Matched Filter Research Papers - Academia.edu (original) (raw)

Although current literature abounds in a variety of edge detection algorithms, they do not always lead to acceptable results in extracting various features in an image. In this paper, we address the problem of detecting blood vessels in retinal images. Blood vessels nsually have poor local contrast and the application of existing edge detection algorithms yield results which are not satisfactory. We introduce an operator for feature extraction based on the optical and spatial properties of objects to be recognized. The gray-level profile of the cross section of a blood vessel is approximated by a Gaussian shaped curve. The concept of matched filter detection of signals is used to detect piecewise linear segments of blood vessels in these images. We construct 12 different templates that are used to search for vessel segments along all possible directions. We discuss various issues related to the implementation of these matched filters. The results are compared to those obtained with other methods. The automatic detection of blood vessels in the retina could help physicians in diagnosing ocular diseases.

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- Engineering, Medical Imaging, Edge Detection, Piecewise Linear
- by sohail sheikh
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- Computer Science, Image Processing, Signal Processing, Nonlinear Optics

An approach to watermarking digital signals using frequency modulation-'Chirp Coding'-is considered. The principles underlying this approach are based on the use of a matched filter to reconstruct a 'chirp stream'code that is uniquely robust. The method is generic in the sense that it can, in principle, be used for a variety of different signal (the authentication of speech and biomedical signals, for example). Further, by generating a bit stream that is signal dependent, chirp coding provides a method of self-authentication, ...

- by Jonathan Blackledge
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- New Media, Signal Processing, Audio Signal Processing, Digital Watermarking
- by Tapio A Saramäki
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- Synchronization, Sampling methods, Mean square error, Matched Filter

This paper presents a unified framework, based on the generalized likelihood (GL), for the detection of targets and the estimation of their direction of arrival (DoA), when operating with modern radar systems that have general antenna array configurations, which contain a mixture of high- and low-gain beams. Adaptive processing structures are presented to remove both side lobe and main lobe

- by Pierfrancesco Lombardo
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- Engineering, Computer Science, Technology, Signal Processing

Currently, a major difficulty for the widespread use of robots in assembly and material handling comes from the necessity of feeding accurately positioned workpieces to robots. ``Bin picking'' techniques help reduce this constraint. This paper presents the application of matched filters for enabling robots with vision to acquire workpieces randomly stored in bins. This approach complements heuristic methods already reported. The concept of matched filter is an old one. Here, however, it is redefined to take into account robot end-effector features, in terms of geometry and mechanics. In particular, the proposed filters match local workpiece structures where the robot end-effector is likely to grasp successfully and hold workpieces. The local nature of the holdsites is very important as computation costs are shown to vary with the fifth power of structure size. In addition, the proposed filters tend to have a narrow angular bandwidth. An example, which features a parallel-jaw hand is developed in detail, using both statistical and Fourier models. Both approaches concur in requiring a very small number of filters (typically four), even if a good orientation accuracy is expected (two degrees). Success rates of about 90 percent in three or fewer attempts have been experimentally obtained on a system which includes a small minicomputer, a 128 Ã 128 pixel solidstate camera, a prototype Cartesian robot, and a ``universal'' parallel-jaw hand.

- by Henrique Martins
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- Information Systems, Computational Geometry, Robot Vision, Crime scene analysis

We present the first New Zealand-wide study of surface wave dispersion, using ambient noise observed at 42 broad-band stations in the national seismic network (GeoNet) and the Global Seismic Network (GSN). Year-long vertical-component time-series recorded between 2005 April 1 and 2006 March 31 have been correlated with one another to yield estimated fundamental mode Rayleigh wave Green's functions. We filter these Green's functions to compute Rayleigh wave group dispersion curves at periods of 5-50 s, using a phase-matched filter, frequency-time analysis technique. The uncertainties of the measurements are estimated based on the temporal variation of the dispersion curves revealed by 12 overlapping 3-month stacks. After selecting the highest quality dispersion curve measurements, we compute group velocity maps from 7 to 25 s period. These maps, and 1-D shear wave velocity models at four selected locations, exhibit clear correlations with major geological structures, including the Taranaki and Canterbury Basins, the Hikurangi accretionary prism, and previously reported basement terrane boundaries.

