Radiation from microstrip transmission lines

The radiation properties of a microstripline configuration are investigated. The electric field produced by a microstripline on a printed circuit board is calculated analytically using the magnetic vector potential and numerically using the method-of-moments technique, for comparative purposes. To simplify the calculations the microstripline is replaced by an open-wire transmission line. A frequency of 100 Hz, which is in the range known to cause problems with FCC compliance of digital products, is used. The objective is to calculate the electric field one would expect to measure at a test site used for FCC compliance measurements, as opposed to the free-space results obtained when ground reflections are not considered. It is shown that replacing the microstrip structure with a two-wire transmission line for the calculations, although not rigorous, provides suitable accuracy for EMC applications.<>