Low frequency field prediction applied to CISPR 25 test setups

Abstract

Modern automotive systems integrate a variety of electrical and electronic components. To estimate the radiated emissions, the standard CISPR 25 describes the absorber-lined shielded enclosure (ALSE) method, which is the most important standardized field measurement method. However, it suffers from the need for a large anechoic chamber. To reduce costs and more conveniently integrate radiated emission investigations into the product design cycle, alternative methods that predict emissions without such a chamber are necessary. These methods measure currents, voltages, or fields close to the setup’s vicinity, and with the help of appropriate models, CISPR 25 quantities can be calculated. However, the known methods often fail at frequencies below 30 MHz. This dissertation introduces two new methods based on electric near-field measurements to overcome the problems. The first method uses extrapolation and interpolation of the measured data to create a Huygens’ surface. The field at 1 m distance can be calculated from the Huygens’ surface. The second method finds electrostatic dipoles from the measured data. The fields from the dipoles can be estimated at 1 m distance. This dissertation uses measurements and full-wave simulation to verify the accuracy of the proposed methods.