Slow wave microstrip line and its application in miniaturization

Abstract

This article presents a technique for miniaturization. The miniaturization is brought about by reducing the velocity of the wave, a phenomenon called slow wave propagation. The technique is demonstrated in this work using a microstrip line. Electromagnetic simulations show that the slow wave microstrip line has a cut-off frequency of 18.76 GHz and hence behaves like a low pass filter. The low pass nature is also confirmed from the lumped equivalence. The fabrication complexity is reduced by replacing a substrate filled with plated vias with a substrate bearing three rows of plated vias beneath the microstrip line, both of which show similar performances. The slow wave concept is confirmed from the value of group delay and is found to be enhanced in the slow wave line by 21.21%. Implementation of slow wave also results in a 36.3% increase in the effective permittivity. Parametric studies are conducted to analyze the slow wave phenomenon. For proof of concept, the technique is compared to the standard Chebyshev filter. The proposed structure reduces area by 40%. The proposed structure is then fabricated and performance is measured. The measured and simulated results are in good agreement.