A Miniaturized Wireless Neural Implant with Body-Coupled Power Delivery and Data Transmission

Joonsung BAE 한국생물공학회 2022 한국생물공학회 학술대회 Vol.2022 No.9

The Signal Transmission Mechanism on the Surface of Human Body for Body Channel Communication

Joonsung Bae,Hyunwoo Cho,Kiseok Song,Hyungwoo Lee,Hoi-Jun Yoo IEEE 2012 IEEE transactions on microwave theory and techniqu Vol.60 No.3

<P>The signal transmission mechanism on the surface of the human body is studied for the application to body channel communication (BCC). From Maxwell's equations, the complete equation of electrical field on the human body is developed to obtain a general BCC model. The mechanism of BCC consists of three parts according to the operating frequencies and channel distances: the quasi-static near-field coupling part, the reactive induction-field radiation part, and the surface wave far-field propagation part. The general BCC model by means of the near-field and far-field approximation is developed to be valid in the frequency range from 100 kHz to 100 MHz and distance up to 1.3 m based on the measurements of the body channel characteristics. Finally, path loss characteristics of BCC are formulated for the design of BCC systems and many potential applications.</P>

A 45 <tex> $\mu$</tex>W Injection-Locked FSK Wake-Up Receiver With Frequency-to-Envelope Conversion for Crystal-Less Wireless Body Area Network

Joonsung Bae,Hoi-Jun Yoo IEEE 2015 IEEE journal of solid-state circuits Vol.50 No.6

<P>A dedicated ultra-low power fully integrated FSK wake-up receiver (WuRx) for wireless body area network (WBAN) is implemented in 0.18 μm CMOS technology with 0.7 V supply voltage. For low power consumption, a body channel communication (BCC) physical layer (PHY) is adopted with an 80 MHz carrier frequency. Moreover, an injection-locking digitally-controlled oscillator (IL-DCO) is used to provide an extraordinary gain and frequency-to-envelope conversion in the simple and power-efficient envelope detection receiver architecture. The IL-DCO plays an important role in amplifying and demodulating the received FSK signal under a tight power budget. Finally, for low system cost without any external components and calibration overhead, a successive approximation register (SAR) auto-calibration algorithm is proposed to promptly calibrate the frequency drift of the IL-DCO. As a result, the fabricated 1 mm <SUP>2</SUP> single-chip WuRX consumes 45 μW with a data rate of 312 kb/s, providing an 80 MHz reference frequency with 0.25% stability within 102 μs calibration time. The proposed WuRX delivers a stable reference clock to the main transceiver for crystal-less WBAN applications.</P>

The Effects of Electrode Configuration on Body Channel Communication Based on Analysis of Vertical and Horizontal Electric Dipoles

Joonsung Bae,Hoi-Jun Yoo Professional Technical Group on Microwace Theory a 2015 IEEE Transactions on Microwave Theory and Techniqu Vol. No.

<P>The effects of electrode configuration on body channel communication (BCC) are studied for the development of body channel characteristics, such as frequency response, path loss, and resilience to other interferers. First, this paper introduces nine types of electrode configurations according to the arrangement and direction of both transmitting and receiving electrodes on the body. Each configuration is then modeled by means of vertical and horizontal electric dipoles. From Maxwell's equations, the complete equations of vertical and horizontal electric fields on the human body, followed by the ratios of the received electric field to the transmitted electric field, are obtained to find the theoretical body channel characteristics and the effect of electrode configurations on the body channel. The theory is verified with measurement results using a network analyzer and balun transformer. In addition to the channel characteristics, the influence of BCC and RF interference on the body channel is investigated and discussed along with receiving electrode configurations. Based on the measurement results, we found that vertical electrodes in the transmitter and horizontal electrodes with longitudinal direction in the receiver is the optimal configuration for BCC in regard to transmission gain, environmental sensitivity, and interference resilience. Finally, we suggest an effective parameter for BCC, which is equivalent reference distance to determine the proper electrode size for the required frequency response. The relation between the parameter and the electrode size is formulated for the purpose of proper electrode utilization in the design of BCC systems as well as in many potential applications.</P>

A Low Energy Injection-Locked FSK Transceiver With Frequency-to-Amplitude Conversion for Body Sensor Applications

