(Invited) High Temperature Wireless Smart Sensor Technology Based on Silicon Carbide Electronics

Abstract

Smart Sensor Systems that can operate at high temperatures are required for a range of aerospace applications [1]. For example, for future aerospace propulsion systems to meet the requirements of decreased maintenance, improved performance, and increased safety, the inclusion of intelligence into the propulsion system design and operation is necessary. These propulsion systems must incorporate technology that will monitor propulsion component conditions, analyze the incoming data, and modify operating parameters to optimize propulsion system operations. This implies the development of sensor systems that will be able to operate under the harsh environments present in an engine. Likewise, operation in Venus exploration missions require systems that can operate at near 475ºC, which is the Venus planetary surface temperature. Overall, the goal is to make intelligent vehicle systems by developing Smart Sensor Systems operational in harsh environments. A Smart Sensor System as described here implies the use of sensors combined with electronic processing capability. The definition of a Smart Sensor may vary, but typically at a minimum a Smart Sensor is the combination of a sensing element with processing capabilities provided by a microprocessor [2]. A more expansive view of a Smart Sensor System is a complete self-contained sensor system that includes the capabilities for data storage, processing with a model of sensor response and other data, self-contained power, and an ability to transmit or display informative data to an outside user. However, given the harsh environments inherent in propulsion systems, the development of engine-compatible electronics for engine applications is not straightforward. The use of sensors and complex electronics in these environments implies operation at temperatures above 300°C. While silicon integrated circuits (ICs) have enabled complex, room-temperature circuits to be miniaturized onto small chips, the extension of this technology to temperatures above 300 °C appears impractical. However, silicon carbide (SiC) electronics have the potential to meet a range of engine application needs [3]. Operation at 500°C has been demonstrated for thousands of hours; these time frames are now viable for implementation to engine conditions for extended periods. This would allow high temperature signal processing at temperatures far beyond that capable in silicon electronics [4]. This paper discusses the demonstration of a first generation high temperature wireless system that includes basic components of a Smart Sensor System including a pressure sensor, circuitry, power scavenging, and an antenna operating at a range of temperatures up to 475ºC. The various components of the system included a capacitive pressure sensor, a silicon carbide field effect transistor, passive components such as resistors and capacitors, and a thin film antenna. These components were integrated onto a single alumina substrate and this unit was mounted in a pressures chamber with a quartz window through which data was transmitted from high temperature to ambient conditions. Power was provided predominantly by power scavenging at temperatures of 300°C. The power scavenging modules were located separately from pressure sensor/telemetry due to size restrictions in the pressure chamber. High temperature wireless transmission at a distance of 1 meter using this approach was demonstrated at 475º C from 70-100 psi for more than one hour with a response curve shown in Figure 1.This work is intended to be a building block towards enabling more complex, integrated high temperature Smart Sensor Systems that can be applied in a range of harsh environment applications. This paper will also give a brief overview of the status of high temperature electronics and its use and applications ranging from distributed engine control to Venus seismometry.