scholarly journals High-Efficiency Crossed-Loop 4G LTE Antenna for All Display Metal-Rimmed Smartphones

2018 ◽  
Vol 2018 ◽  
pp. 1-7
Author(s):  
Jaehyun Choi ◽  
Woonbong Hwang ◽  
Chisang You ◽  
Byungwoon Jung ◽  
Wonbin Hong
Keyword(s):  
Frequency Spectrum ◽  
High Efficiency ◽  
Ground Plane ◽  
Low Frequency ◽  
Total System ◽  
High Radiation ◽  
Ground Clearance ◽  
Loop Topology ◽  
4G Lte ◽  
Very High

A symmetrically crossed-loop antenna featuring very high radiation efficiency across the entire LTE frequency bands for metal-rimmed smartphones with only 2 mm ground clearance is proposed, analyzed, and verified. The employment of even and odd modes is utilized to achieve wide bandwidth across 698–960 MHz (low-frequency spectrum), 1710–2170 MHz (middle-frequency spectrum), and 2300–2690 MHz (high-frequency spectrum). Empirical analysis confirms the crossed-loop topology results in a 180° phase shift of the electric current distribution on the ground plane, resulting in enhancement of the radiation resistance. As a result, the devised LTE antenna exhibits more than 48% to 75% total system efficiency across the entire band of interest, which is the highest efficiency reported in literature for metal-rimmed smartphones with extremely small ground clearance.

Compact high-efficiency pentahedron and quatrefoil shape antennas with enhanced gain for GSM1800, 3G, 4G-LTE energy harvesting applications

2020 ◽  
pp. 1-12
Author(s):  
Geriki Polaiah ◽  
K. Krishnamoorthy ◽  
Muralidhar Kulkarni
Keyword(s):  
Energy Harvesting ◽  
High Efficiency ◽  
Ground Plane ◽  
Variation Method ◽  
Length Variation ◽  
Efficiency Gain ◽  
Rf Power ◽  
Peak Efficiency ◽  
Slot Antennas ◽  
4G Lte

Abstract In this paper, three compact, high-efficiency, gain enhanced antennas, and corresponding rectifiers have been proposed for GSM1800, 3G, and 4G-LTE energy harvesting applications. The inverted L-stub is placed on the ground plane of the monopole antenna to get the desired frequency band of GSM1800 MHz. The feed length variation method has been adopted for the slot antennas to obtain the required frequency of 3G and 4G-LTE cellular bands. The performance of antennas is analyzed with the inverted L-stub, feed length variation, and the reflector distance. The maximum gain achieved with the reflector positioned at a distance of λ/4 from the antenna backside is three times greater than the gain obtained without the reflector. The prototype antennas and rectifiers have been simulated, fabricated, measured various parameters, and compared with the simulation results. The antennas provide more than 82% radiation efficiency and an enhanced gain of greater than 5.6 dB. The peak efficiency of rectifiers of more than 30% has been achieved. The aforementioned three antennas are integrated with their corresponding rectifiers for operating at 1.8, 2.1, and 2.3 GHz frequencies. The proposed rectennas are formidably suitable for the reception of RF power from the cellular bands.

Application of the Hilbert-Huang Transform to Pick up Surface Roughness

2004 ◽  
Vol 471-472 ◽  
pp. 668-671 ◽  
Author(s):  
Jian Hua Wu ◽  
Zheng Qiang Yao ◽  
Y. Jin
Keyword(s):  
Surface Roughness ◽  
High Efficiency ◽  
Low Frequency ◽  
Shape Error ◽  
Hilbert Huang Transform ◽  
Mode Decomposition ◽  
Analysis Theory ◽  
Surface Image ◽  
Spectral Data Analysis ◽  
Very High

The surface roughness is evaluated by decomposing micro-errors from irregular surface image. The wave of surface is designated as signals including high-frequency, mid-frequency, and low-frequency signal, that denote roughness, waveness and the geometry shape error. Hilbert-Huang transform is a promising revolutionary technique for spectral data analysis, which is used to extract roughness from surface. It overcomes the imprecise result of the traditional surface roughness calculation and avoids the complication of the Wavelet analysis. Theory of Empirical Mode Decomposition (EMD) is given in the paper. This method is initially applied in picking up surface roughness, and it is proved to be of very high efficiency and simplicity.

scholarly journals Near quantitative synthesis of urea macrocycles enabled by bulky N-substituent

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yingfeng Yang ◽  
Hanze Ying ◽  
Zhixia Li ◽  
Jiang Wang ◽  
Yingying Chen ◽  
...  
Keyword(s):  
High Efficiency ◽  
Molecular Structures ◽  
High Yield ◽  
Kinetic Control ◽  
High Concentration ◽  
Weak Association ◽  
Quantitative Synthesis ◽  
Thermodynamic Stabilization ◽  
Discrete Structures ◽  
Very High

