TABLE OF CONTENTS Circular disk resonators are used, for example, as microstrip filters, circulators including ferrite material, and patch antennas. Resonating sectors of disks also offer an excellent RF ground for a limited bandwidth [63]. Sectoral disk configuration are frequently found in broadband bias networks (Section 6.8.4). Disk resonators are open-ended radial lines. Resonances can be understood as standing radial waves that are reflected at the open end of the radial line and in the cylindrical axis. Before we analyze the dynamic properties of a disk including the static case, we analyze the wave propagation in a radial transmission line and derive the input impedance for an open-circuited termination.
A radial transmission line, as illustrated in Figure 6.87, consists of two circular, parallel, conducting plates, separated by a dielectric substrate of height h. The line is stimulated by a source connected to the inner periphery at radius r i. The line is terminated by a load impedance Z L at the outer periphery at radius r L following the notation in [64, 65]. We assume that the electromagnetic field has no variation along the circumference. Because the height is assumed to be very small ( h ? ?), waves with axial dependence are also excluded. This means also that all modes with radial components vanish. Thus, we restrict our analysis to waves that possess only a longitudinal electrical field component E z and a transversal magnetic field component H
