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Raised cosine filter-based empirical mode decomposition

IET signal processing 2011年第2期5卷 121-129页

作者： Roy, A. Doherty, J. F. Penn State Univ Dept Elect Engn University Pk PA 16802 USA

The empirical mode decomposition (EMD) is a relatively new method to decompose multicomponent signals that requires no a priori knowledge about the components. In this study, a modified algorithm using raised cosine interpolation is proposed which the authors refer to as raised cosine empirical mode decomposition. The decomposition quality of this proposed technique is controllable via an adjustable parameter. This results in better performance than the original approach which produces faster convergence or lower final error under different conditions. An efficient fast Fourier transform-based implementation of the proposed technique is presented. The signal decomposition performance of the new algorithm is demonstrated by application to a variety of multicomponent signals and a comparison with EMD algorithm is presented. Computational complexity of the two techniques is compared.

关键词： interpolation filtering methods in signal processing Interpolation and function approximation (numerical analysis) Integral transforms in numerical analysis empirical mode decomposition computational complexity fast Fourier transforms signal processing raised cosine interpolation multicomponent signal decompostion raised cosine filter filtering theory signal processing theory fast Fourier transform

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signal spectral modelling for airborne radar in the presence of windshear phenomena

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IET RADAR SONAR AND NAVIGATION 2011年第7期5卷 796-805页

作者： Moscardini, C. Berizzi, F. Martorella, M. Capria, A. Univ Pisa Dept Informat Engn I-56122 Pisa Italy CNIT Natl Interuniv Consortium Telecommun RaSS Natl Lab I-56124 Pisa Italy

A number of significant airplane accidents have resulted from windshear encounters during takeoff or landing. In these situations the radar signal received may be affected by a strong ground clutter that may make the conventional windshear detection algorithms implemented on ground-based systems unusable. Typically, the solution to this problem is to employ a clutter rejection filter and then process the filter output to derive weather information. In this study, a parametric bimodal spectral model of the raw radar signal from an airborne Doppler weather radar is proposed. The bimodal shape of the model has been defined as a superposition of clutter and windshear. The model can be used to define a windshear detection algorithm that can also directly estimate the physical weather parameters by using the estimated model parameters without using a clutter rejection pre-filter. Owing to the impossibility of testing a windshear detection system in a realistic environment, a simulated windshear data base has been developed by National Aeronautics and Space Administration (NASA) and Federal Aviation Administration (FAA) during their windshear research programme. The purpose of this study is to define a parametric bimodal spectral model and demonstrate its validity on the NASA-FAA windshear certification data set.

关键词： radar signal processing airplane accidents meteorological radar ground clutter clutter rejection pre-filter windshear detection system simulated windshear data windshear research programme bimodal shape conventional windshear detection algorithms windshear phenomena Doppler radar NASA-FAA windshear certification data set takeoff Radar equipment, systems and applications physical weather parameters National Aeronautics and Space Administration filtering methods in signal processing ground-based systems spectral analysis Atmospheric, ionospheric and magnetospheric techniques and equipment raw radar signal Federal Aviation Administration airborne Doppler weather radar landing windshear encounters clutter rejection filter signal spectral modelling estimated model parameters wind parametric bimodal spectral model radar clutter weather information General aspects of aircraft, space vehicles and satellites filtering theory airborne radar air accidents

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Robust adaptive L_∞-gain neural filtering for non-linear systems in the presence of bounded disturbances

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IET CONTROL THEORY AND APPLICATIONS 2011年第4期5卷 630-639页

作者： Wu, H. -N. Li, H. -X. Beijing Univ Aeronaut & Astronaut Beihang Univ Sci & Technol Aircraft Control Lab Sch Automat Sci & Elect Engn Beijing 100191 Peoples R China City Univ Hong Kong Dept Mfg Engn & Engn Management Kowloon Hong Kong Peoples R China

This study deals with the problem of robust adaptive L-infinity-gain neural filter design for a class of uncertain systems with unknown non-linearities and persistently bounded disturbances. A neural filter is constructed for the signal estimation of the system, where two radial basis function neural networks (NNs) are employed to approximate the estimates of the unknown non-linearities in the state dynamics and measurement equation of the system, respectively. The addressed problem is to design such a filter such that the state estimation error is uniformly ultimately bounded and the signal estimation error satisfies an L-infinity-gain performance. The linear matrix inequality (LMI)-based condition for the existence of a robust adaptive L-infinity-gain neural filter is provided. In the proposed filtering scheme, by using the orthogonal projection of the state estimation error onto the null space of the linear measurement distribution matrix, the weight update laws of NNs are represented in terms of the available measurement residual. Furthermore, using the existing LMI optimisation technique, a suboptimal neural filter can be obtained in the sense of minimising an upper bound of the L-infinity-gains. Finally, a simulation example is given to illustrate the effectiveness of the proposed design method.

