Studies on stacked patch antennas for WLAN applications

Abstract

The need for wireless computer communications is growing day by day; with WLAN, WiMAX and UWB technologies emerging as the major technologies in this field currently. As the communication is wireless in nature, an antenna is one of the main requirements of these systems. Typically for the WLAN systems, an antenna is required at the router as well as at the computer terminal that is preferably inexpensive, compact and rugged in nature. Microstrip antennas therefore act as one of the viable choices for such systems which can be preferably designed as multiband antennas with suitable bandwidths that are capable of covering multiple wireless applications for efficient utilization of the resources. A lot of complex techniques are available in the literature that can be used to design and develop Microstrip antennas for these wireless applications; a simpler technique in this context is the use of Stacked/Multilayer Microstrip patch antennas. As the effective height of the antenna increases when multiple substrate layers are used in the antenna structure, and the resulting antenna has loosely bound EM (electromagnetic) fields and that are radiated out better into free space. This leads to an increase in the antenna bandwidth if the two substrates are of same/ close by dimensions and multiple frequencies can be radiated out if the patch antennas are of varying dimensions. Therefore the purpose of this thesis is to investigate the behavior and the design and development of Stacked Patch antennas for wireless applications like WLAN, WiMAX and UWB etc and the methods to develop Stacked Microstrip patch antennas (MSAs) that exhibit multi-frequency and a wideband behavior at these bands. A defected ground structure (DGS) is another variation that can be incorporated into the antenna structure to enhance the existing bandwidth or get a multiband behavior from the stacked MSAs. On the basis of dimensions and shape of defect in ground plane, the protected distribution of current density in the ground plane is interrupted, leadi