Resonator Losses Research Articles

ЗБУДЖЕННЯ ХВИЛІ TЕ01 У КРУГЛОМУ ХВИЛЕВОДІ ЗА ДОПОМОГОЮ ВИЩИХ ТИПІВ КОЛИВАНЬ ВІДКРИТОГО РЕЗОНАТОРА

Subject and Purpose. Peculiarities of the TE01 wave excitation in a circular waveguide located in the center of the flat mirror of a hemispherical open resonator (OR) are studied using the OR oscillation type TEM30q and the OR degenerate oscillation type TEM in the extremely high frequency (EHF) range. Methods and Methodology. The efficiency of the circular-waveguide TE01 wave excitation using the TEM30q and TEM11q types of OR oscillations is evaluated through the factor of antenna surface utilization. Amplitude distributions of the OR oscillation fields were measured by the trial body method. Results. It has been established that the efficiency, h, of the TE01 wave excitation in the circular waveguide is not high when it is by use of the OR oscillation ТЕМ30q. Things are different when the TE01 wave is excited with the inner ring of the TEM11q degenerate oscillation field whereby the h value shoots up to 95.5%, the circular waveguide section radius being a = 0.993w0, where w0 is the radius of the field spot of the main oscillation type TEM00q on the OR flat mirror. The experimental studies have confirmed that the TE01 wave excitation in the waveguide has high efficiency. The attachment of the circular oversized waveguide section worsens the OR loss by no more than 0.9 dB. The presence of the circular waveguide makes the TEM3012 oscillation type transform into the TEM1112 degenerate oscillation. Conclusions. The considered OR can be used as a storage resonator in the construction of electromagnetic pulse compressors in the EHF range, since the resonant system loss increases insignificantly, and the circular waveguide itself is oversized. It is easy to implement an interference switch in such a waveguide.

Resonance loss due to the polarization accumulation effect induced by phosphorus vacancies for enhancing electromagnetic wave absorption

CoP nano-cubes with phosphorus vacancies were successfully synthesized, and the phosphorus vacancies make the impedance adaptation region move to low frequency. The great impedance matching and loss capacitance resulted in excellent MA performance.

Resonance characteristics and energy losses of an ultra-high frequency ZnO nanowire resonator

An ultra-high frequency (UHF, 300 MHz∼3 GHz) nano mechanical resonator based on defect-free zinc oxide nanowire (ZnO NW) was fabricated through a top-down processing method. Using UHF detection technology based on a lock-in amplifier, through optimized measurement of high-performance equipment, it was detected at room temperature that the ZnO NW resonator could operate at a resonance frequency of nearly 650 MHz and a quality factor Q ≈ 1000∼2500, and its force sensitivity could reach 1 f N·Hz−1/2. The deformation, driving force and first-order resonance frequency of the resonator were calculated using the continuum model and compared with the experimental data. The resonance characteristics of ZnO NW resonators under piezoelectric excitation were analyzed and compared with that under electromagnetic excitation. The effects of various loss factors on the resonance characteristics were analyzed, with emphasis on the generation mechanism of piezoelectric loss, clamping loss and eddy current loss and their effects on quality factor and force sensitivity. The ZnO NWs used in this paper have piezoelectric effect, which is rare in other NWs, and are difficult to be fabricated in a bottom-up manner. And experiments show that for ZnO NWs resonators, piezoelectric excitation has obvious advantages in Q value compared with electromagnetic excitation. Unlike the bottom-up wet etch processing method, the resonant beam structure is well protected by the top-down processing method to reduce internal defects, and the top-down fabrication method is easier to integrate into the fabrication process of integrated circuits, which provides great potential for the applications of NW resonators, such as quantum electromechanical systems and high-frequency signal processing.

High temperature infrared-radar compatible stealthy metamaterial based on an ultrathin high-entropy alloy.

In this work, a high temperature infrared (IR) and radar compatible stealthy metamaterial based on ultrathin high-entropy alloy are proposed. From room temperature to 600°C, the fabricated radar absorption layer (RAL) can have wideband absorption in X-band (8.2-12.4 GHz) with average absorption 78% owing to magnetic resonance and ohmic loss. The ultrathin high-entropy alloy film is further design as infrared shielding layer (ISL) due to low-emissivity property. The ISL and RAL consist of the IR-microwave compatible stealth metamaterial. It can give rise to the strong reduction of both radar wave reflection and infrared thermal emission. Its bandwidth (absorption over 90%) is 2.15 GHz. In the infrared atmosphere window, it can suppress a half of thermal radiation. This is realized by the subtle combination between the RAL and specifically designed ISL that control the infrared emission and microwave absorption. These results show that they are practically very promising for the application of a radar-infrared bi-stealth technology in high temperature environment.

