419 research outputs found
On Artificial Magneto-Dielectric Loading for Improving the Impedance Bandwidth Properties of Microstrip Antennas
In the present paper we discuss the effect of artificial magneto-dielectric
substrates on the impedance bandwidth properties of microstrip antennas. The
results found in the literature for antenna miniaturization using magnetic or
magneto-dielectric substrates are revised, and discussion is addressed to the
practically realizable artificial magnetic media operating in the microwave
regime. Using a transmission-line model we, first, reproduce the known results
for antenna miniaturization with non-dispersive material fillings. Next, a
realistic dispersive behavior of a practically realizable artificial substrate
is embedded into the model, and we show that frequency dispersion of the
substrate plays a very important role in the impedance bandwidth
characteristics of the loaded antenna. The impedance bandwidths of reduced size
patch antennas loaded with dispersive magneto-dielectric substrates and
high-permittivity substrates are compared. It is shown that unlike substrates
with dispersion-free permeability, practically realizable artificial substrates
with dispersive magnetic permeability are not advantageous in antenna
miniaturization. This conclusion is experimentally validated.Comment: 22 pages, 14 figures, 5 tables, submitted to IEEE Trans. Antennas
Propaga
Compact Circularly Polarized Patch Antenna Using a Composite Right/Left-Handed Transmission Line Unit-Cell
A compact circularly polarized (CP) patch antenna using a composite right/left-handed (CRLH) transmission line (TL) unit-cell is proposed. The CRLH TL unit-cell includes a complementary split ring resonator (CSRR) for shunt inductance and a gap loaded with a circular-shaped slot for series capacitance. The CSRR can decrease the TM10 mode resonance frequency, thus reducing the electrical size of the proposed antenna. In addition, the asymmetry of the CSRR brings about the TM01 mode, which can be combined with the TM10 mode by changing the slot radius. The combination of these two orthogonal modes with 90° phase shift makes the proposed antenna provide a CP property. The experimental results show that the proposed antenna has a wider axial ratio bandwidth and a smaller electrical size than the reported CP antennas. Moreover, the proposed antenna is designed without impedance transformer, 90° phase shift, dual feed and ground via
Miniature Planar Antenna Design for Ultra-Wideband Systems
Demand for antennas that are compact and operate over an ultraâwideband (UWB) frequency range is growing rapidly as UWB systems offer high resolution imaging capability and high data rate transmission in the order of Gb/s that is required by the next generation of wireless communication systems. Hence, over the recent years the research and development of UWB antennas has been widely reported in literature. The main performance requirements sought from such antennas include: (1) low VSWR of <2; (2) operation over 7.6 GHz from 3 to 10.6 GHz; and (3) good overall radiation characteristics. Significant size reduction and low manufacturing cost are also important criteria in order to realize a costâeffective and miniature system. Other desirable requirements include compatibility and ease of integration with RF electronics
Miniaturized Microwave Devices and Antennas for Wearable, Implantable and Wireless Applications
This thesis presents a number of microwave devices and antennas that maintain
high operational efficiency and are compact in size at the same time. One goal
of this thesis is to address several miniaturization challenges of antennas and
microwave components by using the theoretical principles of metamaterials,
Metasurface coupling resonators and stacked radiators, in combination with the
elementary antenna and transmission line theory. While innovating novel
solutions, standards and specifications of next generation wireless and
bio-medical applications were considered to ensure advancement in the
respective scientific fields. Compact reconfigurable phase-shifter and a
microwave cross-over based on negative-refractive-index transmission-line
(NRI-TL) materialist unit cells is presented. A Metasurface based wearable
sensor architecture is proposed, containing an electromagnetic band-gap (EBG)
structure backed monopole antenna for off-body communication and a fork shaped
antenna for efficient radiation towards the human body. A fully parametrized
solution for an implantable antenna is proposed using metallic coated stacked
substrate layers. Challenges and possible solutions for off-body, on-body,
through-body and across-body communication have been investigated with an aid
of computationally extensive simulations and experimental verification. Next,
miniaturization and implementation of a UWB antenna along with an analytical
model to predict the resonance is presented. Lastly, several miniaturized
rectifiers designed specifically for efficient wireless power transfer are
proposed, experimentally verified, and discussed. The study answered several
research questions of applied electromagnetic in the field of bio-medicine and
wireless communication.Comment: A thesis submitted for the degree of Ph
Design and realization for radar cross section reduction of patch antennas using shorted stubs metamaterial absorbers
This thesis is devoted to analyzing of the Radar Cross Section (RCS) of rectangular patch
antenna using Metamaterial Absorber (MMA) and the analysis of its reducing techniques. The
addressed theme has a great complexity and it covers various areas that include designing and
optimization of target geometrical model of rectangular patch antenna structures and making it
compatible with respect to metamaterial geometry. Analyses have been made to optimize and
validate the structure performances that include numerical methods for electromagnetic field
computation, MMA behavior, characterization, extraction of parameters, antenna radiation
performance analyses, simulation, fabrication, testing, and optimization with back validating
the designs.
