Impedance Resonator Research Articles

Microwave Dielectric Properties and Defect Behavior of xTiO2-(1-x)SiO2 Glass

xTiO2-(1-x)SiO2 (x = 2.9~8.2 mol%) glass specimens were synthesized using the flame hydrolysis technique. This study aimed to elucidate the influence of TiO2 incorporation on the optical characteristics, defect behavior, and microwave dielectric performance of these materials. UV–vis and near-infrared spectroscopic analyses were employed to investigate the hydroxyl and optical bandgap properties. Electron paramagnetic resonance (EPR) and AC impedance spectroscopy were utilized to examine oxygen vacancies, Ti3+ defects, and their respective behaviors. The findings revealed that, with increasing TiO2 content, the generation and migration of defects became more favorable, consequently leading to higher dielectric losses. The imaginary component of the electric modulus experimental data was fitted using the modified Kohlrausch–Williams–Watts (KWW) function, while the frequency-dependent AC conductivity was analyzed using the Jonscher power law. The calculated activation energy exhibited a decreasing trend with increasing TiO2 content, consistent with the characteristics of doubly ionized oxygen vacancies, suggesting the involvement of identical charge carriers in the relaxation and conduction mechanisms. Notably, the 8.2TiO2–91.8SiO2 glass specimen demonstrated exceptional microwave dielectric performance, exhibiting εr = 4.13, Q × f = 57,116 GHz, and τf = −4.32 ppm/°C, rendering it a promising candidate for microwave substrate applications.

Compact diplexer based on SIR feeders, T-shaped resonators, and UIR components for mobile wireless systems

Utilizing T-shaped resonators, Uniform Impedance Resonator (UIR) and Step Impedance Resonator (SIR) feeders, this research presents a new compact microstrip diplexer developed for wireless networks. The diplexer's frequency responses with narrowband features reduce interference and enhance signal integrity, which are critical for current communication systems, and it targets channel frequencies of 3.2 and 4.7 GHz. It exhibits insertion losses of 0.3 and 0.7 dB, return losses of 30 and 19 dB, and isolation between channels surpassing 30 dB, guaranteeing minimum cross-talk and robust signal transmission. Modern mobile environments rely on quick signal processing and data transmission speeds, which are improved by incorporating negative group delay (NGD). The diplexer has been low-profile and suitable for devices with limited space due to its compact design and construction on an FR4 substrate. It is a viable option for mobile communication applications, as confirmed by thorough simulations and experimental validations.

Dual-mode Low Noise Large Range Magnetic Sensor based on Giant Magnetoimpedance Effect

Magnetic sensors are widely used in the fields of navigation, transportation, robotics, automation, and medical equipment, and the performance requirements of sensors are getting higher and higher. In this article, a bimodal magnetic sensor with two advantages of a large number of processes and low noise is proposed. The sensor consists of a 640μH core-wound inductor in series with a 100pF capacitor. When the external magnetic field changes, the magnetization state of the core in the inductor changes, the inductance value also changes, while the resonant frequency and impedance value of the sensor change with the magnetic field.<br>In this paper, the giant magnetic impedance characteristics of the RLC series circuit were analyzed, and the relationship between magnetic permeability, inductance value, and external magnetic field was established, and the series resonant frequency of the circuit was simulated to calculate the characteristics of the circuit with respect to the inductance variation.Then, two test systems were set up to test the resonance frequency versus magnetic field and the noise characteristics of the sensor.<br>In impedance mode, the effects of capacitance, drive signal frequency, and static bias magnetic field on the sensor noise floor were first analyzed to determine the optimal parameters of the sensor. When the series capacitance of the sensor is 100pF, the drive signal frequency is 1MHz, and the static bias magnetic field is 7.66Oe, the sensor has the optimal performance with an equivalent noise floor of about $200 p T / \sqrt{H z} @ 1 H z$,an impedance rate of change sensitivity of 160.6%/Oe, and a linear range of about 2Oe.In the frequency mode, the sensor operates linearly up to 25Oe, and using a logistic regression model to fit the resonant frequency to the magnetic field variation, the fit reaches 0.9974, and when the static bias magnetic field is about 7.66Oe, the sensor sensitivity is about 47kHz/Oe.<br>Not only that, with commercial components costing only ¥10 and excellent performance, the sensor has great market potential compared with other common different kinds of magnetic sensors on the market.

