Omnidirectional Performance Research Articles

High-Performance and Omnidirectional Thin-Film Amorphous Silicon Solar Cell Modules Achieved by 3D Geometry Design.

High-performance thin-film hydrogenated amorphous silicon solar cells are achieved by combining macroscale 3D tubular substrates and nanoscaled 3D cone-like antireflective films. The tubular geometry delivers a series of advantages for large-scale deployment of photovoltaics, such as omnidirectional performance, easier encapsulation, decreased wind resistance, and easy integration with a second device inside the glass tube.

A MIMO Reversed Antenna Array Design for gsm1800/td-scdma/lte/wi-max/wiLan/wifi

A triband MIMO antenna used for gsm1800/td-scdma/lte/wi-max/wiLan/wifi has been proposed in this paper. The design with the size of 32 m∗73.6 mm is fabricated on FR4 substrate (thickness is 1.6 mm). This antenna consists of two reversed monopole meandered radiators and defected ground structure which work together to achieve impedance match and enhance isolation for all operating bands. According to the subsequent measured results, the working frequency domains are at gsm1800 (1.71 GHz–1.88 GHz), td-scdma (1.88 GHz–2.025 GHz), lte (2.1–2.35, 2.48–2.51), wi-max (3.5 GHz, 5.5 GHz), wiLan (5.725 GHz–5.8 GHz), and wifi (5.8 GHz–5.88 GHz) approximately. Besides, the measured radiation patterns (gain total) are also well at these working frequency domains and the omnidirectional performance has been achieved for the reversed MIMO antenna array. Furthermore, the realized isolation is more than 15 dB, 24.2 dB, and 22 dB at the first, the second, and the third working frequency band, respectively.

Development of multi‐band ultra‐high‐frequency sensor for partial discharge monitoring based on the meandering technique

To design high-sensitivity sensors is one of the critical issues to be solved for ultra-high-frequency (UHF) partial discharge (PD) detection in substations. Commonly-used UHF sensors usually use ultra-wideband antennas for the frequency bands ranging from 300 MHz to 1.5 GHz. To avoid interference in the frequency bands, such as signals generated from mobile phones, a new multi-band UHF sensor is proposed based on the loop antenna theory and meandering technique, which reduces the sensor size, provides high sensitivity and exhibits omnidirectional performance. The sensor works in the bandwidth ranges of 480–520, 800–850 and 1100–1200 MHz, and has sensitivity of more than 10 mm. The PD detection platform was set up, three typical insulation defects, such as corona discharge, surface discharge and free metal particle discharge, were designed, and then the tests were performed to compare the performance of the multi-band sensor and broadband sensor. The results show that the multi-band sensor's bandwidth covers the main spectra of PD signals, thereby can be used for detecting most kinds of PD signals. The sensor's sensitivity is higher than that of the broadband sensor with its size occupying only 5% of the latter, meeting the requirements for detection of PD sources in substations.

Enhanced omni-directional performance of copper zinc tin sulfide thin film solar cell by gradient index coating

Many types of thin-film solar cells have a top, transparent conducting oxide (TCO) coating (such as aluminum-doped zinc oxide (AZO)) through which light is transmitted and current collected. In this paper, we demonstrate an effective antireflective coating for TCO surfaces using a gradient index coating formed from co-sputtered AZO and silicon dioxide (SiO2) targets that reduces reflection loss from the TCO. When applied to an active solar device, the power conversion efficiency of the solar cell increased by >10% when measured at normal incidence and >20% at angles 10° or greater.

A NOVEL LOW-PROFILE QUADRIPOD KETTLE ANTENNA WITH ENHANCED BANDWIDTH

The design of a novel low proflle antenna is presented in this paper. By a cross-shaped structure shorted to the ground plane through shorting probes, the size reduction is achieved. A top-loading ring-disc is successfully employed to broaden the impedance bandwidth. Moreover, with the uniformly-arranged shorting pins and a circular sleeve structure placed on the ground, a good omnidirectional performance in the horizontal plane is obtained. An antenna prototype has been implemented and characterized. A measured impedance bandwidth for VSWR • 2 of about 135% ranging from 1500 to 7800MHz is achieved, and a monopole-like radiation pattern is also produced. The height of the proposed antenna is very low with 0:07‚ tall. The proposed antenna is very suitable for indoor base station and the UWB applications.

