Design and optimization of a mobile device PCB - PIFL multiband antenna for GSM applications

Abstract

The latest trend in handset design is slim smart phones that require small, thin, light weight and wideband multiband internal antennas. This trend poses two major challenges in designing a mobile device antenna: how to use a single antenna to cover all the required frequency bands and then how to make the same antenna small enough so that multiple antennas can be deployed within the same device. Although a printed Inverted-F antenna (PIFA) has been a suitable candidate due to its simple modeling and easier fabrication using a printed circuit board (PCB), it has a limitation of a narrow bandwidth characteristic. To address this issue and yet obtain multiband operations for GSM applications, this paper presents the structural optimization of a PIFA antenna which is capacitively loaded with an inverted-L element. The antenna covers GSM-900 and GSM-1800.The results obtained show that the PIFL antenna lower and upper bandwidths determined at -10dB is over 110MHz and 500MHz respectively which covers the above mentioned bands very well with very low return losses of -30dB and -30dB at resonant frequencies 925MHz and 1.795GHz respectively