Compensation method for the coupling error between the EUT and TEM cell in E-field probe isotropic calibration

TEM cell is widely used as a standard field generating device in the calibration of electric field probes. It is recommended that the EUT shall not exceed one-third of the distance between the floor and the septum in the TEM cell. It will be shown that for measuring isotropic responses of E-field probe (by rotating the probe under a constant incident field), even if the probe meets the one third requirement, the couplings between the probe and the TEM cell are non-negligible. As a result, the total E field inside the TEM cell varies during the rotation of the probe. In this paper, a novel compensation method is presented to remove the coupling effect. The method is based on recognizing the fact that the position of the E-field probe with respect to the TEM cell is periodic through the rotation of the probe. Electric field can be correlated to the rotational angle. Both theoretical analyses and experiment verifications are provided.