System analysis of a fully-integrated capacitive angular sensor

Contact-less angle measurement principles are far superior to standard potentiometers in terms of service life and reliability. Still, their usage is limited due to sophisticated analog and digital signal processing mandatory to fully exploit their features. This paper presents the design of a fully-integrated angular speed sensor system based on a capacitive carrier frequency measurement principle. To optimize the performance, we combined a synchronous demodulation strategy with an external resonance filter serving both as clock reference and noise protection. This filter was extended by an additional low-pass easing implementation of the demodulator and compensating for internal signal delays. For system simulation, a simple analytical model based on Fourier synthesis was found to be superior to a conventional SPICE simulation. This efficient, time-domain-based verification method allowed performing an exhaustive analysis and optimization of the complete sensor system.