Design and Analysis of a Re Entrant Microwave Cavity and Its Application for a High Performance Accelerometer

Abstract

Accelerometers with high resolution are required for tracking and navigation in launch vehicles, spacecrafts, missiles and other strategic applications. Pendulous integrating gyroscopic accelerometer and force balanced accelerometers cover the need for high accuracy guidance and navigation system. However, they require high precision fabrication, high piece part count and hence have low reliability. Moreover, these sensors are very expensive. The flexure mass accelerometer utilises a microwave resonator to provide inertial grade output. It also requires a complex fabrication process for the development and assembly of the proof mass. Moreover, its sensing electronics is complex and requires a large number of components. In this thesis, a microwave resonator is investigated, which offers a solution to the requirement of a high precision accelerometer for an inertial navigation system with low complexity, simple fabrication and high reliability. A differential re-entrant cavity sensor has been integrated with low noise cavity stabilized oscillator-based sensing electronics to achieve a high resolution and scale factor accelerometer. The cavities for the proposed accelerometer can be easily fabricated with conventional machining techniques. An improved approach is proposed in the present work to calculate the resonance frequency, its sensitivity, and quality factor of re-entrant cavities, having diverse taper shapes of the re-entrant post. The proposed closed-form expressions for resonance frequency are based on the chain matrix approach for tapered coaxial transmission lines. Analytical expression for various cases are used to evaluate the quality factor of these cavities. The calculated results for the resonance frequency, its sensitivity and quality factor have been verified with electromagnetic simulations and experiments, and the error in the proposed closed-form expression is found to be lt 4%...