Closed-form expressions for estimating maximum radiated emissions from the traces of a Printed Circuit Board

Abstract

The ever-increasing clock speed of Printed Circuit Board (PCB) has imposed many challenges on the circuit designers, one of which is to pass Electromagnetic Compatibility (EMC) compliance testing. It is essential to predict PCB radiated emissions prior to a compliance test to save cost and time. Conventionally, PCB Differential-Mode (DM) and Common- Mode (CM) radiated emissions are estimated using the expressions developed by using Hertzian dipole or magnetic dipole antenna for electrically short traces. However, in high-speed PCB, traces are electrically long, thus making them efficient radiators. In this paper, closed-form expressions are derived for estimating the DM/CM radiated emissions from electrically long PCB traces using long dipole. A simple double layer microstrip PCB structure is fabricated to investigate the radiated emissions from its traces. The computed results based on the developed model were verified by comparing with other works and measurements taken in a semi-anechoic chamber. This developed model can be enhanced further as an expert system to predict the radiated emissions at the design stage of product development.