- by Martha Savage
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- Geology, Geophysics, Time Series, Timing Analysis

This paper discusses about design of common wireless communication services recognition for three different standards, i.e. Global System for Mobile Communications (GSM), Universal Mobile Telecommunications System (UMTS) or Wideband Code division Access (WCDMA), and Long Term Evolution (LTE), also known well as 2G, 3G, and 3.9G respectively. To recognize them using a common system, we propose performing within synchronization channel detection since the similarity in cell search procedures i.e. always detect synchronization signals. To minimize resources, we prefer using autocorrelation to detect GSM and LTE synchronization signals and match filter for UMTS synchronization signal. However, it is not enough to distinguish each others. Therefore, we also propose to recognize the peak period of the autocorrelation output as a main concept to distinguish the standards. We design this system using symplify DSP tool and simulate in simulink. The simulations are performed within AWGN channel and show good performance even with 10 dB SNR. Moreover, FPGA implementation for target device Virtex 4 XC4VLX200, the proposed design can be implemented within 24171 look up tables (LUTs).

The conventional receiver for DS-CDMA communications is the RAKE receiver which is a matched filter (MF), matched to the operations of spreading, pulse shape filtering and channel filtering. The RAKE receiver assumes a sparse/pathwise channel model so that the channel matched filtering gets done pathwise, with delay adjustment and decorrelation per path and maximum-ratio combining of path contributions at the symbol rate. Original RAKE receivers work with continuous delays, which are tracked by an Early-Late scheme. This requires signal interpolation and leads to suboptimal treatment of diffuse portions in the channel impulse response. These disadvantages can be avoided by a discrete-time RAKE, operating at a certain oversampled rate. Proper sparse modeling of the channel is an approximation problem that requires exploitation of the limited bandwidth of the pulse shape. We propose and simulate a number of sparse channel approximation algorithms along the lines of Matching Pursuit, of which the Recursive Early-Late (REL) approach appears most promising. We also analyze and simulate the effect of channel estimation on the RAKE output SINR.

- by Massimiliano Lenardi
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- Channel Estimation, Matched Filter, Channel model, Rake receiver

Baseline (USBL) tightly-coupled integration technique to enhance error estimation in low-cost strapdown Inertial Navigation Systems (INSs) with application to underwater vehicles. In the proposed strategy the acoustic array spatial information is directly exploited resorting to the Extended Kalman Filter implemented in a direct feedback structure. The determination and stochastic characterization of the round trip travel time are obtained resorting to pulse detection matched filters of acoustic signals modulated using spread-spectrum Code Division Multiple Access (CDMA). The performance of the overall navigation system is assessed in simulation and compared with a conventional loosely-coupled solution that consists of solving separately the triangulation and sensor fusion problems. From the simulation results it can be concluded that the proposed technique enhances the position, orientation, and sensors biases estimates accuracy.

- by Paulo Oliveira
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- Spread Spectrum, Spatial Information, Sensor Fusion, Matched Filter

This paper presents recent results in the development of novel ultrafast technologies based on the generation and application of stabilized optical frequency combs. By using novel active resonant cavity injection locking techniques, filtering, modulation and detection can be performed directly on individual components of the frequency comb enabling new approaches to optical waveform synthesis, waveform detection and matched filtering, with effective signal processing bandwidths in excess of 1 THz.

