Synthesis of Waveguide Single Junction Four-Port Circulators With Turnstile Resonators

X-band waveguide single junction four-port circulators with two types of turnstile resonators are theoretically and experimentally analyzed for the best bandwidth and power capacity performance in this article. These two resonators consist of coupled X-shape ferrite disks and composite assembly with ferrite disks and ceramic post. Utilizing these two different configurations, TM111 and TM011 modes can both resonate at the same frequency and four-port circulation condition can be established. Characteristic equations and mode charts are derived for the resonators with proper boundary conditions and approximations. Field distribution simulations are conducted for power capacity comparison in terms of E-field breakdown and H-field nonlinear effect. Experiments of circulator prototypes are performed to verify the theoretical treatments and simulations. Measurements show that the circulator with X-shape disk resonator realizes the best performance with a 15-dB isolation bandwidth of 6.9% and peak power capacity of 31 kW.