ANALYSIS OF COUPLING BETWEEN DIGITAL SIGNAL ON FPCB AND MOBILE HANDSET ANTENNA

Abstract

Digital harmonics, which may reduce the radio frequency (RF) sensitivity of a system, can be coupled with an antenna in a mobile handset. Especially, the digital signals which flows a flexible printed circuit board (FPCB) can be coupled with an antenna and which seriously degrade the system sensitivity. This article explores the coupling mechanisms of digital harmonics on an FPCB with an antenna in terms of the characteristic mode current and the concept of reaction. The signal and ground lines in an FPCB are modeled as a loop path exciting a characteristic mode current, and the mechanisms of the coupling between the digital signal and the antenna port are analyzed.