therefore production costs. Moreover, the triband structure can be configured to provide passbands with identical 3-dB fractional bandwidth and whose center frequency can be equally spaced. In the proposed prototype design presented here the passband frequencies are set to 3.6, 4.6, and 5.6 GHz that corresponds to WiMAX, 5G, and WLAN applications. The consequence of employing open-circuited transmission lines in the design results in a relatively large structure, which can be overcome by employing higher dielectric constant substrate. The proposed triband filter was designed to achieve identical 3-dB fractional bandwidth of 11.9%. Measured results confirm inter-band isolation better than 30-dB. The theoretical model is consistent with the measured results.

Design of Highly Selective Dual Band Band Stop Filter using Dual-Path Step Impedance Resonator

In this article, the primary focus is on improving selectivity through the design of a dual-band bandstop filter (BSF), which is the abbreviation for bandstop filter. For the design of the filter, a dual-path Step Impedance Resonator, or DP-SIR, is utilised. A theoretical analysis of the suggested DP-SIR structure is presented in this body of work. At 3.76 and 11.04 GHz, the proposed architecture produces a dual-band BSF with fractional bandwidths of 50.5% and 16.36%, respectively. The comprehensive study demonstrates that the resonant frequencies can be controlled by adjusting the electrical length of the SIR. In addition, it has been found that dual-path SIR is involved in the production of finite frequency transmission poles, which results in an improvement in selectivity. This was discovered by accident. The results of the measurements and the simulations are fairly consistent with one another.

Analytical Modeling of Three-Section Coaxial Stepped Impedance Resonators for the Design of Compact Tx Bandpass Filters

This article focuses on the synthesis equations of three-section coaxial stepped impedance resonators (SIRs) for the design of Tx bandpass filters and on the benefits of adding a third section compared with using a two-section SIR. In this topology, the three coaxial structures fit inside ones another. In terms of the electrical scheme, the model is a succession of coaxial sections in a cascade, where the ground conductor of one becomes the central core of the next and vice versa. An advantageous property of SIRs is that they allow the size and the distance from the next harmonic to be controlled. The SIR effect depends on the ratio of the characteristic impedances of two adjacent coaxial TEM sections. For a resonator based on three sections, two impedance ratios need to be considered to electrically characterize the resonator in terms of fundamental resonant frequency and transmission zeros. Thanks to the equations obtained by modeling its frequency behavior, we are able to show the added value of changing such a resonator from two to three sections. This makes it possible to enlarge the minimal gap between the cylinders, decreasing the sensitivity to technological variations in manufacture and improving immunity to multipactor phenomena under constrained conditions of height and bandwidth. It also makes the first transmission zero frequency and fundamental frequency independent, as the relative proximity of these two frequencies has an impact on the quality factor and the power handling of the structure. To demonstrate the advantages, we designed an example of a three-section fourth-order filter in the L-band. This was compared with equivalent two-section filters, considering electrical performances and power handling, particularly the multipactor effect. This filter was fabricated in aluminum and tested. The experimental results are presented and discussed.

A wideband monopole antenna with diplexer and rectifier for simultaneous energy harvesting and data communication

A wideband coplanar waveguide fed monopole antenna with diplexer and rectifier for microwave wireless power transmission and communication is proposed. The antenna is comprised of an asymmetric ground plane with an open stub, a rectangular monopole, and a square loop with a gap at the bottom. A microstrip line diplexer is implemented by using stepped impedance resonator slots to split the signal without extra matching circuits. A microwave rectifier based on the voltage doubler topology is designed for wireless power transmission. The prototypes are fabricated, measured, and compared with the simulated results. Measured results demonstrate that the −10 dB impedance bandwidth (1.42 GHz) of the antenna reaches 69.6% (1.33–2.75 GHz), the diplexer minimum insertion losses ( S 21 $$ \left|{S}_{21}\right| $$ , S 31 $$ \left|{S}_{31}\right| $$ ) are 2.13 dB, 3.27 dB at pass band frequencies, the output isolation ( S 23 $$ \left|{S}_{23}\right| $$ ) better than 20 dB from 1 to 3 GHz, and the peak RF to DC conversion efficiency of a rectifier is 56%. The integration of the proposed antenna, diplexer, and rectifier novel configuration is suitable for simultaneous wireless power transmission and communication applications.

Novel Stepped Impedance Microstrip Bandpass Filters for Radar Applications

In this paper, the design and realization of A Novel Microstrip Stepped Impedance Resonator Bandpass Filters with two selected center frequencies (f0) 12GHz and 16GHz presented. For The design of Band pass Filters “Rogers 6035HTC" substrate material with relative dielectric constant of 3.55, Standard thickness of 0.020” (0.508mm), thickness of pec is 0.035mm and simulated on High Frequency System Simulator (HFSS). Both the designed filters performances are discussed and compared with literature. The designed Stepped Impedance microstrip BPFs have insertion loss of &lt;1dB with the optimal average performance of 37% and 32% FBW, and return losses are 47 dB and 32dB, which is reported better when compared with the reference designs.

