一种采用新型复合沟道GaN HEMTs低噪声分布式放大器

设计研制了一种新型的低噪声分布式放大器,采用了栅长为1μm的低噪声复合沟道Al0.3Ga0.7N/Al0.05Ga0.95N/GaN HEMT (CC-HEMT). 给出了低噪声分布式放大器的仿真和测试结果. 测试结果显示低噪声分布式放大器在2~10GHz频率范围内,输入和输出端口驻波比均小于2.0,相关增益大于7.0dB,带内增益波纹小于1dB . 在2~6GHz频率范围内,噪声系数小于5dB;在2~10GHz频率范围内,噪声系数小于6.5dB; 测试结果与仿真结果较吻合.     

Electrolyte‐Gated n‐Type Transistors Produced from Aqueous Inks of WS2 Nanosheets

Solution‐processed, low cost thin films of layered semiconductors such as transition metal dichalcogenides (TMDs) are potential candidates for future printed electronics. Here, n‐type electrolyte‐gated transistors (EGTs) based on porous WS₂ nanosheet networks as the semiconductor are demonstrated. The WS₂ nanosheets are liquid phase exfoliated to form aqueous/surfactant stabilized inks, and deposited at low temperatures (T < 120 °C) in ambient atmosphere by airbrushing. No solvent exchange, further additives, or complicated processing steps are required. While the EGTs are primarily n‐type (electron accumulation), some hole transport is also observable. The EGTs show current modulations > 10⁴ with low hysteresis, channel width‐normalized on‐conductances of up to 0.27 µS µm^?1 and estimated electron mobilities around 0.01 cm² V^?1 s^?1. In addition, the WS₂ nanosheet networks exhibit relatively high volumetric capacitance values of 30 F cm^?3. Charge transport within the network depends significantly on the applied lateral electric field and is thermally activated, which supports the notion that hopping between nanosheets is a major limiting factor for these networks and their future application.     

The effect of small-signal AC voltages on C–V characterization and parameter extraction of SiO2 thin films

The effect of different small-signal ac voltage amplitudes on C–V curves characterized by thin SiO₂ based p-type MOS capacitor with aluminum gate is reported. When the small-signal ac voltage is comparable to the gate bias, the thickness of SiO₂ thin films extracted from the accumulation capacitance is found to be independent of small-signal ac voltage amplitudes, but the flat band voltage shift and interface state density associated with the variation of depletion layer capacitance are dependent on small-signal ac voltage amplitudes. They all increase with the small-signal ac voltage amplitudes. The experimental results reveal that the optimum small-signal ac voltage should be less than 100 mV. The mechanisms involving the depletion layer changes with small-signal ac voltages in SiO₂ thin films are also discussed in this paper.     

Floating Point CGRA based Ultra-Low Power DSP Accelerator

Journal of Signal Processing Systems - Coarse Grained Reconfigurable Arrays (CGRAs) are emerging as energy efficient accelerators providing a high grade of flexibility in both academia and...     

Voltage pulses change neural interface properties and improve unit recordings with chronically implanted microelectrodes

Current neuroprosthetic systems based on electrophysiological recording have an extended, yet finite working lifetime. Some posited lifetime-extension solutions involve improving device biocompatibility or suppressing host immune responses. Our objective was to test an alternative solution comprised of applying a voltage pulse to a microelectrode site, herein termed "rejuvenation." Previously, investigators have reported preliminary electrophysiological results by utilizing a similar voltage pulse. In this study we sought to further explore this phenomenon via two methods: 1) electrophysiology; 2) an equivalent circuit model applied to impedance spectroscopy data. The experiments were conducted via chronically implanted silicon-substrate iridium microelectrode arrays in the rat cortex. Rejuvenation voltages resulted in increased unit recording signal-to-noise ratios (10%/spl plusmn/2%), with a maximal increase of 195% from 3.74 to 11.02. Rejuvenation also reduced the electrode site impedances at 1 kHz (67%/spl plusmn/2%). Neither the impedance nor recording properties of the electrodes changed on neighboring microelectrode sites that were not rejuvenated. In the equivalent circuit model, we found a transient increase in conductivity, the majority of which corresponded to a decrease in the tissue resistance component (44%/spl plusmn/7%). These findings suggest that rejuvenation may be an intervention strategy to prolong the functional lifetime of chronically implanted microelectrodes.     

