Finite-difference time-domain analysis of a stacked dual-frequency microstrip planar inverted-F antenna for mobile telephone handsets

In this paper, me describe a stacked, dual-frequency microstrip planar inve rted-F antenna (DF-PIFA) for mobile telephone handsets that can concurrentl y work in two frequency-bands, viz,, those associated with the GSM and DCS 1800 systems operating at 0.9 GHz and 1.8 GHz, respectively. The proposed m icrostrip DF-PIFA is fed by a coaxial line, as opposed to two separated fee d lines used in the conventional design. The design is carried out in a sys tematic manner and involves two steps. We begin,vith an initial configurati on of the PIFA that is based on a standard design for a microstrip patch an tenna fed by a coaxial line and is derived from an empirical approximation in conjunction with a transmission line model. Next, we employ a computer-a ided design (CAD) tool, based on the nonuniform finite-difference time-doma in (NU-FDTD) Maxwell solver, to optimize the performance characteristics of the DF-PIFA, including the return loss, the matching of the input impedanc e, and the far-field radiation patterns.