Investigation of High-Power Limits of Stub Tuners by Means of Electromagnetic Simulation

Two effects limiting high-power performance of a 2.45-GHz R26-waveguide stub tuner have been investigated by means of electromagnetic simulation: electric breakdown and microwave power dissipation in tuning stub. In the case of electric breakdown, increasing rounding radius of the stub edge from 1 mm to 4 mm was found to decrease maximum electric field strength 2.25- times, leading to fivefold increase of tuner power-handling capacity. Estimation of power dissipated in the tuning stub, based on average surface current density and stub conductivity, shows that stub overheating is not the most critical limiting factor. The described methodology can be applied to any type of waveguide and tuning stub structure.