- by Peter Delfyett
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- Quantum Physics, Signal Processing, Ultrafast Optics, Matched Filter

Nous traitons du problème de l'intégration longue pour la détection de cible mobile dans le contexte applicatif radar, à partir de données non-cohérentes et cohérentes en Doppler. Nous présentons les résultats de plusieurs techniques d'intégration longue qui sont considérées comme des extensions de filtre adapté classique. Nous étendons également la transformée de Radon au cas Doppler. Nous avons mis en oeuvre et testé, en terme de performance, différentes classes d'algorithme d'intégration longue. Pour chaque méthode, nous donnons les avantages et les inconvénients de leur emploi dans le cadre applicatif radar.

- by Frederic Barbaresco
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- Algorithm, Matched Filter

PWM AC drives generate high differential mode motor voltages due to the reflected wave phenomenon. The common-mode voltage produced by a PWM inverter also has fast transitions that result in high peak currents to ground. For low power AC drives this can present several issues, such as pump-up of the DC bus and failure of the power module due to high instantaneous currents that are often undetected because of the typical sampling algorithm used. In this paper, existing drive output filter solutions are reviewed and a new filter design is presented, which has integrated differential-mode and common-mode impedance with damping matched to typical cable surge impedance. This eliminates reflections of both differential-mode and common-mode traveling waves, and also reduces peak cable charging currents. Experimental results are provided to demonstrate that the new filter has improved performance to reduce motor differential-mode and common-mode voltage, and drive output common-mode current, thus mitigating the issues specifically seen with low power AC drives. Complete design details for the filter and a particular implementation of the integrated differential-mode and common-mode reactor are also presented.

- by Todd Shudarek
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- Engineering, Sampling methods, Matched Filter, Filter Design

Applications of digital signal processing in telecommunications are considered, taking into account the characteristics of telecommunications systems, aspects of digital transmission, digital switching, digital signal processing in... more

In the modern age, High-resolution radar images can be achieved by employing SAR technique. It is well known that SAR can provide several times better image resolution than conventional radars. The exploration for efficient image denoising methods still remains a valid challenge for researchers. Despite the difficulty of the recently proposed methods, mostly of the algorithms have not yet attained a pleasing level of applicability; each algorithm has its assumptions, advantages, and limitations. This paper presents a review of synthetic aperture radar. Behind a brief introduction in our work we are especially targeting the noise called backscattered noise in SAR terminology which causes the appearance of speckle Potential future work in the area of air flight navigation, mapping Weather Monitoring & during natural disaster like earth quake. The SAR having the capability, to make human visibility beyond optical vision, is also discussed.

This article addresses the development of and recent advances in the rapidly growing jield of optical pattem recognition. In optical pattern recognition there are two basic approaches; namely, matched filtering and associative memories. The first employs optical correlator architectures and the latter uses optical neural networks (NN's). This paper reviews various types of optical correlators and NN's applied to real-time pattern recognition and autonomous tracking. Techniques of scale and rotational invariant jiltering are also given. Recent approaches using wavelet transfom filtering, phase only jiltering, high capacity composite filters, and phase representation f o r improvement in pattern discrimination are also provided.

- by Don Gregory
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- Biomedical Engineering, Pattern Recognition, Neural Networks, Neural Network

Dans le Haut Atlas marocain, les formations rouges d'âge permo-triasique ou postérieur constituent une source potentielle d'érosion et de risques naturels du fait de leur dominance argileuse. L'objectif de cette étude est de voir si la richesse en information spectrale et spatiale du capteur ASTER peut mettre en évidence ces formations. L'approche développée consiste en une caractérisation des différents faciès à l'aide des données de haute résolution spectrale prises sur le terrain avec un spectroradiomètre, ainsi que des données de réflectance au sol du capteur ASTER calibrées par rapport aux spectres acquis au sol. Les rapports de bandes et les indices spectraux du visible et de l'infrarouge moyen appliqués à l'image ont montré la richesse en oxydes de fer (hématite, goethite) et la dominance argileuse de ces faciès. L'analyse spectrale par correspondance (Matched Filtering) appliquée en utilisant des signatures prototypes prises sur l'image en référence aux points de mesure a permis une cartographie des différents faciès de la zone. Les résultats ont permis de déterminer la minéralogie dominante dans ces formations, qui est constituée essentiellement d'illite. La cartographie basée sur les rapports de bandes, les indices spectraux et l'analyse spectrale a permis l'identification des zones à haut potentiel d'érosion hydrique. La confrontation à la réalité de terrain et à une carte géologique précise a montré le potentiel des données d'ASTER à identifier ces formations. L'hétérogénéité du milieu rend cependant la tâche un peu difficile avec la végétation éparse et le degré d'altération des roches.

