Resonator Losses Research Articles

A novel high-Q contour mode resonator

This work presents a novel silicon-based capacitive Edge-Radial Contour Mode (ERCM) resonator. Various loss mechanisms of the resonators are investigated via numerical calculations and simulations, the energy loss of the ERCM resonator is mainly dominated by thermoelastic and anchor loss. To suppress thermoelastic loss and anchor loss while maintaining a larger anchor radius, a supporting structure based on a four-ring release hole array was designed, which has significantly reduced anchor loss and motional impedance. By incorporating a four-ring spoke array within the circular disk, the resonator demonstrated more than 4 times enhancement in quality factor (Q) and an 81% reduction in motional impedance. The Q factor reaches 91,000 at frequency of 23.7MHz. Besides, the nonlinear behaviors of the resonator were studied. The nonlinear coefficients of the two resonators were modulated by optimizing the doping types to be 1.93×1010m-2 and -5.62×109m-2, respectively. These studies provide a deep understanding of the nonlinear behaviors of ERCM resonators and their potential application in tunable narrow-bandwidth filters and high-sensitive sensors.

Electromagnetic wave absorbing behavior of nano-Fe1Co0.8Ni1@C single-layer core-shell and nano-Fe1Co0.8Ni1@SiO2 @C double-layer core-shell composite particles

To effectively explore the influence of nano core-shell structure on the absorption properties of Fe1Co0.8Ni1@X composite particles, three groups of Fe1Co0.8Ni1@C single-layer core-shell structures with varying C coating layer thicknesses and Fe1Co0.8Ni1@SiO2@C double-layer core-shell structure magnetic composite particles were prepared via chemical liquid phase deposition and high-temperature carbonization, and corresponding electromagnetic absorption properties were investigated. The study revealed that the prepared nano core-shell Fe1Co0.8Ni1@X composite particles exhibited a near-spherical shape with particle size of approximately 100 nanometers. The core of the FeCoNi alloy particles was FCC polycrystalline with C coating layer thicknesses ranging from 2 to 3 nm, 10–20 nm, to 30–50 nm, while Fe1Co0.8Ni1@SiO2@C composite particles with SiO2 coating layer thicknesses of 5–10 nm and C coating layer thicknesses of 2–3 nm. As the C coating layer thickness increased, the specific saturation magnetization intensity showed a decreasing trend while the coercivity exhibited an increasing trend, all composite particles presented soft magnetic properties. With the increase of the C coating layer thickness, the real and imaginary parts of the dielectric constant of composite particles continued to rise, while real part of the permeability showed minimal change and imaginary part of permeability exhibited significant variation. Polarization relaxation and electric conduction were observed as C layer thickness increased and magnetic loss primarily including eddy current loss and resonance loss. Additionally, the peak of the dielectric loss of the composite particles demonstrated a shift towards higher frequency with increasing C coating layer thickness, and the dielectric loss of the Fe1Co0.8Ni1@SiO2@C double-layer coating structure sample was lower than that of the Fe1Co0.8Ni1@C. The attenuation constant of Fe1Co0.8Ni1@C composite particles increased with C coating layer thickness and rising continuously with the electromagnetic wave frequency. The double-layer coating structure exhibited a lower attenuation constant than single-layer coating structure and FeCoNi alloy particles, which presented the best impedance matching. Compared with the Fe1Co0.8Ni1 alloy particles, the electromagnetic wave absorption performance of the Fe1Co0.8Ni1@C composite particles was enhanced in both high and low frequency bands, and with the increase of the C coating layer thickness the main absorption frequency band of the samples with the same thickness shifted towards lower frequency. Furthermore, the thickness of sample decreased from 1.5mm to 2.0 mm to 1–1.5 mm as the C coating layer thickness increased. Maximum reflection loss |RLmax| of 61.76 dB and effectively absorbed bandwidth of 4.64 GHz was obtained for Fe1Co0.8Ni1@C composite particle.

