An automated electromagnetic-field strength measurement system with a magnetic-field probe

An automated electromagnetic-field strength measurement system and its applications are described which are for the purpose of mapping the electromagnetic-field strength distribution inside and outside vehicles exposed to electromagnetic field. The system is comprised of three subsystems: electromagnetic-field generation unit, data transmission stage using a magnetic-field probe and a fiber-optic link, and data control/processing stage consisting of a graphic computer and peripherals. The system is capable of measuring field strength levels between 40 and 85 dBµA/m with errors within ± 1 dB in a frequency range of 20-200 MHz. The time required for making measurements at a single measurement point at intervals of 2 MHz from 20 to 200 MHz is about three min. Magnetic-field strength measurements at every interior position of a vehicle exposed to electromagnetic fields inside an anechoic chamber were made using this system. The field strength of the vehicle interior was found to vary with the polarization of an electromagnetic wave, the direction of irradiation, and the body shape of the vehicle.