Substrate Height Research Articles

CVD growth of large-area monolayer WS2 film on sapphire through tuning substrate environment and its application for high-sensitive strain sensor

Large-area, continuous monolayer WS2 exhibits great potential for future micro-nanodevice applications due to its special electrical properties and mechanical flexibility. In this work, the front opening quartz boat is used to increase the amount of sulfur (S) vapor under the sapphire substrate, which is critical for achieving large-area films during the chemical vapor deposition processes. COMSOL simulations reveal that the front opening quartz boat will significantly introduce gas distribute under the sapphire substrate. Moreover, the gas velocity and height of substrate away from the tube bottom will also affect the substrate temperature. By carefully optimizing the gas velocity, temperature, and height of substrate away from the tube bottom, a large-scale continues monolayered WS2 film was achieved. Field-effect transistor based on the as-grown monolayer WS2 showed a mobility of 3.76 cm2V−1 s−1 and ON/OFF ratio of 106. In addition, a flexible WS2/PEN strain sensor with a gauge factor of 306 was fabricated, showing great potential for applications in wearable biosensors, health monitoring, and human–computer interaction.

Spider Monkey Optimization Algorithm-Based Optimal Design of Wideband EBG Structure for Certain Uncertainty Parameters

EBG structures have evolved as an emerging technology in recent years in the domain of microstrip antenna performance enhancement for wireless applications. They contain innovative structures, shapes, and materials that can be found in numerous industrial and military utilizations. The dimensions considered for the substrate of a microstrip antenna which propagates by using metal molecules (cells) are smaller than its kinetic wavelength ([Formula: see text]). This uncertainty in the arrangement increases both bandwidth and efficiency of an antenna when placed on the modified surface. Uttermost the literature surveys on the computational features of the EBG architecture, uncertainly there is little discussion on the development of the design and its effectiveness in challenging external conditions. This research is aimed to have optimized design values and respective control factors of an antenna like substrate height (h), breadth of EBG patch (p) and width of the gap between adjoining cells of EBG (d). Hence, an optimal design of wideband EBG architecture is done utilizing spider monkey optimization (SMO) process to advance the performance of micro-strip antenna. The result values highlighted through simulation outcomes exhibit the performance of the proposed optimal EBG structure outperforms than the standard EBG in the terms of reflection phase, transmission loss, magnitude of [Formula: see text], [Formula: see text], and gain comparison. The outcomes of this technique provide enhance in its bandwidth up to 11.25 GHz, return loss of −31 dB, gain of 5.5 dB and from [Formula: see text]comparison the magnitude of measured with EBG to magnitude of measured with optimal EBG is increased by 7.5% is observed.

Innovative Decentralized Configuration Design of Chipless RFID Tag: Toward a Cost-Effective and Efficient Code Density

In this article, a compact chipless RFID tag with a small size and high data density is proposed. The tag consists of nested octagonal loops arranged in a concentric configuration. Each two neighboring resonating elements are decentrally coupled by two connector lines at obverse sides. The small size of the tag is achieved through embedding multiple octagonal elements in a nested arrangement, which share the same side, and through connecting the neighboring elements. The tag configuration is designed and optimized to improve the resonating modes with respect to the number of resonating elements. The number of generated resonating modes (N) is mathematically obtained by N= 2n-1, such (n) is the resonating elements number. An 11-bits data capacity is presented in the proposed tag within a physical dimension of 10 × 10 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , resulting high data density of 11 b/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The proposed tag is realized on Rogers RT/Duroid 5880 substrate having substrate height h=0.508 mm, relative permittivity ϵ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>r</i></sub> = 2.2, and loss tangent δ = 0.0009. The proposed tag is designed and simulated using CST Studio Suite®. The tag’s performance is initially evaluated through simulation and analyzed for effectiveness. The tag is then fabricated and measured, and the results are compared to ensure agreement between simulation and measurement. The tag advantages are compact size, high data density, and improved resonating modes. The operating frequency range of the proposed tag is 7.5 GHz–15 GHz.

