Research on frequency robustness of multi-frequency electrical impedance tomography based on Four-Parameter Sine-fit algorithm

The multi-frequency electrical impedance tomography (EIT) system can obtain multi-frequency impedance information by applying multi-frequency excitation signals to the human body, achieving more complete reconstruction of human impedance images. Most multi-frequency EIT systems use multi-frequency orthogonal sequence demodulation, which requires high accuracy of the frequency of the excitation signal. In this paper, the Four-Parameter Sine-fit algorithm is used for demodulation, which can improve the frequency robustness of the multi-frequency EIT system. The simulation experiments show that under the condition of amplitude noise, the performance of the algorithm in this paper is similar to that of the multi-frequency orthogonal sequence demodulation algorithm. Under the condition of frequency offset 0.5%, the amplitude error of the Four-Parameter Sine-fit algorithm for 500KHz signal demodulation is only 15% of that of the orthogonal demodulation algorithm, and the amplitude error for 1MHz signal demodulation is only 5% of that of the orthogonal demodulation algorithm. The performance is significantly better than that of the orthogonal demodulation algorithm.