Bandwidth design of ferrite-based circulators

This paper reports on the RF design of planar ferrite-based RF circulators with bandwidth control through the height of the ferrite-puck and the DC magnetic biasing. The analysis is performed with the aid of a commercially-available finite-element solver for a design frequency of 3.9 GHz. The study reveals that by varying the ratio of ferrite height to substrate height within the circulator cavity from 0.1 to 1, the 1-dB bandwidth varies between 5 and 36.2%. While conventional RF circulators are designed for a fill factor equal to 1, this study shows that maximum bandwidth is obtained for a fill factor of 0.82.