- by Kamal Taj-Eddine
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- Spectral analysis, Iron Oxide, Natural hazard, Matched Filter

- by Taj-Eddine Kamal
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- Spectral analysis, Iron Oxide, Natural hazard, Matched Filter

Software defined radios ( S D R ) are highly configurable hardware platforms that provide the technology for realizing the rapidly expanding third (and future) generation digital wireless communication infrastructure. Many sophisticated signal processing tasks are performed in a SDR, including advanced compression algorithms, power control, channel estimation, equalization, forward error control and protocol management. While there is a plethora of silicon alternatives available for implementing the various functions in a S D R , field programmable gate arrays (FPGAs) are a n attractive option for m a n y of these tasks for reasons of performance, power consumption and configurability. Amongst the more complex tasks performed in a high data rate wireless system is synchronization. This paper is about carrier and timing synchronization in SDRs using FPGA based signal processors. W e describe and examine a QPSK Costas loop for performing coherent demodulation, and report o n the implications of a n FPGA mechanization. Symbol timing recovery is addressed using a differential matched filter control system. A tutorial style approach is adopted to describe the operation of the timing recovery loop and considerations for FPGA implementation are outlined. 195 0-7695-0871-5/00 $10.00 0 2000 IEEE

If several closely spaced targets fall within the same radar beam and between two adjacent matched filter samples in range, monopulse information from both of these samples can and should be used for estimation, both of angle and of range (i.e., estimation of the range to sub-bin accuracy). Similarly, if several closely spaced targets fall within the same radar beam and among three matched filter samples in range, monopulse information from all of these samples should be used for the estimation of the angles and ranges of these targets. Here, a model is established, and a maximum likelihood (ML) extractor is developed. The limits of the number of targets that can be estimated are given for both case A, where the targets are in a beam and in a range "slot" between the centers of two adjacent resolution cells (that is, from detections in two adjacent matched filter samples), and case B, where the targets are in two or more adjacent slots (among three or more adjacent samples). A minimum description length (MDL) criterion is used to detect the number of targets between the matched filter samples, and simulations support the theory.

- by Peter Willett
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- Data Mining, Multidisciplinary, Maximum Likelihood, Monopulse Radar

This contribution treats the simulation of pulse Doppler radar system by using PC and MATLAB Simulink. The simulator has been implemented through hardware represented in the AT computer interface card while the software was build with C++ language. The phase detector unit was built using MATLAB Simulink programs. Various MTI systems were studied and sample results for single canceller and matched filtering are shown.

- by Khalil Sayidmarie
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- System Simulation, Matched Filter, Doppler Radar, PHASE DETECTOR

For a non-coherent MIMO radar system, the maximum likelihood estimator (MLE) of the target location and velocity, as well as the corresponding CRLB matrix, is derived. MIMO radar's potential in localization and tracking performance is... more

- by Rick S Blum
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- Aerospace Engineering, Signal Processing, Target Tracking, Kalman Filter

We review our understanding of the electrical properties of the lower and upper atmosphere along with various possible sources of the electromagnetic energy near and far above the Earth's surface. The transport of electromagnetic energy from the atmosphere to the ionosphere and then to the magnetosphere and back to the Earth's surface via ionosphere and lower atmosphere is discussed. The electromagnetic coupling of various regions is also discussed. r

