К анализу метрологических характеристик интегрирующих аналоговых преобразователей цифровых вольтметров

В работе выполнен анализ метрологических характеристик помехозащищенных интегрирующих вольтметров, в которых используются в качестве входных устройств интегрирующие преобразователи частотного или временного типа. Так как свойства интегрирующих вольтметров полностью определяются видом входного устройства, сравнительный анализ характеристик вольтметров выполнен на основе исследования схем входных устройств.In this paper we analyzed the metrological characteristics of interference tolerant integrating voltmeters, in which integrating transducers of frequency or time type as input devices are used. Since the properties of integrating voltmeters are completely determined by the type of the input device, a comparative analysis of the characteristics of voltmeters based on the investigation of schemes of input devices is carried out

Waveguide Modulator for Interference Tolerant Functional Near Infrared Spectrometer (fNIRS)

Many crew-related errors in aviation and astronautics are caused by hazardous cognitive states including overstress, disengagement, high fatigue and ineffective crew coordination. Safety can be improved by monitoring and predicting these cognitive states in a non-intrusive manner and designing mitigation strategies. Measuring hemoglobin concentration changes in the brain with functional Near Infrared Spectroscopy is a promising technique for monitoring cognitive state and optimizing human performance during both space and aviation operations. A compact, wearable fNIRS system would provide an innovative early warning system during long duration missions to detect and prevent vigilance decrements in pilots and astronauts. This effort focused on developing a waveguide modulator for use in a fNIRS system

Interference Mitigation for Cognitive Radio MIMO Systems Based on Practical Precoding

In this paper, we propose two subspace-projection-based precoding schemes, namely, full-projection (FP)- and partial-projection (PP)-based precoding, for a cognitive radio multiple-input multiple-output (CR-MIMO) network to mitigate its interference to a primary time-division-duplexing (TDD) system. The proposed precoding schemes are capable of estimating interference channels between CR and primary networks, and incorporating the interference from the primary to the CR system into CR precoding via a novel sensing approach. Then, the CR performance and resulting interference of the proposed precoding schemes are analyzed and evaluated. By fully projecting the CR transmission onto a null space of the interference channels, the FP-based precoding scheme can effectively avoid interfering the primary system with boosted CR throughput. While, the PP-based scheme is able to further improve the CR throughput by partially projecting its transmission onto the null space.Comment: 12 pages, 4 figures, submitted to the IEEE Trans. Wireless Communications in April 201

Dynamic Geospatial Spectrum Modelling: Taxonomy, Options and Consequences

Much of the research in Dynamic Spectrum Access (DSA) has focused on opportunistic access in the temporal domain. While this has been quite useful in establishing the technical feasibility of DSA systems, it has missed large sections of the overall DSA problem space. In this paper, we argue that the spatio-temporal operating context of specific environments matters to the selection of the appropriate technology for learning context information. We identify twelve potential operating environments and compare four context awareness approaches (on-board sensing, databases, sensor networks, and cooperative sharing) for these environments. Since our point of view is overall system cost and efficiency, this analysis has utility for those regulators whose objectives are reducing system costs and enhancing system efficiency. We conclude that regulators should pay attention to the operating environment of DSA systems when determining which approaches to context learning to encourage

К анализу метрологических характеристик интегрирующих аналоговых преобразователей цифровых вольтметров

В работе выполнен анализ метрологических характеристик помехозащищенных интегрирующих вольтметров, в которых используются в качестве входных устройств интегрирующие преобразователи частотного или временного типа. Так как свойства интегрирующих вольтметров полностью определяются видом входного устройства, сравнительный анализ характеристик вольтметров выполнен на основе исследования схем входных устройств.In this paper we analyzed the metrological characteristics of interference tolerant integrating voltmeters, in which integrating transducers of frequency or time type as input devices are used. Since the properties of integrating voltmeters are completely determined by the type of the input device, a comparative analysis of the characteristics of voltmeters based on the investigation of schemes of input devices is carried out

Signal selective doa tracking for multiple moving targets

A new algorithm for signal selective tracking of the directions-of-arrival (DOAs) of multiple moving targets with an array of passive sensors is presented. A new method based on the principles of maximum likelihood estimation and cyclostationarity is used to generate initial angle estimates which, in turn, are refined by a Kalman filter. Source angle dynamics are used to achieve correct data association. High performance is obtained with relatively low computational complexity.Peer ReviewedPostprint (published version

Sensing-Throughput Tradeoff for Interweave Cognitive Radio System: A Deployment-Centric Viewpoint

Secondary access to the licensed spectrum is viable only if interference is avoided at the primary system. In this regard, different paradigms have been conceptualized in the existing literature. Of these, Interweave Systems (ISs) that employ spectrum sensing have been widely investigated. Baseline models investigated in the literature characterize the performance of IS in terms of a sensing-throughput tradeoff, however, this characterization assumes the knowledge of the involved channels at the secondary transmitter, which is unavailable in practice. Motivated by this fact, we establish a novel approach that incorporates channel estimation in the system model, and consequently investigate the impact of imperfect channel estimation on the performance of the IS. More particularly, the variation induced in the detection probability affects the detector's performance at the secondary transmitter, which may result in severe interference at the primary users. In this view, we propose to employ average and outage constraints on the detection probability, in order to capture the performance of the IS. Our analysis reveals that with an appropriate choice of the estimation time determined by the proposed model, the degradation in performance of the IS can be effectively controlled, and subsequently the achievable secondary throughput can be significantly enhanced.Comment: 13 pages, 10 figures, Accepted to be published in IEEE Transactions on Wireless Communication