Joonsung Bae,Long Yan,Hoi-Jun Yoo IEEE 2011 IEEE journal of solid-state circuits Vol.46 No.4

<P>An energy-efficient 920 MHz FSK transceiver for wireless body sensor network (BSN) applications is implemented in 0.18 μm CMOS technology with 0.7 V supply. A transceiver architecture based on injection-locked frequency divider (ILFD) is proposed for the low energy consumption. In the receiver, the ILFD in the signal path converts the received FSK signal to amplitude-modulated signal which is applied to the next envelope detector. In the transmitter, the ILFD is used as digitally-controlled oscillator (DCO) which directly modulates the FSK signal with digital data. The DCO replaces the frequency synthesizer to eliminate the crystal oscillator (XO), which leads to reduce power consumption and cost. The transceiver can detect whether injection locking occurs or not, and calibrates the frequency drift of DCO over temperature variation thanks to ILFD based architecture. The receiver and transmitter consume 420 μW and 700 μW , respectively, at - 10 dBm output power with a data rate of 5 Mb/s, corresponding to energy consumption of 84 pJ per received bit and 140 pJ per transmitted bit.</P>

A 3.9 mW 25-Electrode Reconfigured Sensor for Wearable Cardiac Monitoring System

Long Yan,Joonsung Bae,Seulki Lee,Taehwan Roh,Kiseok Song,Hoi-Jun Yoo IEEE 2011 IEEE journal of solid-state circuits Vol.46 No.1

<P>A low power highly sensitive Thoracic Impedance Variance (TIV) and Electrocardiogram (ECG) monitoring SoC is designed and implemented into a poultice-like plaster sensor for wearable cardiac monitoring. 0.1 Ω TIV detection is possible with a sensitivity of 3.17 V/Ω and SNR > 40 dB. This is achieved with the help of a high quality (Q-factor > 30) balanced sinusoidal current source and low noise reconfigurable readout electronics. A cm-range 13.56 MHz fabric inductor coupling is adopted to start/stop the SoC remotely. Moreover, a 5% duty-cycled Body Channel Communication (BCC) is exploited for 0.2 nJ/b 1 Mbps energy efficient external data communication. The proposed SoC occupies 5 mm × 5 mm including pads in a standard 0.18 μm 1P6M CMOS technology. It dissipates a peak power of 3.9 mW when operating in body channel receiver mode, and consumes 2.4 mW when operating in TIV and ECG detection mode. The SoC is integrated on a 15 cm × 15 cm fabric circuit board together with a flexible battery to form a compact wearable sensor. With 25 adhesive screen-printed fabric electrodes, detection of TIV and ECG at 16 different sites of the heart is possible, allowing optimal detection sites to be configured to accommodate different user dependencies.</P>

A 60 kb/s–10 Mb/s Adaptive Frequency Hopping Transceiver for Interference-Resilient Body Channel Communication

Cho, Namjun,Yan, Long,Bae, Joonsung,Yoo, Hoi-Jun IEEE 2009 IEEE journal of solid-state circuits Vol.44 No.3

<P> An interference-resilient 60 kb/s–10 Mb/s body channel transceiver using the human body as a signal transmission medium is designed for multimedia and medical data transaction in body-area network. The body antenna effect which interferes with signals in the human body channel is examined. The body-induced interferences degrade the SIR of the signal to <TEX>$-$</TEX>22 dB in the worst case. In order to overcome the body antenna effect, a 4-channel adaptive frequency hopping scheme using the 30–120 MHz band is introduced to the body channel transceiver. A direct-switching modulator using dual frequency synthesizers and a DLL-based demodulator are proposed for 10 Mb/s FSK and the 4.2 <TEX>$\mu \hbox{s}$</TEX> hopping time. The transceiver fabricated with 0.18 <TEX>$\mu \hbox{m}$</TEX> CMOS withstands <TEX>$-$</TEX>28 dB SIR and its operating distance is over 1.8 m with <TEX>$-$</TEX> 25 dB SIR. Its energy consumption is 0.37 nJ/b with <TEX>$-$</TEX>65 dBm sensitivity. </P>

