Incorporation of a dc bias in a high-Q 3d microwave cavity

We report a technique for applying a dc bias in a 3d microwave cavity. This is achieved by isolating the two halves of the cavity with a dielectric and directly using them as dc electrodes. By embedding a variable capacitance diode in the cavity, we tune the resonant frequency with a dc voltage at room temperature, demonstrating the introduction of a dc bias into the 3d cavity without compromising its high quality factor.