CHAPTER 2
TRANSMISSION LINE CONCEPTS AND NETWORKS
2.1 INTRODUCTION
This book addresses the design of microwave wideband bandpass filters. These filters are normally constructed using a variety of transmission lines, for example, microstrip line (MSL), coplanar waveguide (CPW), slotline (SL), and so on. It has been commonly recognized that transmission line model is the first and the most simplified choice for analyzing and synthesizing transmission line filters. By employing the distributed and/or lumped elements, polynomial-based transfer function could be exactly or approximately represented from the network synthesis. However, in practical design, both circuit- and EM-based optimization procedures have to be carried out to take into account the frequency dispersion, losses, discontinuities, and other parasitic effects. Besides the network synthesis, transmission line theory is also necessary in characterizing the resonant behavior of a line resonator, and it transfers a complex field analysis to a simple circuit theory. The most common filter-type structures can be classified as a generalized two-port network. If the input and output parameters are known, the transmission poles and zeros of the filters can be theoretically determined by performing the network analysis using impedance-, admittance-, scattering- or ABCD-matrix parameters. Therefore, the transmission line concept and relevant network parameters are indispensable in analyzing and characterizing a variety of passive ...