WIDEBAND OMNIDIRECTIONAL PRINTED DIPOLE ANTENNA WITH COUPLING FEED FOR WIRELESS COMMUNICATION APPLICATIONS

The wideband and omnidirectional performance of a printed dipole antenna with a novel coupling feed structure is presented. Besides using printed dipole for omnidirectional radiation patterns, the coupling feed structure, which includes the transmission line coupling to a slot line to efiectively improve the impedance matching, can be used for bandwidth enhancement. A wideband impedance characteristic of about 45.6% for VSWR • 2 ranging from 1.54 to 2.45GHz is obtained. The omnidirectional radiation patterns in the whole operation bands are achieved which the un-roundness in H-plane is less than 1.6dB. It is su-cient for accommodating recent wireless communication services such as DCS1800, PCS1900, UMTS, IMT2000, Wibro, etc. Furthermore, the proposed antenna should be a good candidate as a unit of the omnidirectional array. A prototype has been fabricated and tested, and the experimental results validate the design procedure.

Enhanced broadband and omnidirectional performance of Cu(In,Ga)Se2 solar cells with ZnO functional nanotree arrays

An effective approach is demonstrated for enhancing photoelectric conversion of Cu(In,Ga)Se2 (CIGS) solar cells with three-dimensional ZnO nanotree arrays. Under a simulated one-sun condition, cells with ZnO nanotree arrays enhance the short-circuit current density by 10.62%. The omnidirectional anti-reflection of CIGS solar cells with various ZnO nanostructures is also investigated. The solar-spectrum weighted reflectance is approximately less than 5% for incident angles of up to 60° and for the wavelengths primarily from 400 nm to 1000 nm. This enhancement in light harvesting is attributable to the gradual refractive index profile between the ZnO nanostructures and air.

Enhanced broadband and omni-directional performance of polycrystalline Si solar cells by using discrete multilayer antireflection coatings

The performance enhancement of polycrystalline Si solar cells by using an optimized discrete multilayer anti-reflection (AR) coating with broadband and omni-directional characteristics is presented. Discrete multilayer AR coatings are optimized by a genetic algorithm, and experimentally demonstrated by refractive-index tunable SiO₂ nano-helix arrays and co-sputtered (SiO₂)x(TiO₂)₁₋x thin film layers. The optimized multilayer AR coating shows a reduced total reflection, leading to the high incident-photon-to-electron conversion efficiency over a correspondingly wide range of wavelengths and incident angles, offering a very promising way to harvest more solar energy by virtually any type of solar cells for a longer time of a day.

Omnidirectional study of nanostructured glass packaging for solar modules

ABSTRACTAntireflective light trapping glass nanostructures fabricated by a non‐lithographic process are investigated for their angle dependent properties to improve the omnidirectional performance of solar modules. Optical transmission and solar cell module I‐V measurements are used to understand the dependence of angular performance of nanostructures in the packaging glass. Nanostructures 100–400 nm in height demonstrate an increase in solar light transmission both for normal as well as oblique incidence and measurements show that a ~200‐400 nm nanostructure height is optimum for solar modules, providing an absolute increase of 1% in the power conversion efficiency at normal incidence and a gain in short circuit current density over a 120° angular cone of solar incidence. This shows that packaging glass texturing can be an important and often‐overlooked method to yield substantial gain in solar module efficiency. Copyright © 2012 John Wiley & Sons, Ltd.

The Influence of Audiovisual Ceiling Performance on the Relationship Between Reverberation and Directional Benefit

Acoustically, directional microphone hearing aids are less able to improve signal-to-noise ratio in more-reverberant environments. However, because auditory-visual (AV) omnidirectional performance is more likely to approach the ceiling level in less-reverberant environments, listeners may perceive a smaller directional benefit in these environments. The first objective of this study was to investigate the influence of AV ceiling performance on the relationship between reverberation and directional benefit. The second objective was to determine whether a modified speech intelligibility index (mSII) model could predict directional benefit across AV listening conditions with different levels of reverberation. Nineteen adults with sensorineural hearing loss were recruited. Directional benefit was measured using the auditory-only (AO) Hearing in Noise Test (HINT) and the AV version of the Connected Speech Test (CST) in environments containing either low or moderate levels of reverberation (reverberation time = 0.2 sec and 0.7 sec, respectively). The AO mSII was calculated for both speech materials. To predict AV directional benefit, the AO mSII was converted to the AV mSII using the correction equations specified by American National Standards Institute S3.5-1997 (R2007) and the new equations developed based on the data collected in a low-reverberation sound booth in a previous study. As the test environment became more reverberant, a decrease in directional benefit was measured using the HINT. In contrast, the results of the AV CST revealed that directional benefit was higher in the more-reverberant condition. Although the mSII model accurately predicted the HINT-measured directional benefit, the model using the American National Standards Institute correction equations underestimated the directional benefit measured using the AV CST in both reverberation conditions. Applying the newer equations, the model resulted in a more accurate prediction in the low-reverberation condition. However, AV directional benefit in the moderately reverberant condition was still underestimated. Hearing aid users would achieve the greatest directional benefit in situations in which they do not reach ceiling performance. The present study suggests that in the real world these situations may include face-to-face communication occurring in environments with higher reverberation. The opposite trends demonstrated by the HINT and AV CST highlight the importance of using ecologically valid laboratory testing to estimate the real-world effectiveness of a hearing aid and its technology. As a likely result of the difference in the effect on speech cues between noise and reverberation, the new equations developed from the low-reverberation booth failed to predict AV directional benefit in the more-reverberant environment. The mSII model with visual cue correction equations would be able to provide accurate predictions for AV directional benefit when the acoustic environments are similar to the ones used to derive the equations.

