Self-Consistent Modeling of Waveguide Circulator Under Realistic Magnetic Field for Industrial Applications

An RF waveguide circulator is a ferromagnetic passive device with three or four ports, which is used to protect other RF components from excessive signal reflection. The previous studies on the design and development of the circulators deal with achieving broad bandwidth and high transmission efficiency using finite element method (FEM) simulations with a homogenous applied bias field. This work takes a step further and presents a novel self-consistent approach to modeling a ferrite waveguide circulator by solving electromagnetic and magnetostatic equations simultaneously. The comparison between the homogenous and the non-homogenous field models shows the importance of coupling a magnetic circuit to an electromagnetic simulation. The more realistic circulator design presented here still has a broad bandwidth of 180 MHz, insertion loss less than 0.24 dB, reflection, and isolation better than 20 dB operated at the center frequency of 2.45 GHz. It can be used to replace an industrial waveguide circulator, which has only a 50 MHz bandwidth. Hence, by increasing the bandwidth of a circulator, one can reduce the number of units for a dual-frequency magnetrons operating concurrently at 2,430 and 2,480 MHz with a working power of 3 kW each employed in the microwave plasma system.