Electric and Magnetic Fields from Simple Circuit Shapes

Abstract

If one wants to avoid empirical recipes and the “wait and see if it passes” strategy, the calculation of radiated fields from electrical circuits and their associated transmission cables is of paramount importance to proper EMI control. Unfortunately, precisely calculating the fields radiated by a modern electronic equipment is a hopeless challenge. In contrast to a CW transmitter, where the radiation source characteristics (e.g., transmitter output, antenna gain and pattern, spurious harmonics, feeder and coupler losses, etc.) are well identified, a digital electronic assembly, with its millions of input/output circuits, printed traces, flat cables and so forth, is impossible to mathematically model with accuracy -at least within a reasonable computing time- by today’s state of the art. The exact calculation of the E and H fields radiated by a simple parallel pair excited by a pulse train is already a complex mathematical process.