Degradation Of Quality Factor Research Articles

Thermodynamic modeling and performance analysis of photovoltaic-thermal collectors integrated with phase change materials: Comprehensive energy and exergy analysis

Phase change materials (PCMs) integrated with photovoltaic-thermal (PVT) collectors can simultaneously generate and store electrical and thermal energy. However, design optimization requires accurate modeling of the complex heat transfer processes in PCMs under varying operating conditions. This study introduces an efficient simulation approach with generalized Nusselt number correlations to enable precise and rapid analysis of PCM thermal performance. A numerical model is developed to quantify heat fluxes, node temperatures, energy and exergy outputs across PCM solid, melting, and liquid states. Extensive analysis is conducted to explore the impact of irradiation, ambient temperature, PCM thickness, tilt angle, and wind speed on PVT performance. Key findings include: (1) thermal energy yield exceeds electrical output by 2.8 times owing to PV's low efficiency, while electrical exergy dominates thermal exergy by 5.3 times highlighting electric output's primacy; (2) electrical output chiefly depends on irradiation, while thermal energy and exergy are highly sensitive to ambient temperature and wind speed; (3) thermal energy escalates 4.5 times faster than electrical energy with irradiation rise, but thermal exergy drops sharply from 10.1 to 0.34 W as ambient temperature increases from 0 to 35 °C due to quality factor degradation. The study provides new generalized correlations, validated model, and extensive performance assessment to advance PCM-based PVT collector design.

Research on Packaging Reliability and Quality Factor Degradation Model for Wafer-Level Vacuum Sealing MEMS Gyroscopes.

MEMS gyroscopes are widely applied in consumer electronics, aerospace, missile guidance, and other fields. Reliable packaging is the foundation for ensuring the survivability and performance of the sensor in harsh environments, but gas leakage models of wafer-level MEMS gyroscopes are rarely reported. This paper proposes a gas leakage model for evaluating the packaging reliability of wafer-level MEMS gyroscopes. Based on thermodynamics and hydromechanics, the relationships between the quality factor, gas molecule number, and a quality factor degradation model are derived. The mechanism of the effect of gas leakage on the quality factor is explored at wafer-level packaging. The experimental results show that the reciprocal of the quality factor is exponentially related to gas leakage time, which is in accordance with the theoretical analysis. The coefficients of determination (R2) are all greater than 0.95 by fitting the curves in Matlab R2022b. The stable values of the quality factor for drive mode and sense mode are predicted to be 6609.4 and 1205.1, respectively, and the average degradation characteristic time is 435.84 h. The gas leakage time is at least eight times the average characteristic time, namely 3486.72 h, before a stable condition is achieved in the packaging chamber of the MEMS gyroscopes.

CMOS Power Amplifier With Novel Transformer Power Combiner

A novel transformer combiner structure for wattlevel CMOS power amplifier design is presented in this letter. The proposed active skewered transformer (AST) utilizes the slab inductor as the secondary winding and overcomes the quality factor degradation issue when input cells are increased. Slab inductor has been previously used in the distributed active transformer (DAT) as the primary winding and achieved superior passive efficiency for the transformer combined CMOS power amplifier. However, we find that the slab inductor could be more beneficial as the secondary winding when we are aiming for higher output power from the CMOS power amplifier. The full-wave EM simulation has been performed and shows the advantage of AST over the conventional series-combining transformers (SCTs). Finally, a 2.4GHz CMOS power amplifier is designed based on the AST structure and fabricated in 0.18um CMOS process. The measured output power and power-added efficiency of the proposed power amplifier satisfying LTE specification with 5/20MHz bandwidth are recorded as 26.0/25.0dBm and 24.0/20.9%, respectively.

Effective electromechanical coupling coefficient () enhancement of a Lamb wave resonator with trapezoid grooves configuration

A first-order () Lamb wave resonator (LWR) with a trapezoid grooves configuration on the top surface of the aluminum nitride membrane between interdigital electrodes is proposed in this paper. Both the simulation and experiment results demonstrate that the can be enhanced with the depth of the trapezoid grooves increasing. Meanwhile, the spurious modes can be suppressed by the trapezoid grooves. A 75% improvement on the has been achieved in a 2.45 GHz mode LWR with trapezoid grooves with spurious modes free. The reaches up to 5.47% without quality factor degradation.

