| dc.description.abstract | The success of future multi-functional communication, radar, sensing, and countermeasure
systems heavily rely on ultrawideband (UWB) antennas. UWB antennas
have a very high demand in electromagnetic compatibility (EMC) testing,
radar calibration, satellite tracking, reflector feeds, remote sensing, wideband instrument
for snow measurements (WISM), medical imaging, through-wall imaging,
and UWB radar systems. In an ideal case, these multi-faceted systems require
the use of a single UWB “one-size-fits-all” antenna that satisfies the bandwidth and
radiation requirements compared to using multiple narrowband antennas saving
time, labor, and overall cost of the system.
This dissertation delves into the theory, design, and feasibility of one of the
kinds of a single UWB antenna or a single integrated UWB antenna system for
their potential use in the characterization or calibration of weather radars or other
UWB communication systems. Firstly, detailed Maxwell-Garnett particle mixing
analytical models are presented and evaluated based on their performance and
error analysis. The correct analytical model is identified and used in the synthesis
of tunable artificial dielectric material (TADM) at microwave (S-band) and mm-Wave
(W-band) frequencies for applications such as RF substrates for antennas
and microwave components such as filters. This technique allows for the utilization
of cost-effective materials that already offer outstanding thermal properties and
seamless compatibility with a multi-layer fabrication process, can now be equipped with desired tunable εeff and loss tangent characteristics. The measured results
show substantial reductions of 45% in εeff and 38% in loss tangent values in the
S-band, along with reductions of 32% and 72% in εeff and tanδ, respectively,
in the mm-Wave frequency band. Impressively, the simulated, calculated, and
measured results demonstrate an excellent level of agreement.
To see the feasibility of using commercially available state-of-the-art UWB
antennas for in-situ characterization of radars, a detailed analysis is carried out
based on the idea of using a single UWB probe antenna for radars operating in
the L-, S-, C-, X-, Ku-, and K-bands. This analysis shows in detail that using
commercially available UWB antennas is not suitable for in-situ measurements
due to their wide beamwidth performance, especially for weather radars operating
in the most commonly used S-band at 3 GHz. To solve this challenge, several
solutions are presented. Among the solutions presented based on using corrugated
horns and multi-layer or hyperbolic dielectric lenses, the Maxwell-Garnett theory
that laid the foundation of the design of tunable artificial dielectrics is also applied
in the synthesis of a UWB graded-index (GRIN) artificial dielectric lens antenna
(ADLA). Proposed novel solutions make the use of these commercially available
antennas viable for radars and communication systems.
A UWB open-boundary dual-polarized quad-ridged horn antenna (QRHA)
having an impressive absolute bandwidth of more than 30 GHz (32:1) covering 1-
32 GHz, is then presented making it an ideal choice for UWB communication and
radar systems covering a wide range of applications relying on common frequency
bands including L, S, C, X, Ku, and K. The unique design allows for a favorable
impedance matching, acceptable stable and narrow-beamwidth performance, and
most importantly no-pattern degradation at higher frequencies which is a common
concern for most ridged-horn antennas designed thus far. | en_US |
