EMI Radiation Mitigation for Heatsinks Using Characteristic Mode Analysis

Electromagnetic interference (EMI) radiation is one of the vital problems that design engineers may face. As the frequency of an electronic device increases, the potential for a heatsink to act like a radiating antenna also increases. In this paper, characteristic mode (CM) analysis has been applied to investigate the radiation mechanism for the flat heatsink. With the eigencurrent distribution from CM analysis, it can be verified that the radiation characteristics of the flat heatsink behaves like a patch antenna, and the resonant frequencies predicted with CM agree favorably with cavity model. Meanwhile, the optimal position to put the absorbing material can be identified with the dominant eigencurrent distribution. With this proposed method by applying CM analysis, a better shielding performance and less consumption can be achieved.

I. Introduction

A heatsink is a heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium, often air or a liquid coolant, where it is dissipated away from the device, thereby allowing regulation of the device's temperature at optimal levels [1], [2]. In a modern electronic device such as a cellphone or a laptop, the fast operation of devices leads to heat generation due to switching losses. This heat needs to be dissipated through a heatsink to keep the devices within safe operating conditions. However, as integrated circuit (IC) clock and data speeds continue to increase to beyond 1 GHz, the wavelength of radiation emitted from the IC package becomes on a similar order of magnitude as the physical dimensions of the IC heatsink. This improves the ability of the heatsink to act as an efficient antenna to radiate noise from the IC.