Wireless micromachined ceramic pressure sensors

In high temperature applications, such as pressure sensing in turbine engines and compressors, high-temperature materials and data retrieval methods are required. The microelectronics packaging infrastructure provides well-developed, high temperature ceramic materials, processing tools, and processing techniques that have the potential for applicability in high temperature sensors. A completely passive wireless telemetry scheme, which relies on a frequency shift output, has been integrated with the sensors, thereby eliminating the need for contacts, active elements, or power supplies to be contained within the sensor. This simplicity of sensor design allows the sensor to be exposed to elevated temperatures. As a proof-of concept, a wireless micromachined ceramic pressure sensor has been designed, fabricated, tested, and, compared with theoretical models. Sensors have been operated up to 200/spl deg/C and in pressure ranges from 0-1 bar and from 0-100 bar. The measured sensitivity of a fabricated sensor, expressed in frequency shift per pressure difference, is 2.6 MHz/bar, which compares well to the theoretically determined sensitivity of 2.2 MHz/bar.