HIGH IMPEDANCE SURFACES FOR ANTENNA DESIGN

Abstract

Electromagnetic band gap (EBG)ntechnology has become a significant advancement in thenRF and microwave applications. Due to their unique electromagnetic properties of surface wave suppression and in-phase reflection, they have been investigated for diverse applications including improvement of antenna performance, Radar cross section (RCS) reduction and many others. Many phenomenal efforts havenbeen undertaken in the design of such structures to make them suitable for a wide range of RF and Mircowave applications. In this dissertation work, various prototypes of such structures have been designed and analyzed with respect to the frequency of operation, compactness and suitability with planar technology. Three-layer mushroom and its different prototypes are proposed for L-band frequencies and analyzed for reflection phase and dispersion characteristics. For fabrication simplicity the planar structure has been designed for the ground reflector of a bow-tie slotted patch antenna for WLAN/WiMax application. The structure has been modified in a fashion to make it polarization dependent and thus converting LP radiations of the patch antenna into CP radiations. The complete design resonates for dual band in WLAN range while giving CP radiation along with lower backlobes and broadside radiation pattern. The fabricated results show close agreement with the simulated results. Eventually, a polarization dependent HIS is proposed for the application of polarization reconfigurable antenna using varactor diode. The HIS works at 3.3GHz and can be used to achieve polarization reconfiguration (LHCP/RHCP) for dipole antenna