Conductive Materials Composite Electromagnetic Noise Absorber

INTRODUCTION ELECTROMAGNETIC INTERFERENCE issues can arise anywhere in electronic equipment with unpredictable and troublesome effects. These issues challenge hardware design engineers, and the challenges escalate as today’s electronic equipment becomes both thinner and multifunctional. For example, modern cellular phones are being equipped with high-speed microprocessors, wireless LANs, Bluetooth, MP3s, cameras, motion sensors, touch screens, GPS and many other devices. Although there have been significant advances in device and PCB design technology that reduce electromagnetic interference (EMI), RF noise remains one of the most difficult problems facing design engineers. Shielding with a conductive material is the most common way of solving RF noise problems. Widely used commercial shielding products include: shield can, conductive gasket, and foiland mesh-type tapes. The shielding solution envelops the noise source, increases the grounding level, and suppresses radiated noise. However, modern electronic devices operate at hundreds of MHz with harmonic noise emissions in the GHz region. At these high frequencies, the reflected signal in a conductive shielding system can cause serious problems for the shielded device itself and/or for other adjacent components. Moreover, highly integrated electronic systems can create very complex issues around RF noise that cannot be eliminated with simple shielding and grounding techniques. Recently introduced electromagnetic absorbing products can provide a relatively easy solution for reducing unwanted RF noise. This sheet-type absorbing product is a composite material with magnetic particles embedded in a polymer. It has good noise attenuation performance from hundreds of MHz to several GHz. These materials, with their unique electromagnetic and physical characteristics, have already been used effectively in a variety of applications.