A digital demodulation method for electrical tomography based on sine wave rectification

In this paper, a digital demodulation method used for AC-based electrical tomography systems is presented. The demodulation result can be easily obtained by rectifying the sinusoidal measurement signal in a digital way. The proposed demodulation method has some distinguished characteristics: (a) with a concise configuration, it can be implemented on simple digital signal processors without hardware multipliers, e.g. Complex Programmable Logic Device (CPLD); (b) no reference signals are involved, (c) according to the requirements of precision and Signal-to-Noise Ratio (SNR), the demodulation process can be accomplished within k/2 (k=1, 2, 3, ...) sine wave periods; and (d) the effectiveness of the proposed method is not influenced by the starting time of demodulation. Mathematical analysis and numerical simulation results are presented to prove the feasibility and effectiveness of the digital demodulation method based on sine wave rectification.