The Experts below are selected from a list of 24258 Experts worldwide ranked by ideXlab platform
R A Scholtz - One of the best experts on this subject based on the ideXlab platform.
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ultra wide bandwidth time hopping spread spectrum Impulse radio for wireless multiple access communications
IEEE Transactions on Communications, 2000Co-Authors: Moe Z Win, R A ScholtzAbstract:Attractive features of time-hopping spread-spectrum multiple-access systems employing Impulse Signal technology are outlined, and emerging design issues are described. Performance of such communications systems in terms of achievable transmission rate and multiple-access capability are estimated for both analog and digital data modulation formats under ideal multiple-access channel conditions.
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Impulse radio how it works
IEEE Communications Letters, 1998Co-Authors: Moe Z Win, R A ScholtzAbstract:Impulse radio, a form of ultra-wide bandwidth (UWB) spread-spectrum Signaling, has properties that make it a viable candidate for short-range communications in dense multipath environments. This paper describes the characteristics of Impulse radio using a modulation format that can be supported by currently available Impulse Signal technology and gives analytical estimates of its multiple-access capability under ideal multiple-access channel conditions.
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comparisons of analog and digital Impulse radio for wireless multiple access communications
International Conference on Communications, 1997Co-Authors: R A ScholtzAbstract:Attractive features of time-hopping spread-spectrum multiple access systems employing Impulse Signal technology are outlined and emerging design issues are described. Performance of such communications systems in terms of multiple-access capability is estimated for both analog and digital data modulation formats under ideal multiple access channel conditions.
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multiple access with time hopping Impulse modulation
Military Communications Conference, 1993Co-Authors: R A ScholtzAbstract:A time-hopping modulation format employing Impulse Signal technology has several features which may make it attractive for multiple-access communications. These features are outlined, an estimate of the multiple-access capability of a communication system employing this format under ideal propagation conditions is presented, and emerging design issues are described. >
Moe Z Win - One of the best experts on this subject based on the ideXlab platform.
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ultra wide bandwidth time hopping spread spectrum Impulse radio for wireless multiple access communications
IEEE Transactions on Communications, 2000Co-Authors: Moe Z Win, R A ScholtzAbstract:Attractive features of time-hopping spread-spectrum multiple-access systems employing Impulse Signal technology are outlined, and emerging design issues are described. Performance of such communications systems in terms of achievable transmission rate and multiple-access capability are estimated for both analog and digital data modulation formats under ideal multiple-access channel conditions.
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Impulse radio how it works
IEEE Communications Letters, 1998Co-Authors: Moe Z Win, R A ScholtzAbstract:Impulse radio, a form of ultra-wide bandwidth (UWB) spread-spectrum Signaling, has properties that make it a viable candidate for short-range communications in dense multipath environments. This paper describes the characteristics of Impulse radio using a modulation format that can be supported by currently available Impulse Signal technology and gives analytical estimates of its multiple-access capability under ideal multiple-access channel conditions.
Xin Zhang - One of the best experts on this subject based on the ideXlab platform.
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time frequency analysis based on ensemble local mean decomposition and fast kurtogram for rotating machinery fault diagnosis
Mechanical Systems and Signal Processing, 2018Co-Authors: Lei Wang, Qiang Miao, Xin ZhangAbstract:Abstract A time–frequency analysis method based on ensemble local mean decomposition (ELMD) and fast kurtogram (FK) is proposed for rotating machinery fault diagnosis. Local mean decomposition (LMD), as an adaptive non-stationary and nonlinear Signal processing method, provides the capability to decompose multicomponent modulation Signal into a series of demodulated mono-components. However, the occurring mode mixing is a serious drawback. To alleviate this, ELMD based on noise-assisted method was developed. Still, the existing environmental noise in the raw Signal remains in corresponding PF with the component of interest. FK has good performance in Impulse detection while strong environmental noise exists. But it is susceptible to non-Gaussian noise. The proposed method combines the merits of ELMD and FK to detect the fault for rotating machinery. Primarily, by applying ELMD the raw Signal is decomposed into a set of product functions (PFs). Then, the PF which mostly characterizes fault information is selected according to kurtosis index. Finally, the selected PF Signal is further filtered by an optimal band-pass filter based on FK to extract Impulse Signal. Fault identification can be deduced by the appearance of fault characteristic frequencies in the squared envelope spectrum of the filtered Signal. The advantages of ELMD over LMD and EEMD are illustrated in the simulation analyses. Furthermore, the efficiency of the proposed method in fault diagnosis for rotating machinery is demonstrated on gearbox case and rolling bearing case analyses.