A Planar MICS Band Antenna Combined With a Body Channel Communication Electrode for Body Sensor Network

Namjun Cho,Taehwan Roh,Joonsung Bae,Hoi-Jun Yoo IEEE 2009 IEEE transactions on microwave theory and techniqu Vol.57 No.10

<P>A 2.5 times 1.8 cm<SUP>2</SUP> medical implant communication service band antenna is combined with an electrode for body channel communication. The proposed design enables a body sensor network controller to communicate with health-care devices located on and inside a patient's body. The spiral microstrip antenna with its radiating body and ground plane placed side-by-side has the thickness of 2 mm and can be attached to human skin conveniently. The propagation loss of the body channel is measured when the proposed antenna is used as the skin interface for BCC in the 10-70-MHz band, and the results are compared with the cases of Ag/AgCl and circular dry electrodes. The equivalent-circuit model of the antenna as the electrode is also derived from the measured impedance characteristics. The <I>LC</I> resonance structure to drive the on-body antenna with its capacitance increased due to the skin contact reduces the power consumption of the TX buffer by >50%. The<I>S</I> <SUB>11</SUB>-parameter of the on-body antenna, its radiation pattern, and the signal loss inside the human body are investigated.</P>

A 10.4 mW Electrical Impedance Tomography SoC for Portable Real-Time Lung Ventilation Monitoring System

Sunjoo Hong,Jaehyuk Lee,Joonsung Bae,Hoi-Jun Yoo IEEE 2015 IEEE journal of solid-state circuits Vol.50 No.11

<P>An electrical impedance tomography (EIT) SoC is proposed for the portable real-time lung ventilation monitoring system. The proposed EIT SoC is integrated into belt-typefabric system with 32 electrodes and can show the dynamic images of the lung ventilation on the mobile devices. To get high fidelity images, a T-switch is adopted for high off-isolation between electrodes more than 60 dB, and I/Q signal generation and demodulation can obtain both real and imaginary part of images. For the real-time imaging, an on-chip fast demodulation scheme is proposed, and it can also reduce speed requirements of ADC for low-power consumption. The proposed EIT SoC of 5.0 mm × 5.0 mm is fabricated in 0.18 μm CMOS technology, and consumes only 10.4 mW with 1.8 V supply. As a result, EIT images were reconstructed with 97.3% of accuracy and up to 20 frames/s real-time lung images can be displayed on the mobile devices.</P>

An Impedance and Multi-Wavelength Near-Infrared Spectroscopy IC for Non-Invasive Blood Glucose Estimation

Kiseok Song,Unsoo Ha,Seongwook Park,Joonsung Bae,Hoi-Jun Yoo IEEE 2015 IEEE journal of solid-state circuits Vol.50 No.4

<P>A multi-modal spectroscopy IC combining impedance spectroscopy (IMPS) and multi-wavelength near-infrared spectroscopy (mNIRS) is proposed for high precision non-invasive glucose level estimation. A combination of IMPS and mNIRS can compensate for the glucose estimation error to improve its accuracy. The IMPS circuit measures dielectric characteristics of the tissue using the RLC resonant frequency and the resonant impedance to estimate the glucose level. To accurately find resonant frequency, a 2-step frequency sweep sinusoidal oscillator (FSSO) is proposed: 1) 8-level coarse frequency switching (f<SUB>STEP</SUB> = 9.4 kHz) in 10-76 kHz, and 2) fine analog frequency sweep in the range of 18.9 kHz. During the frequency sweep, the adaptive gain control loop stabilizes the output voltage swing (400 mV<SUB>p-p</SUB>). To improve accuracy of mNIRS, three wavelengths, 850 nm, 950 nm, and 1,300 nm, are used. For highly accurate glucose estimation, the measurement data of the IMPS and mNIRS are combined by an artificial neural network (ANN) in external DSP. The proposed ANN method reduces the mean absolute relative difference to 8.3% from 15% of IMPS, and 15-20% of mNIRS in 80-180 mg/dL blood glucose level. The proposed multi-modal spectroscopy IC occupies 12.5 mm 2 in a 0.18 μm 1P6M CMOS technology and dissipates a peak power of 38 mW with the maximum radiant emitting power of 12.1 mW.</P>