Microwave absorption properties of one-step formed CNTs/Fe3O4-carbonyl iron superflexible buckypaper by directional pressure filtration

In order to realize the integration of structure and function of microwave-absorbing materials, carbon nanotubes/magnetic nanoparticle buckypaper (CNT/MNP BP) self-supporting, ultra-flexible, ultra-thin and ultra-light composites were prepared by composing CNTs with MNPs through directional pressure filtration technology. The BP composite, with a bulk density of 0.62 g/cm3 and a thickness of 0.21 mm, can be uninterruptedly tightly wound around a 4 mm diameter glass rod many times without structural damage. The microwave-absorbing properties and magnetic properties of the CNT/MNP composites with different compositions and contents were systematically analyzed. The CNT-Fe3O4 Buckypaper with 33.3 wt% Fe3O4 content (CF33.3 %) has the best electromagnetic wave absorption capability, with a minimum reflection loss value of −52.01 dB and an effective absorption bandwidth of 4.08 GHz. The VSM test shows that the saturation magnetization strength of CF33.3 % is 38.4 emu/g. The excellent electromagnetic wave absorption performance is attributed to the polarization and conduction losses of CNTs, natural resonance, exchange resonance and eddy current losses of MNPs, and multiple scattering and reflection within the porous network structure of the composites. The CNTs and MNPs has good dispersion in the buckypaper, where CNTs construct a superflexible skeleton besides an excellent conductive network. The self-supporting superflexible CNT/MNP BP composites have a good application prospect in the field of wearable electronic devices in the future.

Evaluating the measurement of the velocity level difference for building constructions which combine Type A and Type B elements

As part of an ongoing research project in the new four-room flanking facility at the National Research Council Canada, the velocity level differences between cross-laminated timber floors/ceilings and lightweight timber framed walls have been measured according to the standard, ISO 10848-1. The apparent sound reduction indices between the pairs of rooms have also been measured according to ISO 10848-1. The measured apparent sound reduction indices are compared to those predicted according to the standard, ISO 12354-1 based on the measured velocity level differences, the resonant transmission losses and the dimensions of the elements of the flanking paths between the room pairs.

REFRACTIVE INDEX BASED DETECTION WITH A HIGH SENSITIVITY BIOSENSOR ENHANCED BY GRAPHENE

Over the past decade, optical sensors have made significant advances. An optical sensor examines the environmental impact through the change of an optical signal and offers advantages such as low cost and label-free detection. In this study, a sensor consisting of a single graphene layer and a slit positioned on the substrate is proposed. The strip gap made to improve the excitation of graphene plasmons allowed to achieve 96.2% high transmission resonance mode. This demonstrates the ability of the sensor surface to detect changing environmental conditions. The results show that the sensitivity of the sensor is 6282 nm/RIU when the sensor surface is exposed to analytes with different refractive indices. The use of a single graphene sheet eliminates the need for a metal resonator and achieves a higher sensitivity compared to some experiments recently published in the literature. Thus, the disadvantage of significant ohmic losses in metal resonators is avoided. Furthermore, a thorough discussion of various factors, including the modification of the strip gap width on the graphene layer and electrical tunability, led to the achievement of optimal sensitivity.

Electromagnetic wave absorption performance of porous geopolymer: Dual effects of fly ash on alkali activation and microwave dissipation

