FULL-WAVE ANALYSIS OF MICROSTRIP FILTERS USING THE NOVEL METHOD OF LI NES

Abstract

Microwave filters have a great importance in communication industry. All microwave receivers and transmitters incorporate filters in thei r designs. Typical commonly used circuits that require filters include mixers, and multiplexers. System applications of filters include radars, communications, surveillance, EMS receivers, satellite communications, mobile communications, direct broadcast satellite systems, personal communication systems (PCS), etc. In many cases, such as PCS, miniature filters are the key for realizing the required reduction in size. Conventional methods of designs cause mainly two• problems: The shift in the center frequency due to the approximations in calculations of the section length, and the increasing of the longitudinal dimensions due to use of multi-longitudinal sections The aim ofthis thesis is to develop a new microstrip compa ct wide band band­ pass filters. A new eigen-mode method, (The Novel Method of Lines) based on the method of lines and the generalized transmission line equations (GTL) is used in the analysis and design of these filters. The neural network approach is used for optimizing the filter bandwidth. In the early time, the method of lines was used to solve two-dimensional

problems, with an approach using analytical calculations perpendicular to the direction of propagation. Further developments are made to solve three-dimensional problems such as resonators and periodic structures. The disadvantage of this approach is that, it can't deal efficiently with arbitrarily or longitudinally inhomogeneous structures.

Recently, the novel method of lines is developed to overcome the last disadvantages. In this algorithm, the structure is divided into cascaded subsections with respect to the propagation direction and the discretization lines are directed along the propagation direction of the wave. Therefore, this technique is very well suited for the analysis of structures, which can be divided into planar homogeneous regions such as coupled lines filters. The main advantage of this algorithm is that, the magnitude and phase of the scattering parameters are directly calculated with an analytical