A Novel Concurrent Dual Band Matching Network for Complex to Real Impedance Matching for RF Applications

A novel and simple technique to match Frequency Dependent Complex Loads (FDCLs) to real source impedance at any two arbitrary frequencies is presented. The proposed structure consists of stubs and two 50 Ohms series transmission lines, making it easy to fabricate. This arrangement allows concurrent operability. It has the versatility to transform all types of complex loads at any frequency ratio, which may not be possible with other conventional techniques. In this brief, the limitations of single section transmission line to transform FDCLs to two complex conjugate loads (CCLs) at two frequencies is thoroughly studied. In the proposed scheme, an L-section is used to match the complex load to source impedance at one frequency; and another section consisting of a transmission line and a combination of open-short stub is used to match the load at other frequency. Three prototype matching networks for frequency ratios 6.5, 2.3 and 1.583 are designed and implemented on ROGERS RO4003 substrate having dielectric constant of 3.38 and substrate height of 20 mils. The simulated and the measured results are in a good accordance.

A Wideband High-Isolation Microstrip MIMO Circularly-Polarized Antenna Based on Parasitic Elements.

This work presents a wideband, all-side square-cut square patch multiple-input, multiple-output circularly-polarized (MIMO-CP) high-isolation antenna. The MIMO-CP antenna contains a two-port square cut on all corners of the square patch, and parasitic elements of 9 × 5 periodic square metallic plates are designed and operated. The outer dimensions of the antenna are 40 × 70 mm2, and the FR4 substrate height is 1.6 mm. The proposed antenna with the parasitic elements improves impedance matching and enhances S-parameters and axial ratio (AR). In the suggested MIMO-CP antenna, a parasitic element is designed and placed around the antenna periodically to reduce mutual coupling (MC) and improve CP. Simulated results show that the suggested antenna has a wide bandwidth (BW) from 4.89 to 6.85 GHz for S11 and was &lt; -10 dB with AR ≤ 3 dB from 5.42 to 6.58 GHz, with a peak gain of 6.6 dB. The suggested antennas have more than 30 dB isolation and a low profile, are affordable, easily made, and are CP. To make a comparison with the measured and simulated results, a MIMO-CP antenna structure was fabricated and tested. The suggested antenna is better in terms of efficiency, envelope correlation coefficient (ECC), diversity gain (DG), channel capacity loss (CCL), and total active reflection coefficient (TARC). The proposed antenna is adequate for WLAN applications.

Design and optimization of pi-slotted dual-band rectangular microstrip patch antenna using surface response methodology for 5G applications

Modern wireless network antenna technologies are designed to meet the ever-increasing needs of emerging applications. Hence this paper investigates potential antenna impedance bandwidth performance enhancement techniques based on optimizing independent geometrical parameters of pi-shaped slotted dual-band rectangular microstrip patch antenna (DBRMSPA). The antenna considered in the optimization process is with a slotted patch which improves impedance bandwidth of the antenna. And independent factors are geometrical parameters that influence the antenna's impedance bandwidth (BW) and operating frequency (Fr). The factors are substrate height (Hs), patch length (L), and slot (s2) length (Ls), and the experiment is designed using Computer Simulation Technology (CST) suite 2019 to generate a dataset by varying these parameters in a specific range. Then based on the dataset, response surface methodology (RSM) is applied to develop mathematical models that relate the responses Fr and BW with independent variables. Using analysis of variance (ANOVA), the effects of varying independent factors on both responses and model validation were investigated. Then constrained numerical optimization is applied to determine optimum design parameters. The optimized parameters, substrate height, patch length, and slot (s2) length (Ls) are 0.648 mm, 3.048 mm, and 1.325 mm, respectively. The optimized dual-band antenna, designed with optimized parameters, achieved a target impedance bandwidth (≥4 GHz), 7.2 GHz and 4.17 GHz at 28 GHz and 38 GHz, respectively. Similarly, the antenna's radiation efficiency at 28 GHz and 38 GHz is 75.457% and 88.6237%, respectively. The proposed antenna also gives a gain of 6 dBi at 28 GHz and 4.15 dBi at 38 GHz. And VSWR is less than 2 throughout its impedance bandwidth. All of these results were generated using the CST EM solver and validated using the Ansys High Frequency Simulation Software (HFSS) with good agreement. As a result, the proposed potential performance enhancement techniques provide an antenna with a wide impedance bandwidth suitable for 5G mobile communication applications.

