THE EFFECT OF AN AIR-GAP ON THE COUPLING BETWEEN 2 PLANAR MICROSTRIP LINES

The finite difference (FD) technique is used to investigate the air ga p effect on the coupling between two planar microstrip fines. The stri p fines are embedded between a dielectric substrate and a dielectric o verlay. The air gap between the substrate and the overlay is present d ue to the thickness of the strips and/or the roughness of the planar s urfaces. A quasi-static FD technique based on the solution of Laplace' s equation is used to solve the potential distribution in the region a round the strips. The FD mesh is truncated by an artificial boundary t o allow for a numerical solution with the available computer resources . At this artificial boundary an approximate boundary condition is use d to truncate the FD mesh. From the potential distribution, the charge and the capacitance and inductance matrices of the stripline system a re evaluated. The coupling or cross-talk between the fines is then def ined and computed. The effects of the conducting strips thickness and the properties of the materials between the strips on the coupling are illustrated through numerical examples. (C) 1996 Published by Elsevie r Science Ltd