ANALYSIS AND DEVELOPMENT OF MILLIMETER-WAVE WAVE-GUIDE-JUNCTION CIRCULATOR WITH A FERRITE SPHERE

This paper presents a class of new easy-to-fabricate ferrite-sphere-ba sed waveguide Y-junction circulators for potentially low-cost millimet er-wave applications. A new three-dimensional modeling strategy using a self-inconsistent mixed-coordinates-based modal field-matching proce dure is developed to characterize electrical performance of the propos ed circulator. It is found that the circulating mechanism of the ferri te-sphere post is different from its full-height ferrite counterpart i n that the new structure operates in a turnstile fashion with resonant characteristics, while the conventional device operates on a transmis sion cavity model. Extensive comparable studies between the new and co nventional circulators are made to show that the electrical behaviors of the new structure are also distinct and radial power-density profil es are not stationary, as in the case of the full-height ferrite post circulator for different geometrical parameters. Results obtained by t he analysis technique are compared with the available results for a fu ll/partial-height ferrite circulator, showing an excellent agreement. Our calculated and measured results are also presented for W-band circ ulators with the proposed ferrote-sphere technique, indicating some in teresting characteristics such as the frequency offset behavior of the isolation and reflection curves. In addition, radial power-density pr ofiles are plotted inside and outside the ferrite sphere to illustrate its intrinsic circulating mechanism, as well as its difference, as co mpared to its full-height ferrite structure.