scholarly journals Optimization of the UWB Feed Antenna Position in Reflector Applications

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Nurhan Türker Tokan
Keyword(s):  
High Performance ◽  
Phase Error ◽  
Design Procedure ◽  
Reflector Antenna ◽  
Slot Antenna ◽  
Stable Phase ◽  
Phase Center ◽  
Center Position ◽  
Reflector System ◽  
Novel Method

In reflector system design, achieving high stability of phase center position with changes in frequency in reflector feed antennas is highly desired. However, obtaining highly stable phase center is not possible for UWB feed antennas, specially for planar ones. Thus, an optimum positioning for the UWB feed antenna should be defined. Optimization of the positioning of the feed antenna is essential since this process lowers resulting phase error losses significantly. In this work, a novel method for optimizing the UWB feed position of a prime focus reflector antenna from phase and amplitude recordings of the measured radiated field is introduced. An automatic and fast design procedure, based on Genetic Algorithms, is described. The proposed methodology has been numerically and experimentally assessed. The procedure is introduced by an application example to one of the most commonly used UWB feed antennas in high-performance reflector antenna systems: Linear Tapered Slot Antenna (LTSA). A LTSA antenna operating in 6–25 GHz frequency band is designed and manufactured. The performance of the method is quantified in terms of its phase error losses inE- andH-planes for reflector illumination.

ULTRA WIDEBAND RADIATOR WITH A STABLE PHASE CENTER FOR A REFLECTOR ANTENNA

2020 ◽  
Author(s):  
Д.В. БОСОМЫКИН ◽  
А.П. ВОРОНЦОВ ◽  
И.В. ПРИЩЕПА ◽  
А.А. ГАВРИЛОВ ◽  
А.В. ПРОРЕШКИН ◽  
...  
Keyword(s):  
Frequency Ratio ◽  
Reflector Antenna ◽  
Antenna System ◽  
Ultra Wideband ◽  
Stable Phase ◽  
Orthogonal Polarization ◽  
Phase Center ◽  
Directional Characteristics ◽  
Hybrid Coupler ◽  
Vivaldi Antenna

Предложен широкополосный излучатель со стабильным фазовым центром (ФЦ) для использования в составе облучателя зеркальной антенны. Излу ортогональных поляризациях и круговой поляризации при использовании квадратурного питания. Рабочая полоса по уровню КстU ≤ 2 обеспечивается при коэффициенте перекрытия по частоте более 1:16. Исследованы характеристики направленности облучателя зеркальной антенны на базе антенны типа Вивальди, представлены результаты расчетов и измерений его параметров. Обоснована пригодность для использования в составе облучателя сверхширокополосной зеркальной антенной системы в режиме суммарного и разностного формирования диаграммы направленности (ДН). It is presented the wideband irradiator with a stable phase center for use in a reflector antenna irradiator. The irradiator is based on a smoothly expanding slot. It has two coaxial feeds to form dual linear orthogonal polarization. Circular polarization radiation can be achieved with an additional hybrid coupler. The VSWR≤2 bandwidth is obtained for a frequency ratio of more than 1:16. The directional characteristics of the irradiator of a reflector antenna based on a Vivaldi antenna are investigated, the results of calculations and measurements of its parameters are presented. The suitability of the irradiator for use as a part of the irradiator of the ultra-wideband reflector antenna system is justified.

Ultra-High Temperature Ceramics (UHTCs) via Reactive Sintering

2007 ◽  
Vol 336-338 ◽  
pp. 1159-1163 ◽  
Author(s):  
Guo Jun Zhang ◽  
Wen Wen Wu ◽  
Yan Mei Kan ◽  
Pei Ling Wang
Keyword(s):  
Phase Composition ◽  
High Temperature ◽  
Oxidation Resistance ◽  
High Performance ◽  
Thermal Protection ◽  
Ambient Pressure ◽  
Stable Phase ◽  
Reactive Sintering ◽  
Dissociation Temperature ◽  
Monolithic Ceramics

Current high temperature ceramics, such as ZrO2, Si3N4 and SiC, cannot be used at temperatures over 1600°C due to their low melting temperature or dissociation temperature. For ultrahigh temperature applications over 1800°C, materials with high melting points, high phase composition stability, high thermal conductivity, good thermal shock and oxidation resistance are needed. The transition metal diborides, mainly include ZrB2 and HfB2, have melting temperatures of above 3000°C, and can basically meet the above demands. However, the oxidation resistance of diboride monolithic ceramics at ultra-high temperatures need to be improved for the applications in thermal protection systems for future aerospace vehicles and jet engines. On the other hand, processing science for making high performance UHTCs is another hot topic in the UHTC field. Densification of UHTCs at mild temperatures through reactive sintering is an attracting way due to the chemically stable phase composition and microstructure as well as clean grain boundaries in the obtained materials. Moreover, the stability studies of the materials in phase composition and microstructures at ultra high application temperatures is also critical for materials manufactured at relatively low temperature. Furthermore, the oxidation resistance in simulated reentry environments instead of in static or flowing air of ambient pressure should be evaluated. Here we will report the concept, advantages and some recent progress on the reactive sintering of diboride–based composites at mild temperatures.

