Calibration of near field measurements using microstrip line for noise predictions

In this paper, near-field measurements from a microstrip line, obtained using an NEC probe, are presented for frequencies over a wide bandwidth from 250 MHz to 3 GHz. Near-field measurements obtained using the NEC probe are in good agreement with HFSS simulation results and analytical models. It has been shown through experimental near-field measurements and numerical simulations that the return current on the ground plane of a microstrip line, although small in areas on the ground plane away from the signal line, produces a significant magnetic field. Circuits placed above the area where the magnetic field strength is large will experience strong electromagnetic interference. Near-field measurements help with placement of circuits to realize systems with minimal electromagnetic coupling. This research work is leading to the development of design guidelines for reducing the effect of EMI in microelectronic systems.