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- W2883394110 abstract "Researchers seek to design small meander line antennas for radio frequencyidentification (RFID) applications, while taking into consideration theachievement of best performance parameters of the antenna: impedance, returnloss, voltage standing wave ratio (VSWR), radiation efficiency, gain, directivityand etc. Various planar meander line antennas were proposed which have thelowest resonant frequency and maximum radiation efficiencies for a fixed area,using multi-parameter optimization routines. The design in planar form withmaximum radiation efficiency was optimized with the inclusion of matchingstructure for complex impedance matching with RF transceiver chip CC1101 for433 MHz RFID applications. The design was also optimized for impedance matchwith commonly used transmission lines (50 ohms characteristic impedance) for2.45 GHz applications. The antennas were fabricated using circuit in plastic (CiP)technique with screen printed silver conductor on 3mm FR4 and plastic substratesrespectively. The technique allows the creation of a waterproof antenna forunderground (mining geophysics, environmental monitoring, etc.) and underwater(swimmer communications, tidal monitoring, etc.) applications, because theantenna unit is completely sealed in a thin plastic coating. The impedance, bandwidth, return loss and radiation efficiency of these antennas are the mainparameters reported.Since the discovery of graphene, its electrical, mechanical and electronicproperties have been explored. The high conductivity, low fabrication cost,flexibility, controllable isotropic and anisotropic behavior are some of the mainproperties of graphene which make the technology fascinating for electricalengineers and antenna designers. It can be used for antenna applications in theTerahertz frequency band either as a two dimensional, infinitely thin, planar sheetor in the form of one dimensional rolled up graphene known as carbon nanotubes.A pole-zero analysis on the input impedance of carbon nanotube (CN) dipoleantennas with different lengths was used to explain the damped plasmonicresonances of these dipoles with increasing length. We used model basedparameter estimation to approximate the input impedance of the antennas with arational function in the complex frequency domain. Despite the dispersive nature of CNs, the imaginary part of the poles and zeros are respectively the integermultiples and odd multiples of the imaginary part of the first pole and zero.However, the real parts of impedance at the poles are almost constant, while thepattern was not observed for the real part of zeros. Carbon nanotube dipolesoperating between 43-53GHz are well matched if the source impedance is muchhigher than 50 ohms, and even higher than 12.9kΏ. The fundamental resonances(f0) of carbon nanotube dipoles plotted versus their inverse-half-length (1/L) arelinearly related, but the intercept of the fitted straight line is non-zero unlike thatfor perfect electric conductor (PEC) dipoles. This leads to a non-linear variationin wavelength scaling of CN dipoles. The resonant CN antennas are relativelymuch shorter than PEC dipoles of equivalent size.The fundamental properties of carbon nanotube straight wire dipole and Yagi-Uda antennas were determined using theoretical and numerical modelling. Theinsertion loss, radiation efficiency and Q-factor have been reported usingclassical Hallen’s-type integral equation, based on quantum mechanicalconductivity. Contrary to the properties of metal antennas with dimensions lessthan 0.01 m, the addition of parasitic elements in a Yagi-Uda antenna with carbonnanotubes does not lead to significant changes in the radiation characteristics asthe induced current in the parasitic elements is very small. The radiationefficiency of the Yagi-Uda antenna shows little change. The radiation efficiencyof these antennas when compared with the Pfeiffer’s maximum efficiency boundlies well below the maximum efficiency limit. The ����-factor of carbon nanotubeantennas limited by their radiation efficiency was compared to the fundamentallimits proposed by Chu and Thal and although the ���� -factor of the nanotubeantennas is very small, it is still larger than the fundamental limits. This analysiswas also extended to carbon nanotube loop antennas operating in transmittingmode. The extinction properties of carbon nanotube loop antennas were alsoinvestigated and compared with ordinary metallic loop antennas.Since graphene is an ideal candidate for THz antenna applications due to itsexcellent electrical and mechanical properties, the conductivity and scatteringproperties of monolayer graphene were explored over a wide frequency range.Two monolayer graphene samples having different dimensions printed on aplastic (PET) substrate were measured using horn waveguides at microwave frequencies. Cascade matrix theory was applied to calculate scattering parametersof monolayer graphene patch on PET substrate assuming a frequencyindependent surface conductivity ������������ (manufacture’s specification) and to deembedthe surface conductivity of graphene from measured transmissionparameter s21. De-embedding ������������ from measured reflection parameter s11 wasperformed using transmission line theory. The theoretically modelled Sparameterswere in good agreement with measured S-parameters of graphene.The measured conductivity of graphene using proposed formulations was in goodagreement with the theory. The results were compared with previously publishedconductivity measurements of mono and multi layered graphene.This work on graphene and carbon nanotube antenna properties is a contributiontowards THz antenna applications and we intend to extend this work to explorethe properties of graphene meander line antennas which have not been reported to date." @default.
- W2883394110 created "2018-08-03" @default.
- W2883394110 creator A5035642398 @default.
- W2883394110 date "2018-01-01" @default.
- W2883394110 modified "2023-09-24" @default.
- W2883394110 title "Screen Printed and Graphene and Carbon Nanotube Antennas at UHF and EHF - Design, Modelling and Measurement." @default.
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