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Ultra-wideband radar noise reduction for target classification

IET RADAR SONAR AND NAVIGATION 2008年第4期2卷 315-322页

作者： Hantscher, S. Reisenzahn, A. Diskus, C. G. Johannes Kepler Univ Linz Inst Microelect & Microsensors A-4040 Linz Austria

The authors describe a calibration procedure for ultra-wideband (UWB) radar systems in order to measure the frequency-dependent transfer function or radar cross-section, respectively, of objects with a high computational efficiency. The benefit of using UWB pulses is that only one measurement is required for covering several GHz. However, the signal processing steps contain a deconvolution operation producing spike artefacts. They were successfully removed by the calculation of frequency-dependent signal-to-noise ratio and a following Wiener filtering. The proposed method was verified by some elementary targets of which the size of the objects were determined.

关键词： radar signal processing radar cross-section deconvolution operation spike artefacts deconvolution Wiener filters transfer functions target classification Radar equipment, systems and applications calibration procedure UWB radar noise reduction filtering methods in signal processing ultra wideband radar systems Wiener filtering ultra wideband radar signal processing radar cross-sections signal classification frequency-dependent transfer function

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Extended Kalman filter for estimating aircraft orientation from velocity measurements

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IET RADAR SONAR AND NAVIGATION 2008年第1期2卷 12-16页

作者： Ehrman, L. M. Lanterman, A. D. Georgia Inst Technol Sch Elect & Comp Engn Atlanta GA 30332 USA

A coordinated flight model for estimating the orientation of an aircraft under track from velocity measurements into an extended Kalman filter (EKF) framework is placed here. In doing so, it makes two contributions. First, the EKF provides a rigorous framework for addressing this problem, blending modelling error and measurement error. Second, the EKF supplements the estimated orientation with a measure of the uncertainty in that estimate. Such estimates of uncertainty are crucial in a number of applications, including using the orientation estimates to approximate the radar cross section of the aircraft under track, in an attempt to identify targets. The EKF's performance is demonstrated using both a straight-and-level manoeuvre and a complicated manoeuvre recorded on-board a manoeuvring F-15. In both cases, the state estimates of the EKF are similar to the results obtained from a coordinated flight model. The true orientations almost always fall within one standard deviation of the estimates, as determined by the estimated covariance.

关键词： measurement errors extended kalman filter Velocity, acceleration and rotation measurement state estimation velocity measurements filtering methods in signal processing aircraft Filters and other networks measurement error aircraft orientation radar cross section Kalman filters radar applications Radar equipment, systems and applications blending modelling error standard deviation velocity measurement

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New block filtered-X LMS algorithms for active noise control systems

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IET signal processing 2007年第2期1卷 73-81页

作者： Das, D. P. Panda, G. Kuo, S. M. Cent Elect Engn Res Inst Digital Syst Grp Pilani 333031 Rajasthan India Natl Inst Technol Dept Elect & Commun Engn Rourkela 769008 Orissa India No Illinois Univ Dept Elect Engn De Kalb IL 60115 USA

New block formulations for an active noise control (ANC) system using only convolution machines are presented. The proposed approaches are different from conventional block least-mean-square (LMS) algorithms that use both convolution and cross-correlation machines. The block implementation is also applied to the filtering of the reference signal by the secondary path estimate. In addition to the use of the fast Fourier transform (FFT), the fast Hartley transfonn (FHT) is used to develop transform-domain ANC structures for reducing computational complexity. In the proposed approach, some FFT and FHT blocks are removed to obtain an additional reduction of the computational burden resulting in the reduced-structure of FFT-based block filtered-X LMS (FBFXLMS) and FHT-based block filtered-X LMS (HBFXLMS) algorithms. The computational complexities of these new ANC structures are evaluated.

关键词： Digital signal processing Integral transforms FHT convolution filtering methods in signal processing active noise control systems computational complexity fast Fourier transforms fast Hartley transform block filtered-X LMS algorithms active noise control fast Fourier transform filtering theory secondary path estimate FFT ANC system convolution machines

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Mathernatical-morphology-based edge detectors for detection of thin edges in low-contrast regions

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IET IMAGE processing 2007年第3期1卷 269-277页

作者： Jiang, J.-A. Chuang, C.-L. Lu, Y.-L. Fahn, C.-S. Natl Taiwan Univ Dept Bioind Mechatron Engn Taipei 106 Taiwan Natl Taiwan Univ Sci & Technol Dept Comp Sci & Informat Engn Taipei 106 Taiwan Natl Taiwan Univ Inst Biomed Engn Taipei 106 Taiwan

A new edge detector based on mathematical morphology to preserve thin edge features in low-contrast regions as well as other apparent edges is proposed. A quad-decomposition edge enhancement process, a thresholding process, and a mask-based noise filtering process were developed and used to enhance thin edge features, extract edge points and filter out some meaningless noise points, respectively. Moreover, five bipolar oriented edge masks were also designed to remove most of the incorrectly detected edge features. Many experiments were conducted to evaluate and compare the performance of the proposed algorithm and several conventional ones. Pratt's figure of merit achieved by the proposed algorithm was as high as 92.5. The comprehensive experimental results show that the proposed algorithm is capable of preserving thin edge details successfully in low-contrast regions and is robust against noise.