Millimeter-Wave Frequency-Reconfigurable Filtering Antenna with High Frequency Turning Ratio

To solve the small frequency ratio of the frequency-reconfigurable antenna operating at the millimeter-wave band, a millimeter-wave dual-band frequency-reconfigurable filtering antenna is proposed. The proposed filtering antenna consists of a reconfigurable bandpass filter and an ultra-wideband double-layer Vivaldi antenna. The reconfigurable bandpass filter comprises of several components, including parallel coupled lines, stepped impedance resonator (SIR), PIN diodes, U-shaped branches, and bias network. The reconfigurable filter is integrated in the feedline of the Vivaldi antenna, which provides a simple structure and offers flexibility for further expansion. The reconfigurable characteristic is realized by controlling the electrical length of the open circuit stepped impedance resonator through two PIN diodes, which not only acts as a switch but also affects the impedance matching within the millimeter wave band. Firstly, the equivalent circuit model of the SIR loaded with PIN diode and bias network is analyzed and simulated to achieve dual-band reconfigurability in the Ka-band. The bias network consists of fan-shaped branches and high-impedance microstrip lines, which suppresses the flow of RF signals. Two notches are introduced by the two U-shaped branches, which are placed beside the parallel coupling line without affecting the performance of the reconfigurable filter. The realized two notches are located in the non-operating frequency band between the two reconfigurable bands, which enhances the out-of-band performances of the reconfigurable filter. Then, to suppress the unnecessary coupling effect and concentrate the energy on the feedline of the Vivaldi antenna, some metallized vias are loaded at the two sides of the feedline. Finally, a metal cavity is introduced to isolate the radiation and filtering components, and some metal columns are loaded inside the cavity for improving the self-resonance of the metal cavity, which effectively improves the cross-polarization level of the filtering antenna. The measured results show that the proposed antenna operates in the range from 25.9 to 28.6 GHz with a maximum gain of 8.83 dBi when the PIN diodes are in the ON state, and in the range from 32.6 to 35.9 GHz with a maximum gain of 9.97 dBi when the PIN diodes are in the OFF state. The center frequency ratio of two reconfigurable frequency bands reaches 1:1.26, and the cross-polarization levels are all less than -20 dB in both operating bands.

Quarter-Wavelength Two-Section Coaxial Stepped Impedance Resonators for Harmonics Suppression in Tx Bandpass Filters

Quarter-Wavelength Two-Section Coaxial Stepped Impedance Resonators for Harmonics Suppression in Tx Bandpass Filters

Synthesis of Four‐Coupled‐Line Based Wideband Coupler With Inherent Filtering Feature and Its Modification

ABSTRACTIn the paper, a compact wideband filtering quadrature coupler is proposed, which utilizes the inherent filtering feature of the unequal‐width four‐coupled‐line (FCL) for the first time. Simply by assigning four terminals of the FCL as open‐circuited, the functions of power division, quadrature phase, and inherent filtering response are obtained simultaneously within a wideband. It also has the merits of high directivity and low insertion loss. Since the proposed FDC has the inherent filtering feature without adding extra resonators, the size is the smallest (0.29λg × 0.13λg), and the structure is the simplest when compared with state‐of‐the‐art wideband FDCs. Moreover, based on the derived universal impedance matrix of the unequal‐width FCL, the FCL‐based coupler, as well as other multiport circuits, can be theoretically analyzed. For validation, a prototype is implemented. Measurements show that the proposed coupler exhibits a bandwidth of over 45% under the conditions of 10‐dB return loss, 10‐dB isolation, 0.5‐dB amplitude imbalance, and 5° phase difference error. Besides, the stopband rejection is more than 15 dB, and the rectangle coefficient (RC = |BW20 dB/BW3 dB|) reaches 1.74. Further, as a modification, the high‐frequency selectivity characteristic (RC = 1.11) can be obtained by simply inserting λ/2 stepped impedance resonators with less influence on in‐band performance and little increase in size.

