Uhf
Mostrando 1-12 de 35 artigos, teses e dissertações.
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1. Radiation Efficiency of an Electrically Small Dual-band UHF Microstrip Patch Antenna Using Wheeler Cap Method
Abstract Determining the radiation efficiency of an antenna is a difficult task that becomes challenging when it is about electrically small antennas. This work investigates the applicability of the Wheeler cap method to measure the radiation efficiency of a UHF dual-band compact microstrip patch antenna. An overview of Wheeler method is presented. An adapta
Journal of Microwaves, Optoelectronics and Electromagnetic Applications. Publicado em: 2022
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2. Development of a microwave absorbing material based on molybdenum-doped niobium pentoxide
Abstract This work aimed to perform the characterization of electrical properties of niobium pentoxide, Nb2O5, pure and doped with molybdenum, prepared by powder metallurgy route and to do a comparative analysis of the influence of this material when sintered in a muffle or in a microwave oven. The results showed that the doping of the niobium pentoxide with
Cerâmica. Publicado em: 2019-01
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3. Minimum Activation Power of a Passive UHF RFID Tags: a Low Cost Method
ABSTRACT: RFID is an automatic contactless identification method based on radio frequency (RF). The reading process depends of the power of electromagnetic signal received by a tag. Thus an accurate characterization of RFID tags is crucial for early adopter in aerospace industry. The present study shows the preliminary approach to characterize the reading di
J. Aerosp. Technol. Manag.. Publicado em: 07/05/2018
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4. Sharp Rejection and Wide Stopband Microstrip Lowpass Filters using Complementary Split Ring Resonators
Abstract Chebyshev microstrip lowpass filters with improved performance, achieved by means of circular complementary split ring resonators (CSRR), are presented. CSRR particles exhibit frequency rejection bandwidths in the vicinity of their resonant frequencies that can be used to meliorate both selectivity and stopband in microstrip lowpass filters. Two con
J. Microw. Optoelectron. Electromagn. Appl.. Publicado em: 2018-03
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5. Optimized Limited Size Printed Bowtie Antenna for UHF RFID Readers
Abstract A novel design of a printed bowtie antenna without a ground plane and with size below a quarter wavelength for RFID readers is presented. Due to the lack of a ground plane, the designed antenna has omnidirectional characteristics and is insensitive to small permittivity deviations. For matching purposes without introducing gain distortion, a shortin
J. Microw. Optoelectron. Electromagn. Appl.. Publicado em: 2017-12
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6. A flat-gain LNA based on LTCC technology at UHF (300-500 MHz)
Abstract This paper presents a design and simulation of a low noise amplifiers (LNA) with all passives elements embedded on low temperature co-fired ceramic (LTCC) substrate. Simulation results in ANSYS Designer and CST Studio Suite reveal that the proposed LNA has a flat-gain of 23.34 dB from 300 to 500 MHz, a noise figure below 0.73 dB and a compact size o
J. Microw. Optoelectron. Electromagn. Appl.. Publicado em: 2016-09
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7. Radio-Wave Propagation Model for UHF Band in Different Climatic Conditions with Dyadic Green’s Function
AbstractThis article proposes a deterministic radio propagation model using dyadic Green's function to predict the value of the electric field. Dyadic is offered as an efficient mathematical tool which has symbolic simplicity and robustness, as well as taking account of the anisotropy of the medium. The proposed model is an important contribution for the UHF
J. Microw. Optoelectron. Electromagn. Appl.. Publicado em: 2015-06
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8. An efficient method of EM field modification around transmitting stations
AbstractAn efficient practical method for the electromagnetic (EM) fields reduction around transmitting stations has been developed. The project has been stimulated by the necessity to reduce the field levels in the vicinity of transmitting stations, including FM, UHF, cellular base stations and other radiocommunication services, to obey regulations concerni
J. Microw. Optoelectron. Electromagn. Appl.. Publicado em: 2015-06
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9. Dairy cow monitoring by RFID
Dairy cows identification and monitoring on small cattle farms are usually based on the utilization of barcode technology. This kind of identification technology is unsuitable for dairy cows milking and feeding process automation. Radio Frequency Identification (RFID) technology is a better solution in this case. This paper describes the research and impleme
Scientia Agricola. Publicado em: 2012-02
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10. EVALUATION OF RADIO PROPAGATION MODELS FOR FIXED RECEPTION OF DIGITAL TV SIGNALS ON UHF BAND / ESTUDO DE MODELOS DE RADIOPROPAGAÇÃO PARA RECEPÇÃO FIXA DE TV DIGITAL NA FAIXA DE UHF
Com o advento da TV digital no Brasil, a necessidade de reuso dos canais para diferentes entidades, e a importância das emissoras oferecerem a melhor qualidade de serviço para seus usuários, dentre outros fatores, criam um ambiente propício para o estudo de modelos de predição de cobertura para que tanto as emissoras possam dimensionar corretamente sua
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 07/11/2011
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11. Predição de cobertura radioelétrica em terrenos irregulares iluminados por fonte de onda esférica: uma abordagem via equações integrais e CBFM
Este trabalho trata da predição da propagação direta e reversa de campos eletromagnéticos sobre terrenos irregulares para a faixa de VHF-UHF (30 MHz a 3 GHz), necessária para o planejamento de comunicações sem fio. O terreno é modelado como sendo um condutor elétrico imperfeito com altura invariante na direção perpendicular de propagação e com
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 03/10/2011
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12. Modelos e técnicas para simulação de sistemas UHF de identificação por rádio frequência (RFID)
Este trabalho apresenta a tecnologia de Identificação por Rádio Frequência (RFID), e tem como principal objetivo a definição de modelos que permitam a simulação de ambientes que utilizem esta tecnologia. Para o desenvolvimento destes modelos de simulação, são extensamente abordados alguns dos principais desafios enfrentados por sistemas RFID: (i)
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 23/08/2011