| 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 laminate 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. The sensor design consists of the sealed cavity structure with one or two flexible ceramic membranes. This structure is integrated with an RLC series resonant circuit. Models were developed to aid in the design of the mechanical and electrical elements of the sensor, as well as to predict the behavior of the sensors when exposed to external pressure. The passive wireless telemetry scheme utilizes the magnetic coupling that exists between an antenna coil of the data retrieval scheme and the inductor coil of the pressure sensor. A model of the data retrieval scheme was developed and compared to the pressure data of the sensors. Ceramic pressure sensors were tested from 0–7 bar and 25–400°C. The pressure sensor experiments showed that this concept is valid and the models predict the behavior of the pressure sensors and the data retrieval scheme. Temperature tests showed sensitivity of the pressure sensors to temperature, as well as temperature limitations of the ceramic laminate material for reliable operation of the pressure sensors. |