Hierarchical core-shell FeS2/Fe7S8@C microspheres embedded into interconnected graphene framework for high-efficiency microwave attenuation

With the imminent era dominated by high-tech electronic products, the development of high-efficiency electromagnetic wave absorption materials has become a critical task. Rational component regulation and structural design are considered to be effective methods to optimize the electromagnetic wave absorption performance of materials. Herein, we first prepared a Fe-PBA@ PDA@GO precursor via solvothermal method; then, vulcanization was used to develop a FeS2/Fe7S8@C@rGO composite with a core-shell heterostructure, in which core-shell FeS2/Fe7S8@C microspheres were embedded on the wrinkled reduced graphene oxide layer. FeS2/Fe7S8@C@rGO, as a multi-component composite, demonstrates superior impedance matching and can thus capture more electromagnetic waves, while the multiple losses facilitate the dissipation of incident electromagnetic waves. Concretely, FeS2/Fe7S8@C@rGO can display significant attenuation of incident electromagnetic waves through multi-interface polarization, dipole polarization, resonance loss and eddy current loss. Additionally, the three-dimensional hierarchical structure not only improves the conductive loss, but also promotes multiple reflections and scattering. The FeS2/Fe7S8@C@rGO composite exhibits a minimum reflection loss of −62.7 dB and an effective absorption broadband (6.1 GHz) with a filler loading of 20 wt% at 2.2 mm, and the effective absorption bandwidth reaches 7.6 GHz at a layer thickness of 2.5 mm. These results provide a valuable reference for the preparation of high-performance microwave absorbers through composition adjustment and controlled structural design.

Experimental acoustic modal analysis of a tenor saxophone.

This paper presents an application of the Experimental Acoustic Modal Analysis (AMA) on a vintage 10 M Conn tenor saxophone. This technique originates from the traditional Modal Analysis which is commonly adopted to determine the dynamic behaviour of solid structures. The methodology is based on the measurement of Frequency Response Functions (FRFs) as a ratio of the acoustic pressure, measured by means of a set of microphones positioned along the saxophone body, and the volume velocity produced by an acoustic source and measured at the instrument input. The microphones are housed on the stripped saxophone keys by means of tailored three-dimensional printed adapters. The AMA makes use of the FRFs to extract modal parameters, such as resonance frequencies, loss factors, and mode shapes. These parameters pertain to the cavity modes of the saxophone passive resonator. The analysis has been performed for three different notes (B ♭, B, and C) and for two registers of the instrument in order to show the potential of the technique. Moreover, the influence of the mouthpiece volume on the cavity modes has been shown. The information obtained by AMA can find useful application in the validation of analytical or numerical models of this kind of musical instruments.

Observation of magnetic Feshbach resonances between Cs and Yb173

We report the observation of magnetic Feshbach resonances between $^{173}\mathrm{Yb}$ and $^{133}\mathrm{Cs}$. In a mixture of Cs atoms prepared in the $(f=3,{m}_{f}=3)$ state and unpolarized fermionic $^{173}\mathrm{Yb}$, we observe resonant atom loss due to two sets of magnetic Feshbach resonances around 622 and 702 G. Resonances for individual Yb nuclear spin components ${m}_{i,\mathrm{Yb}}$ are split by its interaction with the Cs electronic spin, which also provides the main coupling mechanism for the observed resonances. The observed splittings and relative resonance strengths are in good agreement with theoretical predictions from coupled-channel calculations.

Construction of 3D conductive network by flower-like V2O3 synergy with magnetic NiCo for superior electromagnetic wave absorption performance

Reasonable structural design and excellent composition are crucial for constructing excellent electromagnetic absorbers. In this research, NiCo@C/V2O3 composites were prepared by solvothermal method and annealing treatment using three-dimensional flower-like vanadium oxide as the matrix. The three-dimensional flower-like V2O3 and NiCo magnetic particles endow the composite with multiple scattering and reflection, conduction loss, resonance, and eddy current loss, thereby exhibiting excellent electromagnetic wave (EMW) absorption performance. The results show that when the matching thickness is 1.8 mm, the minimum reflection loss (RLmin) can reach -57.40 dB. Meanwhile, the effective absorption band (EAB) can cover 5.36 GHz at 1.6mm, and exhibits extremely low matching thickness. In addition, our research can provide ideas for the design of vanadium oxy-compound absorbing materials.

