Design And Fabrication Of Aperture Coupled Microstrip Patch Antennas With Arbitrarily Shaped Apertures

ABSTRACT

A linearly-polarized aperture coupled microstrip antenna design is characterized and optimized using FEKO antenna simulation software. One of the major drawbacks of these microstrip antennas is their narrow bandwidth. Aperture coupled being one of the feeding technique has proven to be a solution to this problem. In this research a patch antenna that is coupled to a microstrip-line by an aperture in the intervening ground plane has been designed and fabricated and implemented. The shape and the size of the aperture and the location of the patch relative to the aperture are the crucial parameters for the aperture coupled microstrip antennas. Arbitrarily shaped coupling apertures have been considered by investigating their contributing effect on the radiation characteristics of the antenna. The goal of this thesis is to explore the shape and the size and location of the patch relative to the aperture. These have been considered by investigating their performance effects through electromagnetic principles. The aim of this study was to investigate an aperture shape that provides better coupling of the radiated power from the feed line to the patch element while at the same time giving lower back- lobe radiation level from the aperture. The aperture shapes investigated were rectangular shaped, H-shaped and Diamond shaped. It was found that H-shaped aperture coupled antenna provides higher coupling and reduced backward radiation levels as compared to the other aperture shapes. It was also found that the signal coupling level is greatest when the patch is centered over the aperture. The numerical analysis was carried out using the Electrical Field Integral Equation technique with moment method using software called FEKO. This software uses the triangular patch modeling as the basis function. The antenna characteristics such as the VSWR, S-parameters, radiation pattern, and input impedance were simulated for the various shapes of coupling apertures. The antennas prototypes using each of these aperture shapes were fabricated using FR4 PC boards joined together. Ideally the antenna was to be characterized in an echoic chamber and the result compared with the simulated data. However due to lack of an echoic chamber, the data obtained in an open space was compared with the simulated ones for similarity of patterns. The obtained results were found to be in good correlation.