Figure 6. a) The optical spectrum with a central wavelength of 1559.5 nm and a modulation period of 1.31 nm, b) oscilloscope trace of the bound state pulse sequence, c) RF spectrum of the output pulse train, d) the autocorrelation trace of the 2nd order soliton molecules, e) optical spectra of the 3rd and 4th order soliton molecules, and f) autocorrelation trace of the 3rd and 4th order soliton molecules.
For wearable capacitive electrocardiogram (ECG) acquisition, capacitive electrodes may cause severe motion artifacts due to the relatively large friction between the electrodes and the dielectrics. In some studies, water can effectively suppress motion artifacts, but these studies lack a complete analysis of how water can suppress motion artifacts. In this paper, the effect of water on charge decay of textile electrode is studied systematically, and an electrode controllable humidification design using ultrasonic atomization is proposed to suppress motion artifacts. Compared with the existing electrode humidification designs, the proposed electrode humidification design can be controlled by a program to suppress motion artifacts at different ambient humidity, and can be highly integrated for wearable application. Firstly, the charge decay mode of the textile electrode is given and it is found that the process of free water evaporation at an appropriate free water content can be the dominant way of triboelectric charge dissipation. Secondly, theoretical analysis and experiment verification both illustrate that water contained in electrodes can accelerate the decay of triboelectric charge through the free water evaporation path. Finally, a capacitive electrode controllable humidification design is proposed by applying integrated ultrasonic atomization to generate atomized drops and spray them onto textile electrodes to accelerate the decay of triboelectric charge and suppress motion artifacts. The performance of the proposed design is verified by the experiment results, which shows that the proposed design can effectively suppress motion artifacts and maintain the stability of signal quality at both low and high ambient humidity. The signal-to-noise ratio of the proposed design is 33.32 dB higher than that of the non-humidified design at 25% relative humidity and is 22.67 dB higher than that of non-humidified electrodes at 65% relative humidity.
Two different structures of single photon avalanche diode(SPAD) fabricated by 0.13 m flash process technology are presented. The structure-1 uses low implanted p-well surrounding the active area as the guard ring which prevents the periphery breakdown, while for the structure-2, a virtual guard ring with the deep retrograde nwell doping is designed. The characteristics of the two detectors with the same active area diameter are presented. The two SPAD structures exhibit relatively different dark and light performance. The first structure exhibits a typical dark count rate of 18 kHz at the room temperature and a maximum photon detection efficiency of 15%, while the second structure exhibits a dark count rate of 23 kHz and a maximum photon detection efficiency of 28%. The comparison of the two structures is therefore promising for the further advanced SPAD design.
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