A novel programmable frequency divider for quantization noise (QN) suppression in fractional-phase-locked loops (PLLs) is presented in this paper. The proposed phase switching multi-modulus frequency divider (PS-MMFD) utilizes a novel glitch-free phase switching (PS) divide-by-0.5/1/1.5/2 cell to reduce the frequency division step to 0.5 and its QN induced by modulation is thus suppressed by additional 6 dB. Compared with other frequency dividers used for QN suppression, the proposed glitch-free PS-MMFD is more robust, can operate at higher input frequency and consumes less power. Detailed analysis and implementation of the proposed glitch-free PS-MMFD is demonstrated, followed by experimental results from a fully integrated fractional-PLL utilizing the proposed QN suppression technique. Implemented in a 0.18 m CMOS process, the proposed glitch-free PS-MMFD occupies an area of 0.38 mm 0.25 mm and consumes 5 mA from a 1.8-V supply at an input frequency of 2 GHz. Measurement results also demonstrate the additional 6-dB QN suppression by the proposed technique.Index Terms-Glitch-free, phase switching (PS), phase switching multi-modulus frequency divider (PS-MMFD), phase-locked loops (PLLs), quantization noise (QN) suppression.
The reliability and validity of common physical activity (PA) questionnaires are not well investigated in college students. This study aims to evaluate the reliability and validity of common subjective instruments in measuring PA and sedentary behaviour (SB) among college students. A total of 142 college students were included through convenience sampling. Each participant was asked to wear Actigraph wGT3X-BT accelerometers and fill physical activity logs (PAL) for 7 consecutive days. The Global Physical Activity Questionnaire (GPAQ), the International Physical Activity Questionnaire long-form (IPAQ-LF), and short-form (IPAQ-SF) were interviewed by face-to-face at both day 0 and day 8. Reliability was evaluated by intraclass correlation coefficient (ICC), while the validity was evaluated by Spearman correlation coefficient and Bland–Altman statistics. The instruments showed moderate reliability in reporting total PA (ICC = 0.50–0.62) and SB (ICC = 0.47–0.52), while moderate validity in reporting moderate and vigorous PA (MVPA) (r = 0.37–0.42), but fair to poor validity in reporting SB (r = 0.09–0.28). Bland–Altman plots showed that all the instruments would underestimate MVPA and overestimate SB. Thus, in Chinese younger adults, the GPAQ, IPAQ-LF, IPAQ-SF, and PAL provide limited but acceptable reliability and validity in measuring MVPA and SB, among which GPAQ might be the most valid instrument.
The clinical applications of capsule endoscopes have been increasing consistently since the invention of a passive capsule endoscope was made [1]. Though the capsule endoscopes are effective in detecting large lesions along human digestive tract, they cannot meet doctors' requirements of active control of the capsules to carefully examine small lesions. The poor precision of positioning system is one of the major hurdles blocking robots from approaching the accurate position of suspected areas. In this paper, we propose a novel algorithm to exploit the radiation patten of a radio frequency (RF) tag inside the capsule, which forms shadows or traces on a set of receiver arrays. According to the shape of the traces and the radiation pattern, the position of the radiation source, i.e. the tag inside the capsule can be calculated with our algorithm. The details of our algorithm are presented with the simulation results in the paper. With the settings under medical constraints, the degree of positioning precision in simulation is improved to less than 1cm horizontally and 2cm vertically.
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