Multifunctional acoustic and mechanical metamaterials prepared from continuous CFRP composites.

The imperative advance towards achieving "carbon neutrality" necessitates the development of porous structures possessing dual acoustic and mechanical properties in order to mitigate energy consumption. Nevertheless, enhancing various functionalities often leads to an increase in the structural weight, which limits the feasibility of using such structures in weight-sensitive applications. In accordance with the outlined specifications, a novel structural design incorporating carbon fiber reinforced polymer (CFRP) composites alongside mechanical and acoustic metamaterials has been introduced for the first time. This innovative construction exhibits a lightweight composition with excellent mechanical and acoustic characteristics. Experimental findings demonstrate that with meticulous planning and fabrication, CFRP composite structures can achieve a balance of lightweight construction, high strength, exceptional energy absorption, and remarkable resilience. By introducing membrane and reasonable cavity design, the structure can produce low broadband noise reduction performance by a local resonance effect and impedance matching mechanism of metamaterials. The structural sound insulation capability breaks traditional mass law, resulting in an exceptionally broadband sound insulation peak (bandwidth of nearly 1000 Hz). Furthermore, the sound absorption characteristic of the structure surpasses that of the melamine sponge at frequencies below 300 Hz, demonstrating superior low-frequency sound absorption properties. The proposed structure provides new approaches for the design of multifunctional lightweight superstructures.

Formulas and measurements of the complex resonances envelope of a 2-conductor transmission line including skin effect, proximity effect, and dielectric losses

In practical energy and communication applications a transmission line is not terminated with its characteristic impedance. Consequently, to avoid reflections it is utilised in frequencies where its physical length is significantly smaller or larger than the wavelength along it. Common examples are low-voltage energy transmission across the residential AC network, cables of household equipment and internal circuitry such as printed circuit boards. The resonance frequencies of the input impedance of any transmission line pose significant worst-case scenario cases where its magnitude becomes significantly larger or smaller than the magnitude of its characteristic impedance. Even though it is commonly accepted that the input impedance resonances attenuate and asymptotically reach the characteristic impedance with increasing frequency, analytical calculation of this attenuation at the intermediate bandwidth where resonances occur, remains a challenge. In this work it is shown that when the skin effect, proximity effect, and dielectric losses are considered, measurement and calculation can approximately coincide. Furthermore derivation of formulas that describe this complex attenuating envelope, is performed. This envelope indicates above which frequency the input impedance can be approximated with a constant complex characteristic impedance. Finally, a comparison with measurements is presented, exhibiting the significance of all frequency-dependent transmission line properties.

Combined Impedance and Electron Paramagnetic Resonance Spectroscopy for Investigating the Dynamics of Li/Solid Li‐ion Conductor Interfaces

AbstractElectrochemical impedance spectroscopy (EIS) is a widely used tool for the electrochemical characterization of all‐solid‐state batteries (ASSBs) with Li‐metal anodes. However, an unambiguous interpretation of the observed impedance response often requires additional independent information on the actual interfacial phenomena obtained. The measurement methodology presented in this study allows to conduct electron paramagnetic resonance (EPR) spectroscopy and EIS concurrently. Therefore, the informative power of EIS experiments can be significantly improved via monitoring of structural changes of paramagnetic lithium at the electrochemical interface. As the solid‐electrolyte‐lithium interface is a critical part of all‐solid‐state batteries, this study employs a model oxide solid electrolyte in contact with lithium metal. During the polarization of the cell with thin evaporated lithium electrodes, the ratio between positive and negative peaks (a/b) of the EPR signal momentarily rises, which indicates an accumulation of lithium on one side of the electrolyte. The peak ratio a/b then drops abruptly, accompanied by current irregularities. Both are indicative of a diminishing contact area, and as a result, finer lithium morphologies form. Shortly after that, a contact loss is observed. The change of the EPR signal shape before cell breakdown can hence be associated with the worsening Li‐electrolyte contact, providing a tool for physical in‐situ cell diagnostics.

