Spectral and correlation analysis with applications to middle-atmosphere radars

The correlation and spectral analysis methods for uniformly sampled stationary random signals, estimation of their spectral moments, and problems arising due to nonstationary are reviewed. Some of these methods are already in routine use in atmospheric radar experiments. Other methods based on the maximum entropy principle and time series models have been used in analyzing data, but are just beginning to receive attention in the analysis of radar signals. These methods are also briefly discussed

Time Series Analysis

We provide a concise overview of time series analysis in the time and frequency domains, with lots of references for further reading.time series analysis, time domain, frequency domain

Time Series Analysis

We provide a concise overview of time series analysis in the time and frequency domains, with lots of references for further reading.time series analysis, time domain, frequency domain, Research Methods/ Statistical Methods,

Log spectral estimation for stationary and nonstationary processes

Journal ArticleThis research is concerned with two log spectral estimators in the context of both stationary and nonstationary signals. They differ because in one smoothing is realized before the logarithmic transformation, while the other is smoothed in the logarithimc domain. It is shown that for stationary signals the two estimators are similar, differing in expected value by only a universal constant. The first estimator, however, is smoother. For nonstationary signals, the estimators are biased by different amounts dependent upon the nonstationarity. The difference between the estimators is shown to be a sensitive test for nonstationarity. The estimators are used in the analysis and implementation of two solutions to the problem of blind deconvolution. It is found that the methods are equivalent for stationary signals, bu differ markedly for nonstationary signals in the presence of stationary background noise. Recommendations are made for the practical digital implementation of the practical digital implementation of the log spectral estimators

STATISTICAL ANALYSIS OF EYE GAZE DATA

In this dissertation, we present analysis of eye gaze data in response to simple one-arm movements. We report the presence of long memory property in the eye gaze. Using this property, we model the eye gaze data. The best model involves present arm coordinates as well as lagged eye gaze and arm coordinates. Further analysis for classication of eye gaze under two conditions "Watch" and "Imitate" is presented. This analysis uses time domain and spectral domain methods. In the time domain, properties of higher order crossing (HOC) sequence is investigated for long memory processes. Further, we present its application to eye gaze data. The application reveals differences in the two conditions for some of the subjects. In the spectral domain, logarithmic ratio of spectral densities are assumed to follow either the exponential (EXP) or fractional exponential (FEXP) model form. By applying assumptions on the distribution of periodogram ordinates of long memory processes and using FEXP model, classication of long memory processes are studied using simulations. The results are compared when EXP models are also used. Both techniques are then applied for classication of eye gaze data

HADES RV Programme with HARPS-N at TNG VI. GJ 3942 b behind dominant activity signals

Short- to mid-term magnetic phenomena on the stellar surface of M-type stars cannot only resemble the effects of planets in radial velocity data, but also may hide them. We analyze 145 spectroscopic HARPS-N observations of GJ 3942 taken over the past five years and additional photometry to disentangle stellar activity effects from genuine Doppler signals as a result of the orbital motion of the star around the common barycenter with its planet. To achieve this, we use the common methods of pre-whitening, and treat the correlated red noise by a first-order moving average term and by Gaussian-process regression following an MCMC analysis. We identify the rotational period of the star at 16.3 days and discover a new super-Earth, GJ 3942 b, with an orbital period of 6.9 days and a minimum mass of 7.1 Me. An additional signal in the periodogram of the residuals is present but we cannot claim it to be related to a second planet with sufficient significance at this point. If confirmed, such planet candidate would have a minimum mass of 6.3 Me and a period of 10.4 days, which might indicate a 3:2 mean-motion resonance with the inner planet

Applications of nonuniform sampling in wideband multichannel communication systems

This research is an investigation into utilising randomised sampling in communication systems to ease the sampling rate requirements of digitally processing narrowband signals residing within a wide range of overseen frequencies. By harnessing the aliasing suppression capabilities of such sampling schemes, it is shown that certain processing tasks, namely spectrum sensing, can be performed at significantly low sampling rates compared to those demanded by uniform-sampling-based digital signal processing. The latter imposes sampling frequencies of at least twice the monitored bandwidth regardless of the spectral activity within. Aliasing can otherwise result in irresolvable processing problems, as the spectral support of the present signal is a priori unknown. Lower sampling rates exploit the processing module(s) resources (such as power) more efficiently and avoid the possible need for premium specialised high-cost DSP, especially if the handled bandwidth is considerably wide. A number of randomised sampling schemes are examined and appropriate spectral analysis tools are used to furnish their salient features. The adopted periodogram-type estimators are tailored to each of the schemes and their statistical characteristics are assessed for stationary, and cyclostationary signals. Their ability to alleviate the bandwidth limitation of uniform sampling is demonstrated and the smeared-aliasing defect that accompanies randomised sampling is also quantified. In employing the aforementioned analysis tools a novel wideband spectrum sensing approach is introduced. It permits the simultaneous sensing of a number of nonoverlapping spectral subbands constituting a wide range of monitored frequencies. The operational sampling rates of the sensing procedure are not limited or dictated by the overseen bandwidth antithetical to uniform-sampling-based techniques. Prescriptive guidelines are developed to ensure that the proposed technique satisfies certain detection probabilities predefined by the user. These recommendations address the trade-off between the required sampling rate and the length of the signal observation window (sensing time) in a given scenario. Various aspects of the introduced multiband spectrum sensing approach are investigated and its applicability highlighted