Planar resonators with threefold symmetry with triplets of circumferential walls

One means of tuning planar stripline resonators with top and bottom electric walls and a magnetic sidewall is to include suitable radial and circumferential slots in the resonator plate. The use of a triplet of radial magnetic walls is a standard result in the literature and it has been shown to leave the so-called symmetric pole on the boundary of a planar resonator unperturbed. It is separately understood that a triplet of circumferential magnetic walls in the resonator plate will essentially modify both the dominant symmetric pole and virtual zero only. Both conditions are investigated experimentally. The first-mentioned geometry may enter into the design of three-port circulators using triple impedance poles and the latter in the adjustment of high-quality conventional circulators.