Capacitive Gap Research Articles

Дефектная мода в СВЧ волноводных брэгговских структурах с металлическими штырями

AbstractA waveguide Bragg structure containing equidistant cylindrical pins that are galvanically coupled to a wide wall of the waveguide is used to implement frequency response functions characterized by the presence of a band gap. Characteristics of a defect mode of the microwave photonic crystal with a pin element as a defect with an n – i – p – i – n structure with controlled conductivity placed in the capacitive gap are experimentally studied and calculated. Controlled reflectance of a microwave signal with a dynamic range of greater than 50 dB is obtained at the frequency of the defect mode.

Evaluation of Photoelectric Characteristics of a Volume DBD Excited by Power Density Modulation

Photoelectric characteristics are an important reference for high-voltage discharges and are closely related to the excited mode of the high-voltage source. In this paper, we built a large-scale volume dielectric barrier discharge (DBD) system, which is composed of multilayer parallel-plate DBD electrodes and is excited by a high-voltage source in the power density modulation (PDM) mode. Subsequently, we analyzed the applied energy equation and evaluated the DBD systems photoelectric characteristics. The results show that the energy values of different applied voltage cycles during a PDM period exhibit significant differences. However, the average energy in a PDM period is approximately constant. Moreover, the equivalent capacitance of the DBD cell is a function of both the applied voltage and energy density. For the DBD cell, with the increase in both the applied voltage and energy loaded on the DBD cell, the total equivalent capacitance (C) is approximately constant, the dielectric capacitance (C d ) increases exponentially and decreases linearly, while the discharge gap capacitance (C g ) decreases and increases in the same cases. In addition, the relative intensities of the discharge emission increase and the energy efficiency ratios of the relative photoquantum yield of active species decline with the increase in both the applied voltage and energy density loaded on the DBD cell. The experimental results have been analyzed by evaluating the influence of the electrical parameters, and the underlying physical principles have been discussed. This paper clearly demonstrates that the photoelectric characteristics of the DBD reactor are significantly influenced by both the applied voltage and energy density, thus providing helpful insights into the energy evaluation and application of high-voltage discharges.

Isolation enhanced circularly polarized patch antenna array using modified electric‐field‐coupled resonator

A modified electric-field-coupled (MELC) resonator featuring negative permittivity is proposed to enhance the inter-element isolation of a circularly polarized (CP) patch antenna array operated at Chinese compass navigation satellite system (CNSS) downlink band. The resonator comprises two capacitive gaps and a common inductive strip connected to the ground plane by two metal vias. A suspended microstrip line excitation is employed to efficiently design and investigate the MELC resonator whose constitutive parameters are subsequently extracted. A dual-element CNSS antenna array has been prototyped and measured. The experimental results demonstrate that under the assistance of the proposed MELC resonator, a mutual coupling reduction of 15 dB has been achieved while maintaining good impedance matching and CP radiation performance. Details of the design considerations along with simulation and measurement results are presented and discussed.

Improved design of CELC meta-resonators for bandwidth improvement and miniaturization of patch antenna

For metamaterial resonators, the essential figure of merit is its effective medium ratio (EMR), which is defined as the ratio of the resonant wavelength and lattice constant. In this paper, an altered topology of the electric-inductive–capacitive (ELC) metamaterial with an improved EMR is proposed. The proposed structure shrinks the electrical footprint of the conventional ELC resonator by accommodating additional inductance by meandering the arms of the resonator and fitting interdigital capacitors in the capacitive gap. The metamaterial properties of the proposed structure are investigated by parameter extraction, and analytical formulations are carried out for finding its resonant frequency. The proposed metamaterial structure is employed for performance enhancement and miniaturization of a standard patch antenna. A 3 × 4 array of the modified complementary resonators is etched in the ground plane of a patch antenna. A significant 293% improvement in bandwidth, with a miniaturization factor (unloaded frequency/loaded frequency) of 1.33 is achieved. The entire antenna resides in a small area of 37.5 mm × 37.5 mm. The design is substantiated both by simulation and experimental results, which complement each other. The presented design can be used for Mobile WiMAX (2.5–2.69 GHz) applications.

