Mobile antenna performance improvement by ground mode tuning using a closed loop

Abstract

An antenna with a modified ground plane is proposed for modern mobile devices in the wireless communications. The proposed antenna design comprises a planar inverted-F antenna with a feeding capacitor (C-F) at the top side of the ground plane, and an additional closed loop with lumped inductors (L-1 and L-2) at the end of the ground plane. The closed loop is connected to the small ground plane for ground mode tuning so that the ground mode resonant frequency is equal to the operating frequency. In the simulation, the -10dB bandwidth is 140MHz (from 2.39 to 2.53GHz) without the closed loop, and is 320MHz (from 2.34 to 2.66GHz) with the proposed closed loop. The measured efficiency is 61% on average from 2.3 to 2.6GHz for the proposed antenna, and is 36% for the reference antenna. The ground mode resonance can be easily tuned, and the proposed technique is a versatile approach for antenna performance improvement.