Predicting TEM cell measurements from near field scan data

A procedure is proposed for predicting TEM cell measurements from near field scans by modeling near-field scan data using equivalent sources. The first step in this procedure is to measure the tangential electric and magnetic fields over the circuit. Electric and magnetic fields are estimated from probe measurements by compensating for the characteristics of the probe. An equivalent magnetic and electric current model representing emissions is then generated from the compensated fields. These equivalent sources are used as an impressed source in an analytical formula or full wave simulation to predict measurements within the TEM cell. Experimental verification of the procedure using a microstrip trace and clock buffer show that values measured in the TEM cell and calculated from near field scan data agree within a few decibels from 1 MHz to 1 GHz.