Challenges of Isotropy in Standardized 3-Axes EMF Measurements

The paper proposes a new method that processes 3-axes E-field measurement data in order to achieve better isotropy and reduced uncertainty of the measurement system. Typically, the frequency selective E-field measurement procedure assumes ideal sine radiation pattern of dipoles involved in the 3-axis sensor. The difference between the ideal sine and the real radiation patterns of the sensor is then evaluated and expressed as an added uncertainty of the measurements across all angles of ray arrival to the sensor. The method proposed in this paper consists of post-processing of the measured values at each axis element, based on real radiation patterns of elements of a 3-axis probe. In this way, with a typical probe element radiation pattern, the uncertainty of the measurements due to difference between ideal and real radiation patterns of the sensor can be significantly reduced. The paper illustrates the method using examples of long (up to wavelength) dipole probes.