Research And Design Of Ultra Low Power And Low Noise Analog Front End Integrated Circuit For Wearable Electrophysiological Monitoring System

With the development of wireless body area network (WBAN), wearable healthcare system has become hotspot in the area of integrated circuits (ICs) design for recent years. Moreover, real-time monitoring electrophysiological signal plays an important and significant role in modern medical research and clinical practice. This thesis aims to the research and design of the analog-front-end (AFE) for wearable electrophysiology acquisition system, and low-power and low-noise strategies are emphasized throughout the thesis.Firstly, the system architecture of wearable healthcare system based on WBAN, the amplitude and frequency characteristics of widely used electrophysiological signals, and the bio-potential electrodes and their circuit models are studied. Then, the noise and interference encountered in the process of electrophysiology acquisition are analyzed. Finally, according to the above analyses, the specifications of the AFE IC are defined.The research method of analyses from system level, AFE architecture, core modules, key components and so on and joint optimization is employed in the thesis. Moreover, the key circuit techniques are also studied, such as chopper modulation and double offset reduction loops. And the significant design points of the AFE include low noise, high CMRR, high input impedance and so on.A prototype of8-channel programmable AFE is implemented in0.35μm2P4M CMOS technology, and has been manufactured and verified. The measurement results show that the AFE exhibits a band pass frequency response characteristic, and the low pass corner is programmable, which is digitally controlled from112Hz to1130Hz. And the mid band gain is also programmable, which is digitally adjusted from42dB to78dB. Moreover, Measurement results show an input referred noise of0.97μVrms (0.5-100Hz), an input impedance of1000MΩ@10Hz, and a CMRR of114dB. The measurement results also tell us that an electrode offset voltage up to54mV can be cancelled. The AFE consumes101μA from2.7V power supply, and achieves a noise efficiency factor (NEF) of11.3. Compared with other state-of-art implementations, it can be seen that the proposed AFE achieves high enough performance. Finally, a complete wireless ECG monitoring system incorporating the custom AFE is demonstrated, showing successful recordings of a capture ECG waveform using a smart phone.