High resolution PCB field intensity by near aperture field transformation

Most of RE (radiation emission) from PCB (print circuit board) will cause the system fail to pass the EMI regulation and degrade the sensitivity in communication system. Since the size of cellular communication system is smaller and smaller, the sensitivity of system is degraded by near field EMI. This paper proposes a technique to predict the high resolution surface current density on PCB by planar aperture field above the PCB. The GEMS which is based on the FDTD (finite difference time domain) is used to simulate the current density on the PCB. The aperture field of two kinds of PCB antenna with dual bands are measured by planar near field scanner. The measured data is transformed to the surface of PCB to get the surface current density on the PCB. The results of PCB current density from both measurement and simulation are quite similar.