Cam Nguyen - One of the best experts on this subject based on the ideXlab platform.
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power efficient switching based cmos uwb transmitters for uwb communications and radar systems
IEEE Transactions on Microwave Theory and Techniques, 2006Co-Authors: Rui Xu, Cam NguyenAbstract:This paper presents a new carrier-based ultra-wideband (UWB) transmitter architecture. The new UWB transmitter implements a double-stage switching to enhance RF-power efficiency, reduce dc-power consumption, and increase switching speed and isolation, while reducing circuit complexity. In addition, this paper also demonstrates a new carrier-based UWB transmitting module implemented using a 0.18-mum CMOS integrated pulse generator-switch chip. The design of a UWB sub-nanosecond-switching 0.18-mum CMOS single-pole single-throw (SPST) switch, operating from 0.45 MHz to 15 GHz, is discussed. The design of a 0.18-mum CMOS tunable Impulse generator is also presented. The edge-compression phenomenon of the Impulse Signal controlling the SPST switch, which makes the generated UWB Signal narrower than the Impulse, is described. Measurement results show that the generated UWB Signal can vary from 2 V peak-to-peak with 3-dB 4-ns pulsewidth to 1 V with 0.5 ns, covering 10-dB Signal bandwidths from 0.5 to 4 GHz, respectively. The generated UWB Signal can be tuned to cover the entire UWB frequency range of 3.1-10.6 GHz. The sidelobe suppression in the measured spectrums is more than 15 dB. The entire CMOS module works under a 1.8-V supply voltage and consumes less than 1 mA of dc current. The proposed carrier-based UWB transmitter and the demonstrated module provide an attractive means for UWB Signal generation for both UWB communications and radar applications
Xuefeng Chen - One of the best experts on this subject based on the ideXlab platform.
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fault diagnosis for a wind turbine generator bearing via sparse representation and shift invariant k svd
IEEE Transactions on Industrial Informatics, 2017Co-Authors: Boyuan Yang, Xuefeng ChenAbstract:It is always a primary challenge in fault diagnosis of a wind turbine generator to extract fault character information under strong noise and nonstationary condition. As a novel Signal processing method, sparse representation shows excellent performance in time–frequency analysis and feature extraction. However, its result is directly influenced by dictionary, whose atoms should be as similar with Signal's inner structure as possible. Due to the variability of operation environment and physical structure in industrial systems, the patterns of Impulse Signals are changing over time, which makes creating a proper dictionary even harder. To solve the problem, a novel data-driven fault diagnosis method based on sparse representation and shift-invariant dictionary learning is proposed. The Impulse Signals at different locations with the same characteristic can be represented by only one atom through shift operation. Then, the shift-invariant dictionary is generated by taking all the possible shifts of a few short atoms and, consequently, is more applicable to represent long Signals that in the same pattern appear periodically. Based on the learnt shift-invariant dictionary, the coefficients obtained can be sparser, with the extracted Impulse Signal being closer to the real Signal. Finally, the time–frequency representation of the Impulse component is obtained with consideration of both the Wigner–Ville distribution of every atom and the corresponding sparse coefficient. The excellent performance of different fault diagnoses in a fault simulator and a wind turbine proves the effectiveness and robustness of the proposed method. Meanwhile, the comparison with the state-of-the-art method is illustrated, which highlights the superiority of the proposed method.
