Analysis of microstrip-patch antennas incorporating arbitrarily-shaped apertures
Dharmadhikary, Vasant M
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Microstrip antennas have received extensive attention as they have many attractive features, such as lightweight, small size, low profile and ease of fabrication. One of the inherent limitations when using these antennas is their limited bandwidth. Aperture coupling has proven to be a reliable and a robust feeding technique for these antennas as they are suitable for wide-bandwidth designs. A microstrip patch antenna that is coupled to a Microstrip-line by an aperture in the intervening ground plane has been designed and implemented in this work. Arbitrarily shaped coupling slots have been considered by investigating their contributing effect on the radiation characteristics of the antenna. Aperture shape and size are the crucial parameters that are considered for the aperture-coupled microstrip antennas. Our publications [109-110] have been based on a hybrid formulation combining the Method of Moments (MOM) and the Finite Difference Time Domain method (FDTD) for which, as a student, I take credit. It should also be taken as a contribution that the ingenuity of interfacing one kind of basis functions, Rao- Glitton-Wilson (RWG) for the surface with another type, the volume function for FDTD for the cavity. The aim of this work was to look for an aperture shape that gives significantly improved coupling of the radiated power from the feed-line to the resonant patch element and at the same time giving lower back-lobe radiation level from the slot. Rectangular, Circular, Bowtie and H-shaped apertures were of Micros investigated and it was found that the H-shaped aperture coupled antennas provide higher coupling and reduced backward radiation levels as compared to the other aperture shapes. The numerical analysis carried out employed the Electric Field Integral Equation technique with the Moment Method using the software called FEKOﾮ, which employs the triangular patch modelling scheme as the basis function. The antenna characteristics such as the radiation pattern, S-parameters, and input impedance were simulated for the various shapes of coupling apertures. The antenna prototypes utilizing each of these aperture shapes were constructed and tested in the laboratory and the experimental results compared with the simulated ones. The obtained results were found to be in good correlation.