Tae-Ha Kwon

Zinc oxide thin film doped with Al2O3, TiO2 and V2O5 as sensitive sensor for trimethylamine gas

Abstract To obtain a sensitive sensor for TMA gas, ZnO-based films were fabricated by a rf magnetron sputtering method using targets added with Al2O3, TiO2, or V2O5. The films were heat-treated at a temperature between 400°C and 800°C for 60 min in oxygen. It was found that the sensitivity and selectivity of the films for TMA gas at 300°C increased by doping with 4.0 wt% Al2O3, 1.0 wt% TiO2 and 0.2 wt% V2O5. The sensor with the doped film 120 nm thick and annealed at 700°C for 60 min in oxygen exhibited fairly excellent sensitivity and selectivity to TMA, and electrical stability. Upon exposure to odors from a mackerel, the sensor using this film could trace well its deterioration during storage.

An adaptive bandwidth phase locked loop with locking status indicator

This paper presents a new structure of phase locked loop (PLL) which changes its loop bandwidth according to the locking status. The proposed PLL consists of a conventional PLL and locking status indicator (LSI). The LSI decides the operating bandwidth of loop filter. When the PLL becomes out of lock, the PLL increases the loop bandwidth and achieves fast locking. When the PLL becomes in-lock, this PLL decreases the loop bandwidth and minimizes phase noise output. The PLL can achieve fast locking and low phase noise output at the same time. Proposed PLLs locking time is less than 100/spl mu/s and spur is -60dBc. It is simulated by HSPICE in a CMOS 0.35/spl mu/m process. Supply voltage and operating frequency are 3.3V and 1.28GHz, respectively.

Implementation of Extended Kalman Filter for Real-Time Noncontact ECG Signal Acquisition in Android-Based Mobile Monitoring System

Noncontact electrocardiogram (ECG) measurement using capacitive-coupled technique is a very reliable long-term noninvasive health-care remote monitoring system. It can be used continuously without interrupting the daily activities of the user and is one of the most promising developments in health-care technology. However, ECG signal is a very small electric signal. A robust system is needed to separate the clean ECG signal from noise in the measurement environment. Noise may come from many sources around the system, for example, bad contact between the sensor and body, common-mode electrical noise, movement artifacts, and triboelectric effect. Thus, in this paper, the extended Kalman filter (EKF) is applied to denoise a real-time ECG signal in capacitive-coupled sensors. The ECG signal becomes highly stable and noise-free by combining the common analog signal processing and the digital EKF in the processing step. Furthermore, to achieve ubiquitous monitoring, android-based application is developed to process the heart rate in a realtime ECG measurement.

A low jitter phase-lock loop based on a new adaptive bandwidth controller

This paper presents the analog adaptive phase-locked loop (PLL) architecture with a new adaptive bandwidth controller to reduce locking time and minimize jitter in PLL output for wireless communication. It adaptively controls the loop bandwidth according to the locking status. The adaptive bandwidth control is implemented by controlling charge pump current depending on the locking status. It is simulated by HSPICE and achieves the primary reference sidebands at the output of the VCO at approximately -80dBc

PACKET TRAFFIC MANAGEMENT IN UBIQUITOUS HEALTHCARE SYSTEM

Recent advances in wireless sensor network (WSN) envisaging ubiquitous healthcare system that simplifies the monitoring and treatment of patients. WSN also pose several challenges to ubiquitous healthcare applications. As healthcare application commonly handle two different types of data such as wave-like data of ECG and linear waveform-independent data of body temperature, blood pressure and oxygen content. As wave-like data requires a higher sampling rate than waveform-independent data, the transmission of wave-like data in WSN causes traffic congestion and, consequently, loss of vital signal in transmission. With the increasing number of sensor nodes involved in the WSN field, network congestion issue is rapidly coming known as a tangible issue in healthcare system that must be addressed in order to maintain data reliability. Sensor nodes have very limited computational resources due to its energy consumption. To reduce traffics in WSN communication, the biomedical data are sent when they had very serious problems. The collaboration among sensors through task mapping based in-network processing is adapted to achieve higher processing power and reduce traffics in WSN. System analysis shows that the data packet loss in the ubiquitous healthcare system is dramatically reduced after the implementation of this process. By adapting fall detection, not only the numbers of packets received by the base station are greatly reduced but also the traffic overload problems in WSN are also resolved.