Quad Band Filter with Controllable Transmission Zeros using Vertical and Diagonal Coupling of Triple and Dual Step Impedance Resonators

Quad Band Filter with Controllable Transmission Zeros using Vertical and Diagonal Coupling of Triple and Dual Step Impedance Resonators

Planar dual-band bandpass filter with regular harmonic suppression

Abstract This paper presents a dual-band bandpass filter with regular harmonic suppression. The proposed third-order filter consists of two microstrip stepped impedance resonators and single substrate integrated waveguide resonator. The mismatches in their higher order resonant frequencies are utilized to suppress the regular harmonics. The passbands are centered at f1 = 2.4 GHz and f2 = 3.5 GHz with fractional bandwidths of 5% and 7.5%, respectively. The measured midband insertion and return losses are better than 2.55 and 14.5 dB for the first, whereas for the second band, they are better than 1.95 and 14 dB. The filter offers at least 33 dB suppression of first three higher order regular harmonics of f1 and f2.

Electromagnetic wave absorption property of crosslinked holey Fe/FeO/Fe2O3/RGO nanocomposite

Integrating graphene with magnetic materials that possess tailored morphologies, structures, and abundant heterointerfaces is an effective strategy for optimizing electromagnetic (EM) wave absorption performance. Here, a straightforward three-step method for synthesizing holey Fe/FeO/Fe2O3 nanosheet (FO)/reduced graphene oxide (FORGO) nanocomposites as high-performance EM wave absorbers was presented. The process involves anchoring holey Fe/FeO/Fe₂O₃ nanosheets onto reduced graphene oxide (RGO) and forming crosslinking structures between the holey nanosheets and RGO as the graphene oxide (GO) concentration exceeds 3 mg ml⁻1. By adjusting the FO/RGO ratio, both EM wave absorption performance and impedance matching can be effectively tuned. FORGO4 achieves a maximum reflection loss of −28.17 dB and an effective bandwidth (below −10 dB) of 4.10 GHz at a thickness of 2.18 mm. Leveraging the unique morphology and structure, along with the dielectric and magnetic components, a multifaceted synergistic mechanism—encompassing multiple reflection/scattering, interface polarization, dipole polarization, conductive loss, eddy current loss, exchange resonance, and optimal impedance matching—is demonstrated in the EM wave dissipation processes. Additionally, the significant contribution of multiple interface polarizations triggered by heterointerfaces to EM wave attenuation is noted. However, quantifying the contribution of interface polarization remains challenging. Density functional theory (DFT) simulations based on first principles are employed to verify the interface polarization.

Ultrawideband Flexible and Intensity-Tunable Metamaterial Absorber Based on Lossy Stepped Impedance Resonator

Ultrawideband Flexible and Intensity-Tunable Metamaterial Absorber Based on Lossy Stepped Impedance Resonator

Balanced tri- and quad-band BPFs based on SIR with improved passbands selectivity

Abstract In this paper, balanced tri- and quad-band bandpass filters (BPFs) with high selectivity and controllable center frequencies and bandwidths are proposed. In the tri-band BPF design, two differential-mode (DM) passbands are formed by utilizing a stub-loaded resonator (SLR) and a uniform impedance resonator (UIR). The coupling structure of the proposed BPF realizes the third DM passband. Moreover, the center frequencies and bandwidths of the three DM passbands can be controlled by the lengths of resonators and the gaps between the resonators. In order to improve the DM selectivity further, the source-load-coupled structure is introduced. In addition, common-mode (CM) suppression is achieved by using L-shaped balanced microstrip line to slotline transition structures, achieving the independence between CM responses and DM ones. Therefore, the design procedure can be simplified greatly. In order to validate the practicability, one balanced tri-band BPF operating at 2.5, 3.5 and 4.5 GHz is designed and fabricated. Moreover, by adding a short stub to the UIR located in the symmetrical plane, one flexible resonance frequency is generated, which is used to design the balanced quad-band BPF. By manufacturing and measurement, the measurement and simulation are in good agreement.

