Method of estimating the maximum radiated interference field of electronic equipment by using randomly assigned phase terms

Using the electric field strength measurement value vicinal to electronic equipment set up in a factory, investigation was made by the experimental method stipulated by VCCI, that is, by both theory and experiment, estimating the maximum value of the electric field strength measured for the set-up of electronic equipment at the test site by the 10-m test method. In the estimation method proposed, the electric field strength in the vicinity of electronic equipment is measured in cylindrical form, the phase of the measurement point is assigned by uniform random number and, employing the integral expression of electric field using these values, the maximum value of the electric field strength of the estimation surface is estimated. In the investigation, even in the case of assigning phase by random numbers, it was found theoretically possible to estimate within 6-dB accuracy the maximum value of the electric field strength of the estimation surface. Moreover, as a result of investigating the accuracy of the estimation method using a spherical dipole antenna as a radiation interference source, it was confirmed experimentally that the deviation between the estimated value and measurement value is roughly below 4 dB over a frequency of 100 MHz to 1 GHz.