Multi-mode analysis of surface losses in a superconducting microwave resonator in high magnetic fields.

This paper reports on a surface impedance measurement of a bulk metal niobium-titanium superconducting radio frequency (SRF) cavity in a magnetic field (up to 10T). A novel method is employed to decompose the surface resistance contributions of the cylindrical cavity end caps and walls using measurements from multiple TM cavity modes. The results confirm that quality factor degradation of a NbTi SRF cavity in a high magnetic field is primarily from surfaces perpendicular to the field (the cavity end caps), while parallel surface resistances (the walls) remain relatively constant. This result is encouraging for applications needing high Q cavities in strong magnetic fields, such as the Axion Dark Matter eXperiment because it opens the possibility of hybrid SRF cavity construction to replace conventional copper cavities.

A Novel Buckle‐Free Large Rib Microdisk with Submicrometer Thickness

Thin large microdisks, that are key for dense spectral microcomb generation at visible to UV wavelengths, face challenges in fabrication. One of the most difficult issues is the buckling effect that significantly reduces the cavity optical quality factor. This work introduces a novel rib disk structure that significantly mitigates the buckling effects. Using this approach, we obtained millimeter size buckle-free microdisks with sub-micron thickness and high optical quality factor exceeding $10^7$.

Elastic strain engineered nanomechanical GaN resonators with thermoelastic dissipation dilution up to 600 K

Conventionally, mechanical resonators exhibit evident degradation in quality factor and large frequency fluctuation at elevated temperatures above room temperature. Here, we show that the quality factor of up to 105 of a highly stressed GaN on Si nanomechanical resonators experiences little change as temperature increasing to 600 K and the temperature coefficient of the resonance frequency (TCF) is as low as several ppm/K, several times lower than those of the conventional GaN mechanical resonators. The high quality factor and low TCF at high temperatures are attributed to the high stress and the geometrical nonlinearity of dynamical strain in the GaN resonator, where the dissipation caused by the change of the material properties with the increasing temperature is compensated by the increased stiffness. This observation violates the universality of thermal energy dissipation in mechanical resonators. The results provide a universal strategy for engineering nanomechanical resonators with ultrahigh sensitivity and ultralow noise.

Complex Permittivity and Permeability Extraction of Ferromagnetic Materials For Magnetically Tuned Microwave Circuits

Ferromagnetic materials, such as ferrites, are employed for magnetically tuned radio frequency (RF) circuits. Ferrites exhibit both electric permittivity and magnetic permeability and independent RF characterization of these two properties is crucial for accurate design and modeling of RF circuits. A method that independently extracts each property over Wi-Fi frequencies is presented here, where complex permittivity and permeability of ferrite nano-particles are extracted using resonance frequency sensitivity of a 3D printed metallic cavity to various samples under test and their placement in the cavity. Air-filled 3D printed rectangular cavity using acrylonitrile butadiene styrene (ABS) are shielded using copper sheets; the structure of air-filled cavity is designed to excite TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">101z</sub> as the dominant resonance mode that resonates at 2.4 GHz. A cylindrical shape material under test (MUT) was added to the cavity at different positions for high electric and magnetic fields, while the resonant frequency change and degradation in quality factor of the resonant cavity are employed for accurate independent extraction of electric permittivity and magnetic permeability of MUT. The sample was prepared with volumetric distribution of 60:40 nanoparticles to glue ratio. In particular, a 3D printed composite sample of ABS with NiFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> magnetic nanoparticles is placed in positions of high electric or high magnetic energy densities of the metallic cavity, while any changes in resonant frequency and its frequency selectivity are observed from the cavity insertion loss characteristics. Both perturbation theory (as analytical) and finite element method (as numerical) techniques are employed for extraction of complex permittivity and permeability of NiFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> . The perturbation theory provides accurate extraction, which is also numerically confirmed using curve fitting of the full wave simulated scattering parameters to the measured results.

Active mode selection by defects in lithium niobate on insulator microdisks.

