INVESTIGATION OF ELECTROMAGNETIC BAND GAP STRUCTURES FOR MICRO STRIP PATCH ANTENNA

Abstract

The main objective of this dissertation “Investigation of Electromagnetic Band Gap Structures for Micro Strip patch Antenna” is to design and simulate the various electromagnetic band gap (EBG) structure in order to investigate their frequency band gap region and reflection phase characteristic for micro strip antenna parameter improvement. Range of frequency region at which wave cannot propagate in the material is known as frequency band gap region and variation in phase of a reflected wave is produced by a surface determined by the reflection phase property. Two dimensional mushroom-like EBG structures have been investigated in this dissertation. The equivalent LC circuit of EBG structure acts as two dimensional electric filter to block the flow of wave. Frequency band gap property is investigated by dispersion diagram, scattering parameter method and reflection phase property is investigated by wave guide method. Electromagnetic Interference (EMI) is a source of noise problems in electronic devices. The EMI is attributed to coupling between sources of radiation and components placed in the same media such as substrate or chassis. This coupling can be either through conducting currents or through radiation. The radiation of electromagnetic (EM) fields is supported by surface currents. Thus, minimization of these surface currents is considered a major and critical step to suppress EMI. In this dissertation, A novel EBG strategy is presented to confine surface currents in antenna substrate. Traditional use of lossy materials and absorbers suffers from considerable disadvantages including mechanical and thermal reliability leading to limited life time, cost, volume, and weight. Here, a new method of EM noise suppression is introduced into micro strip patch antennas using mushroom-type EBG structures. These structures are suitable for suppressing surface currents within a frequency band denoted as the band gap. The effectiveness of the EBG as an EMI suppresser is demonstrated using numerical simulations CST Software. Applications of EBG structure in micro strip antennas are investigated, in which surface wave of micro strip antenna substrate is suppressed by dual layer of EBG around the micro strip patch. Significant improvement in return loss and bandwidth has been achieved. v EBG structure also exhibit property of artificial magnetic conductor (AMC) in a certain frequency range. Phase of reflected wave do not change in this frequency region. PEC ground plane in micro strip antenna gives 180 degree phase shift, which rise the disadvantage of distractive interference between incident wave and reflected wave of micro strip antenna .When PEC ground plane is replaced by AMC ground plane, it gives the constructed interference. Micro strip antenna with AMC ground plane has been investigated. Significant improvement in return loss has been achieved of micro strip antenna.