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 high-temperature ceramic materials, fabrication tools, and well-developed processing techniques that have the potential for applicability in high-temperature sensing. Based on this infrastructure, a completely passive ceramic pressure sensor that uses a wireless telemetry scheme has been developed. The passive nature of the telemetry removes the need for electronics, power supplies, or contacts to withstand the high-temperature environment. The sensor contains a passive LC resonator comprised of a movable diaphragm capacitor and a fixed inductor, thereby causing the sensor resonant frequency to be pressure-dependent. Data is retrieved with an external loop antenna. The sensor has been fabricated and characterized and was compared with an electromechanical model. It was operated up to 400 C in a pressure range from 0 to 7 Bar. The average sensitivity and accuracy of three typical sensors are: 141 kHz Bar 1 and 24 mbar, respectively.

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SUMMARYThis work reports functional wireless ceramic micromachined pressure sensors operating at 450 °C, with demonstrated materials and readout capability indicating potential extension to temperatures in excess of 600 °C. These devices are self-packaged and are operating in actual high-temperature environments, not in simulated hot-plate testbeds. A resonant readout technique is employed, in which a planar spiral inductor and a pressure-sensitive capacitor form a passive LC circuit, the resonance frequency of which is sensitive to the external applied pressure, and which can be read out using a simple external loop antenna.

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