Bandwidth enhancement of rectangular microstrip patch antenna using multi-slot technique.

Hatem H. Abbas
Dr. Jabir S. Aziz

Abstract: The microstrip patch in its pure form cannot satisfy the bandwidth requirements for most wireless communication systems. The general philosophy of most of the bandwidth enhancement techniques is to add one or more resonant structures to the microstrip patch configuration. These additional elements may be in the form of slots or other patches. This thesis introduces the design and analysis of bandwidth enhancements for a microstrip patch antenna using different slot configurations. Other techniques for bandwidth enhancement are also presented in this thesis and simulated using Microwave Office. First; thick substrate with direct probe feed is applied in order to enhance the antenna bandwidth; different thicknesses (h = 0.2, 0.4, 0.6, and 0.8 cm) are used, and the maximum bandwidth produced by this technique using thickness of 0.8 cm is 80 MHz ( about 7 % of the central frequency). Stacked patch antenna is also examined, in the stacked geometry the patch radiators are employed one above the other with intervening dielectric layers, Bandwidth of about 140 MHz (which is about 7 % of the central frequency) is achieved using stacked MPA technique. Another technique used in order to increase the bandwidth further using one parasitic rectangular patch placed along the radiating edge of the fed rectangular patch with small gap between them. The bandwidth achieved by this technique is about 510 MHz which is about 25.5 % of the central frequency. These techniques produce wide bandwidth but with the use of relatively large antenna size by increasing its thickness or its area.Regular and irregular shaped slots are loaded into the rectangular patch of the antenna to study their effect on the antenna performance. The effect of changing the number, position, and dimensions of the slots on the antenna bandwidth have also been studied by simulating the antenna performance with two, three, four, and more slots loaded into the rectangular patch of the antenna. Microwave Office is used as simulation tool to simulate the antenna performance in this thesis. The results of this work show that an enhancement of about five times of the original bandwidth can be achieved by using more than one slot with proper position selection. Bandwidth performance of the antenna with circular polarization have been examined and compared to that of antenna with linear polarization and the study shows that both antennas have the same bandwidth performance.