- by Rajesh Singh
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- Atmospheric Science, Parameter estimation, Matched Filter, Fine Structure Constant

A novel switched excitation method for linear frequency modulated excitation of ultrasonic transducers in pulse compression systems is presented that is simple to realise, yet provides reduced signal sidelobes at the output of the matched filter compared to bipolar pseudochirp excitation. Pulse compression signal sidelobes are reduced through the use of simple amplitude tapering at the beginning and end of the excitation duration. Amplitude tapering using switched excitation is realised through the use of intermediate voltage switching levels, half that of the main excitation voltages. In total five excitation voltages are used creating a quinary excitation system. The absence of analogue signal generation and power amplifiers renders the excitation method attractive for applications with requirements such as a high channel count or low cost per channel. A systematic study of switched linear frequency modulated excitation methods with simulated and laboratory based experimental verification is presented for 2.25 MHz non-destructive testing immersion transducers. The signal to sidelobe noise level of compressed waveforms generated using quinary and bipolar pseudo-chirp excitation are investigated for transmission through a 0.5 m water and kaolin slurry channel. Quinary linear frequency modulated excitation consistently reduces signal sidelobe power compared to bipolar excitation methods. Experimental results for transmission between two 2.25 MHz transducers separated by a 0.5 m channel of water and 5% kaolin suspension shows improvements in signal to sidelobe noise power in the order of 7-8 dB. The reported quinary switched method for linear frequency modulated excitation provides improved performance compared to pseudo-chirp excitation without the need for high performance excitation amplifiers.

- by Steven Freear
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- Materials Engineering, Mechanical Engineering, Algorithms, Data Compression

Dynamic loading constraints due to maneuver and gust loads are an important design consideration for novel aircraft configurations. Incorporating these constraints in the early design process with an appropriate level of fidelity presents a significant challenge, due both to the need for more detailed aerodynamics and control modeling, and to the stochastic nature of the gust encounter problem. This paper presents a stochastic gust analysis approach that is suitable for a multidisciplinary design optimization setting that incorporates dynamic loading constraints. The analysis approach employs Lyapunov and matched filter theory methods to address the stochastic nature of the gust response. A set of gust simulation studies are carried out to assess the relative importance of the various physics involved in aircraft gust encounters and the effects of different modeling assumptions. The study demonstrates the importance of modeling rigid body motion, pitch dynamics, and aircraft flexibility, but shows that for gust encounters at typical flight conditions, a quasisteady aerodynamics assumption is reasonable for load predictions over the majority of the wing acerage, meaning that full unsteady aerodynamic simulations are likely not required for typical gust lengths.

In the global positioning system (GPS), code acquisition involves searching all possible code-phase candidates for the existence of satellites. Although code-phase search using a matched filter (MF) is efficient for one satellite, computational complexity increases if numerous satellites have to be searched simultaneously. In this study, a low-complexity routing correlator (RC) that can acquire multiple satellites is proposed. The rationale behind the RC is to fully utilise partial correlation values, which are by-products during the code acquisition process. Traditionally, each satellite's partial correlation values are instantly summed to decide its existence only. The partial correlation values in the RC, in contrast, can be shared to derive the correlation results of multiple satellites. By sharing and reusing these temporary correlation values, the proposed RC can simultaneously tackle multiple satellites and output the corresponding correlation results, as if there are multiple MFs operating at the same time. In addition, using the RC will not degrade the signal-to-noise ratio. A low-complexity acquisition unit employing the RC for GPS coarse/acquisition (C/A) codes is demonstrated, and the simulation results show that the computational complexity is reduced by about 94%, compared to the conventional MFs.

