(A) low power analog front-end for bio-impedance measurement using small body area

Abstract

Bio-impedance method is a good candidate for the future hand-held health monitoring devices since it is simple, inexpensive and noninvasive. This thesis presents the analog front-end for the bio-impedance measurement applications. In contrast to the conventional health monitoring devices, proposed analog front-end enables that the heart rate and pulse wave velocity (PWV) can both be monitored using only small body area, which is 1.5cm $\times$ 7cm. The measurement results show that the heart rate and PWV can be measured reliably using the proposed analog front-end. In addition, the programmable analog front-end architecture is proposed. Employing a high resolution ADC and direct digitizing, lots of complex analog circuitry can be removed. This proposed architecture gives programmability to both users and designers since most of signal processing is taken place in the digital domain. The system specification for this architecture is investigated and the building blocks are implemented and simulated in 0.18$\mum$ CMOS technology following the required specifications. Finally, the low power instrumentation amplifier (IA) and the current source are presented. The IA and the current source are the most important and power consuming building blocks in the bio-impedance measurement system. The proposed capacitor-based IA can save much power due to the absent of static bias currents while it still gives good performance. The proposed switched current-controlled current source is also low power solution removing static power dissipation. The proposed IA and current source are also implemented and simulated in 0.18$\mum$ CMOS technology. The simulation results show that the proposed IA and current source have competitive performance comparing to the state-of-the-art IAs and current sources.