Improving the High-Frequency Attenuation of Shunt Capacitor, Low-Pass Filters

Todd H. Hubing, Missouri University of Science and Technology
James L. Drewniak, Missouri University of Science and Technology
Richard E. DuBroff, Missouri University of Science and Technology
Christopher N. Olsen
Thomas Van Doren, Missouri University of Science and Technology

This document has been relocated to http://scholarsmine.mst.edu/ele_comeng_facwork/1677

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Abstract

Circuit board mounted, shunt capacitive filters are less effective at high frequencies because of the mutual inductance (M) that exists between the input and output ports. An approximate expression for the mutual inductance is M=(muh/2pi)ln(h/a); where h=via length and a=radius of the via connecting the capacitor to the return plane. The reduced mutual inductance associated with the new, three-terminal, surface-mounted capacitor results in more than 15 dB increased attenuation compared to two-terminal capacitors over the 0.3-6.0 GHz range with 50 Ω source and load terminations