Optical characterization of a novel miniature microwave inductively coupled plasma source in nitrogen flow

A miniature microwave (MMW) inductively coupled plasma (ICP) source is characterized by optical emission spectroscopy and by optical imaging of nitrogen plasma. The MWW source operates in two different modes (H-mode and hybrid-E/H mode) with different plasma parameters and different emission morphologies, depending on the absorbed microwave power (Pabs). The measured spectra of the second positive system (N2(C-B)) and of the first negative system (N2+(B-X)) of nitrogen reveal an electron density ne = (6.4 ± 1.7)×1018 m-3 and a gas temperature of Tg = (650 ± 20) K for Pabs = 12 W at a pressure of 1000 Pa. By increasing the absorbed power to Pabs = 78 W the parameters increase to ne = (3.5 ± 1.7)×1019 m−3 and Tg = (1600 ± 100) K. The discharge morphology in hybrid and H-mode is different. While in the H-mode the plasma resembles a ‘donuts’ shape, the hybrid mode has a very narrow shape close to the walls and to the gap capacitor of the resonator. For our discharge conditions the power absorption is limited to 158 W, above which the discharge spontaneously switches from H-mode to hybrid mode.

RF Channel-Select Micromechanical Disk Filters-Part II: Demonstration.

This Part II of a two-paper sequence presents fabrication and measurement results for a micromechanical disk-based RF channel-select filter designed using the theory and procedure of Part I. Successful demonstration of an actual filter required several practical additions to an ideal design, including the introduction of a 39-nm-gap capacitive transducer, voltage-controlled frequency tuning electrodes, and a stress relieving coupled array design, all of which combine to enable a 0.1% bandwidth 223.4-MHz channel-select filter with only 2.7 dB of in-band insertion loss and 50-dB rejection of out-of-band interferers. This amount of rejection is more than 23 dB better than a previous capacitive-gap transduced filter design that did not benefit from sub-50-nm gaps. It also comes in tandem with a 20-dB shape factor of 2.7 realized by a hierarchical mechanical circuit design utilizing 206 micromechanical circuit elements, all contained in an area footprint of only [Formula: see text]. The key to such low insertion loss for this tiny percent bandwidth is Q 's >8800 supplied by polysilicon disk resonators employing for the first time capacitive transducer gaps small enough to generate coupling strengths of Cx/Co ∼ 0.1 %, which is a 6.1× improvement over previous efforts. The filter structure utilizes electrical tuning to correct frequency mismatches due to process variations, where a dc tuning voltage of 12.1 V improves the filter insertion loss by 1.8 dB and yields the desired equiripple passband shape. Measured filter performance, both in- and out-of-channel, compares well with predictions of an electrical equivalent circuit that captures not only the ideal filter response, but also parasitic nonidealities that distort somewhat the filter response.

Nanoparticle using parallel split rings and implementation of chain for creating Fano resonance with polarization independence for energy harvesting in mid-infrared

In optical devices, the polarization of the incident wave affects the Nano particle characteristics. Therefore, designing a polarization-independent device is significant in the process of designing optical structures. On the other hand, the concept of Fano resonance and dark mode has been utilized for achieving more energy enhancement. In this paper, we have developed a symmetrical Nano antenna by employing Fano resonance, which is independent of the incident wave polarization. The proposed Nano antenna is modified in mid infrared regime for biosensing and energy harvesting applications. The designed metamaterial antenna is made by Nano split ring resonators with etched capacitive gaps, which are utilized for concentrating energy. The introduced Nano antenna has a bright and dark mode with a weak enhancement of electric field. The effect of the incident wave polarization is investigated at wave incident angles between 0° and 45° to illustrate the independency of the polarization due to the symmetrical shape of the Nano antenna. In order to trigger the dark mode and enhance the electric field, a Nano chain is incorporated in the final structure. This arrangement has led to increasing of electric field drastically. Furthermore, the figure of merit has been calculated as an advantageous factor in sensing the surrounding materials with various refractive indices. Our findings illustrated that the chain arrangement has caused a peak in the linear form of the extinction cross section of the Nano antenna. This in turn has resulted in the appearance of Fano resonance with no impact on the resonance frequency that has been originally adjusted by capacitive gaps and inductive strips.

