Oscillator Architectures and Enhanced Frequency Synthesizer

A voltage controlled oscillator (VCO), that generates a periodic signal whose frequency is tuned by a voltage, is a key building block in any integrated circuit systems. A sine wave oscillator can be used for a built-in self testing where high linearity is required. A bandpass filter (BPF) based oscillator is a preferred solution, and high quality factor (Q-factor) is needed to improve the linearity. However, a stringent linearity specification may require very high Q-factor, not practical to implement. To address this problem, a frequency harmonic shaping technique is proposed. It utilizes a finite impulse response filter improving the linearity by rejecting certain harmonics. A prototype SC BPF oscillator with an oscillating frequency of 10 MHz is designed and measurement results show that linearity is improved by 20 dB over a conventional oscillator. In radio frequency area, preferred oscillator structures are an LC oscillator and a ring oscillator. An LC oscillator exhibits good phase noise but an expensive cost of an inductor is disadvantageous. A ring oscillator can be built in standard CMOS process, but suffers due to a poor phase noise and is sensitive to supply noise. A RC BPF oscillator is proposed to compromise the above difficulties. A RC BPF oscillator at 2.5 GHz is designed and measured performance is better than ring oscillators when compared using a figure of merit. In particular, the frequency tuning range of the proposed oscillator is superior to the ring oscillator. VCO is normally incorporated with a frequency synthesizer (FS) for an accurate frequency control. In an integer-N FS, reference spur is one of the design concerns in communication systems since it degrades a signal to noise ratio. Reference spurs can be rejected more by either the lower loop bandwidth or the higher loop filter. But the former increases a settling time and the latter decreases phase margin. An adaptive lowpass filtering technique is proposed. The loop filter order is adaptively increased after the loop is locked. A 5.8 GHz integer-N FS is designed and measurement results show that reference spur rejection is improved by 20 dB over a conventional FS without degrading the settling time. A new pulse interleaving technique is proposed and several design modifications are suggested as a future work

Improving Kinematic Accuracy of Soft Wearable Data Gloves by Optimizing Sensor Locations

Bending sensors enable compact, wearable designs when used for measuring hand configurations in data gloves. While existing data gloves can accurately measure angular displacement of the finger and distal thumb joints, accurate measurement of thumb carpometacarpal (CMC) joint movements remains challenging due to crosstalk between the multi-sensor outputs required to measure the degrees of freedom (DOF). To properly measure CMC-joint configurations, sensor locations that minimize sensor crosstalk must be identified. This paper presents a novel approach to identifying optimal sensor locations. Three-dimensional hand surface data from ten subjects was collected in multiple thumb postures with varied CMC-joint flexion and abduction angles. For each posture, scanned CMC-joint contours were used to estimate CMC-joint flexion and abduction angles by varying the positions and orientations of two bending sensors. Optimal sensor locations were estimated by the least squares method, which minimized the difference between the true CMC-joint angles and the joint angle estimates. Finally, the resultant optimal sensor locations were experimentally validated. Placing sensors at the optimal locations, CMC-joint angle measurement accuracies improved (flexion, 2.8° ± 1.9°; abduction, 1.9° ± 1.2°). The proposed method for improving the accuracy of the sensing system can be extended to other types of soft wearable measurement devices

An efficient method for visualization and growth of fluorescent Xanthomonas oryzae pv. oryzae in planta

<p>Abstract</p> <p>Background</p> <p><it>Xanthomonas oryzae </it>pv. <it>oryzae</it>, the causal agent of bacterial blight disease, is a serious pathogen of rice. Here we describe a fluorescent marker system to study virulence and pathogenicity of <it>X. oryzae </it>pv. <it>oryzae</it>.</p> <p>Results</p> <p>A fluorescent <it>X. oryzae </it>pv. <it>oryzae </it>Philippine race 6 strain expressing green fluorescent protein (GFP) (PXO99_GFP) was generated using the <it>gfp </it>gene under the control of the neomycin promoter in the vector, pP<it>neo</it>-<it>gfp</it>. The PXO99_GFPstrain displayed identical virulence and avirulence properties as the wild type control strain, PXO99. Using fluorescent microscopy, bacterial multiplication and colonization were directly observed in rice xylem vessels. Accurate and rapid determination of bacterial growth was assessed using fluoremetry and an Enzyme-Linked ImmunoSorbant Assay (ELISA).</p> <p>Conclusion</p> <p>Our results indicate that the fluorescent marker system is useful for assessing bacterial infection and monitoring bacterial multiplication <it>in planta</it>.</p