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 degrees 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 degrees C. (C) 2014 Elsevier B.V. All rights reserved.