scholarly journals A Review on the Development of Rotman Lens Antenna

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Shruti Vashist ◽  
M. K. Soni ◽  
P. K. Singhal
Keyword(s):  
High Performance ◽  
Beam Steering ◽  
Phase Error ◽  
Antenna System ◽  
Surveillance Systems ◽  
Electronic Warfare ◽  
Design Concepts ◽  
Low Profile ◽  
True Time ◽  
The One

Rotman lenses are the beguiling devices used by the beamforming networks (BFNs). These lenses are generally used in the radar surveillance systems to see targets in multiple directions due to its multibeam capability without physically moving the antenna system. Now a days these lenses are being integrated into many radars and electronic warfare systems around the world. The antenna should be capable of producing multiple beams which can be steered without changing the orientation of the antenna. Microwave lenses are the one who support low-phase error, wideband, and wide-angle scanning. They are the true time delay (TTD) devices producing frequency independent beam steering. The emerging printed lenses in recent years have facilitated the advancement of designing high performance but low-profile, light-weight, and small-size and networks (BFNs). This paper will review and analyze various design concepts used over the years to improve the scanning capability of the lens developed by various researchers.

Kinetic model for calcium sulfate α-hemihydrate produced hydrothermally from gypsum formed by flue gas desulfurization

2015 ◽  
Vol 48 (3) ◽  
pp. 827-835 ◽  
Author(s):  
Mingliang Tang ◽  
Xuerun Li ◽  
Yusheng Shen ◽  
Xiaodong Shen
Keyword(s):  
Flue Gas ◽  
Calcium Sulfate ◽  
High Performance ◽  
Transformation Process ◽  
Flue Gas Desulfurization ◽  
Synthesis Process ◽  
Stable Phase ◽  
Hydrothermal Conditions ◽  
Simple Method ◽  
Kinetics Of

Modeling of the kinetics of the synthesis process for calcium sulfate α-hemihydrate from gypsum formed by flue gas desulfurization (FGD) is important to produce high-performance products with minimal costs and production cycles under hydrothermal conditions. In this study, a model was established by horizontally translating the obtained crystal size distribution (CSD) to the CSD of the stable phase during the transformation process. A simple method was used to obtain the nucleation and growth rates. A nonlinear optimization algorithm method was employed to determine the kinetic parameters. The model can be successfully used to analyze the transformation kinetics of FGD gypsum to α-hemihydrate in an isothermal batch crystallizer. The results showed that the transformation temperature and stirring speed exhibit a significant influence on the crystal growth and nucleation rates of α-hemihydrate, thus altering the transformation time and CSD of the final products. The characteristics obtained by the proposed model can potentially be used in the production of α-hemihydrate.

scholarly journals A Novel Method of Assessment for Monitoring Neuromuscular Fatigue in Australian Rules Football Players

2019 ◽  
Vol 14 (5) ◽  
pp. 598-605 ◽  
Author(s):  
Joel Garrett ◽  
Stuart R. Graham ◽  
Roger G. Eston ◽  
Darren J. Burgess ◽  
Lachlan J. Garrett ◽  
...  
Keyword(s):  
High Performance ◽  
Recovery Phase ◽  
Neuromuscular Fatigue ◽  
Football Players ◽  
Alternative Method ◽  
Jump Test ◽  
Australian Rules Football ◽  
Novel Method ◽  
Run Test ◽  
Method Of Assessment

Purpose: To compare the sensitivity of a submaximal run test (SRT) with a countermovement-jump test (CMJ) to provide an alternative method of measuring neuromuscular fatigue (NMF) in high-performance sport. Methods: A total of 23 professional and semiprofessional Australian rules football players performed an SRT and CMJ test prematch and 48 and 96 h postmatch. Variables from accelerometers recorded during the SRT were player load 1D up (vertical vector), player load 1D side (mediolateral vector), and player load 1D forward (anteroposterior vector). Meaningful difference was examined through magnitude-based inferences (effect size [ES]), with reliability assessed as typical error of measurements expressed as coefficient of variance. Results: A small decrease in CMJ height, ES −0.43 ± 0.39 (likely), was observed 48 h postmatch before returning to baseline 96 h postmatch. This was accompanied by corresponding moderate decreases in the SRT variables player load 1D up, ES −0.60 ± 0.51 (likely), and player load 1D side, ES −0.74 ± 0.57 (likely), 48 h postmatch before also returning to prematch baseline. Conclusion: The results suggest that in the presence of NMF, players use an alternative running profile to produce the same external output (ie, time). This indicates that changes in accelerometer variables during an SRT can be used as an alternative method of measuring NMF in high-performance Australian rules football and provides a flexible option for monitoring changes in the recovery phase postmatch.

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