Electrodynamic analysis of a sinusoidal antenna for small wave sizes

Background. The work is aimed at developing and researching rigorous methods for calculating thin-wire structures with a complex generatrix shape, having small wave sizes, as well as studying the physical processes occurring in them. A special case of such structures is a sinusoidal antenna operating in a standing current wave mode. Aim. In progress the solution of internal and external problems of electrodynamics is carried out for a sinusoidal antenna of small wave sizes located above an infinitely extended ideal reflector. The currents on the elements of the structure are calculated, its input resistance and radiation characteristics are determined. Methods. The research is based on a strict electrodynamic approach, within the framework of which, for the specified structure in the thin-wire approximation, an integral representation of the electromagnetic field is formed, which, when considered on the surface of conductors together with boundary conditions, is reduced to a system of Fredholm integral equations of the second kind, written relative to unknown current distributions on conductors (internal task). Results. A mathematical model of the radiating structure is proposed, determined: the input resistance of the structure and the basic characteristics of its radiation. It is shown that the operating range of a sinusoidal antenna in the standing wave mode is determined by the quality factor of the input impedance resonances; An increase in the width of the sinusoidal conductor leads to a decrease in the resonant frequencies of the input resistance with a simultaneous increase in the quality factor of the resonances. Conclusion. From a practical point of view, the use of the considered structure allows significantly reduce the dimensions in comparison with a thin electric vibrator, however in this case, the operating range will be correspondingly narrowed, which is determined, due to the weak dependence of the radiation characteristics on frequency, by the quality factor of the resonances. The current distribution on the generatrix of the structure can be considered as a «projection» standing surface wave localized in the plane of a sinusoidal conductor, and resulting from the superposition of forward and backward surface (slow) waves propagating at a speed significantly lower than the speed of light. To further clarify the physics of the processes occurring in the structure, one should use spectral analysis of current functions and study the distributions of the electromagnetic field in the near zone of the structure.

Equivalent circuit analysis of a higher order mode coaxial reentrant cavity

An equivalent circuit analysis has been proposed for co-axial reentrant cavities which have been used extensively in Multiple-beam Klystron (MBK). Formulation for the equivalent capacitance and inductance of coaxial reentrant cavities (single and double reentrant cavity) have been obtained and used for the calculation of cavity parameters, i.e. resonant frequency and characteristic shunt impedance. The unloaded quality factor of the cavities has been obtained using Wheeler’s incremental inductance rule. Simulations of coaxial reentrant cavities have been carried out using CST studio and simulation results have been compared with the results obtained from the proposed analysis. A good agreement between the results has been obtained.

A dongle-sized bandwidth-reconfigurable filtenna for UWB/5G-n77 band applications

ABSTRACT This paper presents a frequency reconfigurable filtenna for efficiently switching between ultra-wideband (UWB) and 5G-n77 band. The filter section with the UWB state of operation is realised by a stepped impedance open stub loaded at the middle of a stepped impedance resonator. Switching to 5G-n77 band is accomplished by appending two open-circuited uniform impedance stubs to the UWB filter section through PIN diodes. The antenna section is coplanar waveguide (CPW) fed and is based on a quasi-self-complementary design with a half- hexagonal-shaped radiator. The microstrip to CPW transition is realised by connecting the ground planes through vias. The overall size of the filtering antenna is 18.5 mm × 57 mm. The filtering antenna has stable radiation patterns with good agreement between simulated and measured results. The peak gain in 5G-n77 band and UWB band is 4 dBi.