Derivation and Simulation on the Academic Profile of the Mecanum Wheel

Mecanum wheel can provide a Omni-directional movement, so to design the academic profile of the Mecanum Wheel become the first problem to be solved. this paper make a projection of the Mecanum wheel to the set of planes that perpendicular to the wheel axes, Derivate the academic profile of the wheel. Use the data to build the model of the wheels. Then import the model to ADAMS to validate the equation we got. The simulation results indicate they have a good Omni-directional mobile performance.

Design and analysis of slot antenna with band notch function

In this article, the design, simulation, and construction of a novel wide rectangular slot antenna fed by a 50 Ω coplanar waveguide (CPW) are presented and investigated for multifunctional communication systems. The physical dimension of the antenna is 29 mm (length) × 32 mm (width) × 1.6 mm (thickness). Detailed simulations and experimental investigations are performed to understand its behavior and to optimize for 2.4 GHz wireless local area network (WLAN) and ultra wideband (UWB) operations. The proposed slot antenna is etched on an FR4 substrate with a thickness of 1.6 mm and relative permittivity of 4.4. To improve the impedance matching, a stepped stub structure with CPW feed technique is used. According to the measured results, the proposed antenna has a large bandwidth from 2.1 to 11.6 GHz for voltage standing wave ratio (VSWR) less than 2, totally satisfying the requirement of 2.4 GHz WLAN and UWB systems, while providing the required band notch function from 5.1 to 5.9 GHz. The study of time domain characteristics and surface current distributions also indicate the band-notched function of the antenna. The radiation patterns display nearly omnidirectional performance and the antenna gain is stable except for the rejected frequency band (5.1–5.9 GHz). Moreover, group delays are within 1.5 ns except for the notch-band. It is observed that the simulated and experimental results have good agreement with each other. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.

A Novel Planar Slot Array Antenna With Omnidirectional Pattern

A novel planar slot array antenna with omnidirectional radiation pattern in the horizontal plane is proposed. The antenna has a simple structure based on a stripline. Its fabrication employs a low-cost and accurate planar printed technique. A series of rectangular-shaped loop slots are etched on two parallel ground planes, and act as radiators. The basic principle of operation of the antenna is discussed in this study. An antenna with eight back-to-back slots is designed by employing the genetic algorithm (GA) implemented on a cluster system to achieve good omnidirectional radiation characteristics. A prototype antenna is fabricated and measured. The measurement results agree with the simulation data and show that this antenna possesses encouraging features. For example, at the working frequency of 5.8 GHz, it has a well-formed omnidirectional pattern with maximum gain variation less than 0.5 dB in the horizontal plane, a high gain level of 10 dBi, side lobes 10 dB below the main lobe and no beam squint. Meanwhile, this antenna achieves an impedance bandwidth of 4.6% of the center frequency (5.68-5.95 GHz) for S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> <; -10 dB and exhibits stable omnidirectional performance over the impedance bandwidth.

Compact USB Camera-Based Navigation Device with Repetitive Compensation of Input Signals for Omnidirectional Inchworm Robot

In this paper, we describe the design and development of a navigation device for a 3-DOF inchworm robot. The robot has been developed to provide flexible and omnidirectional microscopic operations. The robot can move in any direction in the manner of an inchworm. However, many positioning errors exist because of an assembling error in four piezoelectric actuators and two electromagnets. In this report, we propose a USB camera-based navigation device with a signal compensation function. In experiments, we have succeeded in controlling the robot on an octagonal path, freely controlling the posture angle. When we compensate the input signal, the positioning time decreases to 62.9% of that when there is no compensation. The robot is 35 mm3, so we can attach it to various devices. As the navigation device is also compact, we can carry the device easily and set it up in a small work area. The design procedure to realize flexible and omnidirectional positioning and basic performance are also discussed.