关键词： filtering theory edge detection Computer vision and image processing techniques mask-based noise filtering process quad-decomposition edge enhancement process mathematical-morphology-based edge detector Pratt figure mathematical morphology bipolar oriented edge mask filtering methods in signal processing image enhancement low-contrast region thresholding process Optical, image and video signal processing image segmentation

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Weighted least squares near-equiripple approximation of variable fractional delay FIR filters

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IET signal processing 2007年第2期1卷 66-72页

作者： Liu, J.-C. You, S.-J. Tatung Univ Dept Elect Engn Taipei Taiwan

The weighted least squares (WLS) method is a well-known method for designing a finite impulse response (FIR) filter. And some authors have reported that if a suitable frequency response weighting function is used to design the filter, the WLS method can produce an equiripple result. However, the weighting function for minimax optimality of WLS design is hard to derive analytically. By an iterative method with an adjustable elaborately constructed weighting function, this idea is extended to design a near-equiripple variable fractional delay FIR filter. The proposed method is superior to the fixed-weighting WLS design in the peak absolute error by about 6.6874 dB. The algorithm converges very rapidly. From the simulation, it typically produces a design which is only about 1 dB away from the truly equiripple solution in two iterations and converges to within 0.0056 dB in eight iterations.

关键词： frequency response finite impulse response filter Digital signal processing filtering methods in signal processing delay filters minimax optimality signal processing theory Interpolation and function approximation (numerical analysis) least squares approximations frequency response weighting function WLS method variable fractional delay FIR filters equiripple filters FIR filters iterative method weighted least squares near-equiripple approximation

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Knowledge-based recursive least squares techniques for heterogeneous clutter suppression

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IET RADAR SONAR AND NAVIGATION 2007年第2期1卷 106-115页

作者： De Maio, A. Farina, A. Foglia, G. Univ Naples Federico 2 Dipartimento Ingn Elettron & Telecommun I-80125 Naples Italy Alenia Marconi Syst I-00131 Rome Italy Elettron SpA I-00131 Rome Italy

The design of knowledge-based adaptive algorithms has been dealt with for the cancellation of heterogeneous clutter. To this end, the application of the recursive least squares (RLS) technique has been revisited for the rejection of unwanted clutter, and modified RLS filtering procedures have been devised accounting for the spatial variation of the clutter power as well as of the disturbance covariance persymmetry property. Then the authors introduce the concept of knowledge-based RLS and explain how the a priori knowledge about the radar operating environment can be adopted for improving the system performance. Finally, the authors assess the benefits resulting from the use of knowledge-based processing both on simulated and on measured clutter data collected by the McMaster IPIX radar in November 1993.

关键词： radar signal processing recursive least squares technique Radar theory apriori knowledge filtering methods in signal processing radar clutter radar operating environment Interpolation and function approximation (numerical analysis) adaptive filters least squares approximations knowledge-based adaptive algorithm RLS filtering heterogeneous clutter cancellation recursive filters interference suppression

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Cornputationally fast techniques to reduce AWGN and speckle in videos

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IET IMAGE processing 2007年第4期1卷 319-334页

作者： Sen, D. Swamy, M. N. S. Ahmad, M. O. Concordia Univ Dept Elect & Comp Engn Montreal PQ H3G 1M8 Canada

Fast schemes to reduce additive white Gaussian noise (AWGN) and speckle in videos are presented. The proposed schemes use a change detection technique to measure the interframe motion and carry out estimations in both the spatial and temporal directions of the video. In the case of AWGN reduction, the well-known edge adaptive Wiener filter is used to perform the spatial estimation. Two different filters to carry out temporal estimation are presented based on novel weighted scalar Kalman and weighted running average filters, respectively. These temporal estimators are a)plied on the spatial estimate to obtain the spatiotemporal estimate. A new method is then used to appropriately combine the spatial and spatiotemporal estimates in order to obtain the final estimate of the uncorrupted signal. To achieve speckle reduction, we use an unbiased homomorphic system. that comprises an edge adaptive filter for spatial estimation and the weighted running average filter for temporal estimation. The effectiveness of the various proposed algorithms is demonstrated and compared with that of some of the existing schemes through extensive simulations. It is found that the use of a change detection technique, instead of the popularly used complex motion estimation and compensation technique, to measure the interframe motion results in a considerable reduction of processing time. The proposed schemes perform equally well or better than an the existing schemes in reducing the noise in videos.

