ABSTRACT
This chapter discusses the circuit board design techniques to prevent many common Electromagnetic interference (EMI) problems. A key difference between signal integrity and EMI is amplitude. Where signal integrity deals with millivolts and milliamps, EMI issues often deal with microvolts and microamps. Many medical devices today include both analog and digital circuits. Good Printed Circuit Board (PCB) design is at the heart of good EMI design. The chapter examines how to layout these components to minimize EMI, and then looks at different PCB construction techniques and methods. Multilayer boards are preferred to double-sided boards. For low frequency signals high frequency isolation is provided if the power and ground planes are connected through a ferrite bead. Many high frequency radiated EMI emissions are caused by poor power decoupling. Some claims have been made for reduced board emissions with the traces inside, due to shielding from the planes.
