Design of High Sensitivity and Linearity Microelectromechanical Systems Capacitive Tire Pressure Sensor using Stepped Membrane

This paper is focused on a novel design of stepped diaphragm for MEMS capacitive pressure sensorused in tire pressure monitoring system. The structure of sensor diaphragm plays a key role fordetermining the sensitivity of the sensor and the non-linearity of the output. First, the structures of twocapacitive pressure sensors with clamped square flat diaphragms, with different thicknesses areinvestigated and their sensitivity and non-linearity are compared together. Finally, for increasing thesensitivity and linearity, a new capacitive pressure sensor with a stepped diaphragm is introduced. Anumerical solution for determination of the accurate sensitivity of the sensor is presented. The resultsshow that the sensitivity of the sensor is increased from 0.063 fF/KPa in flat diaphragm to 0.107fF/KPa in stepped diaphragm and also the non-linearity is decreased from 2.37 to 1.857%. In thisdesign, the sensor sensitivity and output linearity are increased simultaneously.