Lorentz Force Electrical Impedance Detection Using Step Frequency Technique**Supported by the National Natural Science Foundation of China under Grant Nos 51137004 and 61427806, the Scientific Instrument and Equipment Development Project of Chinese Academy of Sciences under Grant No YZ201507, and the China Scholarship Council Program under Grant No 201604910849.

Abstract

Lorentz force electrical impedance tomography (LFEIT) inherits the merit of high resolution by ultrasound stimulation and the merit of high contrast through electromagnetic field detection. To reduce the instantaneous peak power of the stimulating signal to the transducer, the sinusoidal pulse and step-frequency technique is investigated in LFEIT. The theory of application of step-frequency technique in LFEIT is formulated with the direct demodulation method and the in-phase quadrature demodulation method. Compared with the in-phase quadrature demodulation method, the direct demodulation method has simple experimental setup but could only detect half of the range. Experiments carried out with copper foils confirmed that LFEIT using the step-frequency technique could detect the electrical conductivity variations precisely, which suggests an alternative method of realization of LFEIT.