Coupled Microwave /Thermal Finite Element Model for High Power Ferrite Phase Shifter

New airborne radar systems require the design of high power, differential phase shift circulators with increased bandwidth and better thermal performance. In this paper, to meet these requirements a magneto static/microwave/thermal method is proposed to model high power ferrite devices. Magnetic loss mechanisms that bottleneck the power handling /frequency performance of microwave systems are included in the model, which also has a temperature dependent saturation magnetization and thermal conductivity. An iterative approach has been implemented which uses the power dissipated by the magnetic losses as the heat source for a thermal finite element solver. Bias field, frequency, magnetic losses and magnetization are used to determine the temperature profile in the ferrite for a given input power. The optimum operating region for temperature stability in high-power differential phase shift devices is deduced to be below subsidiary resonance and above low field loss.