The simultaneous occurrence of aggregation reactions in fly ash (FA) facilitates the uniform dispersion of internal ferrite into the geopolymer. Considering the excellent impedance matching and multiple reflection effects of foam concrete, this paper develops a ‘zero-absorber’ foam geopolymer-based electromagnetic absorbing material. The effects of different densities (400, 600, 800, 1000, 1200 kg/m3) and FA contents (40 %, 50 %, 60 %, 70 %, 80 %) on the electromagnetic absorption performance of foam geopolymer are investigated, respectively. Combined with the iron element distribution and 3D pore structure by SEM and X-CT analysis, the dissipation mechanism of electromagnetic energy by FA and pore structure in foam geopolymer are further explored. Experimental results show that FA can uniformly disperse inherent ferric ions from the matrix into the geopolymer during the polymerization reaction, leading to excellent magnetic losses through magnetic moment orientation adjustment and intermolecular friction interactions without adding external absorber. Additionally, the uniformly dispersed porous structure consumes incident electromagnetic energy through reflection, scattering, coherent attenuation, and interference resonance loss effects. It shows multi-scale electromagnetic absorption effects in the ‘zero-absorber’ foam geopolymer-based electromagnetic absorbing material, including pore structure multiple reflections (millimeter scale), inter-pore wall interference resonance (micrometer scale), and ferric ion magnetic loss (nanometer scale). For the foam geopolymer with 1000 kg/m3 density and 50 % FA, it achieves the optimal electromagnetic absorbing performance with the minimum reflection loss (RL) of −34.9 dB and the effective absorption bandwidth of 14.1 GHz (RL below −10 dB) in 2–18 GHz range.

Thin thickness electromagnetic wave absorbent: Fe3O4 decorated carbon nanofibers composite with designable 3D hierarchical architecture

Designable 3D hierarchical architecture with multi-component heterostructure has been built to form a connected network by fully utilizing the advantages of one-dimensional carbon nanofibers. Fe3O4 decorated carbon nanofibers, which exhibited core-shell microstructures, were successfully prepared by solvothermal and electrospinning technology. Their electromagnetic wave absorption (EWA) performances were explored. The morphology which determined the electromagnetic (EM) parameters can be controlled by adjusting the mass ratio of the raw material. The Fe3O4 decorated carbon nanofibers composite showed an excellent absorbing capability. At a thickness of 2.5 mm, the minimum reflection loss (RLmin) value was −28.28 dB. In particular, the widest effective absorption bandwidth (EAB) can reach up to 2.96 GHz at 1.5 mm. It was more surprising that the effective absorption (RL ≤ −10 dB) occurred when the thickness was only 1.0 mm. The absorption mechanism study revealed that the connected structure facilitated the formation of conductive networks, leading to conductive loss, multiple reflection and scatterings, and interfacial polarization loss. The defects that created during carbonization process enhanced the dipole polarization. The generated magnetic loss which mainly consisted of natural resonance and exchanged resonance loss enhanced the attenuation of EW. Moreover, good impedance matching resulting from the synergistic effect of composition and unique porous network also played an important role. The little filler loading and the thin thickness make the composite have a high EWA performance, which is promising for EWA applications.

Core Loss Measurements of Ni-Zn Ferrites by Resonant Method and Loss Separation based on Magnetization Process

Core Loss Measurements of Ni-Zn Ferrites by Resonant Method and Loss Separation based on Magnetization Process

Global sensitivity analysis of damped sandwich plates using sparse polynomial chaos expansions

The present article aims at performing a global sensitivity analysis of modal properties of a frequency dependent viscoelastic sandwich plate. The latter are evaluated using a finite element model relying on Kirchhoff theory for the elastic faces and the Mindlin-Reissner approach for the viscoelastic layer. The plate’s characteristics are considered as random variables following log normal laws. Sparse polynomial chaos expansions are employed to evaluate Sobol’s indices. For high damping, the resonant frequencies and loss factors turn to be sensitive to the elastic face properties, while in the weak damping case they are mostly affected by the viscoelastic model parameters.

Study on the microwave absorption properties of FeCoNiCrMn/PLA 3D printed composites