A Multiple Resonant Frequencies Sensor for Measuring Permittivity Based on Stepped Impedance Resonator

This paper presented a novel sensor based on a stepped impedance resonator, which can measure the permittivities of materials at different resonant frequencies simultaneously. The multiple resonant frequencies are generated by the fundamental frequency and harmonics. The sensitivity of designed sensor at different resonant frequencies is also analyzed in detail. For verifying the feasibility of the sensor, three different kinds of materials under test are measured. The experimental results demonstrated that the tested resonant frequencies show a multiplicative growth and are consistent with our theoretical analysis. Besides, the higher the tested resonant frequency, the greater the sensitivity. The permittivity of the material under test is derived from these measured resonant frequencies by simulation and calculation. The maximum relative error through simulation and calculation are 3.4% and 26.67%, respectively. Moreover, the proposed sensor also has the advantages of being simple to fabricate, inexpensive to manufacture, and compact in volume.

Miniaturized ultra-wideband filter with independently controlled notch bands for 5.1/6/8 GHz wireless applications.

A novel three-mode step impedance resonator (TSIR) is developed to design a miniaturized multi-pole microstrip planar ultra-wideband (UWB) filter with independently controlled notched bands at different frequencies is presented in this work. The basic UWB filter consists of four L-shaped λ/4 short-circuited stubs operating in the range of i.e. 2.7 to 12.1 GHz with fractional bandwidth (FBW) 127%, and the TSIR is constructed using two T-shaped λ/2 open ended step impedance resonator (SIR) and one λ/4 short-circuited uniform impedance resonator (UIR) is coupled to the basic UWB design in order to achieve the stopbands performance at 5.1 GHz, 6 GHz, and 8 GHz, to supress the unwanted bands of WLAN, Wi-Fi 6E, and X-band satellite communication system, respectively. Commercial full-wave electromagnetic (EM) software HFSS-13 was used to design an ultra-compact structure having size 0.07 λg×0.02 λg on Rogers RT/Duroid 5880 substrate to justify good agreement between simulated and measured S-parameters.

A Design of a Compact Microwave Diplexer in Microstrip Technology Based on Bandpass Filters Using Stepped Impedance Resonator

This paper describes the design of a compact microstrip microwave diplexer based on bandpass filters and a stepped impedance resonator for 4G applications. The diplexer is composed of two band-pass filters (BPF) that operate at 1.8 and 2.5 GHz. Both bandpass filters for the receiver at 1.705-1.895 GHZ and the transmitter at 2.41-2.6 GHZ have a -3dB fractional bandwidth of 10.5 % and 7.6 % respectively. These BPF, suitable for 4G telecommunications, are examined, evaluated, developed, and simulated, yielding theoretically consistent results. With a dielectric permittivity of 4.4 and a thickness of 1.6 mm, FR-4 is employed as a substrate material. The theoretical design and simulation are used to calculate the size and position of the SIR and feed lines. The diplexer has a low insertion loss and a high isolation, and its efficiency is quantitatively analyzed using the HFSS software. This application allows us to swiftly and simply create electrodynamic structures. A diplexer prototype was developed using a typical method of fabricating PCBs, with a structural area of (47.4020x247.063=11711.28 mm2). The obtained simulation results of the proposed circuit are in good agreement with the measurements.

Compact Dual-Band Balanced-to-Unbalanced Filtering Power Divider Design With Extended Common-Mode Suppression Bandwidth

In this letter, a compact dual-band balanced-to-unbalanced filtering power divider (FPD) is proposed, which is implemented by using a pair of U microstrip lines (MLs) and short-ended stepped-impedance resonators (SESIRs). Under different excitations of differential-mode (DM) and common-mode (CM) signals, different coupling between U ML feeder and SESIRs can be achieved, which accordingly realizes efficient DM transmission and CM suppression in the whole band. Peculiarly, dual differential passbands with high-frequency selectivity performance are realized through the hybrid electric–magnetic coupling between folded SESIRs. In addition, good single-port matching and in-band isolation are achieved by introducing a matching branch and an isolation resistor. For verification, a prototype with center frequencies at 2.46 and 5.19 GHz, respectively, is fabricated and measured, which exhibits good consistency with the simulated results.

