Use of Frequency Selective Surface to Prevent SAR and Improve Antenna Performance of Cellular Phones

Abstract

The purpose of this study is to design the low-cost planar inverted-F antenna (PIFA) applicably built in cellular phones with finite integration technique (FIT) for simulation of surface current distribution, radiation efficiency, radiation pattern, and gain. The prototype antenna is constructed with aluminum foil and low-cost FR4 PCB substrate. The antenna is designed with quarter wavelength (lambda/4) of resonant frequencies and fed with 50 Omega matching microstrip. It owns the industrial demanding characteristics of light weight, compactness, low profile, and easy fabrication. The target frequency band is designed for the following cellular phone systems: GSM (Global system for mobile communication: 880-960 MHz), DCS (Digital communication system: 1.71-1.88 GHz, PCS (Personal communication system: 1.85-1.99 GHz), and IMT-2000 (3G: (1.92-2.17 GHz). However, since the bio-effect of specific absorption rate (SAR) by cellular phone gains popular concern, we also try to utilize the unique band-stop or band-pass features of frequency selective surface (FSS) to reduce the SAR. Finally, we design the finite size 2-dimensional periodic structure to integrate with antenna for SAR reduction by decreasing backward radiation. The result shows that the integrated PIFA-FSS module not only reduces the SAR but also improve the antenna gain and radiation efficiency of the cellular phone.