A novel coaxial focus position detection technique based on differential modulation evaluation for laser direct photolithography

In laser direct lithography, coaxial focus position detection techniques are needed to ensure the manufacturing accuracy. The existing coaxial focus position detection techniques include pinhole method, critical angle method, Foucault knife-edge method and astigmatism method, which are susceptible to the intensity fluctuation and have high requirement for the installation and adjustment of the system. Furthermore, the resolution of existing method is generally between 10-20nm. We proposed a novel coaxial focus position detection technique based on differential modulation evaluation. In this study, the imaging space of the lithography lens is coded by grating pattern. And a differential detection system is used to get the substrate height from the image modulated by the lens focus depth. Moreover, this proposed method can eliminate the influence of different reflectivity of the surface of the substrate. Furthermore, the focus detection accuracy is better than 5nm in the case of an objective lens with a numerical aperture of 0.9.

Substrate stimulating technique for Ni-based single crystal superalloy preparation during direction solidification

The grain selector method is a prevailing technique in the manufacturing process of Ni-based single crystal superalloy, however, it cannot control the orientation of single crystal within an appropriate scope. In this study, a novel technique named substrate stimulating method was proposed and DD32 Ni-based single crystal superalloy was prepared. The microstructure evolution was characterized by EBSD and OM, and the temperature field and temperature gradient distribution were predicted by the finite volume method. With a substrate height of 18 mm, the proportion of grains with deviation angles less than 12° and 8° account for 100 % and 99 % at the entrance of spiral selector, compared with 80 % and 51 % by grain selector method, which makes significance sense for optimizing the orientation of single crystal casting and improving the yield of single crystal casting. The morphology and the orientation of the substrate stimulated grains, which are mainly determined by temperature gradient and melt undercooling, could be optimized by adjusting the substrate height and melt pouring temperature.

5G Millimeter Wave Endfire Array Antenna with Printed Inverted-F Structure

In this design, a novel inverted F antenna with a low profile feed structure is proposed for millimeter-wave (mmW) applications. The array element consists of a printed inverted F antenna and a L-shaped parasitic deflector, approximately forming a structure similar to the Yagi-Uda antenna. The gain could be increased and the impedance bandwidth could be broadened by the structure. And, it is important to realize the miniaturization of the antenna element by bending the parasitic deflector based on the traditional deflector without affecting the performance. The proposed antenna has a low feed substrate height (0.254 mm∼0.02λ0), which makes it easy to integrate with planar circuits. As proof, a 1 × 4 array model with an impedance bandwidth of 20.5% (23.0–28.3 GHz) is designed and measured. The inverted F array demonstrated is an important candidate for mmW applications due to its wide bandwidth, miniaturization, ease of integration with planar circuits, and low manufacturing cost.

Analysis of Microstrip Patch Antennas for Effective Bandwidth

Abstract-Local Area networks work in frequency ranges 900 MHz, 3.6 GHz, 4.9GHz, 5 GHz, 5.9 GHz, 6 GHz and 60 GHz. It supports broadband communication and provides end to end communication without any propagation delays. For establishing LAN network, antennas are employed to transmit and receive signals. But the existing antenna designs for wireless LAN cannot accommodate higher bandwidths even though they provide good gain. Microstrip patch antennas are considered as they have high compatibility rates, low volume and are easy to manufacture. This paper proposes the design of a microstrip patch antenna with effective bandwidths at 1 GHz and 2.4 GHz using microstrip feed technique with dielectric materials such as FR 4 Epoxy, Arlon 450 and Taconic35. The results are shown in graphical format and have been tabulated. From the results we can conclude that FR 4 Epoxy with 1.6 mm substrate height has given best results among Taconic 35, Arlon 450 and FR 4 Epoxy. From the results we can conclude that we have achieved better bandwidths when compared to the previous works available. Keywords— Rectangular Microstrip Antenna (RMSA), Circular Microstrip Antenna (CMSA), Voltage Standing Wave Ratio (VSWR), Return Loss (RL), Co-Axial Feeding, Microstrip Feed