The goal of this research is to map land cover patterns and to detect changes that occurred at Alkali Flat and Lake Lucero, White Sands using multispectral Landsat 7 Enhanced Thematic Mapper Plus (ETM+), Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Advanced Land Imager (ALI), and hyperspectral Hyperion and Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data. The other objectives of this study were: (1) to evaluate the information dimensionality limits of Landsat 7 ETM+, ASTER, ALI, Hyperion, and AVIRIS data with respect to signal-to-noise and spectral resolution, (2) to determine the spatial distribution and fractional abundances of land cover endmembers, and (3) to check ground correspondence with satellite data. A better understanding of the spatial and spectral resolution of these sensors, optimum spectral bands and their information contents, appropriate image processing methods, spectral signatures of land cover classes, and atmospheric effects are needed to our ability to detect and map minerals from space. Image spectra were validated using samples collected from various localities across Alkali Flat and Lake Lucero. These samples were measured in the laboratory using VNIR-SWIR (0.4-2.5 m) spectra and X-ray Diffraction (XRD) method. Dry gypsum deposits, wet gypsum deposits, standing water, green vegetation, and clastic alluvial sediments dominated by mixtures of ferric iron (ferricrete) and calcite were identified in the study area using Minimum Noise Fraction (MNF), Pixel Purity Index (PPI), and n-D Visualization. The results of MNF confirm that AVIRIS and Hyperion data have higher information dimensionality thresholds exceeding the number of available bands of Landsat 7 ETM+, ASTER, and ALI data. ASTER and ALI data can be a reasonable alternative to AVIRIS and Hyperion data for the purpose of monitoring land cover, hydrology and sedimentation in the basin. The spectral unmixing analysis and dimensionality eigen analysis between the various datasets helped to uncover the most optimum spatial-spectral-temporal and radiometric-resolution sensor characteristics for remote sensing based on monitoring of seasonal land cover, surface water, groundwater, and alluvial sediment input changes within the basin. The results demonstrated good agreement between ground truth data and XRD analysis of samples, and the results of Matched Filtering (MF) mapping method. G: dry gypsum; G1: Wet gypsum; GV: gypsum mixed with sparse vegetation; CSI: clastic sediment dominated by ferric iron; CSV: clastic sediment dominated by ferric iron mixed with vegetation; W: water; GC: gypsum dominated by calcite; GH: gypsum dominated by halite; V: vegetation; GCV: gypsum dominated by calcite mixed with vegetation; CSHC: clastic sediment dominated by halite and calcite; CSIC: clastic sediment dominated by calcite and ferric iron.

- by Philip Goodell
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- Image Processing, Remote Sensing, Principal Component Analysis, Seasonality

The Takab area, located in north-west Iran, is an important gold mineralized region with a long history of gold mining. The gold is associated with toxic metals/metalloids. In this study, Advanced Space Borne Thermal Emission and Reflection Radiometer data are evaluated for mapping gold and base-metal mineralization through alteration mapping. Two different methods are used for argillic and silicic alteration mapping: selective principal-component analysis and matched filter processing (MF). Running a selective principal-component analysis using the main spectral characteristics of key alteration minerals enhanced the altered areas in PC2. MF using spectral library and laboratory spectra of the study area samples gave similar results. However, MF, using the image reference spectra from principal component (PC) images, produced the best results and indicated the advantage of using image spectra rather than library spectra in spectral mapping techniques. It seems that argillic alteration is more effective than silicic alteration for exploration purposes. It is suggested that alteration mapping can also be used to delineate areas contaminated by potentially toxic metals.

- by soroush modabberi
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- Cartography, Image Processing, Remote Sensing, Methodology

In this paper, the difference in performance between using a matched filter and an integrate and dump filter to implement a correlator in a GPS receiver is studied; in case of infinite and of limited bandwidth; and in case of infinite and of finite sampling frequency. Obviously, the matched filter outperforms the much easier to implement integrate and dump filter on accuracy of synchronization and BER. But the extra hardware it takes to implement the matched filter is substantial. For off-line computer processing of IF samples, this cost is not an issue.

