TABLE OF CONTENTS The ever increasing demand for microstrip circuits being operated at higher and higher frequencies during the last decades has required an improvement in the methods of microstrip analysis. This trend was associated with the growing commercial exploitation of the microstrip technique in monolithic microwave integrated circuits, where hardware tuning after circuit fabrication is very difficult, and only known in some particular cases. In the following, we will discuss the key features of major published analysis methods, as shown in Figure 3.1 [1, 2].
At the beginning, electrostatic methods prevailed, using the method of conformal transformation [3 5], the finite difference method [6 8], integral equation [9], and variational method [10, 11]. Conformal mapping is frequently applied to planar transmission lines to analyze the propagation of waves at lower frequencies where dispersion effects are negligible. Therefore, this method will be treated in more detail in Section 3.1. Regarding the finite difference method, the solution of the Laplace equation in the cross-sectional area is approximated by the simultaneous solution of a set of linear equations. Following this method, the field region under analysis is subdivided into a net of small squares with assigned discretized electrostatic potentials. In order to develop the set of equations, the potential at a given point is measured and the potential of all directly adjacent mesh points are expanded in Taylor's series about the considered point. Neglecting higher-order expansion terms, a simple algebraic relation is derived between the centered and...
