Microstrip line on ground plane with closely spaced perforations—fringe fields and formulas by synthetic asymptote

Accurate CAD formulas of a microstrip line on a ground plane with periodic perforations, closely spaced and at quasistatic frequencies, are derived (error <5%) for applications in multilayer circuits such as an LTCC package. By a novel technique of a synthetic asymptote, the formula has just one arbitrary constant and two separate fringe-field terms, from the strip and from the perforation. The separation gives clear physical insights into the effects of fringe fields on both the capacitance and inductance. One insight is that the effective dielectric constant may be made to rise above the actual dielectric constant of the substrate with perforation. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 201–204, 2002.