关键词： signal processing theory radial basis function neural network Optimisation techniques filtering theory control nonlinearities adaptive control signal processing Digital signal processing signal estimation error suboptimal neural filter Stability in control theory measurement equation linear matrix inequality Nonlinear control systems state estimation bounded disturbance LMI optimisation technique signal estimation robust control Algebra Self-adjusting control systems state dynamics robust adaptive L∞ gain neural filtering nonlinear control systems nonlinear system filtering methods in signal processing uncertain systems linear matrix inequalities orthogonal projection linear measurement distribution matrix uncertain system optimisation Neural computing techniques radial basis function networks state estimation error

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Intra- and inter-frame prediction in bandwidth scalable coding of wideband speech

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IET signal processing 2011年第2期5卷 164-170页

作者： Song, G. -B. Samsung Elect Co Ltd Elect Examinat Div Elect & Elect Examinat Bur Taejon 302701 South Korea

This study discusses a predictive coding scheme that utilises both the intra-frame correlation (here referred to as redundancy between frequency bands) and inter-frame correlation in bandwidth scalable coding of wideband speech. Prediction error filters that combine intra-frame prediction with inter-frame prediction in a cascade connection are examined. Three representative intra-frame functions that have been developed in the area of bandwidth extension (BWE) are considered to see how well they exploit the intra-frame correlation. In addition, some resulting changes are investigated when they are combined with the predictive vector quantiser that exploits the inter-frame correlation. The performances of the Gaussian mixture model-based and hidden Markov model-based BWE functions are similar in the context of intra-frame coding, but both of them significantly outperform the linear BWE function in the same context. However, it is also observed that the linear function is the most promising in the context of the joint predictive coding of intra-frame and inter-frame. These results are supported by some statistical tests.

关键词： hidden Markov model bandwidth scalable coding correlation methods prediction error filters bandwidth extension quantisation (signal) wideband speech coding filtering methods in signal processing speech coding statistical testing intraframe coding Speech and audio coding Gaussian processes linear BWE function hidden Markov models Gaussian mixture model Speech processing techniques interframe correlation prediction predictive vector quantiser intraframe correlation prediction filtering theory predictive coding scheme Markov processes statistical tests

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Ultra-wideband quasi-self-complementary antenna with band-rejection capability

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IET MICROWAVES ANTENNAS & PROPAGATION 2011年第13期5卷 1613-1618页

作者： Lin, C-C. Huang, C-Y. Su, J-Y. Chinese Air Force Acad Dept Math & Phys Sci Kaohsiung 820 Taiwan Natl Kaohsiung Normal Univ Dept Elect Engn Kaohsiung 802 Taiwan

This study presents a printed quasi-self-complementary antenna fed by a 50 Omega microstrip line. A quarter-circular disc and a counterpart quarter-circular slot on the ground plane are used in ultra-wideband applications. It has been proved that the optimal design of the antenna configuration can generate an ultra-wide impedance bandwidth with reasonable radiating properties. Furthermore, with an inverted L-shaped slit embedded on the quarter-circular disc, good performance of band-rejection capability is achieved. This allows relaxation of filtering spectrum in the ratio frequency front-end. Details of the parameters and experimental results of the constructed prototypes are discussed.

