Temperature Compensation of an Air-Filled Stacked Ring Resonator

A temperature-compensated resonator based on stacked rings is proposed in this letter. The resonator is made of several layers of machined dielectric substrates where the copper rings stand. These rings define an air-filled TE
₀₁₁
cavity with an unloaded quality factor better than 1800. Due to a low sensitivity of the air gap between the layers and metallic contact of the TE
₀₁₁
mode, a cavity with low building constraints (no vias and no connection between layers) is realized. Furthermore, a multilayer design allows the introduction of a controlled amount of dielectric material in the cavity with a negative thermal coefficient of permittivity to realize temperature compensation of the device and to counteract its natural thermal expansion. Thus, this compensation layer allows proper management of a frequency drift from of -18 to +18 MHz for a temperature range of 20 °C-80 °C. However, there is a tradeoff, and the quality factor decreases as the compensated layer is inserted. A guideline demonstrating the performance of the design and the compensation technique is thus presented in this letter.