Time filter

Source Type

New York, NY, United States

Gu J.-F.,Frequency Electronics | Zhu W.-P.,Concordia University at Montreal | Swamy M.N.S.,Concordia University at Montreal
IEEE Transactions on Signal Processing | Year: 2015

In this paper, we address the problem of estimating the two-dimensional (2-D) directions of arrival (DOA) of multiple signals, by means of a sparse L-shaped array. The array consists of one uniform linear array (ULA) and one sparse linear array (SLA). The shift-invariance property of the ULA is used to estimate the elevation angles with low computational burden. The signal subspace is constructed by the cross-covariance matrix (CCM) of the received data without implementing eigendecomposition. The source waveforms are then obtained by the estimated elevation angles, which together with each sensor of the SLA, considered as a linear regression model, is used to estimate the azimuth angle by the modified total least squares (MTLS) technique. Our new algorithm yields correct parameter pairs without requiring the computationally expensive pairing operation, and therefore, has at least two advantages over the previous L-shaped array based algorithms: less computational load and better performance due to the use of SLA and CCM. Expressions for the asymptotic mean-squared error (MSE) of the 2-D DOA estimates are derived. Simulation results show that our method provides accurate and consistent 2-D DOA estimation results that could not be obtained by the existing methods with comparable computational complexity. © 2015 IEEE. Source

Subirats A.,CEA Grenoble | Garros X.,CEA Grenoble | El Husseini J.,CEA Grenoble | Royer C.L.,CEA Grenoble | And 2 more authors.
IEEE Transactions on Electron Devices | Year: 2013

The impact of single charge trapping on the threshold voltage Vt of ultrascaled fully depleted silicon-on-insulator transistors is investigated through dynamic variability measurements and 3-D electrostatic simulations. In these undoped Si channel devices, Vt shifts induced by individual trapping events are exponentially distributed with distribution tail similarly as in BULK devices. This typical dependence is explained by the high sensitivity of Vt - with a bell-like shape - on the position of the trap over the channel. The tail, on the other hand, is attributed to defects in the buried oxide. Finally, device scaling is showed to increase dynamic Vt variability. In particular, the impact of a single charge on Vt is found to scale with the inverse of the device area. © 1963-2012 IEEE. Source

Kumar P.,Jaypee University of Information Technology | Masa-Campos J.L.,Frequency Electronics
Advanced Electromagnetics | Year: 2016

This paper presents the design, fabrication and measurement of dual polarized microstrip patch antennas for ultra wideband (UWB) applications with notch at 5-6 GHz band. The proposed antenna rejects the wireless local area network (WLAN) signals and work properly in the entire remaining ultra-wideband. Two antennas are designed for two different frequency bands of ultra wideband and both antennas together produce the entire ultra wideband with notch at 5-6 GHz band. The antennas are fed by a 50 Ω coaxial probe and the entire design is optimized using CST Microwave Studio. The bandwidth of 3.1-5 GHz is achieved by the optimized design of Antenna-1 and the bandwidth of 6-10.6 GHz is achieved by the optimized design of Antenna-2. The bandwidth of the optimized combined antenna is 3.1-10.6 GHz with elimination of the 5-6 GHz band. Both antennas are simulated, developed and measured. The simulated and measured results are presented. The two designed dual polarized antennas i.e. Antenna-1 and Antenna-2 can be used for 3.1-5 GHz band and 6-10.6 GHz band dual polarized applications, respectively, and the combined antenna structure can be used for UWB dual polarized applications with elimination of 5-6 GHz band signals. © 2016, Advanced Electromagnetics. All rights reserved. Source

Chen J.,Nanjing University of Posts and Telecommunications | Chen J.,Frequency Electronics | Mao P.,Nanjing University | Xu R.,Nanjing University of Posts and Telecommunications | And 6 more authors.
Optics Express | Year: 2015

We have demonstrated a straightforward strategy to realize magnetic field enhancement through diffraction coupling of magnetic plasmon (MP) resonances by embedding the metamaterials consisting of a planar rectangular array of U-shaped metallic split-ring resonators (SRRs) into the substrate. Our method provides a more homogeneous dielectric background allowing stronger diffraction coupling of MP resonances among SRRs leading to strong suppression of the radiative damping. We observe that compared to the on-substrate metamaterials, the embedded ones lead to a narrow-band hybridized MP mode, which results from the interference between MP resonances in individual SRRs and an in-plane propagating collective surface mode arising from light diffraction. Associated with the excitation of this hybridized MP mode, a twenty-seven times enhancement of magnetic fields within the inner area of the SRRs is achieved as compared with the pure MP resonance. Moreover, we also found that besides the above requirement of homogeneous dielectric background, only a collective surface mode with its magnetic field of the same direction as the induced magnetic moment in the SRRs could mediate the excitation of such a hybridized MP mode. © 2015 Optical Society of America. Source

Wang X.,Nanjing University of Posts and Telecommunications | Wang X.,Frequency Electronics | Liu Q.,Nanjing University of Posts and Telecommunications | Bu Y.,Nanjing University of Posts and Telecommunications | And 6 more authors.
RSC Advances | Year: 2015

Accurate and reliable temperature measurement of many special inaccessible objects is a challenging task. Optical temperature sensing is a promising method to achieve it. The current status of optical thermometry of rare-earth ion doped phosphors is reviewed in detail. Based on the mechanisms of optical temperature sensing of different phosphors, temperature dependent luminescence spectra, the fluorescence intensity ratio technique in the data fitting process, and errors of the energy difference between thermally coupled levels, we describe the recent developments in the use of optical thermometry materials. The most important results obtained in each case are summarized, and the main challenges that we need to overcome are discussed. Research in the field of phosphor sensors has shown that they have significant advantages compared to conventional sensors in terms of their properties like greater sensitivity, freedom from electromagnetic interference, long path monitoring, and independence of compatibility with electronic devices. © The Royal Society of Chemistry 2015. Source

Discover hidden collaborations