- by Carine Bruyninx
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- Global Positioning System, Matched Filter, Sampling Frequency, Synchronisation

We present a simple and fast technique for the design of ring resonator-based optical filters. The technique is based on tapering the ring scattering parameters to achieve the optimal filter response. A perturbation method is developed for the linearization of the resulting design problem. The design problem is then formulated as an optimization problem. The optimal filter design is achieved by solving a constrained linear least square problem. This optimization problem can be solved efficiently to get the global optimal design. Our technique has been verified using different proposed targeted filter responses.

- by Mohamed Swillam
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- Convex Optimization, Optimization Problem, Matched Filter, Optical physics

—Matched and mismatched filters are considered important parts of a radar signal processing unit. In this paper, we present an approach to optimize the matched filters and mismatched filters in short range pulse radars. For radar, the matched filter coefficients are the complex conjugates of transmitted code. We used binary phase codes as transmitted pulse. The disadvantage of binary phase codes is having high sidelobe levels in the output of correlation function. Thus, we decided to use optimization algorithms for finding binary phase codes with minimum peak sidelobe levels (MPS). After that, we succeeded in producing mismatched filter coefficients (Mis-co) for each code using floating point genetic algorithm (FGA) and we could generate and test the filter coefficients with maximum peak to sidelobe level ratio (PSR). For testing the filter, we plotted ambiguity function for each set of coefficients and tested the filter with Doppler shift.

- by Hesam Ghaferi
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- Genetic Algorithms, Radar Signal Processing, Matched Filter

A successive interference cancellation (SIC) algorithm is developed for the interception of signals transmitted on a CDMA forward link. The system is modelled after the IS-95 standard but the results are also applicable to other CDMA systems such as the wideband CDMA (W-CDMA) and IS-2000 standards. In realistic systems, the different forward link channels are de-orthogonalised, leading to performance degradation in conventional matched filter (CMF)-type receivers. Simulation results indicate that the proposed SIC receiver ameliorates the detrimental effects of de-orthogonalisation, interference and multipath, exhibiting significant gains in traffic capacity over the capacity of a CMF. The numerical simulations also show that the proposed receiver is relatively insensitive to system imperfections. The techniques developed in this paper can be used for interception, surveillance, reconnaissance or monitoring of CDMA signals; to relax the strict requirements on power control; and to improve the capacity of CDMA systems.

- by Michael Ready
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- Distributed Computing, Signal Processing, Algorithm, Numerical Simulation

This work presents a multi-temporal study (years 2000, 2004 and 2007) of saline soils based on multispectral Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images. Its main contribution is the evaluation of different remote sensing methodologies for mapping saline soils in areas highly affected by soil degradation. The study area is located in SE Spain (between the cities of Elche and Alicante) and is characterized by a semiarid climate and the presence of numerous saline soils and salt-flats. Imaging spectroscopy techniques such as Matched Filtering (MF) and Mixture Tuned Matched Filtering (MTMF) techniques were used for mapping saline soils. Two different approaches were applied for mapping saline soils: 1) using image based spectra of saline and non-saline training areas, and 2) using the spectrum of the halite mineral as a proxy to the spectra of saline soils, because halite concentrations are significant in the saline soils of the study area. MF and MTMF mapping techniques were applied in both methodological approaches. Accuracy assessment was evaluated with the Receiver Operating Characteristic (ROC) plot technique. A validation procedure was applied with an independent saline and non-saline validation dataset. Training and validation saline and non-saline pixels were limited to areas with low vegetation coverage to avoid spectral interferences.

- by Magaly Koch and +1
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- Remote Sensing, Soil Salinity, Biological Sciences, Environmental Sciences

We propose and demonstrate a digital holographic technique for 3D object recognition and classification. One Fresnel digital hologram of each of the 3D objects to be classified is recorded. The electronic holograms are processed digitally to retrieve 3D object information as 2D digital complex images. We use this method to classify four physical objects in a 3D scene into two classes. Results are presented from an experiment to demonstrate the proof of the concept.

