Niroo-Jazi, Mahmoud
(2012).
Nimble Radiation-Pattern Antennas Using Agile Frequency Selective Surfaces.
Thèse.
Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en télécommunications, 176 p.
Résumé
The synergy gained between frequency selective surfaces as partially
reflective/transparent screens and reflector antennas is exploited to present a new class of
reconfigurable antennas for tactical communication systems in this thesis. The potentials
of frequency selective surfaces in creating controllable electromagnetic shutters are
theoretically and experimentally explored to fully take advantages of them in increasing
the functionality of traditional reflector antennas. The related transmission line models of
the corresponding sheets are also extracted to interpret their electromagnetic responses.
To control the scattering responses of these shutters, high frequency switches are
precisely incorporated into their constructing periodic elements. The possible DC-biasing
feed schemes of active elements are investigated and the relevant reconfiguration
mechanisms dictated by these schemes are identified. Furthermore, the effect of required
biasing feed lines on the transmission/reflection responses of screens is evaluated. The
adverse effects of non-ideal active elements are also examined to elaborate the screens
according to the desired transmission/reflection responses.
In the proposed new class of multi-functional reconfigurable antennas, an appropriate
radiation mechanism is utilized, and a simple design guideline based on the key
principles of reflector antennas and frequency selective surfaces is presented. The
designed planar frequency selective surfaces are applied in this radiation topology as a
controllable electromagnetic window, and their performances are evaluated. The pros and
cons of each antenna in providing different functionalities are investigated to emerge a
new class of antenna called "Nimble-Antenna". Indeed, a nimble-antenna refers to an
antenna with two functionalities, including sweeping its radiation over aIl azimuth angles
and reconfiguring the antenna radiation-pattern between directionallomni-directional
cases.
In the final designed reconfigurable electromagnetic window, a hybrid technique is also
applied to enhance the nimble antenna performances and extend the functionally of the
proposed radiation topology across two different frequency bands. In this structure, the
number of active elements and overall antenna size are also reduced compared to the
other presented prototypes.
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