Fatigue estimation with a multivariable myoelectric mapping function

A novel approach to muscle fatigue assessment is proposed. A function is used to map multiple myoelectric parameters representing segments of myoelectric data to a fatigue estimate for that segment. An artificial neural network is used to tune the mapping function and time-domain features are used as inputs. Two fatigue tests were conducted on five participants in each of static, cyclic and random conditions. The function was tuned with one data set and tested on the other. Performance was evaluated based on a signal to noise metric which compared variability due to fatigue factors with variability due to nonfatiguing factors. Signal to noise ratios for the mapping function ranged from 7.89 under random conditions to 9.69 under static conditions compared to 3.34-6.74 for mean frequency and 2.12-2.63 for instantaneous mean frequency indicating that the mapping function tracks the myoelectric manifestations of fatigue better than either mean frequency or instantaneous mean frequency under all three contraction conditions.     

Analysis, design, and implementation of an active clamp forward converter with synchronous rectifier

The system analysis, circuit design, and implementation of active clamp based forward converter with synchronous rectifier are presented in this paper. To release the energy stored in the leakage inductor and to minimize the spike voltage at the transformer primary side, active clamp circuit included one clamp switch and one clamp capacitor is adopted in the circuit. Based on the partial resonance with the output capacitor of switch and the leakage inductor of transformer, the main switch is turned on at zero voltage switching (ZVS). The clamp switch is also operated at ZVS operation based on the resonance of leakage inductor and clamp capacitor. The synchronous switches are used at the secondary side to further reduce the conduction losses. The experimental results based on the laboratory prototypes are presented to verify the circuit performance.     

X‐Region: A framework for location privacy preservation in mobile peer‐to‐peer networks

While enjoying various LBS (location‐based services), users also face the threats of location privacy disclosure. This is because even if the communications between users and LBS providers can be encrypted and anonymized, the sensitive information inside LBS queries may disclose the exact location or even the identity of a user. The existing research on location privacy preservation in mobile peer‐to‐peer (P2P) networks assumed that users trust each other and directly share location information with each other. Nonetheless, this assumption is not practical for most of the mobile P2P scenarios, for example, an adversary can pretend to be a normal user and collect the locations of other users. Aiming at this issue, this paper presents x‐region as a solution to preserve the location privacy in a mobile P2P environment where no trust relationships are assumed amongst mobile users. The main idea is to allow users to share a blurred region known as x‐region instead of their exact locations so that one cannot distinguish any user from others inside the region. We propose a theoretical metric for measuring the anonymity property of x‐region, together with three algorithms for generating an x‐region, namely, benchmark algorithm, weighted expanding algorithm, and aggressive weighted expanding algorithm. These algorithms achieve the anonymity and QoS requirements with different strategies. Our experiments verify the performance of the algorithms against three key metrics. Copyright © 2013 John Wiley & Sons, Ltd.     

一种采用新型复合沟道GaN HEMTs低噪声分布式放大器

设计研制了一种新型的低噪声分布式放大器,采用了栅长为1μm的低噪声复合沟道Al0.3Ga0.7N/Al0.05Ga0.95N/GaN HEMT(CC-HEMT).给出了低噪声分布式放大器的仿真和测试结果.测试结果显示低噪声分布式放大器在2～10GHz频率范围内,输入和输出端口驻波比均小于2.0,相关增益大于7.0dB.带内增益波纹小于1d8.在2～6GHz频率范围内,噪声系数小于5dB;在2～10GHz频率范围内,噪声系数小于6.5dB;测试结果与仿真结果较吻合.