This thesis presents the research work on the development of a broadband resonant
cavity antenna (RCA) using a two-layer metamaterial based superstrate and a wideband
patch antenna as a primary source. It is shown that the resonant effect in a metamaterial
consisting of two identical patch arrays can be used to design an RCA device for
broadband performance. The large radiation bandwidth of 40∼47% with 1-dB-ripple flat
band response and the maximum gain of ∼13 dBi have been achieved over the
frequency band of 8∼12 GHz. The dimensions of the compact RCA device are 45x45x24 mm3 (or 1.5λx1.5λx0.8λ at 10 GHz). The two-layer metamaterial superstrate
is based on an assembled structure using the two liquid crystal polymer (LCP) film
substrates each with a printed patch array and separated by an air spacer of 4 mm. This
air-based superstrate contributes antenna efficiency; it is lighter and requires less
dielectric material. For comparison, the two-layer metamaterial superstrate design is
implemented using an FR4 board and it has also been demonstrated to provide similar
broadband performance in an RCA device.
The Fano resonance effect in the two-layer metamaterial design has been studied. It
has been discovered that a sharp resonance can be obtained in such metamaterials when
a dielectric spacer is very thin (~100 µm). Analysis of current and electric field
distributions shows that the observed electromagnetically induced transparency (EIT)
associated with the enhanced transmission originates from the effect of trapped-mode
resonance in the two-layer metamaterials. The experimental work was carried out using
both FR4 and LCP based dielectric spacers. It is shown that the LCP based
metamaterials can also be used as an effective absorber near a design frequency of 10
GHz.
A broadband source antenna is based on an optimised coplanar waveguide (CPW)
fed and aperture coupled patch antenna design. By exploiting the coupling effects of a
triple resonances associated with the CPW structure, the aperture, and the patch
element, the broadband patch antenna was obtained and used successfully in the
development of the broadband RCA device. Impedance and radiation bandwidths of the
practical device are measured to be as large as 41% and 43%, respectively. The new
fabrication and assembly methods based on laser micromachining of the PMMA
polymer have been developed for a successful construction of metamaterial structures
and antenna devices