Whispering gallery mode (WGM) optical microcavities are important building blocks in photonic integrated circuits. Operation of such cavities on specific lower- or higher- order transverse modes has much interest in application perspectives. Here, we demonstrate active mode selection by introducing defects in lithium niobate on insulator microdisks. A focused ion beam is applied to precisely inscribe nano slits into the perimeter of the microdisk. The transmission spectra can be significantly thinned out without severe quality factor degradation. Either fundamental or high-order transverse WGMs can be retained by properly designing the size and location of the defects. The approach may have promising applications in single-mode lasing and nonlinear optics.

Octave-Tuning Dual-Core Folded VCO Leveraging a Triple-Mode Switch-Less Tertiary Magnetic Loop

To satisfy the requirements for multi-standard frequency generation, mode-switching oscillators are developed to increase the frequency tuning range without incurring considerable phase noise penalty. However, this improvement in the tuning range is often limited by the parasitics of the circuitry for mode selection and tuning. To address this challenge, this work presents a dual-core octave-tuning VCO using a switch-less tertiary magnetic coupling loop. The design employs the benefits of transformer-switching without incurring switch loss and quality factor degradation and also the benefits of mode switching without the parasitics from the mode selection and tuning network. The VCO employs a non-constant $RC$ scaling for the capacitors’ bank, across the tuning bits, and positive feedback dc-coupled inductive-degenerated output buffer to maximize the tuning range. Implemented in 22 nm fully depleted silicon-on-insulator (FDSOI), the dual-core VCO achieves a 72% tuning at 8–17 GHz and a figure-of-merit-tuning ( $\text {FoM}_{T}$ ) of 208.8 dBc/Hz at 11 GHz. The chip operates from a 0.45 V supply with a power consumption of 17–33 mW and a core area of 0.39 mm2. To the best of our knowledge, the VCO achieves the highest $\text {FoM}_{T}$ and lowest supply for designs over 10 GHz.

Impact of Frequency Mismatch on the Quality Factor of Large Arrays of X-Cut Lithium Niobate MEMS Resonators

This paper investigates the impact of resonant frequency (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ) mismatch on the quality factor (Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">as</sub> ) of large arrays of X-cut Lithium Niobate (LN) Laterally Vibrating Resonators (LVRs) operating around 50 MHz and 400 MHz. The statistical distributions of key device parameters, including resonant frequency, quality factor (Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ), electromechanical coupling (k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ), and static capacitance (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ), are collected from replicas of identical resonators. A Monte Carlo approach is later implemented to simulate the impact of statistical variability on the quality factor of arrays of resonators. By including the effect of interconnects series resistance on the arrays, an excellent agreement between experimental and simulated Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">as</sub> is achieved, demonstrating that frequency mismatch is the major mechanism of quality factor degradation in arrays of parallel resonators. The experimental validation of the model confirms that it can be used as a predictive tool to establish the frequency tolerance requirements in order to attain high Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">as</sub> in arrays.

SPR performance enhancement for DNA hybridization employing black phosphorus, silver, and silicon.

We present the performance enhancement of the surface plasmon resonance (SPR) sensor for deoxyribonucleic acid (DNA) hybridization employing black phosphorus (BP), silver (Ag), and silicon (Si) configurations and numerical analysis. The combination of Ag and BP demonstrates the sensitivity of 91.54°/RIU with degradation of detection accuracy (DA), quality factor (QF), and figure of merit (FOM). To enhance the DA, QF, and FOM, a novel SPR is proposed with Si, which demonstrates a DA and QF of 69 and 1061.6RIU-1, which are 8.53 and 11.04 times, and an FOM of 554.58, which is 4.47 and 5.77 times higher than both the conventional and graphene-based SPR sensors, respectively.

Realization of improved Hackee’s quality factor and photo degradation efficiency of cauliflower shape nanostructured CdO thin films through Cs doping

Cauliflower shape nanostructured Cs-doped CdO (CdO:Cs) thin films were grown using perfume atomizer. A strong (1 1 1) preferential orientation is noticed for the cubic structured CdO:Cs thin films. Surface morphology of CdO was strongly influenced with Cs doping. All the doped films exhibit better transparency than pure CdO. With Cs doping, the absorption edge seems to shift towards lower wave lengths (i.e. higher energies). The 2 wt.% Cs-doped CdO thin film exhibits a minimum resistivity of 0.95 × 10−3 Ω-cm. Increased Hackee’s quality factor realized with Cs doping confirms that the CdO:Cs thin films are well suited for optoelectronic devices especially as transparent electrodes. A maximum photo degradation efficiency of 86.9 % was realized for the 2 wt.% Cs-doped CdO thin film against malachite green under visible light.