Wideband optical absorber based on plasmonic metamaterial cross structure

The optical absorber with Fano response is valuable for various applications such as solar cells or optical sensors. In this paper, we have modeled an optical plasmonic metamaterial absorber which contains a broken cross as an elementary cell along with four rectangular loads to improve the absorbance and achieve a Fano response within a wide bandwidth at 190–245 THz (25%). The bandwidth of the proposed structure is more than conventional metamaterial absorbers. The prototype absorber has a remarkable enhancement in the electric field in comparison with the simple cross model and the reflection value has reduced to − 47 dB. The parametric studies show how the gap capacitance controls the bandwidth, resonance frequency and the reflection value of the absorber, therefore we can consider this technique as a way to enhance the metamaterial absorber’s bandwidth. The proposed structure can be used as an optical refractive index sensor while the Fano line-shape provides a higher figure of merit (FOM) compared with many others. For this structure, the FOM has obtained as 10,660. The Finite Integration Technique with Perfect Boundary Approximation used for the simulation.

A Miniaturized Band-Reject Filter Using Metamaterial Structures on Silicon Substrate for X-Band Application

ABSTRACT This paper presents a miniature-size band-reject filter on a Coplanar Waveguide (CPW) transmission line using series connected complementary split ring resonators (CSRRs) and series capacitive gaps for X-band applications. The band-reject filter has highly miniaturized dimensions and is capable of solving almost all the basic limitations to which the conventional band-reject filters are mostly susceptible. The series connected CSRRs are etched on the signal planes of the CPW transmission line on silicon substrate enabling CMOS compatibility with planar IC technology. It is a concept resulting in higher bandwidth, low insertion loss of 0.5 dB with high rejection of 40 dB in the stop bands better than similar designs. The optimized design of the proposed device is performed using the parametric study of filter characteristics. The proposed devices RF analysis and circuit model are simulated using Ansoft High-Frequency Structural Simulator (HFSS) v13® and Agilent Advanced Design System (ADS) 2009. Measured results are in good agreement with their simulated counterparts and the measured performance is encouraging in all respects.

Compact D-CRLH resonator for low-pass filter with wide rejection band, high roll-off, and transmission zeros

AbstractA compact low-pass filter (LPF) with wide rejection band based on T-type circuit of an enhanced dual composite right-/left-handed (D-CRLH) resonator is presented in this paper. The resonator has only one cell with series and parallel tank circuit. The parallel LC tank circuit has been realized by an interdigital capacitor and one shorted finger, whereas its series LC tank circuit is realized by an air gap capacitance and a short circuit stub. The filter has wide rejection band bandwidth with three transmission zeros (TZs). The filter bandwidth and TZs frequencies are controlled by the D-CRLH element values. The results of the proposed filter demonstrate minimum insertion loss in passband, high roll-off rate, and good figure of merit. The measured results are in good agreement with the simulated results. The detailed filter design is discussed in terms of circuit modeling, dispersion analysis, and full-wave simulation. Finally, the filter size is compact (0.10 λg × 0.15 λg) at cut-off frequency.

Multi-Response Optimization of Micro-WEDM Process Parameters of Ti<sub>49.4</sub>-Ni<sub>50.6</sub> Shape Memory Alloy for Orthopedic Implant Application

The present work deals with the optimization of micro-WEDM process parameters for machining Ti49.4-Ni50.6 shape memory alloy (SMA) for orthopedic implant application. Effect of micro-WEDM parameters viz. Gap voltage, capacitance, wire feed and wire tension on the response variables such as material removal rate, surface roughness, kerf width and dimensional deviation is determined. As Ti-Ni SMA has fascinating properties and bio-compatibility, have been considered for present work. Nine experiments have been performed on micro-WEDM based on an orthogonal array of Taguchi method. Subsequently, the grey relational analysis (GRA) method is applied to determine an optimal set of process parameters. It is observed that optimized set of parameters A3B3C3D1 viz. 140 V gap voltage, 0.4 µF capacitance, wire feed 30 µm/sec and 30% of wire tension determined by using GRA offers maximum MRR and minimum SR, KW and DD. From the Analysis of Variance, it is seen that the process parameter capacitance is the most significant parameter for multi-response optimization with a percentage contribution of 77.91%. Young’s modulus also checked for biocompatibility. Also, SEM images are taken to confirm the results offering better surface quality. Heat treatment process like annealing is found to be the most suitable to recover shape memory effect of WEDMed samples.

