Re-Entrant Cavity Accelerometer With High Bias Stability

Accelerometers with high resolution and high bias stability are required for tracking and navigation in various tactical applications. This paper presents the design and experimental validation of an inertial grade microwave reentrant cavity-based accelerometer with RF readout. A model for the sensitivity of a re-entrant cavity is developed, and its design parameters are optimized to achieve a high scale factor. The RF readout of the sensor uses a cavity-stabilized oscillator (CSO), which is frequency locked to the cavity, to obtain a low close-in phase noise output. This method of locking the oscillator to the cavity is relatively simple and does not require any modulation techniques, as reported in previous works. A mathematical model of flicker noise power spectral density of the CSO is developed to design the CSO components for an accelerometer resolution of 1 μg. A scale factor of 1.25 MHz/g and bias stability of 1 ng were achieved for the fabricated sensor with a measurement range of ±1 g even without using active temperature control. This is one of the best scale factors, and bias stability reported to date in a similar accelerometer fabricated using conventional machining. The proposed design can be used for compact, low-cost inertial grade accelerometers.