Highly selective tri-wideband bandpass filter with adjustable passbands for high-performance space-based assets applications

A straightforward approach to designing a tri-wideband bandpass filter employing an E-shaped stepped impedance resonator loaded by an open-circuited tri-section stepped impedance stub (OSLTSIR) is explored in this paper. Upon analysis, it is ascertained that this resonator offers a distinct advantage by providing increased degrees of freedom for adjusting resonant frequencies, and the strength to generate transmission zeros at lower/upper stopbands. Capitalizing on these attributes, a tri-band bandpass filter is examined by combining this OSLTSIR with a half-wavelength resonator. The incorporation between the OSLTSIRs gives rise to creating a dual-wide band, while the introduced λ/2 resonators led to split the second passband into two, yielding in tri-band performance. The resultant filter operates at 8.25 GHz, 11.1 GHz, and 15.35 GHz with wide fractional bandwidths of 25.57 %, 18.45 %, and 24.6 %, respectively. Resonant frequencies and bandwidth can be controlled with substantial flexibility. The Experimental assessments confirm the existence of seven transmission zeros, showcasing high selectivity and good isolation. Besides, the fabricated structure maintains a compact size of (6.2 × 8.4) mm, about 0.12 λg2. The close agreement between the simulated and measured findings verifies its applicability for space-based asset applications.

Design of dual-band filtering patch antenna based on SIR multimode resonator

Abstract With the development of the communication field, more and more communication devices need multiple single-frequency antennas to work simultaneously. However, using multiple single-frequency antennas results in larger sizes. The miniaturized and dual-band communication system has become a new development trend. This paper designs a dual-band filtering patch antenna based on a multimode resonator, which is cascaded. The filter resonator part adopts step impedance resonance for branch shunt design, which can flexibly control the center frequency of two frequency bands. The filtering antenna utilizes a dual-layer substrate structure and achieves an integrated design through coupling probe feeding. This reduces the horizontal dimensions and improves miniaturization. Multiple radiation nulls are introduced outside the two-passband, and roll-off characteristics are evident. In addition, this design realizes high selectivity in the operating band. The antenna has large gains of 1.71 dBi and 6.25 dBi. It has good filtering and radiation characteristics.

Enhancing Energy Harvesting Efficiency from Ambient Sources through Advanced Materials and Nanotechnology

The utilization of ambient energy sources for powering small-scale electronic devices and sensors has garnered significant attention due to its potential for sustainable and autonomous operation. This research focuses on enhancing the efficiency of energy harvesting from ambient sources, such as vibrations, heat differentials, and electromagnetic fields, through the integration of advanced materials and nanotechnology into energy harvesting systems. The study begins with a comprehensive review of existing energy harvesting technologies, highlighting their limitations in terms of efficiency, scalability, and adaptability to various ambient energy sources. It identifies the key challenges faced in achieving high energy conversion rates and explores the potential of advanced materials and nanoscale structures to address these challenges. One aspect of the research involves the development and characterization of novel materials with superior energy conversion properties. This includes the synthesis of piezoelectric materials for vibration energy harvesting, thermoelectric materials for heat-to-electricity conversion, and nanomaterials for enhancing electromagnetic energy harvesting efficiency. Advanced characterization techniques, such as scanning electron microscopy (SEM) and X-ray diffraction (XRD), are employed to analyze the structural and electrical properties of these materials. Furthermore, the study investigates the design and fabrication of nanostructured energy harvesting devices optimized for specific ambient energy sources. This involves the integration of nanoscale components, such as nanostructured electrodes, into energy harvesting systems to improve energy capture and conversion rates. Finite element analysis (FEA) simulations and experimental testing are conducted to evaluate the performance and efficiency of these nano-enhanced energy harvesting devices under real-world conditions. The research also addresses the optimization of energy harvesting system parameters, including resonance tuning, impedance matching, and energy management circuits, to maximize energy extraction and utilization. Computational modeling techniques, such as multiscale modeling and finite element simulations, are utilized to optimize system configurations and improve overall energy harvesting efficiency. Overall, this research contributes to the advancement of energy harvesting technologies by leveraging advanced materials and nanotechnology, paving the way for sustainable and autonomous power generation from ambient energy sources for a wide range of applications.