The work in this paper is dedicated to the study of wave-absorbing materials for applications in extremely harsh environmental conditions such as seawater and oil. In this paper, FeNiCrMn high-entropy alloy material with corrosion resistance and polylactic acid (PLA) material with high strength and high modulus were used to prepare more environmentally adaptable FeNiCrMn/PLA electromagnetic(EM) microwave-absorbing materials by two-step method of ball milling and melt extrusion.The physical phases, microscopic morphology, EM parameters and mechanical performance of FeCoNiCrMn/PLA composites were characterized using XRD, SEM, Vector Network Analyzer and Universal Testing Machine respectively. The microwave-absorbing properties of FeCoNiCrMn/PLA composites were investigated, and the effects of their components and micro-morphology on the microwave-absorbing and mechanical performance were discussed. The results show that when the FeCoNiCrMn content reaches 25 wt% and the thickness is 4.5 mm, the minimum reflection loss of FeCoNiCrMn/PLA composites reaches −24.58 dB, and the effective microwave-absorbing bandwidth is 2.51 Ghz. The maximum tensile strength and elongation at break of the composites could reach 23.83 MPa and 7.12 %, respectively. The microwave-absorbing ability of FeCoNiCrMn composites is mainly due to their rich EM loss mechanisms, including dielectric losses such as dipole polarization, interface polarization, defect-induced polarization, etc., as well as magnetic losses such as natural resonance, exchange resonance, and eddy current losses. Finally, the wide-angle microwave-absorbing characteristics of FeCoNiCrMn/PLA 3D-printed composites were investigated, the results showed that the composites with FeCoNiCrMn content of 25 wt% had Radar Cross Section (RCS) values lower than −10 dBm² within the microwave incidence angle of −90° < θ < −6° and 6° < θ < 90°, which indicated that the composites had wide-angle microwave-absorbing capability. The materials have microwave-absorbing properties along with a certain degree of mechanical strength, and at the same time have good environmental adaptability. The FeCoNiCrMn/PLA composite wire can be used in FDM technology to prepare structural microwave absorbers, realizing the integration of “material-design-manufacturing”, which has a broad application prospect in the field of EM microwave absorption and 3D printing.

Temperature dependence of microwave losses in lumped-element resonators made from superconducting nanowires with high kinetic inductance

We study the response of several microwave resonators made from superconducting NbTiN thin-film meandering nanowires with large kinetic inductance, having different circuit topology and coupling to the transmission line. Reflection measurements reveal the parameters of the circuit and analysis of their temperature dependence in the range 1.7–6 K extract the superconducting energy gap and critical temperature. The lumped-element LC resonator, valid in our frequency range of interest, allows us to predict the quasiparticle (QP) contribution to internal loss, independent of circuit topology and characteristic impedance. Our analysis shows that the internal quality factor is limited not by thermal-equilibrium QP, but an additional temperature-dependent source of internal microwave loss.

Acoustic Loss in LiNb1−xTaxO3 at Temperatures up to 900 °C

Lithium niobate‐lithium tantalate solid solutions are new piezoelectric crystals that enable to combine the advantages of their edge compounds with respect to the high thermal stability of lithium tantalate and the high Curie temperature of lithium niobate. This study aims to determine of the acoustic losses of bulk resonators with varying Nb/Ta ratios and their correlation with charge transport at temperatures up to 900 °C and at reduced oxygen partial pressures. Techniques such as resonant piezoelectric spectroscopy and contactless resonant ringdown spectroscopy are used to determine the acoustic losses. Further, the electrical conductivity is determined by impedance spectroscopy. A one‐dimensional physical model for vibrating plates is fitted to the data to extract key parameters such as piezoelectric coefficients and elastic modulus as a function of temperature. Noncontacting determination of loss excludes the impact of metal electrodes and reveals up to 300 °C values in the order of Akhiezer‐type losses. Resonators operated at 2 MHz show a rapid loss increase above about 450 °C, which is attributed to the piezoelectric/carrier relaxation. The latter follows from atomistic models using the key parameters mentioned and the electrical conductivity. The modeling includes variation of the resonance frequency and suggests higher resonance frequencies to lower the acoustic loss.