Numerical model & design of wideband band reject filter with closed loop rectangular resonator

ABSTRACT Numerical model of a wideband band reject filter using closed rectangular loop resonator is presented using transmission lines. The prototype design of wide band reject filter centred at 3 GHz with lower cut-off frequency of 2 GHz and upper cut-off frequency of 4 GHz is fabricate from the optimal values obtained from the numeric model on a substrate (FR4) with a dielectric constant of 4.3, loss tangent of 0.02–0.03 and substrate height of 1.6 mm. For bidirectional operations, the length-to-width ratio of filter is 2:1. The impedance of the transmission line which is connected between input and output ports is taken as double the feed line impedance while the impedance of the other half wavelength is considered as four times the feed line impedance. The design has obtained bandwidth of more than 60%. It is observed that the full wave electromagnetic results are in good agreement with the experimental and numerical results.

Design and characterization substrate integrated waveguide antenna for WBANS application

Millimetre-wave frequencies are defined as one of the front-runner contenders for body-centric wireless communication. In this study, low-profile antenna with the substrate integrated waveguide (SIW) has been proposed that operate in the band of the millimetre-wave frequency that has been centred at 60 GHz. The proposed antenna has been implemented with the use of the FR4 substrate with εr and tangent loss of 4.3 and 0.025, respectively. The substrate height and size are 1.5875 mm and 20 mm x 20 mm, respectively. The performance of the antenna is evaluated in off-body (free space) and on-body (human voxel model), through simulation. The proposed antenna has an ultra-wideband (UWB) and a specific absorption rate the maximal (SAR) for (10 g) is 0.0344815 W/kg and for (1 g) is 0.0184723 W/kg. It achieves 74% and 63% efficiency in the off and on-body scenario, respectively. The small antenna with the exceptional matching of impedance, low SAR, broad bandwidth, and good efficiency, a good voltage standing wave ratio good (VSWR), and good front-to-back ratio (FBR). As a result, its characteristics make it one of the best potential candidates for the simultaneous transmission and reception of data at (mm-wave) band for WBAN applications.

Method for optimising the performance of PML in anchor‐loss limited model via COMSOL

Perfectly matched layer has been used for solving anchor-loss limited quality factor in the Micro electromechanical systems. However, setting up a well-behaved perfectly matched layer requires users to change the parameters of a perfectly matched layer to give correct results, while the current existing methods for choosing the right parameters are vague and lack theoretical support. Based on the mathematical theory of perfectly matched layer and simulation results of a beam structure's quality factor, this paper proposes a method for choosing the parameter to optimise the performance of perfectly matched layer in COMSOL. The accuracy of the proposed method is proved by matching the effect of substrate height on beam's quality factor with theory prediction. The author also studies the effect of beam height and beam width on the quality factor of the beam. The results demonstrate that simulated quality factors are in agreement with analytical values when the ratio of height over length is small but will show great divergence when height equals the length. This trend can be observed for the beam width as well. Especially for larger ratio of beam width over beam length, instead of decreasing monotonously as analytical equitation would expect, the simulated quality factor will converge into a stable value of 1700, which matches the result of two-dimensional model for the same beam structure. This means that a three-dimensional model has to be used for estimating the quality factor of a beam structure.

