| dc.description.abstract | Newly emerged Electromagnetic Band Gap (EBG) structures possess multiple frequency
bands that prohibit wave propagation and such stop bands are basically determined by
the periodicity of the structure. Such desirable features make EBG hybrid antenna an
interesting topic. Traditional full-wave techniques lack the efficiency to fully cope with
the complexity of these hybrid structures, since the periodical elements are often much
smaller in size than the accompanying antenna components.
The Haar wavelet based Multi-Resolution Time Domain (MRTD) technique provides
improved numerical resolution over the conventional Finite-Difference Time-Domain
(FDTD) method, as well as simplicity in formulation. One-dimensional, two-dimensional
and three-dimensional level-one codes are developed to assist the numerical modelling
of the hybrid EBG antennas. An explicit form of Perfectly Matched Layer (PML) configuration
is proposed, proved and presented. As a generic approach, its extensions suit
every single level of Haar wavelet functions. A source expansion scheme is proposed
thereafter.
The concept of a multi-band multi-layer EBG hybrid antenna is presented. The theoretical
prediction of antenna resonances is achieved through an effective medium model.
It has been verified via numerical simulations and measurements. The 3D MRTD code is
later applied to simulate such a structure.
In addition, EBG enhanced circularly polarized photonic patch antennas have been
studied. It is demonstrated that split-resonant rings (SRRs) and the like in EBG antennas
can lead to antenna gain enhancement, backward radiation reduction and harmonic
suppression.
Furthermore, a circularly polarized two-by-two antenna array with spiral EBG elements
is presented. The spiral element with ground via is more compact in size than
the traditional mushroom structure, which is proven very efficient in blocking unwanted
surface wave. Hence it reduces the mutual coupling of the array antenna significantly. | |
