60 IEEE JOURNAL ON EMERGING AND SELECTED TOPICS IN CIRCUITS AND SYSTEMS, VOL. 2, NO. 1, MARCH 2012 An Ultra-Low Power ECG Acquisition and Monitoring ASIC System for WBAN Applications Xin Liu, Yuanjin Zheng, Member, IEEE, Myint Wai Phyu, F. N. Endru, V. Navaneethan, and Bin Zhao Abstract—This paper proposes a power and area efficient electrocardiogram (ECG) acquisition and signal processing ap- plication sensor node for wireless body area networks (WBAN). This sensor node can accurately record and detect the QRS peaks of ECG waveform with high-frequency noise suppression. The proposed system is implemented in 0.18- complementary metal–oxide–semiconductor technology with two chips: analog front end integrated circuit (IC) and digital application specific integrated circuit (ASIC), where the analog IC consumes only 79.6 with area of 4.25 mm and digital ASIC consumes 9 at 32 kHz with 1.2 mm . Therefore, this ECG sensor node is convenient for long-term monitoring of cardiovascular condition of patients, and is very suitable for on-body WBAN applications. Index Terms—Analog front end, digital application specific inte- grated circuits (ASIC), electrocardiogram (ECG), QRS detection, signal acquisition, wavelet transform. I. INTRODUCTION R ECENTLY, the research on wireless body area network (WBAN) applications develops rapidly and receives more and more attentions, which various sensors are attached on clothing or implanted in human body. Different biomedical signals are acquired and processed jointly. The recorded vital body parameters and the control commands are wirelessly transmitted between sensor nodes and the base station such as personal digital assistant (PDA) or laptop. The system is further connected with a healthcare center for detailed analysis and diagnosis by medical professionals. In Fig. 1, a typical application example of WBAN techniques are demonstrated. Benefiting from rapid technology advances in wireless commu- nication, signal processing, biomedical sensing, and integrated circuits, the WBAN technology is able to develop miniature, lightweight, ultra-low power physiological healthcare surveil- lance and monitoring devices, for the improvement of human lives [1]–[6]. Manuscript received October 03, 2011; revised January 10, 2012 and February 05, 2012; accepted February 06, 2012. Date of publication March 14, 2012; date of current version April 11, 2012. This work was supported by the Science and Engineering Research Council of A*STAR (Agency for Science, Technology and Research), Singapore (Program of Embedded and Hybrid System Phase II (EHSII), SERC Grant 0521180055). This paper was recommended by Guest Editor H.-J. Yoo. X. Liu, M. W. Phyu, F. N. Endru, V. Navaneethan, and B. Zhao are with the Institute of Microelectronics, A*STAR, 117685 Singapore (e-mail: liux@ime.a- star.edu.sg). Y. Zheng is with the Institute of Microelectronics, A*STAR, 117685 Singa- pore and also with School of Electrical and Electronic Engineering, Nanyang Technological University, 639798 Singapore (e-mail: yjzheng@ntu.edu.sg). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/JETCAS.2012.2187707 Fig. 1. Demonstration of wireless body area network technique. Electrocardiogram (ECG) is the most important indicator among all the vital body parameters, for diagnosing many cardiac diseases. ECG is the electrical representation of the contractile activity of the heart over time, which can be easily recorded using noninvasive electrodes on the chest or limbs. ECG indicates the overall rhythm of the heart and weaknesses in different parts of the heart muscle, and can measure and diagnose abnormal rhythms of the heart [7]. Therefore, there is an increasing demand for long-term and real-time monitoring and analysis of ECG signal for early diagnosis and improved treatment of cardiac diseases. ECG can be represented by a cyclic occurrence of patterns with different frequency contents (QRS complex, P and T waves). In the ECG waveforms, QRS complex reflects the electrical activity within the heart during the ventricular contraction. It provides much information about the state of the heart [8]. In this sense, detecting QRS peaks in the ECG is one of the most important tasks that need to be per- formed. This stage is crucial in basic ECG monitoring systems and is important for all other ECG processing applications [9]. Nevertheless, monitoring ECG signal possesses some chal- lenges as it is considered to be a weak signal. According to [10], the signal amplitude can range from 100 to 4 mV. The main bandwidth of ECG signals spans from 0.1 to 250 Hz, whereby flicker noise is dominant. In addition, this signal is sus- ceptible to common-mode interference from the mains supply and the problem of offset generated by skin–electrode interface. With this kind of condition, the analog front-end should be able to provide enough noise rejection in order to be able to amplify such signal. The gain and bandwidth of the front-end amplifier should be adjustable in order to deal with the different charac- teristic of the signal. For the purpose of ECG monitoring, various types of QRS peak detection algorithms have been proposed, including 2156-3357/$31.00 © 2012 IEEE