Complex Heterodyne Method for Digital Fringe Signal
in an Absolute Gravimeter
1〓Key Laboratory of Earthquake Geodesy, Institute of Seismology, CEA,40 Hongshance Road, Wuhan 430071, China
2〓Wuhan Base of Institute of Crustal Dynamics, CEA, 40 Hongshance Road, Wuhan 430071, China
Abstract:In this paper, the complex heterodyne method is studied to analyze the fringe signal produced during free fall movement in an absolute gravimeter. Firstly, it is necessary to perform a series of complex heterodyne on the high-speed sampling signal in order to iteratively reduce the bandwidth and to move it to dc. Secondly, initial velocity and acceleration can be estimated and a nonlinear fit is used to obtain a acceleration of gravity g. Simulation results with MATLAB indicate that the fit residuals can reach 10-3 μGal level and this ensures accuracy of measurement.