关键词： motion compensation filtering methods in signal processing change detection technique weighted running average filter video signal processing spatiotemporal estimation unbiased homomorphic system interframe motion estimation weighted scalar Kalman filter motion estimation Optical, image and video signal processing speckle Wiener filters AWGN reduction speckle reduction AWGN edge adaptive Wiener filter spatial estimation adaptive Kalman filters Video signal processing temporal estimation additive white Gaussian noise

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Using fractional delay to control the magnitudes and phases of integrators and differentiators

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IET signal processing 2007年第2期1卷 107-119页

作者： Al-Alaoui, M. A. Amer Univ Beirut Dept Elect & Comp Engn Beirut Lebanon

The use of fractional delay to control the magnitudes and phases of integrators and differentiators has been addressed. Integrators and differentiators are the basic building blocks of many systems. Often applications in controls, wave-shaping, oscillators and communications require a constant 90 degrees phase for differentiators and -90 degrees phase for integrators. When the design neglects the phase, a phase equaliser is often needed to compensate for the phase error or a phase lock loop should be added. Applications to the first-order, Al-Alaoui integrator and differentiator are presented. A fractional delay is added to the integrator leading to an almost constant phase response of -90 degrees. Doubling the sampling rate improves the magnitude response. Combining the two actions improves both the magnitude and phase responses. The same approach is applied to the differentiator, with a fractional sample advance leading to an almost constant phase response of 90 degrees. The advance is, in fact, realised as the ratio of two delays. Filters approximating the fractional delay, the finite impulse response (FIR) Lagrange interpolator filters and the Thiran allpass infinite impulse response (IIR) filters are employed. Additionally, a new hybrid filter, a combination of the FIR Lagrange interpolator filter and the Thiran allpass IIR filter, is proposed. methods to reduce the approximation error are discussed.

关键词： Al-Alaoui integrator delays fractional delay phase response filtering methods in signal processing Thiran allpass infinite impulse response filters finite impulse response Lagrange interpolator filters IIR filters hybrid filter FIR filters magnitude response Thiran allpass IIR filters FIR Lagrange interpolator filters Al-Alaoui differentiator signal processing theory sampling rate

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Impact of channel sounder phase noise on directional channel estimation by space-alternating generalised expectation maximisation

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IET MICROWAVES ANTENNAS & PROPAGATION 2007年第3期1卷 803-808页

作者： Taparugssanagorn, A. Alatossava, M. Holappa, V.-M. Ylitalo, J. Univ Oulu Ctr Wireless Commun FIN-90014 Oulu Finland

Multi-input multi-output (MIMO) radio channel sounders commonly employ time-division multiplexing (TDM) technique to switch between transmit and receive antennas. The TDM method offers single-input single-output sounders the MIMO capability in a cost-effective manner. However, the TDM approach leads to errors in MIMO channel measurements because of phase noise in local oscillators. Phase noise varies in the short term during the switching sequence for a MIMO channel sample. The high-resolution space-alternating generalised expectation maximisation (SAGE) algorithm has been efficiently applied for the estimation of the channel parameters. The impact of phase noise on the directional channel parameters, which are estimated by the SAGE algorithm, has been studied. Although the previous studies have investigated long-term random walk noise, we concentrate on the short-term noise which affects consecutive MIMO channel matrix measurements. It has been shown that errors in direction of arrival and direction of departure estimation because of the short-term phase noise can be effectively decreased by time domain filtering of the impulse responses prior to the SAGE processing.

关键词： space-alternating generalised expectation maximisation Communication switching multiinput multioutput radio channel expectation-maximisation algorithm Linear algebra (numerical analysis) directional channel estimation Other topics in statistics time-division multiplexing wireless channels channel estimation local oscillator direction-of-departure estimation random walk noise time-domain analysis impulse response filtering methods in signal processing TDM technique random noise single-input single-output sounder channel sounder phase noise high-resolution SAGE algorithm antenna arrays Antenna arrays transmitting antenna Interpolation and function approximation (numerical analysis) transient response Radio links and equipment time division multiplexing phase noise Communication channel equalisation and identification time domain filtering filtering theory direction-of-arrival estimation MIMO channel matrix measurement MIMO communication receive antenna

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MCMC methods for tracking two closely spaced targets using monopulse radar channel signals

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IET RADAR SONAR AND NAVIGATION 2007年第3期1卷 221-229页

作者： Isaac, A. Willett, P. Bar-Shalom, Y. Univ Connecticut Dept Elect & Comp Engn Storrs CT 06269 USA

Four techniques to successfully track two closely spaced and unresolved targets using monopulse radar measurements have been discussed, the quality of such tracking being a determinant of successful detection of target spawn. The paper explores statistical estimation techniques based on the maximum likelihood criterion and Gibbs sampling, and addresses concerns about the accuracy of the measurements delivered thereby. In particular, the Gibbs approach can deliver joint measurements ( and the associated covariances) from both targets, and it is therefore natural to consider a joint filter. The ideas are compared, and among the various strategies discussed, a particle filter that operates directly on the monopulse measurements seems to be the best.

关键词： maximum likelihood estimation filtering methods in signal processing radar tracking monopulse radar channel signals Gibbs sampling joint filter matrix algebra statistical estimation techniques Radar equipment, systems and applications target tracking tracking targets Monte Carlo methods maximum likelihood criterion particle filtering (numerical methods) Algebra Markov processes particle filter Markov chain Monte Carlo method

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