Waveguide Tuning Stub with Internal Choke

We present working principles, circuit analyses, electromagnetic simulation, and experiments in 2.45-GHz band of a noncontacting waveguide tuning stub structure that incorporates a microwave choke inside the stub. The main advantages of such an internal choke compared to traditional external chokes built in the body surrounding the stub are a substantially lower radiation leakage, smaller overall radius, and the possibility of using air as the choke dielectric.