First Demonstration of Ultra-Thin Glass Panel Embedded (GPE) Package with Sheet Type Epoxy Molding Compound for 5G/mm-wave Applications

Abstract With the number of connected-devices increasing tremendously, communication data rates are projected to be at least 10–100X in the 5G/mm-wave (MMW) technology - much higher than the existing 4G LTE connections.[1], [2] To catch up with the trend, novel packaging technology in the MMW frequency range is required, which will address fundamental MMW technical challenges such as high dielectric loss, degradation of quality factors in passives, increased parasitic, dramatically-enhanced electromagnetic interference, and the reduced radiation efficiency of antenna arrays. State-of-the-art approaches being pursued include organic-core substrates that have a low dielectric constant (Dk) and low dissipation factor (Df) such as fluorine based or liquid-crystal polymer (LCP) substrates in order to achieve enhanced antenna performance and low signal dissipations. These organic-based substrate technologies, however, can neither miniaturize packages nor handle precision signal routings that enable high density packages. To address these challenges, attention is focused on Fan-Out Wafer Level Package (FOWLP) technologies, like eWLB, InFO, and SWIFT, where integrated circuits (ICs) are embedded in epoxy molding compound. [3]–[6] Recently, glass-panel embedding (GPE) technology is emerging as an ideal packaging methodology that enables superior performance along with small form factor, ultra-low-loss, high density, ultra-short interconnects, and low cost. [7] These benefits stem from the advantages of using glass which has excellent properties such as ultra-smooth surface for precision redistribution layer (RDL), exceptional dimensional stability for panel-scalability and tailorability of CTE that allow direct board-attach for improved system performance. In addition, utilizing the epoxy molding compounds as encapsulation material allows the GPE package to be thinner and more robust package with small farm factor. Molding of glass cavity panels also helps with the handling of ultra-thin glass which is seen as a bottleneck towards glass based packaging solutions in production. These facilitates enhanced throughput by allowing more cavity cut outs (more coupons) per panel. This paper presents the first demonstration of ultra-thin GPE with sheet type epoxy molding compound (SMC) for 5G/mm-wave applications. First part of this paper discusses the process-flow used in glass-panel embedding with laminated SMC, including chip placement in glass cavities, lamination of SMC, and the reliability of the package architecture. This paper reports on such a demonstration in 60 μm glass substrates with 40 μm thickness SMC. The second part of this paper focuses on low-loss interconnects for 5G/mm-wave applications and presents the process development of signal routings such as transmission lines and microvias in RDLs as well as through-package vias (TPVs) with via-in-via process. The results suggest that the ultra-thin GPE architecture is a promising packaging technology solution for a variety of applications including high-frequency communications and high-performance computing.

Degradation of Quality Factor of Superconducting Resonators by Remaining Metallic Film and Improved Fabrication Process Using Caldera Planarization

An important figure of merit in microwave superconducting quantum interference device multiplexer (MW-MUX) is the quality factor of superconducting resonators. In advanced industrial science and technology (AIST), the intrinsic quality factor Qi of the resonators in the MW-MUX chips degraded significantly compared to those in the resonator-only chips owing to something during the fabrication process. In this study, we have investigated the damage process by conducting controlled experiments and an SEM-EDX analysis. As a result, we have confirmed that the metallic layers (Pd and Nb) were not removed completely and remained along the edge of the resonator, which resulted in the degradation of Qi. Further, we have invented a new process to overcome this imperfection during the removal of Pd layer using so called “caldera planarization”. The metal line that remained along the edge was not observed in the MW-MUX chips fabricated using this improved process. Finally, we have achieved Qi as high as that of resonator-only chips using the improved process.

