High Efficiency Wideband Ground Radiation Antenna with Parallel Resonance Magnetic Feed Structure

Abstract

By using the resonance characteristics of the Planar Inverted-E (PIE) feed structure, the impedance bandwidth of the conventional antenna is significantly enhanced. But the degradation of antenna radiation efficiency at a certain frequency often occurs. In this thesis, the cause of this efficiency degradation is investigated by analyzing the current mode of the feed structure. The general form of a PIE feed structure is a parallel resonance structure with a shunt lumped capacitor. The impedance of it can be controlled by varying the ratio of the inductance to capacitance. However, as a resonator, various current modes can be generated with the position of the shunt capacitor. When the half λ mode is excited, the mutual coupling between the feed structure and the radiating element is reduced. A solution is proposed in this thesis, which can be achieved by simple modification of the parallel feed structure. Both the reference antenna and the proposed antenna can generate 3:1 VSWR bandwidth of 40 MHz (from 0.85 GHz to 0.89 GHz), but the efficiency of the proposed antenna has been significantly improved both in simulation and measurement. This study has presented a comprehensive analysis in terms of figure-of-merit in radiation efficiency for parallel feeding structure based wideband applications.