Innovative Theory of Low-Pass NGD Via-Hole-Ground Circuit

The via ground (GND) structure constitutes one of the most useful elements for designing high performance printed circuit boards (PCBs). The electrical interconnections with vias become key regular solutions for the implementation of various electronic functions. However, so far, the vias are never being used for designing negative group delay (NGD) circuit. To answer this curious question, an original study on the design feasibility of low-pass NGD function with via ground is introduced in the present paper. After the topological description, the NGD analysis in function of the via parameters is established. The design equations allowing to synthesize the via in function of NGD function specifications are formulated. The developed NGD theory is verified with comparisons between calculations and simulations with a commercial tool. As expected, NGD value in order of hundred-picoseconds over hundred-megahertz cut-off frequencies is obtained with good agreement between the theoretical model and simulation. Furthermore, time domain analyses confirm that the via NGD structure enables to generate output signals in time-advance of arbitrary waveform input signals presenting limited bandwidth.