Wideband Balanced Filters With Intrinsic Common-Mode Suppression on Coplanar Stripline-Based Multimode Resonators

In this paper, two types of coplanar stripline (CPS)-based multimode stepped-impedance resonators are proposed for exploration of wideband balanced filters with intrinsic common-mode (CM) suppression. Such CPS multimode resonators (MMRs) can be readily terminated with either a pair of open- or short-circuited ends with no need of via holes. With resorting to a proper impedance ratio, the first three modes of each MMR are assembled to construct a wide differential-mode (DM) passband. Afterwards, two distinctive broadside-coupled sections are further investigated based on their open- and short-ended circuit models, respectively. Characteristic impedances and effective dielectric constants can be adequately obtained by virtue of an efficient quasi-static approach under the odd- and the even-mode operations. As such, two types of CPS-MMR-based bandpass filters each with five transmission poles are synthetically designed. For experimental validation, the proposed balanced filters are finally fabricated and measured with the help of two identical pairs of balanced-to-balanced microstrip-to-CPS transitions. Theoretical, simulated, and measured results are found in reasonable agreement with each other with/without the transitions, thus demonstrating that the proposed CPS-based MMRs are well characterized with the wideband DM transmission and intrinsic CM suppression.

Embroidered Textile Frequency-Splitting Sensor Based on Stepped-Impedance Resonators

This paper presents an embroidered textile frequency-splitting microwave sensor based on a pair of identical stepped-impedance resonators (SIRs) loading a microstrip transmission line. The sensor is implemented by means of conductive threads. The sensing region of the proposed structure is the capacitive square patch of one of the SIRs. If such region is kept unaltered, the structure is symmetric, and the frequency response (transmission coefficient) exhibits a single transmission zero. However, if symmetry is broken (e.g., through liquid absorption in the sensing region), the frequency response of the proposed sensor exhibits two transmission zeros (frequency splitting). The difference (in frequency and magnitude) between such zeros (or notches) is intimately related to the dielectric properties of the absorbed liquids to be sensed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$/$ </tex-math></inline-formula> detected. The proposed sensing structure is applied to the detection of deionized (DI) water absorption, and to the quantification of the number of DI water drops. The maximum measured sensitivity is found to be 2.70 MHz <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$/ \mu \text{l}$ </tex-math></inline-formula> and 0.03 dB <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$/ \mu \text{l}$ </tex-math></inline-formula> for the incremental frequency and incremental magnitude of the notches.

Design and analysis of clover leaf‐shaped fractal antenna integrated with stepped impedance resonator for wireless applications

SummaryA novel multi‐band clover leaf‐shaped fractal antenna with integrated filtering to reduce higher order harmonics has been proposed. Existing microstrip filtering antennas endure limited gain, narrow impedance bandwidth, and undesired frequency radiations. The proposed antenna is designated to operate simultaneously in following operating bands: 3.35–3.6 GHz for WiMAX, 5.156–5.825 GHz for WLAN, 5.7–6.4 GHz for Intelligent Transport Systems (ITS), and 7.7–8.5 GHz for ITU‐R applications. The proposed patch is realized by combining two semi‐fractal ring microstrip patches like the geometry of a three‐leaf clover with dual‐layered stepped impedance resonator (SIR) integrated at bottom layer of the second substrate. The SIR bandpass filter exhibits odd and even modes suppresses higher order harmonics and undesired radiations. An aperture coupled feeding in the proposed patch offers better bandwidth and impedance matching. The number of iterations is increased to get the desired multiband characteristics. The proposed microstrip fractal antenna has the geometrical dimensions of 50 × 50 × 2 mm3. It is observed that both the simulated and measured results offers peak gain of &gt;5 dBi and better return loss (S11), that is, 3.3–3.6‐GHz band offers S11 of −33.73 dB, 5.15–5.825‐GHz band offers S11 of −36.69 dB, and 5.795–6.4‐GHz band shows the S11 of −36.25 dB, and for 7.725–8.5 GHz, the return loss is −33.209 dB. Harmonics at 6.42 GHz (1.8f0), 7.37 GHz (1.5f0), and 9.04 GHz (1.73f0) has been suppressed and shows linear polarization in the WLAN band and circular polarization in the ITU‐R and WiMAX bands.

Nanoplasmonic Directional Coupler Using Asymmetric Parallel Coupled MIM Waveguides

This article presents the design and analysis of a nanoplasmonic directional coupler using an asymmetric parallel-coupled line metal insulator metal (MIM) waveguide. The proposed plasmonic directional coupler is designed by applying three wire transmission line (TL) model based on the basic TL characteristic parameters of the related asymmetric parallel coupled line structures. To this end, the effective refractive index, propagation length, and characteristic impedance of the related coupled line MIM waveguide structure are obtained by using fullwave simulation software CST microwave studio suite. Specifically, the dual-band nature can be obtained by exchanging the asymmetric coupled line MIM waveguide section with two asymmetric even mode step impedance resonators (SIRs) by adjusting the gap width (g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> ). Subsequently, a side-coupled resonator is designed and analyzed. Hence, the designed coupler is more useful to exchange several plasmonic devices such as power splitters and mixers in photonic integrated circuits (PICs) at a subwavelength scale.