The Effects of Density on the Growth and Temperature Production of Tenebrio molitor Larvae

Tenebrio molitor larvae live, at least partially, inside their feed. Hence, they do not live on a 2D plane but in a 3D environment. However, previous studies mainly focused on the optimal number of larvae for a given surface area, not the available volume. The goal of this study was to assess the growth and survival of mealworms in a standardized semi-industrial setting with a varying density (cm3) and substrate height. A full factorial experimental design was used with five larval densities (0.5–8 larvae/cm3) and four feed heights (1–8 cm) in 60 × 40 cm crates. Furthermore, the in-crate temperature was monitored and linked to the density. The results of this study clearly indicate that mealworm larvae prefer a low density (cm3). At low larvae densities, the substrate height was less important, with a slight preference for a thicker layer. In contrast, at high(er) larval densities, a lower layer thickness resulted in better growth. The in-crate week temperature varied up to 14 °C (25–39 °C) between treatments and could be predicted well based on the number and size of the larvae. These results may help the industry to improve their production efficiency in terms of larvae density, substrate height and room temperature.

Reconfigurable switching between reflecting/absorbing modes in VO2 assisted graphene-coated hemispherical dielectric hole arrays

In this paper, a graphene-coated dielectric hole array is used to design a reconfigurable switchable optical reflector/absorber device. The design benefits from the collective excitation of localized surface plasmon resonances of graphene-coated hole array, providing simpler fabrication fellow and more compact structure with respect to graphene-coated spherical nanoparticle array with similar plasmonic behavior. Geometrical parametric study of the reflecting mode shows that the device has lots of degrees of freedom for spectrum tuning and can highly tolerate fabrication imperfections. Moreover, the reflection rate is slightly affected by the dielectric substrate height, which can be tuned to achieve strong absorption by backing it with a metallic mirror. The designed absorber efficiently captures a wide range of obliquely incident transverse electric (TE) and transverse magnetic (TM) waves. Also, the operating frequency of both reflecting and absorbing modes can be tuned after fabrication, thanks to the two-dimensional nature of graphene material. Finally, using vanadium dioxide (VO2) phase change material, the switchable reflector\\absorber mode of the device is also exhibited.

Study of Dependence of Capacitance of Coupled Stripline on Stripwidth, Frequency and Spacing Between Two Striplines

In this present paper, we studied about the dependance of capacitance of coupled stripline on strip width, frequency and spacing between two striplines. Miniaturized microwave circuits fabricated by extension of integrated circuits (ICs) technology to microwave frequencies are known as Microwave Integrated Circuits (MICs). MICs promise a real revolution leading to both expansion of present markets of microwaves &amp; opening of many new applications including host of non-military uses in India &amp; abroad. With the advent of MICs planar Transmission Lines have been developed which have been proved to be very significant as regards the fabrication of various microwave-components such as: Directional Coupler, Filters, Isolator &amp; Impedance transformers etc. The planar Transmission Lines are: Stripline, Microstripline, Slot line, Coplanar Striplines &amp; their different variant forms such as inverted and suspended striplines &amp; microstriplines etc. Among these microstripline is the most suited due to its open structure, low losses in gigaharz range of frequency, reduced size, improved reliability and eventual cost reduction in mass production. The microstrip transmission line consists of a narrow strip conductor separated from a conducting ground plane by an intervening supporting dielectric substrate as studied by Wheeler and others. The electromagnetic traveling through such structures suffers from some losses like: Conductor loss &amp; Dielectric loss. There is a change of phase of the wave traveling through the structure also. This phase change (shift) depends on the width of metal strip, height of the dielectric substrate, permittivity of the substrate and operating frequency. The present study is devoted to this objective i.e. we have to study the variation of Phase-Shift of the wave within the structure with width of the stripline, height &amp; effective permittivity of the structure &amp; frequency.

