Analysis of cable effects in portable antennas

Abstract

Ground plane may act as a main radiator in most portable antennas. Various cables connected with the ground plane, such as FPCB, speaker wire, and coaxial cables for measurement, can affect the radiation performances of the antenna significantly. In this paper, we use a loop-type ground antenna to examine the cable effects and analyze the effects by an EM simulator HFSS. The loop-type ground antenna is printed on a ground plane that measures 50 × 20mm and is required a ground clearance of 4 × 6 mm. The antenna is operated at Wi-Fi (2.4-2.5 GHz) band. Without any extra cable effects, the resonant frequency is at 2.46 GHz. With extra cable connected to the different points on the ground plane, simulation results show that the resonant frequency and input impedance varies. Based on analysis, we demonstrate that the cable near the electric field maxima on the ground plane has strong influence on the resonant frequency and impedance of the ground antenna.