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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 STEP = 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 p-p ). 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.Index Terms-Adaptive gain control, artificial neural network, frequency sweep sinusoidal oscillator, impedance spectroscopy, near-infrared spectroscopy, non-invasive glucose monitoring.

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Wireless Body Area Network (WBAN) is an emerging technology that combines health care and consumer electronic applications around the human body. There are 3 PHY schemes discussed in the IEEE 802.15.6 Task Group for WBAN standardization [1]: ultra-wide-band (UWB) PHY, narrow-band (NB) PHY, and body channel communication (BCC) PHY. The BCC, which uses the human body as a communication channel based on the near-field coupling mechanism, has advantages over UWB and NB in energy efficiency because it provides low pathloss without the body shadowing effect in low-frequency bands below 150MHz [2][3][4]. However, the previous body channel transceivers (BCTs) were not optimized for WBAN because only phenomenological circuit models were used for the body channel analysis [5] and were unable to satisfy requirements such as energy efficiency, scalability of QoS, interference mitigation, and coexistence at once.In this paper, we report a BCT that not only consumes the lowest energy with very high sensitivity but also is fully WBAN compatible. It is possible because: (1) the signal propagation principle is more thoroughly investigated, (2) resonance matching (RM) and context-aware sensing (CAS) are adopted, and (3) low-power double-FSK modulation is exploited for the full satisfaction of WBAN requirements.According to the experimental data, a BCC signal path can be divided into 2 parts: forward path, and return path as shown in Fig. 2.1.1. Electrodes in contact or in close proximity to the human body constitute the forward path while the floated ground electrodes of TX and RX form the closed-loop return path by capacitive-coupling to the earth ground. The signal path loss has band-pass characteristics, mainly determined by the return path loss because the small capacitance of C R in the return path has the highest impedance value compared with the contact impedance (electrode-to-body) and body impedance. RM cancels the C R effect by inserting a resonating series inductor in the return path. The contact impedance in the forward path varies its value dynamically and even 30dB overall signal path loss variation is observed when the electrode is in contact with or apart from the body. To compensate for channel quality degradation due to contact impedance variation, the CAS observes the contact impedance by recognizing if the electrode is capacitively coupled or resistively coupled to the human body, and then automatically determines the BCT operation mode for the better power efficiency.Figure 2.1.2 shows the overall architecture of the BCT using scalable double-FSK, which is based on UWB-FM [6]. The BCC uses a 40-to-120MHz frequency band while the CAS utilizes a chopper-stabilized AC current-injection source of 1MHz to monitor the differential contact impedance between 2 electrodes. On the TX side, from the frequency synthesizer and divider chain, a low-modulationindex sub-band FSK signal S(t) is transformed into a high-modulation-index wide-band FSK signal W(t) that drives the electrodes. On the RX side, the delayline-based wi...

A wearable neuro-feedback system is proposed with a low-power neuro-feedback SoC (NFS), which supports mental status monitoring with encephalography (EEG) and transcranial electrical stimulation (tES) for neuro-modulation. Self-configured independent component analysis (ICA) is implemented to accelerate source separation at low power. Moreover, an embedded support vector machine (SVM) enables online source classification, configuring the ICA accelerator adaptively depending on the types of the decomposed components. Owing to the hardwired accelerating functions, the NFS dissipates only 4.45 mW to yield 16 independent components. For non-invasive neuro-modulation, tES stimulation up to 2 mA is implemented on the SoC. The NFS is fabricated in 130-nm CMOS technology.

Wireless Body Area Network (WBAN) is an emerging technology that combines health care and consumer electronic applications around the human body. There are 3 PHY schemes discussed in the IEEE 802.15.6 Task Group for WBAN standardization [1]: ultra-wide-band (UWB) PHY, narrow-band (NB) PHY, and body channel communication (BCC) PHY. The BCC, which uses the human body as a communication channel based on the near-field coupling mechanism, has advantages over UWB and NB in energy efficiency because it provides low path-loss without the body shadowing effect in low-frequency bands below 150MHz [2-4]. However, the previous body channel transceivers (BCTs) were not optimized for WBAN because only phenomenological circuit models were used for the body channel analysis [5] and were unable to satisfy requirements such as energy efficiency, scalability of QoS, interference mitigation, and coexistence at once. In this paper, we report a BCT that not only consumes the lowest energy with very high sensitivity but also is fully WBAN compatible. It is possible because: (1) the signal propagation principle is more thoroughly investigated, (2) resonance matching (RM) and context-aware sensing (CAS) are adopted, and (3) low-power double-FSK modulation is exploited for the full satisfaction of WBAN requirements. According to the experimental data, a BCC signal path can be divided into 2 parts: forward path, and return path as shown in Fig. 2.1.1. Electrodes in contact or in close proximity to the human body constitute the forward path while the floated ground electrodes of TX and RX form the closed-loop return path by capacitive-coupling to the earth ground. The signal path loss has band-pass characteristics, mainly determined by the return path loss because the small capacitance of C R in the return path has the highest impedance value compared with the contact impedance (electrode-to-body) and body impedance. RM cancels the C R effect by inserting a resonating series inductor in the return path. The contact impedance in the forward path varies its value dynamically and even 30dB overall signal path loss variation is observed when the electrode is in contact with or apart from the body. To compensate for channel quality degradation due to contact impedance variation, the CAS observes the contact impedance by recognizing if the electrode is capacitively coupled or resistively coupled to the human body, and then automatically determines the BCT operation mode for the better power efficiency. Figure 2.1.2 shows the overall architecture of the BCT using scalable double-FSK, which is based on UWB-FM [6]. The BCC uses a 40-to-120MHz frequency band while the CAS utilizes a chopper-stabilized AC current-injection source of 1MHz to monitor the differential contact impedance between 2 electrodes. On the TX side, from the frequency synthesizer and divider chain, a low-modulation-index sub-band FSK signal S(t) is transformed into a high-modulation-index wide-band FSK signal W(t) that drives the electrodes. On the RX side, the delay-line-based ...

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