Ray dynamics and wave chaos in circular-side polygonal microcavities

We systematically study mode characteristics in circular-side polygonal microcavities (CSPMs), particularly in these cavities with chaotic ray dynamics, in order to gain insights into the wave chaos in the CSPMs. The circular sides could improve the light confinement of the CSPMs as concave mirrors, in that regular islands are formed around the stable fixed points in the Poincar\'e surface of sections (SOS). However, the fixed points become unstable under some specific deformations, and global chaos with quasistable ``star islands'' appears around these fixed points in the Poincar\'e SOS accordingly. The phenomenon can be well explained by the ray dynamic analysis under the second-order approximation, and the results show that the high-order terms play an important role in the motions of light rays and destroy the regular islands in the phase space leading to chaotic ray dynamics. The destruction of regular islands results in degradation of mode quality factors and dispersed mode field distributions according to the finite-element method simulation of the confined modes. Furthermore, an unusual variation of mode quality factor is observed by varying the refractive index of the outside media for the CSPM with chaotic ray dynamics.

Pixelwise JPEG compression detection and quality factor estimation based on convolutional neural network

JPEG compression is one of image degradations that often occurs in image storing and retouching process. Estimating JPEG compression degradation property is important for JPEG deblocking algorithm and image forensic analysis. JPEG degradation exists not only in JPEG file format but also in other image formats because JPEG distortion remains after converting to another image format. Moreover, JPEG degradation property is not always uniform within an image in case that the image is collaged from different JPEG-compressed photos. In this paper, pixelwise detection of JPEG-compression degradation and estimation of JPEG quality factor using a convolutional neural network is proposed. The proposed network outputs an estimated JPEG quality factor map and a compression flag map from an input image. Experimental results show that the proposed network successfully infers the quality factors and discriminates between non-JPEG-compressed images and JPEG-compressed images. We also demonstrate that the proposed network can spot a collaged region in a fake image which is comprised of images that have different JPEG compression properties. Additionally, the network reveals that image datasets Set5 and Set14, often used to evaluate super-resolution algorithms, contain JPEG-compressed low quality images, which are inappropriate for such evaluation.

Understanding Quality Factor Degradation in Superconducting Niobium Cavities at Low Microwave Field Amplitudes.

In niobium superconducting radio frequency (SRF) cavities for particle acceleration, a decrease of the quality factor at lower fields-a so-called low field Q slope or LFQS-has been a long-standing unexplained effect. By extending the high Q measurement techniques to ultralow fields, we discover two previously unknown features of the effect: (i)saturation at rf fields lower than E_{acc}∼0.1 MV/m; (ii)strong degradation enhancement by growing thicker niobium pentoxide. Our findings suggest that the LFQS may be caused by the two level systems in the natural niobium oxide on the inner cavity surface, thereby identifying a new source of residual resistance and providing guidance for potential nonaccelerator low-field applications of SRF cavities.

A microwave sensor for zinc corrosion detection

This article presents a sensor based on zinc wires of different widths deposited on the surface of the ceramic resonator capable of detecting and following the evolution of the corrosion of the zinc material. Electromagnetic studies show that due to the evolution of the corrosion, the progressive degradation of the conductivity of the formed zinc grid (from 6 S/μm to 0.015 S/μm) causes a degradation of the quality factor (from Q0 = 50 to Q0 &amp;lt; 5), a decreased level of the coefficient transmission of the TE101 mode of the resonator (from -8 dB to &amp;lt;-35 dB), and a progressive frequency shift (230 MHz). Experimental measurements of this sensor in a corrosive environment show a gradual shift of the resonance frequency of the TE101 mode, a decreased level of the S21 transmission coefficient, and a degradation of the unloaded quality factor. Confirmed by electronic microscopy and X–Ray analysis, these variations are due to the evolution in the corrosion of zinc wires over time, leading to a creation of corrosion products in these wires.

Divide-by-3 injection-locked frequency dividers using dual-resonance resonator

This paper exploits the application of dual-resonance LC resonator in the design of wide-locking-range injection-locked frequency dividers (ILFDs). The tail-injection and direct-injection divide-by-3 ILFD circuits in a standard CMOS process are realized with a pair of cross-coupled nMOSFETs with a dual-resonance LC-resonator. The locking range enhancement techniques such as linear mixer and quality-factor degradation are used to design wide-locking range divide-by-3 ILFD. At the incident power of 0 dBm the locking range of the divide-by-3 ILFD is 4.6 GHz (43.3 %), from the incident frequency 8.3 to 12.9 GHz.