Analysis of different structures of patch antennas

ABSTRACT: In this thesis, Method of Moment (MoM) based FEKO software version 5.5 was used to simulate patch antennas in different structures. For patch antennas, some of the fields are in the substrate and some of them in air. Due to this reason, it is necessary to calculate the effective dielectric constant which affects the resonant frequency and the wavelength of the wave in the substrate. Simulations were carried out to compute the value of effective dielectric constant of a single substrate layer which has a relative permittivity equal to 2.2 by making use of the standing wave pattern (SWP) generated by FEKO. After that, microstrip patch antennas were simulated based on multi-substrate layers instead of a single layer. Square, circular and triangular patches were simulated by FEKO and the resonant frequencies obtained were compared with other published (experimental, analytical, simulations by other methods) works. The results are close (from 1 to 3GHz difference) for different modes of the circular patch, while they were equal at 4.02 GHz and 7.03 GHz for the triangular and square patches respectively. Slot antennas are used to enhance the bandwidths, but slots may affect the relative permittivity. i.e. the effective permittivity. Triangular and square shape slot antennas were simulated by FEKO and the results were compared among themselves and with the published result for the triangular slot. The results very close. Slots on the patch are widely used. Here a triangular slot for various heights was simulated by FEKO for the rectangular patch. If has been observed that the resonance frequency reduces by the increase of the height. The optimum height for the given design was recorded. Also, circular slots were applied inside the circular patch to improve the return loss, voltage standing wave ratio and the bandwidth. Defected ground structures (DGS) in different shapes (rectangular, phi-shape, c-shape and plus-shape) were used to solve the surface wave problem which is a drawback for patch antennas. The use of this method resulted in gain enhancement. Gain was enhanced by using patch antenna array topology. In this thesis, a 4 element array antenna was designed at 2 GHz and simulated by FEKO. A maximum gain of 13.1dB dB was achieved. Keywords: Effective Dielectric Constant, Gain, return loss, Patch Antenna, Patch Array Antenna. …………………………………………………………………………………………………………………………………………………………………………………………………………