AbstractMacrocycles are unique molecular structures extensively used in the design of catalysts, therapeutics and supramolecular assemblies. Among all reactions reported to date, systems that can produce macrocycles in high yield under high reaction concentrations are rare. Here we report the use of dynamic hindered urea bond (HUB) for the construction of urea macrocycles with very high efficiency. Mixing of equal molar diisocyanate and hindered diamine leads to formation of macrocycles with discrete structures in nearly quantitative yields under high concentration of reactants. The bulky N-tert-butyl plays key roles to facilitate the formation of macrocycles, providing not only the kinetic control due to the formation of the cyclization-promoting cis C = O/tert-butyl conformation, but also possibly the thermodynamic stabilization of macrocycles with weak association interactions. The bulky N-tert-butyl can be readily removed by acid to eliminate the dynamicity of HUB and stabilize the macrocycle structures.

Construction of low-frequency and high-efficiency electromagnetic wave absorber enabled by texturing rod-like TiO2 on few-layer of WS2 nanosheets

2021 ◽  
Vol 548 ◽  
pp. 149158
Author(s):  
Deqing Zhang ◽  
Yingfei Xiong ◽  
Junye Cheng ◽  
Hassan Raza ◽  
Chuanxu Hou ◽  
...  
Keyword(s):  
Electromagnetic Wave ◽  
High Efficiency ◽  
Low Frequency ◽  
Ws2 Nanosheets

Design and Analysis of a High Pitch to Chord Ratio Cascade Representative of Ducted Propfans

1991 ◽  
Author(s):  
A. Weber ◽  
W. Steinert ◽  
H. Starken
Keyword(s):  
Boundary Layer ◽  
Mach Number ◽  
High Efficiency ◽  
Pressure Ratio ◽  
Flow Analysis ◽  
High Pitch ◽  
Integral Boundary ◽  
Pressure Loss Coefficient ◽  
Distribution Boundary ◽  
Very High

Efforts to reduce the specific fuel consumption of a modern aero engine focus in particular on increasing the by-pass ratio beyond the current level of around 5. One concept is the counterrotating shrouded propfan operating at low overall pressure ratio and having only very few fan blades of extremely high pitch/chord ratios. The relative inlet Mach numbers cover a range from 0.7 at the hub to 1.1 at the tip section of the first rotor. A propfan cascade was designed by taking into account two characteristic features of a propfan blade-blade section: • a very high pitch/chord ratio of s/c = 2.25 • an inlet Mach number of M1 = 0.90 which leads to transonic flow conditions inside the blade passage In the design process a profile generator and a quasi-3D Euler solver were used iteratively to optimize the profile Mach number distribution. Boundary layer behavior was checked with an integral boundary layer code. The cascade design was verified experimentally in the transonic cascade wind tunnel of DLR at Cologne. The extensive experimental results confirm the design goal of roughly 5 degree flow turning. A total pressure loss coefficient of less than 1.5% was measured at design conditions. This validates the very high efficiency level the propfan concept is calling for. A 2D Navier-Stokes flow analysis code yields good results in comparison to the experimental ones.

scholarly journals Instantaneous Electromagnetic Torque Components in Synchronous Motors Fed by Load-Commutated Inverters

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3223
Author(s):  
Gabriel Ekemb ◽  
Fouad Slaoui-Hasnaoui ◽  
Joseph Song-Manguelle ◽  
P. M. Lingom ◽  
Issouf Fofana
Keyword(s):  
High Efficiency ◽  
Air Gap ◽  
International Standards ◽  
Synchronous Motors ◽  
Gas Compression ◽  
Variable Frequency Drives ◽  
Torsional Analysis ◽  
Analytical Expressions ◽  
Very High ◽  
Excitation Circuit

This paper proposes time-domain analytical expressions of the instantaneous pulsating torque components in a synchronous machine air gap when supplied by a load-commutated-inverter (LCI) system. The LCI technology is one of the most used variable frequency drives when very high power and low speed are required in applications such as pipeline recompression and decompression, as well as liquefied natural gas compression. In such applications, synchronous motors are used because of their high efficiency resulting from a separated supply of the current to their rotor through the excitation circuit. These applications usually have long and flexible shafts, which are very sensitive to torsional vibration excitation when their natural frequencies interact with any external torque applied to the shaft. A torsional analysis is required by international standards to assess the survivability of the shaft through the overall speed range of the motor. Therefore, the magnitude and frequencies of the motor air-gap torque are needed for such evaluation. The proposed developments are supported by numerical simulations of LCI systems in a large range of operation range. From the simulation results, torque harmonic families are derived and expressed in a parametric form, which confirm the accuracy of the proposed relationships.

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