Novel wideband slot antenna having notch-band function for 2.4 GHz WLAN and UWB applications

In this paper, the design, simulation, and fabrication of a novel printed rectangular slot antenna with a band-notched function suitable for 2.4 GHz wireless local area network (WLAN) and ultra-wideband (UWB) applications is presented and investigated. Two pairs of slits are introduced into the ground plane to realize band-notched function, by tuning the position, length, and width of which a suitable rejected frequency band can be obtained. To improve the impedance matching, a rectangular cut is also made in the ground plane so that the antenna can cover 2–12 GHz frequency range. According to the measured results, the proposed antenna has a large bandwidth totally satisfying the requirement of 2.4 GHz WLAN and UWB systems, while providing the required band-notch function from 5.1 to 5.9 GHz. The study of transfer function and time-domain characteristics also indicates the band-notched function of the antenna. The radiation patterns display nearly omni-directional performance and the antenna gain is stable except in the rejected frequency band (5.1–5.9 GHz). Moreover, group delays are within 1.5 ns except for the notch band. These features make it a promising candidate for UWB wireless applications. Details of this antenna are described, and the experimental results of the constructed prototype are given.

Small global positioning system patch antennas with self-biased NiCo-ferrite films

Magneto-dielectric substrates with thin ferrite films show great potential in realizing small antennas with improved omni-directional performance than those realized on dielectric substrates.This article introduces self-biased NiCo-ferrite films as a practical means to tune a patch antenna by loading a commercially available dielectric substrate. Novel antenna designs with self-biased ferrite films were investigated, and these magnetic antennas have improved the axial ratio from 1.45 to 1.0 dB with respect to the central frequency ranging from 1.575 to 1.561 GHz in the simulations. Experimental global positioning system patch antennas with/without ferrite films were fabricated and tested. The measured results demonstrate that antennas with ferrite films can miniaturize the geometrical dimension by shifting down the resonance. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1162–1165, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25909

Broadband UHF RFID tag antenna with quasi-isotropic radiation performance

Based on the theory of microstrip antenna design and electromagnetic radiation, a kind of tag antenna with a bent meandered dipole and two short-circuited strips is studied in ultra high frequency (UHF) RFID bands to provide broadband and omni-directional performance simultaneously. The proposed antenna was fabricated with a thin copper layer printed on a thin lossy PET substrate for low-cost production. Our simulation and measurement results show the proposed antenna provides a quasi-isotropic radiation pattern and can obtain 200 MHz bandwidth under the condition of voltage standing wave ration (VSWR) less than 2, which is 1.5 dBi for worldwide UHF RFID bands. It is confirmed this kind of antenna is suitable for all different UHF RFID tags in passive RFID applications.

Loop-type ground antenna using resonated loop feeding, intended for mobile devices

A loop-type ground antenna, designed as a rectangular ground clearance connected by a capacitor, is proposed for mobile devices. The electromagnetic mechanism underlying the antenna operation is based on a new feeding method; a capacitor is used to cause a current loop to resonate at the operating frequency band. The proposed antenna is 5×3 mm and is easily implemented within mobile devices. The −10 dB bandwidth of the antenna is 400 MHz, from 2.3 to 2.7 GHz. The radiation pattern it produces shows omnidirectional performance on the horizontal plane.

NOVEL WIDE-SLOT ANTENNA WITH TRAVELING-WAVE EXCITATION FOR BAND-NOTCHED ULTRA-WIDEBAND APPLICATIONS

In this paper, a novel band-notched wide slot antenna for UWB applications has been proposed. The antenna consists of a circularly slotted square ground, two wide-slots separated by a conductive ring, and an equiangular spiral feed line, which excites the antenna through traveling-wave. Experimental prototypes are fabricated and tested. The obtained results indicate that the proposed antenna has a small size and ofiers a broad bandwidth from 3.1 to 12GHz, with a band notch from 3.4 to 3.9GHz. The radiation patterns display nearly omnidirectional performance and the measured group delays are within §1 nanosecond except for the notch band.

Elliptically shaped ultra‐wideband patch antenna with band‐notch features

AbstractA series of ultra‐wideband antenna using an elliptically curved patch is investigated. The band‐notch feature is realized by cutting off a bended slot, which can be tuned. S11 is controllable by the length of the tunable slot. The antenna exhibits good omnidirectional performance across the operation bandwidth. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 736–738, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23191