A method of kth harmonic demodulation for logarithmically processed sinusoidal signal

JiabinJia, Mi Wang

Institute of Particle Science and Engineering,

School of Process, Environmental and Process Engineering University of Leeds, LS2 9JT, UK, prejj@leeds.ac.uk

ABSTRACT

Digital Phase Sensitive Demodulation (PSD) is a classical method to demodulate the sinusoidal response voltages in electrical impedance tomography (EIT). However, due to the use of logarithmic amplifiers in a recently developed compact voltage­applied EIT system, the waveform of logarithmically processed sinusoidal signals is no longer in a form of sinusoidal wave. Therefore, the

conventional PSD cannot be directly implemented. In this paper, a method based on kth harmonic

demodulation is reported, which has been used to demodulate the logarithmically processed sinusoidal signals in the EIT system without the use of inverse process.

Keywords phase sensitive demodulation, logarithmically processed sinusoidal signal, Fourier series, spectrum analysis