EVALUATION OF RADIO-FREQUENCY IMMUNITY TEST FACILITIES BASED ON THE SCATTERED FIELD OF A CONDUCTIVE SPHERE

In the radiation immunity test for telecommunication equipment, an ele ctromagnetic applicator such as chamber, a transmission electron micro scopy (TEM) cell and a general transmission electron microscopy (GTEM) cell are used. Characteristics that include a semianechoic uniformity of the electromagnetic field without a device under test have been ev aluated. However, characteristics that include an electromagnetic fiel d in the presence of the device under test have not been reported. In this paper, it is recognized that these electroamgentic applicators ar e designed in such a way that they can generate an electromagnetic fie ld simulating a plane wave. Based on the electric field distribution g enerated by the plane wave incident on a conducting sphere, the electr ic field is evaluated and compared in the case in which the device und er test is placed within the applicator. Further, evaluation results a re included for the size of the device under test for which the immuni ty test is possible in each applicator. The evaluation method first de rives the theoretical value of the scattered electric field when a pla ne wave is incident on the conducting sphere in free space. Next, thes e theoretical values are compared with the measured electric field val ues around the conducting sphere in each electromagnetic applicator. I t was found that the difference between the measured and the theoretic al results is the smallest and the frequency dependence is the lowest in a semianechoic chamber. In the case of a TEM cell and a GTEM cell, it was found that the difference between the measured and the theoreti cal values is less than +6 dB if the magnitude of the device under tes t is less than one-third the spacing between the inner and outer condu ctors.