Design and evaluation of wireless sensor network routing protocolfor home healthcare

A home healthcare system based wireless sensor network, which can continuously monitor and manage the elderly`s electrocardiogram(ECG) signal at any space at home without space limit is proposed. The communication coverage of wireless network is expended by multi-hop wireless sensor network. In order to send the elderly`s ECG data wirelessly, a small size ECG sensor node was designed to forward the ECG data over multi-hop relay network. The packet acquired by mobile ECG node is transmitted through wireless intermediate nodes to base station for analyzing the packet reception rate. Modified minimum cost forwarding(MMCF) protocol and flooding protocol are designed and implemented to check the transmission efficiency of a packet in a wireless sensor network. The developed MMCF protocol shows an advantage of high reception rate by reduced network traffic.

Non-Intrusive Healthcare System for Estimation of Vascular Condition in IP-Enabled Wireless Network

Abstract A real-time wireless monitoring and analysis methods using the wearable PPG sensor to estimate cardiovascular condition is studiedfor ubiquitous healthcare service. A small size and low-power consuming wearable photoplethysmogram (PPG) sensor is designed as awrist type device and connected with the IP node assigned its own IPv6 address. The measured PPG waveform in the IP node is collectedand transferred to a central server PC through the IP-enabled wireless network for storage and analysis purposes. A monitoring andanalysis program is designed to process the accelerated plethysmogram (APG) waveform by applying the second order derivatives toanalyze systolic waves as well as heart rate variability analysis from the measured PPG waveform. From our results, the features ofcardiovascular condition from individuals PPG waveform and estimation of vascular compliance by the comparison of APG-aging index(AI) and ratio of LF/HF are demonstrated. Keywords : Wearable PPG sensor, Accelerated plethysmogram waveform, Heart rate variability, Vascular compliance, Aging index,IP-enabled wireless network

A ΣΔ Fractional-N PLL with Multiple Charge Pumps and Capacitance Scaling Scheme

A novel SigmaDelta fractional-N PLL architecture for fast locking and fractional spur suppressing is proposed based on the capacitance scaling scheme. Fractional spurs suppressing have been achieved by reducing the magnitude of charge pump current when the PLL is in-lock without degrading fast locking characteristic. The effective capacitance of loop filter (LF) can be scaled up/down depending on operating status for fast locking and fractional spur suppressing while keeping LF capacitors small enough to be integrated into a single PLL chip. It has been simulated by HSPICE in a CMOS 0.35mum process, and shows that locking time is less than 8mus with the small size of LF capacitors, 200pF and 17pF, and 2.8KOmega resistor

A 2.4-GHz latch-structured power amplifier for Bluetooth

A two-stage class E power amplifier operating at 2.4GHz was designed in a 0.25-/spl mu/m CMOS process for class-1 Bluetooth applications. The power amplifier employs a class-E topology in order to obtain high efficiency by exploiting its soft-switching property. The latch-structured design of the preamplifier with auxiliary amplifiers enables its output signal to be as sharp as possible for the soft switching of the next stage power amplifier. This improves the overall efficiency of the proposed power amplifier which has a PAE of 65.8%,a power gain of 20dB and an output power of 20dBm.

Synthesis and Characterization of Copper Oxide nanowires by Facile Heating under Static Air Condition

Large-scaled area and aligned copper oxide nanowires have been synthesized by a vapor-phase approach to the facial synthesis of copper oxide nanowires supported on the surface of a copper gasket. The effects of annealing temperature and time were investigated. Long and aligned nanowires can only formed within a narrow temperature range from 400 to 500℃ for 4 hrs. Annealing copper gasket in static air produces large-area, uniform, but not well vertically aligned nanowires along the copper gasket surface. The surface of copper gasket is converted into bicrystal CuO nanowires was observed after the copper gasket is annealed under static air condition.