The influence of resonator outcoupling and losses on the photon statistics of the LASER

An extension to the quantum-mechanical laser master equation for the density operator is derived to incorporate the beam-splitter effect caused by typical dielectric laser output couplers. This effect gives rise to a significant change in the photon statistical distribution of the part of the laser light reflected back into the resonator and, therefore, may have an influence on the total laser output photon statistics. Different cases without and with additional intra-cavity losses were discussed and their influence on the expected laser photon statistics was deduced. As a result, it was found that the well-known Poisson distribution of laser light is in most cases the result of additional losses or absorption, which act uncorrelatedly on single photons. In a laser with negligible additional losses where outcoupling is dominated by the beam-splitter effect, the photon statistics reveal to be mainly non-Poisson. A Poisson distribution would only occur for very low outcoupling rates, i.e., high finesse cavities. It is found that in the limit of strong outcoupling even the distribution of thermal light can result.

Identification of Q value and angular frequency of smart gear antenna using the resonant return loss of the receiving antenna

A wireless smart gear system has been being developed as a gear health monitoring system. This system works based on the magnetic coupling between its two major elements consisting of a monitoring antenna and a smart gear. In operation, the smart gear works as a working gear in the power transmission system while the monitoring antenna monitors this gear continuously. Specifically, since the monitoring antenna is fixed and kept connecting to a network analyzer during the gear operation, it allows the magnetic coupling to occur and remain thoroughly. As a result, the return loss signal of the monitoring antenna becomes a resonant return loss data of the smart gear system. In this paper, the authors propose a method to use this resonant return loss signal for identifying two parameters called the Q value and the angular frequency of the smart gear side antenna. There are three cases of magnetic coupling that have been considered. These cases are called Open, Short, and Loaded by a 50 [Ω] resistor where the characteristics of the antenna on the smart gear side are changed via its connector by leaving Open or connecting to a Short and a 50 [Ω] resistor modules, respectively. The results indicate that the method is effective for parameter identification of the Q value and the angular frequency of the smart gear side antenna for all three cases. Moreover, the analysis of the validated Q value and the angular frequency also indicates the relation between these two characteristic values and the practical conditions of the smart gear. This finding consolidates the effectiveness of our developing wireless smart gear system.Article HighlightsThis article proposes a parameter identification method for a developing smart gear health monitoring system. By only using the resonant return loss data obtained from the monitoring antenna, there are two characteristic values of the smart gear have been achieved.This article also introduces a completed return loss equation of a magnetically coupled system. This return loss equation is helpful for the computation of characteristic parameters of the magnetically coupled system such as a wireless power transfer system or a coupled antenna system.The results figure out that the identified characteristic parameters and the physical condition of the smart gear side’s antenna circuit are related to each other. This finding affirms the effectiveness of not only the proposed parameter identification method but also the developing smart gear system.

Evaluation of transmission characteristics of differential and common modes of parallel two‐conductor microstrip lines with a Co‐Zr‐Nb film

AbstractThe effect of sheet‐ and film‐type electromagnetic noise suppressors on differential mode (DM) and common mode (CM) transmission characteristics in two parallel lines was investigated. Simple two parallel microstrip lines with a Co‐Zr‐Nb film were used as a test bench. The transmission characteristics of DM and CM were measured by four‐port network analyzer. The ferromagnetic resonance (FMR) and eddy current losses generated in the Co‐Zr‐Nb film were calculated by 3D full wave simulator, and the effects of these losses on the transmission characteristics were estimated. The results show that the transmission characteristics are different in DM and CM because the frequency characteristics of the losses are different according to the different FMR frequency in each mode. Furthermore, the feasibility of the application of the magnetic film as a frequency‐selective CM filter is demonstrated by using the difference in frequency characteristics of loss of DM and CM.

A Resonant Cavity Based on Capacitively Loaded Coaxial Structure for Overhauser Magnetic Sensors

The RF excitation coil is an important component of the Overhauser magnetic sensor, which determines whether the dynamic nucleation polarization of the free radical solution can be carried out smoothly. A capacitance-loaded resonant cavity structure is proposed as the RF excitation of the Overhauser magnetic sensor. The structure and equivalent circuit of the capacitance-loaded coaxial resonant cavity are analyzed and improved on the conventional structure, and the resonant frequency is verified to be consistent with the excitation frequency of the free radical solution by modeling and simulation using COMSOL software. The resonant cavity solid was fabricated, and the cavity was tested by using a vector network analyzer. The results show that the initial resonance point of the homemade resonant cavity is 60.55MHz, and the frequency point can be adjusted to 60.7MHz by adjusting the loading capacitor and tuning capacitor; the resonant cavity return loss S11 is about -19dB, and the quality factor Q value is about 506.