Capacitive Gap Loaded Dual, Triple and Wide Band Loop Antenna *

Capacitive Gap Loaded Dual, Triple and Wide Band Loop Antenna *

Study of Laser-Triggered Vacuum Switch with a Six-gap Rod

In this paper, the triggered polar material structure of the Laser Triggered Vacuum Switch (LTVS) was redesigned and the shape of the main electrode was improved. At last, we know that when the gap length of the LTVS is 12mm and the withstand voltage is 30kV, the LTVS is successfully conducted with 5kV gap voltage and 10mJ laser whose wavelength is 1064nm. Meanwhile, jitter time of the switch is approximately 2ns and the conduction time is approximately 20ns. By comparing the gap voltage, capacitance value, laser power and laser wavelength, the implications of such improvements on the jitter time and conduction time of the switch are discussed.

Development of a micromachined accelerometer for particle acceleration detection

We are reporting on the design, fabrication, and experimental results for a micromachiend accelerometer that is intended to be used in the detection of acoustic signals, where the main requirements include low noise, wide bandwidth, and high linearity. The device design requirements are discussed and analytically modelled. Microfabrication details to build prototypes are provided in detail. The final device structure employs membrane as the suspension mechanism and a proof-mass made from the entire thickness of a wafer that is suspended above a fixed electrode. The proposed manufacturing process allows for precise and independent control of the structural components of the device and the capacitive gap. Prototype devices were fabricated and characterized. Measurements on the device performance demonstrate a 0.6 μg/Hz noise floor with resonance frequency of 5.2 kHz, sensitivity of ∼0.9 pF/g, and open-loop dynamic range of higher than 145 dB while operating at atmospheric pressure. The device meets the requirements for measuring sonar signals in the range of 50 Hz to 5 kHz under low environmental noise conditions.

Compact Microstrip Diplexer Based on CRLH Metamaterial Concept

ABSTRACTIn this paper, a compact microstrip diplexer based on resonant-type metamaterial transmission lines is proposed. The proposed diplexer is designed by cascading two bandpass filters with different center frequencies. The bandpass filter, which the proposed diplexer has been designed based on it, is realized by series of capacitive gaps with grounded stub on the upper metal layer and the complementary spiral resonators unit cell which etching on the ground plane. The proposed diplexer as a three-port device has been designed to operate at two arbitrary frequencies. The simulation results show that the three-port diplexer can separate two different frequencies effectively. In order to confirm the design procedure and the capability of the proposed diplexer in size reduction and selectivity, two prototype devices operative in the center frequencies at 2.4 and 3.5 GHz have been fabricated and tested. Good agreement between measurement and simulation results has been achieved. These one- and two-stage diplexers have the overall sizes of 0.19 λg × 0.05 λg and 0.34 λg × 0.06 λg, respectively. The proposed diplexers have many advantages in terms of compact size, low loss, high isolation, ease of fabrication, and high selectivity.

Influence of Nano Powder Mixed Dielectric Fluid on Surface Finish in Micro Electro Discharge Machining of Zirconia

Background: Powder mixed dielectric fluid is being used recently to cut difficult to cut ceramic materials such as aluminium oxide (Al2O3) and zirconium oxide (ZrO2) where process development and optimization are found to be critical issues. Object: This paper investigates and compares the average surface roughness (Ra) in micro electrical discharge machining (EDM) of electrically nonconductive zirconium oxide (ZrO2) ceramic using clean and tantalum carbide (TaC) nano powder mixed kerosene dielectric fluid. Method: The design of experiment was applied by response surface methodology with face centred composite design. The gap voltage, capacitance and concentration of TaC powder are considered as the variable parameters for the investigation while other conditions are kept constant. Results: The study shows that the powder concentration has a significant negative effect on the average surface roughness of ZrO2. Conclusion: The optimized values of gap voltage and powder concentration are found to be 100 pF, 94.4 V and 6.3 g/l, respectively for a minimum surface roughness in micro-EDM of ZrO2. Without powder introduction, a minimum Ra surface roughness of 170 nm achieves 100 pF and 81 V.