Opportunistic control of crescent shape MIMO design for lower sub 6 GHz 5G applications

AbstractFor lower sub‐6 5G applications, a two‐element crescent angular ring antenna is proposed. The suggested Multiple‐Input–Multiple‐Output (MIMO) antenna has a dimension of 38 × 25 mm2, a substrate height of 1.6 mm, and dielectric material of FR‐4 (lossy) with a dielectric constant of 4.4 and a loss tangent of 0.002. For 50‐Ω impedance matching, a line feed approach is used to improve return loss and achieve −35 dB at 3.5 GHz. Furthermore, there is a fractional bandwidth from 3–6.5 GHz (116.6%) using a monopole ground plane maintained with |S11| &lt; −10 dB. Changing the placements of the radiators improves isolation by −42 dB. For the current crescent shape, the MIMO structure showed a radiation efficiency and gain of 84.25% and 6.2 dBi. Finally, the performance of MIMO metrics of the crescent shape structure like ECC, diversity gain, channel capacity loss, TARC, and mean effective gain is evaluated in addition to good radiation characteristics.

Lagrangian formulation to investigate the effect of coupling on resonant microstrip transmission line

AbstractAn analytical and a numerical study on coupling in microstrip transmission line (MTL) are reported for different split-gap orientations of a single gap square-shaped split-ring resonator (SRR). Taking both magnetic and electric couplings and adopting Lagrangian formulation for this coupled system, mathematical relations are found for each orientation of SRR to determine the connection between coupling co-efficient and resonant mode frequency. It is shown that coupling results in higher resonance frequency when the SRR, with parallel split-gap, has the gap far from the MTL. But, a lower resonance frequency is obtained when the SRR is placed at shorter distances with parallel split-gap near to the MTL. Again, for perpendicular split-gap orientation of SRR, the resonant frequency is found in terms of an effective coupling co-efficient; at shorter distances it is found to be lower than the fundamental resonance frequency of uncoupled SRR and an opposite effect is obtained at longer distances. Using CST Microwave Studio, the resonance frequency for each split-gap orientation of SRR is also studied as a function of separation between MTL and SRR. It is observed that this phenomenon strongly depends on SRR side-length, substrate height, and separation between MTL and SRR.

Dual-band optical imaging system-integrated patch antenna based on anisotropic fractal for earth-observation CubeSats

This paper presents a dual-band optical imaging system-integrated patch antenna based on an anisotropic fractal for Earth-observation CubeSats. The antenna operates at S-band frequencies. The size of the antenna is chosen to match the end face of the CubeSats. The antenna's main characteristics are studied using simulation in Computer Simulation Technology (CST) software; prototypes are developed to verify these characteristics. Double-sided Glass Epoxy Sheet FR-4 is used to develop the antenna prototype. By studying the antenna prototype, realized gain up to 4 dBi and 2.15 dBi at two resonant frequencies of the antennas with different substrate heights are obtained. Small size, low cost, dual-band, and integration with the imaging system allow achieving the entire CubeSat system's efficiency.

Experimental investigation on punching shear behaviour of RC-(R)UHPFRC composite flat slabs without transverse reinforcement

Strengthening existing reinforced concrete (RC) flat slabs by casting a thin layer of ultra-high performance fibre-reinforced cementitious composite (UHPFRC) over the top surface constitutes an efficient solution for significant durability and flexural capacity enhancements. Previous research has shown that also the punching shear capacity can be substantially increased. However, the existing experimental evidence is still limited and does not allow a systematic evaluation of the influence of the governing parameters.In the present work, eight slabs without transverse reinforcement were tested up to punching shear failure. The following parameters were studied: the contribution of the UHPFRC overlay with and without reinforcement bars, the shape of the column (square or rectangular), the effect of the reinforcement ratio in the existing slab, the eccentricity of the punching force and the material of the strengthening layer (UHPFRC or ordinary RC). The height of the RC substrate and UHPFRC layer thickness were kept constant at 180 mm and 40 mm, respectively.The results confirm the significant contribution of the UHPFRC layer to the punching shear strength. The experimental failure loads are compared to the predictions provided by a composite failure criterion based on the Critical Shear Crack Theory and taking into account the contribution of the UHPFRC layer. Good agreement was obtained with the model being capable of reproducing the effect of all the studied variables.