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.