Study of Dependence of Capacitance of Coupled Stripline on Stripwidth, Frequency and Spacing Between Two Striplines

Abstract

In this present paper, we studied about the dependance of capacitance of coupled stripline on strip width, frequency and spacing between two striplines. Miniaturized microwave circuits fabricated by extension of integrated circuits (ICs) technology to microwave frequencies are known as Microwave Integrated Circuits (MICs). MICs promise a real revolution leading to both expansion of present markets of microwaves & opening of many new applications including host of non-military uses in India & abroad. With the advent of MICs planar Transmission Lines have been developed which have been proved to be very significant as regards the fabrication of various microwave-components such as: Directional Coupler, Filters, Isolator & Impedance transformers etc. The planar Transmission Lines are: Stripline, Microstripline, Slot line, Coplanar Striplines & their different variant forms such as inverted and suspended striplines & microstriplines etc. Among these microstripline is the most suited due to its open structure, low losses in gigaharz range of frequency, reduced size, improved reliability and eventual cost reduction in mass production. The microstrip transmission line consists of a narrow strip conductor separated from a conducting ground plane by an intervening supporting dielectric substrate as studied by Wheeler and others. The electromagnetic traveling through such structures suffers from some losses like: Conductor loss & Dielectric loss. There is a change of phase of the wave traveling through the structure also. This phase change (shift) depends on the width of metal strip, height of the dielectric substrate, permittivity of the substrate and operating frequency. The present study is devoted to this objective i.e. we have to study the variation of Phase-Shift of the wave within the structure with width of the stripline, height & effective permittivity of the structure & frequency.