Lung Mechanics Tracking With Forced Oscillation Technique (FOT) Based on CMOS Synchronous Demodulation Principle

In this paper, an area-efficient CMOS integrated solution for lung impedance extraction is presented. The lock-in principle is leveraged for its high effective bandpass selectivity, to acquire information about the airways, through stimulation by FOT (Forced Oscillation Technique). The modulated pressure and flow signals are down-converted by a quadrature voltage commutating passive mixer-first receiver. In addition to its linearity, and unlike the Gilbert cell, it can be biased at zero dc current to alleviate flicker noise contributions. The proposed solution is designed and fabricated in 0.18µm TSMC technology. The chip occupies an active silicon area of 4.7 mm² (including buffers and pads) and dissipates 429.63 µW. The proposed approach offers real time tracking of respiratory mechanics and is expected to be a promising solution for portable health monitoring and cost-effective biomedical devices.