Multi-frequency recursive demodulation method for electrical tomographic systems

Abstract

The invention relates to a multi-frequency recursive demodulation method for electrical tomographic systems. The method is characterized by comprising the following steps: (1) establishing an original equation and a recursive equation according to m component frequencies of an excitation signal and the sampling frequency of a system; (2) with a zero-phase time of the excitation signal as a starting time, according to data of 2m sampling points a measuring signal, which are closely following the starting time, calculating the initial values of a data matrix B and a state matrix P according to the original equation in the step (1); (3) substituting the initial values and the new sample point data into the recursive equation in the step (1) so as to update B and P; and (4) judging whether a demodulation result meets the accuracy requirements of the system, if so, completing the demodulation operation, and outputting the amplitude values and phase data of m frequency components of the measuring signal; otherwise, returning to the step (3). By using the recursive demodulation method disclosed by the invention, data of at least 2m sampling points is required, and due to the increase of the number of sampling points, the demodulation accuracy and the anti-noise capacity can be improved.

Description

technical field [0001] The invention relates to a multi-frequency recursive demodulation method for an electrical tomography system, belonging to the field of distribution parameter measurement. Background technique [0002] Electrical Tomography applies electrical excitation to the measured object and detects the change of its boundary value, and uses specific mathematical means to invert the distribution of electrical parameters inside the measured object, so as to obtain the material distribution inside the object. Compared with other tomography techniques, electrical tomography has the advantages of no radiation, fast response, and low price. [0003] Since electrical tomography is mostly used in the fields of industrial multiphase flow detection and medical detection, the measured object usually exhibits relatively complex electrical characteristics, which change with the change of excitation frequency. Therefore, in order to obtain richer spectrum characteristics of t...

AI Technical Summary

Problems solved by technology

At present, the most commonly used digital phase-sensitive demodulation method is the orthogonal sequence demodulation method. When it is applied to a multi-frequency electrical tomography system, it is required that the length of the sampling sequence must cover an integer number of cycles of the mixing excitation signal (by the lowest frequency component signal period) to demodulate the amplitude and phase information of the measured signal under all frequency components, which greatly reduces the flexibility of the demodulation method, and also limits the further improvement of the demodulation speed

Images