Resonant alpha particle loss in stellarators

Particle resonances in stellarators can produce islands in the space of passing particle orbits without the presence of an unstable Alfvén mode, provided the period of the resonance matches the period of the equilibrium magnetic field. In this case, the equilibrium itself plays the role of a mode amplitude, and the islands appear on surfaces where the orbital helicity matches the field period. At low energy, these surfaces are given by the field line helicity, but at higher energy, cross field drift causes them to move. The resonances are also felt by trapped particles bouncing back and forth on surfaces with matching helicity. The periodic variation of B along these orbits produces local wells, giving loss due to drift while trapped in a well. Stellarator designs that have equilibrium-induced resonance islands exhibit anomalous alpha particle loss and are unsuitable for reactors.

Ultrathin CoNi@Ti3C2Tx composites with sandwich structures for efficient microwave absorption

To obtain high-performance electromagnetic absorbing materials, we designed CoNi@Ti3C2Tx composites by a simple solvent thermal reduction method. Herein, we report the successful decoration of 80 nm CoNi alloy particles on the surface and interlayer of Ti3C2Tx. The calculated results show that the introduction of CoNi particles into the composites leads to dielectric loss and increases in Ms and Hc, significantly enhancing the soft magnetic properties of the CoNi@Ti3C2Tx composites. After adjusting the electromagnetic parameters, the optimal RL value of −51.5 dB is obtained at the frequency of 13.9 GHz, and the corresponding thickness is only 1.1 mm. The expected impedance matching and electromagnetic attenuation properties of the CoNi@Ti3C2Tx composites are attributed to synergic dual loss mechanisms – dielectric loss and magnetic loss – between the CoNi alloy particles and Ti3C2Tx. These are mainly due to conduction loss, dipole polarization, and interface polarization, as well as natural resonance and eddy current losses generated by CoNi nanoparticles. The lightweight and highly reflective CoNi@Ti3C2Tx composites are promising for applications as highly effective electromagnetic absorbers.

Optimization of Anchor Placement in TPoS MEMS Resonators: Modeling and Experimental Validation

In this paper, a semi-analytical model is derived to calculate the anchor loss of TPoS resonators operating in higher-order length extensional modes. This model provides valuable insights on the effect of order, device dimensions, position and number of anchors on the quality factor (Q) of these resonators. Results from this model are in close agreement with the FEM simulations. The optimum position, dimension, and the number of anchors to deliver the highest Q are also discussed. Predictions of the model are validated through characterization of TPoS resonators fabricated to operate at a resonant frequency of around 1 GHz with different number of anchor pairs and position. A <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$23^{rd}$ </tex-math></inline-formula> order resonator with a W/L ratio of 1.5 with three pairs of anchors placed at positions suggested by the model gave a loaded Q of 4431, which is 65% more than the conventional case where anchors are uniformly placed towards the edge, and also an improvement in the insertion loss by 5.5 dB compared to the latter. For resonators where the anchor loss is predominant, our results show that the performance can be improved by placing the anchors at the optimum position, closer to the middle of the resonator than the conventional scheme where anchors are uniformly placed towards the edge.

Firefly Algorithm based LCL filtered grid-tied STATCOM design for reactive power compensation in SCIG based Micro-grid

Microgrids are facing several operational and control issues while integrating with the grid. To deal with it, STATCOM, as one of the emerging power converter circuits, is connected with such microgrids. STATCOM with microgrid introduces current harmonic, inherent resonance, and active power losses related to high switching frequency. Filter design can help attenuate these effects and maintain the predefined standards as in IEEE 519-1992 and IEEE P1547.2-2003. There are also some more points of concern about filter design. Inappropriate filter types and parameters may cause worse filtering, reactive power surplus production, and low power factor. Therefore, this paper suggests that the reactive power compensation capability, as a local area problem, must be attended through the proper designing of LCL filtered grid-tied STATCOM. The parameters are estimated through transient analysis, power quality, and power balance studies for proposed Micro-grid and the results obtained are compared using nature-inspired algorithms such as GA, PSO, and FA over conventional mathematical formulation. The main contributions of this work are; (i) study of system with the inclusion of voltage and frequency-dependent load, (ii) modified STATCOM model clubbing reactive power control feedback and LCL filter with damping resistance, (iii) real and reactive power tracking system using dynamic compensator capabilities, and (iv) suppression of total harmonic distortions along with real and reactive power tracking using advanced tuning for filter parameters with GA, PSO, and FA based algorithms.