Ku-band microwave absorbing properties of submicron monodisperse carbon spheres fabricated by hydrothermal synthesis and carbonization

Carbon materials have been widely used as the absorber for the stealth of military flight equipment in recent years. This study focuses on preparing submicron monodisperse carbon spheres (SMCS) by hydrothermal synthesis and subsequent carbonization. The influence of carbonization temperature (900 ℃, 1000 ℃, 1100 ℃, and 1200 ℃) on the microstructure, phase, specific surface area, pore size distribution, electrical conductivity, complex permittivity, and microwave-absorbing properties of SMCS in the Ku-band (12.4–18.0 GHz) is investigated. The graphitization degree, electrical conductivity, and complex permittivity of SMCS carbonized at 1100 ℃ are all the highest. The C-1100 in paraffin/composites shows a strong dielectric resonance loss, thus improving microwave-absorbing properties. The effective absorption bandwidth (RL < −10 dB) of C-1100 is 4.9 GHz and the minimum reflection loss (RL min) is −18.71 dB at 14.64 GHz with a matching thickness of 1.3 mm.

Analysis of Scalable Resonant DC–DC Converter Using GaN Switches for xEV Charging Stations

In this research, an innovative electric vehicle (EV) charger is designed and presented for xEV charging stations. The key feature of our system is a scalable, interleaved inductor–inductor–capacitor (iL2C) DC-DC converter operation. The proposed system employs two parallel L2C converters with 8-GaN switches on the primary side and a shared rectifier circuit on the secondary side. This configuration not only amplifies the resonant tank internal currents and losses generated by the switches but also improves current sharing. A novel closed-loop technique is proposed with a constant-voltage method of operation, along with a hybrid control scheme of variable frequency + phase shift modulation (VFPSM). To examine the controller and converter’s performance, an experimental demonstration is conducted under varying load conditions, including full load, half load, and light load, where the source voltage and load voltage are maintained at constant levels of 400 Vin and 48 V0, respectively. Furthermore, line regulation is conducted and verified to accommodate a broad input voltage range of 300 Vin–500 Vin and 500 Vin–300 Vin while maintaining an output voltage of 48 V0 at 3.3 kW, 1.65 kW, and 0.33 kW with a peak efficiency of 98.2%.

First thin-disk oscillator with ceramic Yb:LuScO3 in comparison to the operation with ceramic Yb:Lu2O3

We report on the characterization and first laser operation of ceramic Yb:LuScO3 in a thin-disk oscillator. The optical performance achieved with a ceramic Yb:LuScO3 disk is compared to the one obtained with an existing ceramic Yb:Lu2O3 disk for reference. The characterization covers the measurement of the fluorescence spectra, the fluorescence lifetimes, and nomarsky imaging. The investigation on the laser operation covers the measurement of resonator losses, output powers, and thermal behavior during continuous-wave operation in a multimode thin-disk oscillator. An average output power of 149 W and a slope efficiency of 51.8% were achieved with the ceramic Yb:LuScO3 disk which reached a maximum surface temperature of about 150 °C. At the same temperature level, a disk made of the already established ceramic Yb:Lu2O3 delivered 957 W of output power with a slope efficiency of 75.7%.

Improvement of photothermal heating efficiency of Si plasmonic waveguide heaters with ring resonators

We report improved photothermal heating efficiency of Si plasmonic waveguide heaters integrated with ring resonators by enhancing the interaction of the propagating light and metal with a thinner buffer layer. The resonance wavelength was shifted towards a longer wavelength by inputting transverse magnetic mode light, and the amount of shift was influenced by the length of the region deposited with the Co thin film and the gap of the directional coupler. The local temperature rise of 580 K was achieved by injecting 6.3 mW of light, and photothermal conversion efficiency as high as 106 K mW−1 was obtained in a Si plasmonic waveguide deposited with 0.5 μm long Co thin films, showing improvement compared with previous devices. Discussion on the heating efficiency based on the propagation loss and cavity loss in the ring resonators is given based on experimental results, to realize compact photothermal waveguide heaters for various applications.

