Description
Microstrip patch antennas have been extensively explored in the last few decades. Since their inception they have been widely implemented in wireless communication applications but few disadvantages have been a limitation to the performance characteristics of the microstrip patch antennas. As part of literature survey, a novel _-shape microstrip patch antenna (MPA) has been studied which achieved a very wide impedance bandwidth of 55% with decent radiation performance but suffered from degrading broadside gain towards higher frequencies. The wireless communication industry applications demand for smaller and compact antennas which can provide wide impedance bandwidth and good radiation performance occupying less space when installed. This thesis initially presents remedies for problems encountered with the full _-shape MPA which include adding layer on top and also designing metallic strips onto the layer. A comparison of the performance characteristics of all three designs has been made. Then a reduced size (almost 50% than original patch size) half _-shape MPA with optimized design dimensions is presented and the experimental verifications are performed. This antenna has provided a wide impedance bandwidth but at the cost of increased cross-polarization.Next, a cavity backed half _-shape MPA is presented which consists of a copper cavity placed behind the patch antenna mainly to increase the co-polarization gain and reduce the cross-polarization level. The cavity backing has proved to be effective only to a certain extent as it considerably increased the co-polarization gain by 2 dB compared to the earlier half _-shape patch design but nevertheless proved futile in reducing the cross-polarization levels. Finally an optimized cavity backed half _-shape MPA employing defects in the ground plane is presented along with experimental and simulation results. This design has been effective in increasing the co=polarization gain along with reduced cross-polarization while maintaining almost similar antenna performance as the earlier design. The measured results show reasonable agreement with the simulation data.
