Characteristic mode analysis of radiating structures in digital systems

This paper investigates the applicability of the characteristic mode analysis (CMA) to radiating structures in digital systems up to 3 GHz. It is shown that the eigencurrent distribution and the magnitude of the corresponding eigenvalues are two key factors to reduce radiated emission (RE) of potential radiators. A visualization of the eigencurrents provides useful insights into the optimal placement of signal and power routing, grounding, and placement of loads. Typical radiators in digital systems are analyzed, including ungrounded circuit loops, connected circuit boards, and metallic heatsinks. The examples show that a significant reduction of radiated power can be achieved by using CMA and hence, illustrate the usefulness of the proposed method for the EMC design of digital systems.