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A multilayer rectangular dielectric resonator antenna (DRA) operating at a new hybrid mode is presented. The DRA is formed by a dispersion engineered combination of isotropic/anisotropic dielectric layers. These layers are optimized to operate at a degenerate band edge (DBE) mode with the introduction of misaligned anisotropic layers. A prototype DBE-DRA antenna is realized by emulating the anisotropic...
The radar signal processing involves post-processing of the received radar echoes to extract target information. There is an increasing interest to employ radar signals for information gathering and imaging of selected objects with the environment. A more focused interest relates to imaging of concealed items and through-wall imaging fits that category. The challenge faced in through-wall radar sensing...
Through-wall radar imaging is a challenging area of research due to the complex multi-layer and inhomogeneous structure of building walls. The wall distorts and attenuates the radar signal in a way that is not easy to predict, except in the most simple of cases. In this paper a general periodic model is developed and applied to the imaging algorithm. Periodic dielectric wall models for microwave transmission...
A small tri-band GPS antenna is proposed as part of an anti-jamming GPS array. A key aspect of the element is its single feed to achieve circular polarization even when integrated in a small array. This is done via a Wilkinson powder divider together with a quarter-wavelength delay line. Different array configurations are studied to minimize coupling. Design procedures are presented along with the...
In this paper a parallelization process to take advantage of idle CPU resources is discussed. Also the feasibility of utilizing Windows-based desktop computers within an organization to perform EM design optimization is demonstrated. As part of the demonstration, a wideband antenna array was designed and shown to obtain remarkable bandwidth using a textured FSS-like antenna element in a large array.
This paper proposes 4/6-port lumped element printed microstrip circuits composed of dual and coupled transmission lines to realize higher order dispersion behaviors emulating the (degenerate band edge) DBE crystals and magnetic photonic crystals (MPC). Harnessing the maximally flat dispersion of DBE unit cells resulted in a miniature printed antenna with a lambda0/9 times lambda0/9 footprint, 3% bandwidth...
Artificially engineered periodic structures, including photonic crystals and meta-materials, have generated strong interest in the scientific community due to their extraordinary and promising electromagnetic/optical features. Recently, periodic stacks of misaligned anisotropic layers have been shown to realize degenerate band edge (DBE) structures (A. Figotin , et al., Sep. 2005). When magnetic layers...
Many mobile structures (aircrafts, ships and automobiles) require conformal antennas for high data rate connectivity, which brings the need for material compatibility and for structurally reinforced antennas. The latter requirement is particularly challenging for small platforms since a large antenna is needed at these frequencies. For small unmanned air vehicles (UAVs) spanning a few feet, it is...
An alternative miniaturization technique is introduced, based on low-loss ferrite composites. The wave slow down for size reduction is provided by the permeability and permittivity of the ferrite composite, respectively. Ideally, the ferrite should possess equal permeability and permittivity (i.e. epsivpsilar = mupsilar) and must have low loss characteristics for large bandwidths. In this paper a...
Wideband antennas that can operate over a frequency range from 10psilas of MHz up to several GHz is highly desirable, yet a challenge (Kramer et al., 2006). As expected, a major challenge is to keep the size small while maintaining bandwidth. Another and key challenge is the need for a ground plane that does not deteriorate the UWB performance for conformal installations (Kramer et al., 2006). This...
In this work we present the advantages of passive and active matching to lower the operational frequency of VHF/UHF antennas. A multi-segment passive matching circuit is designed via formal optimization to improve the lower frequency of a broadband planar dipole by 25%. Implementation of active networks shows that an impressive matched behavior is also possible. Measurements and simulations are presented.
Using spectrum around 60 GHz for high speed short range wireless systems has led to examination of antennas on chip. System analysis indicates that spatial power combining on chip may allow for a good combination of small size and compatibility with silicon amplifier performance indicates this approach may be the solution of choice. We have shown good agreement between modeled and measured performance...
In recent years, there is a growing interest in compact high-gain antennas with a single feed for civil/tactical wireless communication systems. Electromagnetic band-gap (EBG) structures with embedded antennas/feeds present an attractive solution due to their high directivity and feeding ease. EBGs have been used to obtain highly directive radiation in two forms: (a) as a substrate utilizing defect...
We described a novel wideband material characterization method to accurately measure dielectric permittivities, and transmission characteristics of periodic metamaterials. The measurement system is based on a virtual transmitting aperture synthesized to produce a spot-focused Gaussian beam on the sample under test. This minimizes edge diffractions from the sample and allows for much more accurate...
Low-cost and convenient fabrication techniques are of significant interest for flexible and multifunctional electronics industry. This paper has presented a versatile fabrication process for direct printing of conducting patterns for RF circuits on ceramic-PDMS composite substrates. In order to illustrate this technique, a three-dimensional design of a GPS antenna is produced. Through this promising...
Radar imaging studies of full-scale buildings present serious electromagnetic modeling challenges. The large electrical size makes numerical methods impractical, and the complexity makes ray methods difficult to apply. In this paper we adapt the NEC-basic scattering code (NEC-BSC) [1] to generate simulated radar scattering data for building imaging purposes. The NEC-BSC is based on the uniform geometrical...
We have designed a light weight and low height UWB antenna with omnidirectional coverage for airborne applications. For the given aperture, we attain - 15 dBi gain point at 55 MHz. Thus this antenna is only 15% larger than the theoretical miniaturization limit: 49 MHz. It is also important to note that the realized gain above 200 MHz is constantly above 0 dBi till at least 1 GHz, even at the second...
A body-worn, meandered flare dipole was presented for operation at UHF frequencies. Measurements and simulations provided reference for its performance and applicability. Some mounting options were discussed and additional configurations will be discussed at the conference. As is evident from the given patterns, the body-worn antenna is highly sensitive to its location and mounting. Moreover, considering...
We presented carbon nanotube coated conductive textiles and polymer-ceramic composites for novel load bearing antennas. We showed that the polymer-ceramic composite exhibits high permittivity with very low loss tangent depending on the ceramic-polymer mix ratio. We also discussed that conductive textile coated with carbon nanotubes and gold carry very promising features to achieve high conductivity...
The purpose of the paper is to discuss broadband antenna miniaturization in general. The goal is to illustrate some simple guidelines that can used for miniaturizing a broadband antenna. To demonstrate these guidelines, we use a wire log-spiral antenna which is miniaturized via inductive loading. In this case, the inductive loading is achieved without modifying the antenna structure by increasing...
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