The effect of BaTiO3 on the magnetic behavior of MnZn ferrites at frequencies > 5 MHz

In this article an extensive study is presented on the effect of BaTiO3 on the high frequency performance of MnZn ferrite having a nominal composition Mn0.9Zn0.1Fe2.45O4. It is shown that BaTiO3 at an optimum concentration of 200 ppm wt. is a bulk dopant that dissolves in the spinel lattice leading to microstructures with smaller grain sizes, lower grain boundary resistivities and higher resonance frequencies. Despite an observed increase on the hysteresis losses, the main impact on the magnetic performance is the significant reduction of the high frequency resonance losses. In addition, no dependency has been observed on the particle size of BaTiO3 since nanoparticles produce the same effects as microparticles. Through exploitation of the beneficial effects of BaTiO3, MnZn ferrites with power losses of 195 kW m−3 (5 MHz, 10 mT, 100 °C) or 1125 kW m−3 (10 MHz, 10 mT 100 °C) and a relative initial permeability of 200 could be synthesized. These results belong to the best reported in literature and indicate that the application region of MnZn ferrites can be extended up to application frequencies traditionally dominated by other ferrite material families.

Core-shell PCIP/NiFe2O4/PANI composite: Preparation, characterization, and applications in microwave absorption

Narrow absorption bandwidth is a common problem faced by current electromagnetic wave absorbing materials. Herein, a porous carbonyl iron/NiFe2O4/polyaniline-based wave absorbing composite material with wideband microwave absorption performance was designed by metal pitting technique, co-precipitation and in-situ polymerization. The results of SEM, XPD and XPS show that PCIP/NiFe2O4/PANI nanostructures were successfully synthesized. It is found that NiFe2O4/PANI agglomeration on the PCIP surface significantly enhances the electric loss capability of the composites. When the amount of PANI is 0.7 mL, the composite exhibits broad and strong absorbing properties, and a minimum reflection loss of −45.45 dB is obtained at 2.0 mm. The effective absorption bandwidth reaches 7.5 GHz when the matching thickness is only 2.0 mm. The synergistic effect of multiple absorbing mechanisms such as dipole polarization, interface polarization, conduction loss, natural resonance, exchange resonance and eddy current loss enables it to exhibit good wave absorption performance.

Hierarchical etching-assembly engineering of Fe-based composite microspheres with balanced magnetic-dielectric synergy towards ultrahigh electromagnetic wave absorption

Hierarchical engineering of magnetic-dielectric composite microspheres has attracted increasing attention owing to its potential to enhance electromagnetic wave absorption (EMA) through magnetic-dielectric synergy. However, optimizing magnetic-dielectric balance in composite microspheres at the nanoscale remains a formidable task due to their limited component optimization and microstructural regulation. Herein, a novel approach is proposed to modify conventional carbonyl iron powder (CIP) microspheres via synergistic etching-assembly strategy. By applying a polydopamine coating, successive tannic acid (TA) etching-assembly, and pyrolysis, hierarchical iron@carbon-1/N-doped carbon (Fe@C-1/NC) composite microspheres are obtained. This overcomes the drawbacks of CIP microspheres, including their high density and poor impedance matching, which hinder EMA performance. Hierarchical carbon layer engineering can introduce abundant dipole centers, heterogeneous interfaces, and conductive networks to induce dielectric loss, while magnetic components contribute to magnetic resonance and eddy current loss, as demonstrated by the results. Accordingly, Fe@C-1/NC composite microspheres demonstrate a minimum reflection loss (RLmin) of −70.7 dB and an effective absorption bandwidth of 3.75 GHz at a matching thickness of 2.3 mm. Generally, this work paves the way towards CIP engineering to provide guidance to the future exploration of hierarchical magnetic-dielectric EMA materials.

Frequency selective low-loss transmission in negative curvature hollow-core fibers

A new low-loss negative curvature fiber design, named as the pole-anchored nested tubular negative curvature fiber, which exhibits frequency selective capabilities in the near-infrared region is proposed. This unique approach involves the addition of nested tubular elements anchored by vertical poles, which serve as an in-fiber resonator. The resulting frequency selective resonant loss dips exhibit high finesse and relative loss modulation depth. The concept of frequency selectivity in negative curvature fibers introduces unique possibilities for future applications of hollow-core structures.