It has proved that the auscultation of respiratory sound has advantage in early respiratory diagnosis. Various methods have been raised to perform automatic respiratory sound analysis to reduce subjective diagnosis and physicians' workload. However, these methods highly rely on the quality of respiratory sound database. In this work, we have developed the first open-access paediatric respiratory sound database, SPRSound. The database consists of 2,683 records and 9,089 respiratory sound events from 292 participants. Accurate label is important to achieve a good prediction for adventitious respiratory sound classification problem. A custom-made sound label annotation software (SoundAnn) has been developed to perform sound editing, sound annotation, and quality assurance evaluation. A team of 11 experienced paediatric physicians is involved in the entire process to establish golden standard reference for the dataset. To verify the robustness and accuracy of the classification model, we have investigated the effects of different feature extraction methods and machine learning classifiers on the classification performance of our dataset. As such, we have achieved a score of 75.22%, 61.57%, 56.71%, and 37.84% for the four different classification challenges at the event level and record level.

This paper presents a silicon oscillating accelerometer (SOA) with a new CMOS readout circuit architecture. A phase lock loop (PLL) with a hybrid and antinoise folding PFD is employed to sustain the oscillation of the MEMS oscillator, and the oscillation amplitude is set by an external reference. In addition, a sigma-delta frequency-to-digital converter is combined with the PLL to digitize the accelerometer's frequency output for low power consumption. The MEMS transducer and the readout circuit are fabricated in an 80-μm SOI and standard 0.35-μm CMOS process, respectively. The SOA achieves 0.23-μg bias instability and 1-μg/Hz1/2 acceleration noise density with a ±30 g full-scale, which are equivalent to 4-ppb relative instability and 17-ppb/Hz1/2 relative acceleration noise density. It only consumes 2.7 mW under a 1.5 V supply.

Flexible electronics are compatible with film substrates that are soft and stretchable, resulting in conformal integration with human body. Integrated with various sensors and communication ICs, wearable flexible electronics are able to effectively track human vital signs without affecting the body activities. Such a wearable flexible system contains a sensor, a front-end amplifier (FEA), an analog-to-digital converter (ADC), a micro-controller unit (MCU), a radio, a power management unit (PMU), where the radio is the design bottleneck due to its high power consumption. Different from conventional wireless communications, body channel communication (BCC) uses the human body surface as the signal transmission medium resulting in less signal loss and low power consumption. However, there are some design challenges in BCC, including body channel model, backward loss, variable contact impedance, stringent spectral mask, crystalless design, body antenna effect, etc. In this paper, we conduct a survey on BCC transceiver, and analyze its potential role and challenges in wearable flexible electronics.

Temperature fluctuations seriously damage the performance of resonant accelerometers. Two approaches have been proposed in this paper to address this problem. In structural design, electrostatic softening spring is utilized to modulate the external acceleration on the frequency of resonator’s anti-phase modal without any stress transmission, and thus improve the thermal robustness of the accelerometer. In control circuit, continuous ring-down technique is employed for real-time quality factor (utilized as a virtual thermometer) monitoring, which attenuates measuring hysteresis and improves the precision of temperature compensation. A prototype is implemented to verify the proposed approaches. Experiments show that this accelerometer is insensitive to stress and has better performance of temperature compared with vibration beam resonant accelerometer. The bias stability of acceleration output was improved from 35.2mg to 0.08mg with real-time quality factor compensation ranging from −40°C to +40°C.

The level shifter (LS) circuit has become an indispensable circuit component in both analog and digital systems. In the past decades, there has been an exponential increase in the academic publications for the LS circuits to improve their performances and their applications. Therefore, this review paper provides a comprehensive study of the LS circuit, ranging from circuit topologies and various design methodologies such as sizing methodology, layout design methodology, circuit evaluation methodology, and testing methodology. Finally, we evaluate the state-of-the-art LS circuits and present their performance metrics.

Wearable body sensor nodes require massive data transmission under limited energy. However, it suffers from drastically varying channel loss, which limits its energy efficiency in practical scenarios. This paper presents a power-driven body-channel transceiver (TRX), whose power consumption can be adaptively tuned against varying channel loss. An out-band programmable gain amplifier (PGA) is proposed to save power and generate a quasi-linear correlation between PGA gain and power. By using the quasi-linear gain-power relationship, we propose an auto gain/power control technique to realize on-demand power consumption. In addition, a differential balanced transmitter is designed to eliminate base-band harmonics in on-off keying modulation and increase the power delivered by the transmitter (TX). The TX and receiver (RX) of the prototype were integrated into 1 chip and fabricated in a 55-nm complementary metal oxide semiconductor process. During the measurement, 2 chips were configured as TX and RX, respectively. Both the TX and the RX were wearable, powered by lithium batteries, and attached to the subject’s hands. The prototype achieved a 5.25-Mbps data rate with 16-pJ/bit energy efficiency at a 1.5-m straight-line ground path distance. Furthermore, the proposed TRX maintained stable communication within a 1.5-m distance, while dynamically reducing power consumption.