Electrical impedance tomography IC for lung ventilation monitoring using weaver architecture

Abstract

The newly lung ventilation monitoring EIT IC is proposed. To complement the weak point of previous lung ventilation monitoring EIT IC works, the dual frequency division multiplexing (DFDM) is proposed. Using DFDM, time difference and frequency difference imaging is conducted simultaneously. From the frequency difference imaging result, region of interest (ROI), which is lung shape, is extracted for improving reliability of EIT image. The dual frequency generating Tx and dual frequency receiving Rx is proposed for optimizing DFDM. The hardware cost including power consumption and area is extremely reduced compare to previous work. The look-up table and digital adder based DAC current generator is implemented as the Tx. For reducing harmonic distortion, dynamic element matching and adaptive quantization is used. To increase the SNR, the maximum current injection loop controls the current level high beneath the saturation. The weaver demodulator based read-out front-end is implemented as the Rx. Thanks to the weaver demodulator, the settling time of low pass filter is reduced much more than 10 times compare to previous work. The notch combined low pass filter with trimming scheme increases the attenuation level more than 30dB. Therefore the real-time monitoring of 30fps speed is achieved. The proposed DFDM optimized IC improves the lung ventilation EIT image quality with low hardware cost and low harmonic noise and achieving 30 fps of imaging processing speed.