关键词： radiating properties inverted I-shaped slit ultra wideband antennas ultrawideband quasi-self-complementary antenna band-rejection capability Antenna accessories antenna configuration ratio frequency front-end microstrip line microstrip antennas microstrip lines quarter-circular slot antenna UWB antenna filtering methods in signal processing printed antenna fed resistance 50 ohm Single antennas quarter-circular disc antenna impedance bandwidth slot antennas antenna radiation patterns filtering spectrum antenna feeds filtering theory

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Experimental analysis of various estimators for target range estimation in high resolution radars

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IET signal processing 2011年第7期5卷 680-689页

作者： Yildirim, A. TUBiTAK BiLGEM UEKAE Ankara Turkey

The author analyses the target range estimation errors in pulse compression high-resolution radars (HRRs). Conventional radar signal processors assume a point target model in matched filtering-based detection and tracking. The author demonstrates through simulations that the performance degradation, under the point target assumption, can be significant for HRRs, where targets extend across several detection cells. Also, the author models events of backscatters from illuminated target and clutter as a non-homogenous Poisson process (NHPP). The corresponding maximum likelihood, maximum a posteriori, minimum mean square error and minimum mean absolute error estimators are derived for range estimation. Typical target detection process has been simulated and the performance of NHPP-based estimators has been compared to that of the most commonly used peak estimators, namely, the maximum point and interpolation peak estimators. Simulation results show that the proposed estimators significantly reduce target range estimation errors in HRRs.

关键词： maximum likelihood estimator radar signal processor least mean squares methods clutter maximum likelihood estimation minimum mean absolute error estimator stochastic processes maximum point estimator nonhomogenous Poisson process target detection process NHPP Radar equipment, systems and applications matched filtering-based tracking radar resolution signal detection pulse compression HRR interpolation peak estimator maximum a posteriori estimator filtering methods in signal processing backscatter point target model matched filtering-based detection pulse compression high-resolution radar minimum mean square error estimator target range estimation error radar clutter Interpolation and function approximation (numerical analysis) object detection radar detection filtering theory Other topics in statistics

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Design of halfband filters for orthonormal wavelets using ripple-pinning

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IET signal processing 2011年第1期5卷 40-48页

作者： Tay, D. B. H. La Trobe Univ Dept Elect Engn Bundoora Vic 3086 Australia

The design of halfband filters for orthonormal wavelet with a prescribed number of vanishing moment and prescribed ripple amplitudes is described. The technique is an extension of the zero-pinning (ZP) technique and is called ripple-pinning (RP). In ZP, the positions of stopband minima (of a Bernstein polynomial) are specified explicitly and the stopband maxima (position and amplitude) depend implicitly on the minima. In RP, the amplitude of the ripples is explicitly specified and this leads to a set of non-linear (polynomial) equations with the position of both the minima and maxima as unknowns. An iterative algorithm is proposed to solve the equations and design examples will be presented. Two variations of the RP technique, which allow for the transition band sharpness to be explicitly specified, are also presented.

关键词： iterative methods filtering methods in signal processing Interpolation and function approximation (numerical analysis) stopband minima iterative algorithm halfband filter design nonlinear equation zero-pinning technique orthonormal wavelet wavelet transforms Nonlinear and functional equations (numerical analysis) Filters and other networks ripple-pinning nonlinear equations signal processing theory stopband maxima band-stop filters

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Improved parametric families of intersymbol interference-free Nyquist pulses using inner and outer functions

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IET signal processing 2011年第2期5卷 157-163页

作者： Assimonis, S. D. Matthaiou, M. Karagiannidis, G. K. Nossek, J. A. Aristotle Univ Thessaloniki Dept Elect & Comp Engn Thessaloniki 54124 Greece Tech Univ Munich Inst Circuit Theory & Signal Proc D-80333 Munich Germany Chalmers Dept Signals & Syst SE-41296 Gothenburg Sweden

In this article, the authors introduce and study the performance of two novel parametric families of Nyquist intersymbol interference-free pulses. Using only two design parameters, the proposed pulses yield an enhanced performance compared to the sophisticated flipped-inverse hyperbolic secant (asech) filter, which was recently documented in the literature. Although the construction of parametric families originates from the work of Beaulieu and Damen, the authors' approach is based on the concept of 'inner' and 'outer' functions and for this reason a higher flexibility in the choice of the family members is achieved. The proposed pulses may decay slower than the original raised-cosine (RC) pulse outside the pulse interval, but exhibit a more pronounced decrease in the amplitudes of the two largest sidelobes and this accounts for their improved robustness to error probabilities. It is clearly shown, via simulation results, that a lower bit error rate (BER), compared to the existing pulses, can be achieved for different values of the roll-off factor and timing jitter. Moreover, a smaller maximum distortion as well as a more open-eye diagram are attained which further demonstrate the superiority of the proposed pulse shaping filters.

