Effects of phase differences in GTEM cell measurements

This paper presents the effect on radiated power measured at the GTEM output port if the phase between the radiating dipole moments of the EUT is altered in steps from -180 degree to +170 degree. In current practice it is often assumed that the phase difference between dipole moments does not change the power measured at the GTEM output port. The results from this work disprove this assumption. Results from experiments show a significant change in the measured power when the phase was altered. Simulations using time-domain transmission line method (TLM) performed using the procedures described in standards MIMIC the experimental results and the variation of power magnitude agrees with that of experiments. SuperNEC^TM was used to produce radiation patterns for different phases which are used to gain an insight into the impact of phase. The major outcomes of this work are (1) an insight into an assessment of the impact of phase on power measurement and (2) the expected errors and uncertainties due to phase differences when current procedures are applied.