The MMA structure finds its applications in antenna designing for the reduction of
Monostatic and Bistatic RCS in stealth platform for lower detectable objects. However, there
is still more emphasis needed to devote for in-band frequency response for low RCS of the
antenna. Therefore, making these assumptions, we have been proposing novel designs of
single-band, dual-band, and triple-band MMA structures. These structures provide significant
scattering characteristics and offering flexibility to the designer to control and tune the resonant
frequency, based on the specific applications as compared to that of the other MMAs in the
microwave regime of the Electromagnetic (EM) spectrum.
To explore the research scope, a three dimensional Frequency Selective Surface (FSS)
structure has been analyzed and its simulation responses with respect to parametric analyses
have been made. The research investigation further extended to Electronic Band Gap (EBG)
Structure and Defected Ground Structure (DGS). A hybrid structure of patch antenna is
proposed and designed for an inset feed rectangular microstrip patch antenna operating at 2.45
GHz in the Industrial, Scientific, and Medical (ISM) band. This hybrid structure claims the size
reduction, bandwidth, and gains enhancement.
The main focus of this research work is limited to determine the potential and practical
feasibility of MMAâs to enhance the stealth performance of rectangular patch antennas. For this
purpose, Monostatic and Bistatic RCS simulation and measurements are carried out in an
anechoic chamber and practical methods for Radar Cross Section reduction are discussed and
analyzed
Low-Profile Fully-Printed Multifrequency Monopoles Loaded with Complementary Metamaterial Transmission Line
The design of a new class of multifrequency monopoles by loading a set of resonant-type complementary metamaterial transmission lines (CMTL) is firstly presented. Two types of CMTL elements are comprehensively explored: the former is the epsilon negative (ENG) one by loading complementary split ring resonators (CSRRs) with different configurations on the signal strip, whereas the latter is the double negative (DNG) one by incorporating the CSRRs and capacitive gaps. In both cases, the CMTLs are considered with different number of unit cells. By cautiously controlling the geometrical parameters of element structure, five antenna prototypes coving different communication standards (GSM, UMTS, DMB and WiMAX) are designed, fabricated and measured. Numerical and experimental results illustrate that the zeroth-order resonance frequencies of the ENG and DNG monopoles are in desirable consistency. Moreover, of all operating frequencies the antennas exhibit fairly good impedance matching performances better than -10dB and quasi-omnidirectional radiation patterns
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Patch antenna miniaturization using CSRR
A novel metamaterial structure has been proposed for Electromagnetic Compatibility (EMC) applications. A patch antenna with dimension of 18 mm Ă 13.9 mm and resonating at 5 GHz has been designed and the effect of Double Negative (DNG) metamaterial loading for the patch size reduction as well as a lowering in resonance frequency for the fixed size patch antenna has been proposed. A size reduction of 72.5% in the patch antenna has been obtained with the loading of this metamaterial structure and the effect of loading the metamaterial shows that without reducing the size, the patch antenna can work at 3.7 GHz resonance, providing a lowering in resonance frequency by 26%. The metamaterial structure consists of two concentric loops with an outer radius of 3.1 mm. The width of the ring is 1.0 mm and the split is 0.5 mm and has been designed over a 1.57 mm thick Fr4 substrate. The bending effect of the patch antenna with and without metamaterial loading and its comparison with the planar patch antenna has been also shown here. The metamaterial structure has shown its resonance at 5 GHz and its permittivity and permeability behavior over the desired frequency range has been plotted. The simulation of traditional patch antenna and patch antenna over metamaterial has been compared for its return loss, VSWR, gain and efficiency. Finally, a spice circuit for the S parameter of the metamaterial, patch antenna and patch antenna loaded with metamaterial has been obtained using Matlab and ADS for its equivalence to 3D field solver and its comparison has been plotted for its verification
Compact Antenna with Enhanced Performances Using Artificial Meta-Surfaces
In recent years, artificial metaâsurfaces, with the advantages of smaller physical space and less losses compared with threeâdimensional (3D) metamaterials (MTM), have intrigued a great impetus and been applied widely to cloaks, subwavelength planar lenses, holograms, etc. Typically, one most important part for metaâsurfacesâ applications is to improve the performance of antennas. In this chapter, we discuss our effort in exploring novel mechanisms of enhancing the antenna bandwidth using the magnetoâelectroâdielectric waveguided metaâsurface (MEDâWGâMS), achieving circular polarization radiation through fractal metaâsurface, and also realizing beam manipulation using cascaded resonator layers, which is demonstrated from aspects of theoretical analysis, numerical calculation, and experimental measurement. The numerical and measured results coincide well with each other. Note that all designed antenna and microwave devices based on compact metaâsurfaces show advantages compared with the conventional cases
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