关键词： Electromagnetic compatibility and interference open-eye diagram error probability bit error rate error statistics intersymbol interference-free Nyquist pulses intersymbol interference raised-cosine pulse outer functions timing jitter roll-off factor sophisticated flipped-inverse hyperbolic secant filter pulse shaping filters filtering methods in signal processing signal processing theory pulse shaping inner functions BER filtering theory jitter Other topics in statistics

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Metropolis Monte Carlo for tomographic reconstruction with prior smoothness information

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IET IMAGE processing 2011年第2期5卷 198-204页

作者： Barbuzza, R. Clausse, A. CNEA CONICET RA-7000 Tandil Argentina Univ Nacl Ctr RA-7000 Tandil Argentina

The Metropolis Monte Carlo algorithm was applied to produce tomographic reconstructions from scarce projection data supplemented by prior information about the smoothness of the object. The prior information is represented by means of local energy functions, which are added to the projection error. The proposed prior function is an extension of previous proposals of border filters, the novelty introduced here being an adaptive control of the filter during the reconstruction process. The method was tested on synthetic phantoms and the reconstructions of a real object from a small number of projections. The technique shows good results in images with piecewise homogeneous regions, and can be useful in certain applications, where the scanning views are within an angular range that is either limited or sparsely sampled, as the detection of material defects in non-destructive testing or special anatomical components in medical images. Finally, the method is applied to the reconstruction of an industrial application of a stainless-steel BNC elbow from very few projections.

关键词： local energy functions adaptive control stainless-steel BNC elbow computerised tomography filtering methods in signal processing metropolis Monte Carlo algorithm image reconstruction prior smoothness information Computer vision and image processing techniques production engineering computing Materials testing Optical, image and video signal processing stainless steel nondestructive testing steel industry scarce projection data Testing border filters Metallurgical industries object detection Computerised instrumentation Monte Carlo methods tomographic reconstructions filtering theory Industrial applications of IT Statistics material defect detection Production engineering computing

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Ground vehicle navigation in harsh urban conditions by integrating inertial navigation system, global positioning system, odometer and vision data

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IET RADAR SONAR AND NAVIGATION 2011年第8期5卷 814-823页

作者： Kim, S. -B. Bazin, J. -C. Lee, H. -K. Choi, K. -H. Park, S. -Y. Yonsei Univ Dept Astron Seoul 120749 South Korea Univ Tokyo Inst Ind Sci Ikeuchi Lab Tokyo 1538505 Japan Korea Aerosp Univ Dept Elect Engn Koyang City South Korea Mokpo Natl Univ Dept Elect Engn Cheonranamdo South Korea Natl Res Fdn Div Nucl R&D Management Taejon South Korea

Combining GPS/INS/odometer data has been considered one of the most attractive methodologies for ground vehicle navigation. In the case of long GPS signal blockages inherent to complex urban environments, however, the accuracy of this approach is largely deteriorated. To overcome this limitation, this study proposes a novel ground vehicle navigation system that combines INS, odometer and omnidirectional vision sensor. Compared to traditional cameras, omnidirectional vision sensors can acquire much more information from the environment thanks to their wide field of view. The proposed system automatically extracts and tracks vanishing points in omnidirectional images to estimate the vehicle rotation. This scheme provides robust navigation information: specifically by combining the advantages of vision, odometer and INS, we estimate the attitude without error accumulation and at a fast running rate. The accurate rotational information is fed back into a Kalman filter to improve the quality of the INS bridging in harsh urban conditions. Extensive experiments have demonstrated that the proposed approach significantly reduces the accumulation of position, velocity and attitude errors during simulated GPS outages. Specifically, the position accuracy is improved by over 30% during simulated GPS outages.

关键词： GPS filtering methods in signal processing inertial navigation system inertial navigation harsh urban condition Global Positioning System INS distance measurement Kalman filter ground vehicle navigation Kalman filters Radionavigation and direction finding omnidirectional vision sensor vision data urban environment Spatial variables measurement odometer omnidirectional image

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