Evanescent-mode-resonator-based and antenna-integrated wireless passive pressure sensors for harsh-environment applications

A wireless pressure sensor for high-temperature applications is demonstrated based on a microwave evanescent-mode cavity resonator. Cavity deformation resulting from applied external pressure can be detected by measuring the resonant frequency change of the sensor. Compact sensor size is achieved by loading a cylindrical post inside the cavity resonator. In addition, a patch antenna is seamlessly integrated with the pressure sensor, without additional volume. This pressure sensor is able to survive high temperatures by adopting passive structures and robust ceramic/metallic materials. Fully-dense silicoaluminum carbonitride (SiAlCN) ceramic is used herein owing to its excellent thermal-mechanical properties and manufacturability as a Polymer-Derived Ceramic (PDC). A PDC soft-lithography technique is developed to fabricate the ceramic pressure sensor. In order to wirelessly interrogate the pressure sensor at high temperatures, a robust interrogation antenna is designed and fabricated with a wide fractional bandwidth. Finally, the cavity deformation of pressure sensor versus external pressure is measured at high temperatures up to 800 °C. The resonant frequency decreases from 11.75 to 11.56 GHz, when the applied external force on the sensor increases from 0 to 5 N at 800 °C.