A Low Phase Noise K-Band VCO With a Threshold Voltage-Based Current Source

This letter presents a low-phase-noise voltage-controlled oscillator (VCO) with a threshold-voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm {TH}}$ </tex-math></inline-formula> )-based current source. The proposed current source is insensitive to the supply voltage, and the flicker noise of the transistor in the current source is decoupled, leading to lower phase noise to the resonator. In addition, a small-size differential inductor is adopted to diminish the resonator loss and to increase the quality factor. Fabricated in a 130-nm CMOS technology, the proposed VCO demonstrates a tuning range of 23.8–26.3 GHz (10.4%). It achieved a phase noise of −74.73 dBc/Hz at 100 kHz and −107.36 dBc/Hz at 1 MHz offset frequencies from the 24.005-GHz carrier frequency, respectively. The figure of merit (FoM) reaches −188 dBc/Hz.

On the role of resonance and thermoviscous losses in an implementation of “acoustic black hole” for sound absorption in air

In this work, we propose a mathematical model of a sound-absorbing structure for anechoic duct termination, commonly called the acoustic black hole. The structure consists of a set of rigid rings separated by narrow fluid-filled cavities. There are holes in the centers of the rings, whose radii smoothly vary along the structure. According to the previously published works, wave speed in this structure can theoretically decrease to zero value, which results in the reduction of the reflection coefficient. The proposed model is based on the linearized Navier–Stokes equations formulated in 2D axisymmetric cylindrical coordinates, which are solved numerically in the frequency domain employing the finite element method. This way, thermoviscous losses in the acoustic boundary layer adjacent to the fluid–solid interfaces, especially in the narrow cavities, are accounted for properly. The numerical results show that the absorption of acoustic energy in this structure is connected with resonances taking place in the cavities forming annular resonators, rather than with the acoustic wave slow-down. This effect has not been captured in the previously published models. It is shown that the geometrical details of the structure strongly influence its behavior, indicating the possibility of its optimization to serve as an efficient absorber of acoustic energy in a relatively wide frequency range.

Reconfigurable Acoustic Absorber Comprising Flexible Tubular Resonators for Broadband Sound Absorption

Typical acoustic metamaterial absorbers rely on relatively rigid materials for acoustic resonances, which, however, poses a challenge in reshaping and reconfiguring them. Here, we demonstrate soft reconfigurable acoustic absorbers, which are realized by the use of flexible tubular resonators. Owing to the structural compliance, the tube absorbers promote intriguing acoustic-structure coupling and exhibit hybrid resonances of acoustic and structural modes, which are characterized by Rabi splitting in the strong-coupling regime and Fano-like resonance in the weak-coupling regime. Also, the soft walls of the flexible resonators induce decreased resonance frequencies for low-frequency absorption by reducing the effective sound speed inside the tube. Moreover, we find that these hybrid resonances are critically influenced by the structural loss of the flexible resonators. While elucidating the role of the material rigidity and structural loss in acoustic resonances, this work allows us to design versatile broadband absorbers that can be reconfigured depending on the topology of a target substrate.

Photonic crystal fiber modulator based on surface plasmon resonance

In this paper, a photonic crystal fiber (PCF) modulator based on surface plasmon resonance (SPR) is proposed. Two optical functional materials, liquid crystal and magnetic fluid, were filled in the air holes with aurum film of PCF to excite SPR. After applying electric and magnetic fields, the effective refractive index of the SPP (surface plasmon polaritons) mode in PCF would be changed by liquid crystals and magnetic fluids, which affected the resonance wavelength and loss peak. The modulation feasibility of the structure was verified by the full vector finite element method. The results show that the proposed modulator can independently realize electro-optical and magneto-optical modulation with a characteristic of wavelength tunability. At the wavelength of 1450 nm, the electro-optic modulation voltage reaches 2.5 V, and the extinction ratio reaches a maximum of 46.11 dB/mm. Only 0.43 mm length is required to meet communication requirements. At the same time, the magnetic field sensitivity and extinction ratio of the modulator reach 17.82 pm/Oe and 25.18 dB/mm, respectively, at the wavelength of 1682 nm. The modulator has the characteristics of high extinction ratio, low modulator voltage and miniaturization, which can be used in optical fiber transmission systems that need to be integrated.