With the increasing gate density, the rising clock frequency, printed circuit board (PCB) level simultaneous switching noise (SSN) has become a major bottleneck for the signal integrity in high-speed microprocessors and computers. All approaches that are currently being used to address this problem have been proven inefficient for switching frequencies of 500 MHz and above.
The research work carried out in this study addresses a novel technique for mitigating high-frequency SSN by suppressing the natural parallel-plate resonant modes encountered in traditional power planes. This is done by replacing at least one of the power planes of the power distribution network with a high-impedance electromagnetic surface (HIS). The high-impedance electromagnetic surface, which indeed is an artificial magnetic conductor, prevents any surface wave propagation in its forbidden band-gap, therefore leading to the suppression of resonant modes.
Using full wave electromagnetic simulation and experimental verification, the fundamental limitations of SSN mitigation using standard HIS is investigated. It is found that the thickness of the dielectric substrate and the metal line spacing offered by most PCB technologies are fundamental limitations for achieving broadband simultaneous switching noise mitigation at frequencies below 3 GHz for high-density packaging. This restriction is addressed by developing a new family of HIS, whose surface impedance is mainly controlled by the inductance density. These novel inductively-tuned HIS offer the possibility of mitigating switching noise at frequencies of 1 GHz and below frequencies and can be fabricated using conventional PCB technology.
It is also demonstrated that the combination of these novel HIS with RC dissipative edge termination (DET) leads to broadband simultaneous switching noise mitigation from DC to about 3 or 4 GHz. Finally physics-based compact models that allow the use of the novel power planes with other components for full package simulation are developed and validated for power planes with integrated standard and double-layer HIS. These models utilize only frequency independent lumped-components and are, therefore, particularly attractive for transient analysis.
Source: University of Maryland
Author: Kamgaing, Telesphor