High resolution demodulation technique for Sagnac fibre optics gyroscopes using a low frequency quasi-synchronous clock

Abstract

Abstract A simple technique which employs a low frequency quasi-synchronous clock was developed to measure duty-cycles with high resolution. For the same measurement resolution, the proposed circuit can operate with clock frequencies typically 1000 times lower than in conventional digital duty-cycle measurement system with synchronous clock. The proposed circuit is composed of only two Digital Direct Synthesis integrated circuits and one Complex Programmable Logic Device. Experimental results obtained with a prototype of the proposed time measurement system show that, for an emulated zero-cross fibre optics gyroscope output signal with 100 kHz and Δ T = 100 ns (duty-cycle of 50.25%), a resolution of 100 ps can be achieved using a 10.01 MHz frequency clock.