Transmission Matrix Analysis of Cascaded Discontinuities in the Center Conductor of Microstripline

Abstract

The transmission and reflection properties of the network consisting of a cascade connection of discontinuities in the center conductor of microstripline are analyzed employing transmission matrix approach. Computed and measured values of transmission and reflection coefficients are compared in the lower microwave frequency band. The cascaded discontinuities are proposed to be used in improving the skirt selectivity of the band stop filters.

The taper which is used to match the low impedance line containing the discontinuities, to a normal 50 Ω line is also anlayzed. The input voltage reflection coefficient of the taper is computed by determining the polynomial approximation for logarithmic variation of impedance along the taper, by transmission matrix approach and by employing theory of small reflections. The performance of the linear taper is compared with those of standard tapers like exponential and triangular tapers. Experimental results are also presented.

Indexing terms:

• Cascaded discontinuities
• Linear taper