An investigation of gaps in return planes, decoupling capacitor ESR in resonance suppression, and low-mutual inductance filters

This dissertation, composed of five papers, discusses three topics relevant to EMC. The first topic deals with gapping the return plane. Coupling between circuitry on printed circuit boards can be mitigated by a variety of well-known techniques. One such technique is to isolate circuitry in different areas of the printed circuit board by strategically placing a gap in the return plane. However, this technique is only effective at reducing common-impedance coupling. The paper ‘Traces in Proximity to Gaps in Return Planes’ investigates the effects a gap in the return plane has on the mutual inductance and mutual capacitance between a pair of microstrip traces. Laboratory measurements and numerical simulations show that gaps in the return plane are ineffective at reducing inductive and capacitive crosstalk in most configurations, and in some cases they increase mutual coupling.; The second topic deals with damping power bus resonances with loss. Power bus structures in printed circuit boards with solid power and ground planes exhibit resonances. When the power bus is resonant, the power bus impedance can increase dramatically. The paper ‘Reducing Power Bus Impedance at Resonance with Lossy Components’ explores the effect of component equivalent series resistance (ESR) on power bus resonances. The second paper of this section, ‘The Role of Decoupling Capacitor ESR in Resonance Suppression’, shows how to add lossy components at the edges of a printed circuit board's power bus to lower the power bus impedance at resonance. General guidelines for selecting an optimum ESR are provided and are supported by laboratory measurements and numerical simulations.; The last section of this dissertation consists of two papers about the mutual inductance of low-pass filters. The first paper in this section, ‘Analysis of a Prototype Low-Mutual Inductance, Low-Pass Filter’, discusses the new prototype low-pass filter that has low-mutual inductance. The second paper in this section, ‘Analysis of the Mutual Inductance of a Two-Capacitor Filter’, discusses the design of a two-capacitor filter that has low mutual inductance. This paper also shows how to use an equation for partial inductance to calculate the mutual inductance between the input and output sides of several filter geometries.