6,668 research outputs found
Frequency Estimation for Periodical Signal with Noise in Finite Time
International audienceThe frequency estimation technique with guaranteed ïŹnite time of convergence to a given accuracy of identiïŹcation is presented. The approach for a high frequency noise rejection is proposed. The possibility of switching algorithm introduction for estimation quality improvement is discussed. The proposed solution has order three, that is smaller than in other existent solutions. EfïŹciency of the approach is demonstrated on examples of computer simulation
Extracting cyclostationary features from single carrier signals
This paper contributes to the discussion about the usefulness of cyclostationary feature detection for the purpose of cognitive radio. From a simple but realistic radio signal model and an ideal channel, the power spectral density of the random signal component is derived, and compared with the periodical component that can be retrieved from the signal with a nonlinear operation
Generation of microwave fields in cavities with laser-excited nonlinear media: competition between the second- and third-order optical nonlinearities
We discuss a scheme for the parametric amplification of the quantum fluctuations of the
electromagnetic vacuum in a three-dimensional microwave resonator, and report the preliminary
measurements to test its feasibility. In the present experimental scheme, the fundamental mode of
a microwave cavity is nonadiabatically perturbed by modulating the index of refraction of the
nonlinear optical crystal enclosed therein. Intense, multi-GHz laser pulses, such as those
delivered by a mode-locked laser source, impinge on the crystal to accomplish the n-index
modulation. We theoretically analyze the process of parametric generation, which is related to
the third-order nonlinear coefficient \u3c7(3) of the nonlinear crystal, and assess the suitable
experimental conditions for generating real photons from the vacuum. Second-order nonlinear
processes are first analyzed as a possible source of spurious photons in quantum vacuum
experiments when an ideal, mode-locked laser source is considered. The combination of a crystal
non-null \u3c7(2) coefficient and a real mode-locked laser system\u2014i.e. one featuring offset-fromcarrier
noise and unwanted secondary oscillations\u2014is also experimentally investigated, paving
the way for future experiments in three-dimensional cavities
Controlling chaos in spatially extended beam-plasma system by the continuous delayed feedback
In present paper we discuss the control of complex spatio-temporal dynamics
in a {spatially extended} non-linear system (fluid model of Pierce diode) based
on the concepts of controlling chaos in the systems with few degrees of
freedom. A presented method is connected with stabilization of unstable
homogeneous equilibrium state and the unstable spatio-temporal periodical
states analogous to unstable periodic orbits of chaotic dynamics of the systems
with few degrees of freedom. We show that this method is effective and allows
to achieve desired regular dynamics chosen from a number of possible in the
considered system.Comment: 12 pages, 12 figure
Analyse des signaux AM-FM basée sur une version B-splines de l'EMD-ESA
In this paper a signal analysis framework for estimating time-varying amplitude and frequency functions of multicomponent amplitude and frequency modulated (AMâFM) signals is introduced. This framework is based on local and non-linear approaches, namely Energy Separation Algorithm (ESA) and Empirical Mode Decomposition (EMD). Conjunction of Discrete ESA (DESA) and EMD is called EMDâDESA. A new modified version of EMD where smoothing instead of an interpolation to construct the upper and lower envelopes of the signal is introduced. Since extracted IMFs are represented in terms of B-spline (BS) expansions, a closed formula of ESA robust against noise is used. Instantaneous Frequency (IF) and Instantaneous Amplitude (IA) estimates of a multi- component AMâFM signal, corrupted with additive white Gaussian noise of varying SNRs, are analyzed and results compared to ESA, DESA and Hilbert transform-based algorithms. SNR and MSE are used as figures of merit. Regularized BS version of EMDâ ESA performs reasonably better in separating IA and IF components compared to the other methods from low to high SNR. Overall, obtained results illustrate the effective- ness of the proposed approach in terms of accuracy and robustness against noise to track IF and IA features of a multicomponent AMâFM signal
Stroboscopic Variation Measurement
A new procedure of the linear position measurement which allows to obtain
sensitivity better than the Standard Quantum Limit and close to the Energetic
Quantum Limit is proposed and analyzed in details. Proposed method is based on
the principles of stroboscopic quantum measurement and variation quantum
measurement and allows to avoid main disadvantages of both these procedures.
This method can be considered as a good candidate for use as a local position
meter in the ``intracavity'' topologies of the laser gravitational-wave
antennae.Comment: 13 pages, 2 figures drawn in TeX and 2 figures in postscript,
misprint correcte
Super-Resolution Time of Arrival Estimation Using Random Resampling in Compressed Sensing
There is a strong demand for super-resolution time of arrival (TOA) estimation techniques for radar applications that can that can exceed the theoretical limits on range resolution set by frequency bandwidth. One of the most promising solutions is the use of compressed sensing (CS) algorithms, which assume only the sparseness of the target distribution but can achieve super-resolution. To preserve the reconstruction accuracy of CS under highly correlated and noisy conditions, we introduce a random resampling approach to process the received signal and thus reduce the coherent index, where the frequency-domain-based CS algorithm is used as noise reduction preprocessing. Numerical simulations demonstrate that our proposed method can achieve super-resolution TOA estimation performance not possible with conventional CS methods
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