Application of embedded edge terminations to reduce the edge radiation and noise in high-speed printed circuit boards

With the increase in the core frequencies of devices and reduction of edge rates of the drivers, it is becoming very important to limit the noise and radiation from printed circuit boards (PCBs). In order to meet the regulatory radiation limits of the FCC and other agencies worldwide, a stringent "design for electromagnetic compatibility" approach is necessary. A major source of noise in high-speed PCBs is the power plane resonances, which are excited by the multiple reflections of radial wwaves from edges of circuit boards. This noise due to the radial waves is also a major contributor to the edge radiation from PCBs. This paper reports further resutls on a technique to suppress the power plane resonance's using a magnetically lossy material embedded between the power and ground planes of a circuit board. In this paper we present the effect of this lossy material on the edge radiation from the PCB. We also present further measurements showing the reduction of power distribution noise by the application of this material as an edge terminator. The material used here to edge-terminate the PCB is a high resistivity material, which depends on its characteristic magnetic loss to dampen the radial waves. The near-field measurement technique is used on a single layer circuit board to show the reduction of edge radiation from the board. Time domain measurements with a sampling scope show a reduction in the power distribution noise when pulses are reflected from the edges of a board with edge terminations.