Improvement of Deep Reactive Ion Etching Process For Motional Resistance Reduction of Capacitively Transduced Vibrating Resonators

Motional resistance is one of the most important performance metrics for high qualitfy factor, low power, and complementary metaloxide semiconductor (CMOS)-compatible capacitively transduced vibrating micromechanical resonators. The motional resistance is primarily set by the electrode-to-resonator air gap that can be formed by deep reactive ion etching (DRIE) process. Although the state-of-the-art DRIE technologies can achieve a narrow capacitive air gap down to 1 m or less, the effective gap tends to be larger than designed values due to the sidewall roughness known as scalloping. Systematic modifications of all key process parameters are presented in this article for lowering the sidewall roughness to result in an up to 2x reduction of the effective capacitive transducer gap, which could lead to an up to 16x decrease of the effective motional resistance.

Design and fabrication of a continuously tuned capacitor by microfluidic actuation

This paper presents the design and fabrication of a continuously tunable RF MEMS capacitor using micro fluidics as a tuning parameter. The impedance variation principle is based on the modification of the capacitor gap permittivity produced by the presence of deionized (DI) water and its displacement in a channel inserted between electrodes. In addition, the electric field distribution changes in an equiponderant way according to the DI water positions in the channel. This change modifies the capacitive coupling, the stored energy and, consequently, the self-resonant frequency. The fabrication process is based on two parts: metallic paths having a spiral form, and obtained by electroplating a 7 µm thick gold layer to constitute electrodes; and fluidic channels, realized by super imposing two SU-8 films. The measurements show a nonlinear variation of the capacitor value according to the water positions. The tuning range is very large, reaching to 4650% for capacitance, and 335% for resonant frequency. However, the quality factor reaches Qmax = 79 at 550 MHz if the capacitor is empty and decreases with the fluid displacement to Qmin = 3.13.

A Wideband, Low-Noise Accelerometer for Sonar Wave Detection

This paper presents the development of a high-performance micromachined capacitive accelerometer for detection of sonar waves. The device is intended to replace existing hydrophones in towed array sonar systems, and thus, needs to meet stringent performance requirements on noise, bandwidth, and dynamic range, among others. The in-plane, single-axis accelerometer is designed based on a mode-tuning structural platform. A frame was used instead of a solid plate for the proof-mass of the device, allowing us to push undesired vibration modes beyond the operating bandwidth of the device while enabling us to employ a portion of the area for capacitive sensing elements. The designed accelerometer was fabricated on a silicon-on-insulator wafer with 100- $\mu \text{m}$ device layer with capacitive gaps of $\sim 2.2~\mu \text{m}$ . The sensitivity of the accelerometer is 4 V/g with a noise spectral density of better than ${{350~{\mathrm {ng}}/}}\sqrt {\mathrm {{Hz}}} $ . The fundamental resonant frequency of the device is 4.4 kHz. The open-loop dynamic range of the accelerometer, while operating at atmospheric pressure, is better than 135 dB with a cross-axis sensitivity of less than 30 dB.

3D Absorptive Frequency-Selective Reflection and Transmission Structures With Dual Absorption Bands

This paper presents a 3D absorptive frequency-selective reflection structure (AFSR) and absorptive frequency-selective transmission structure (AFST) with one reflection/transmission band and two absorption bands. The 3D AFSR utilizes the intrinsic reflection band and higher order absorption band of a wideband 3D absorber. By simply loading a printed gap capacitor in the structure, the reflection band can be easily tuned by varying the capacitance of the capacitor. A design example is presented, with a reflection band of 24.7% fractional bandwidth (FBW), a lower absorption band of 72.5% FBW, and a higher absorption band of 48.6% FBW. A 3D AFST composed of the 3D AFSR and a parallel-plate waveguide is then proposed. Its general operating principle is demonstrated, such that the 3D AFST can be seen as a combination of a 3D AFSR and a 3D band-pass FSS, which can independently contribute to the absorption and transmission, respectively. A set of guidelines is proposed to facilitate the design. A prototype of the proposed AFST is fabricated and measured. The measured results show that the transmission band is with a minimum insertion loss of 0.4 dB and an FBW of 30%. Moreover, the lower and higher absorption bands are with 63.9 % and 47.6 % FBW, respectively. The proposed AFST has a simpler structure, wider lower absorption bandwidth, and thinner thickness compared with previous structures.