- by Joby Joseph
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- Digital Holography, Wavelets, Object Recognition, Matched Filter

PiQASso is a Question Answering system based on a combination of modern IR techniques and a series of semantic filters for selecting paragraphs containing a justifiable answer. Semantic filtering is based on several NLP tools, including a dependency-based parser, a POS tagger, a NE tagger and a lexical database. Semantic analysis of questions is performed in order to extract keywords used in retrieval queries and to detect the expected answer type. Semantic analysis of retrieved paragraphs includes checking the presence of entities of the expected answer type and extracting logical relations between words. A paragraph is considered to justify an answer if similar relations are present in the question. When no answer passes the filters, the process is repeated applying further levels of query expansions in order to increase recall. We discuss results and limitations of the current implementation.

A prototype confirmation landmine detector, based on electrical impedance tomography (EIT), that can operate under realistic environmental conditions, has been developed. Laboratory and field experiments demonstrated that it is possible to reliably reconstruct, on the scale of the electrode spacing (in width and depth), conductivity perturbations due to a shallow, buried antitank mine or similar object, in a variety of soils (black earth, clay, sand) down to depths equal to the dimensions of the object (1 to 1.5 electrode spacings, equivalent to 14 to 21 cm for a 64 electrode, 1 m × 1 m array). These represent the first EIT images of real landmines computed from measured data. Occasional problems were encountered with electrical contact in very dry soils, with excessive insertion pressure being required for reliable electrode contact. However, poor contacts could be detected and the offending probe was either reinserted or compensation was applied. A matched filter detection algorithm based on a replica of the object of interest was developed and shown to effectively reduce the false alarm rate of the detector. EIT is especially suited for wet lands and underwater, where other mine detectors perform poorly. Experiments in a water and sediment filled tank have demonstrated that detection of minelike objects in such an environment with a submerged array is feasible. These experiments represent the first EIT measurements of targets using an electrode array submerged underwater. EIT may also have an application in locating intact mines in the berms formed by mine clearing equipment. The EIT sensor head could be made cheaply enough to be disposable and remotely inserted to improve safety.

- by John McFee and +1
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- Geophysics, Geoscience and remote sensing, Electrical Impedance Tomography, Field Experiment

In this paper a comparative analysis of sidelobe levels at matched and mismatched filters depending on input signal-to-noise ratio is presented. The analysis was performed for various types of sequences. The sidelobe level of the mismatched filter output is lower than the sidelobe level of the matched filter output up to some threshold level of the input signal SNR value. Below that level, the sidelobe level is determined by the noise level and the difference between filters elapses.

- by Aleksa Zejak
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- Nonlinear filters, Comparative Analysis, Matched Filter, Pulse Compression

In this paper, a system analysis of needs and possible application of DIRLS mismatched filter in portable surveillance radar PR-15 is presented. Transmitting pulses are binary phase intra-pulse modulated. Because of limited peak power, the usage of longer radar pulses is necessary in long distance mode of operation. Applied binary M sequences have insufficient good autocorrelation properties so a method of side-lobs suppression became needed. We designed and verified the signal processing unit for this kind of compressors on a digital radar signal synthesis and processing platform based on DDS and FPGA technology.

Automated segmentation of blood vessels in retinal images can help ophthalmologists screen larger populations for vessel abnormalities. However, automated vessel extraction is difficult due to the fact that the width of retinal vessels can vary from very large to very small, and that the local contrast of vessels is unstable. Further, the small vessels are overwhelmed by Gaussian-like noises. Therefore the accurate segmentation and width estimation of small vessels are very challenging. In this paper, we propose a simple and efficient multiscale vessel extraction scheme by multiplying the responses of matched filters at three scales. Since the vessel structures will have relatively strong responses to the matched filters at different scales but the background noises will not, scale production could further enhance vessels while suppressing noise. After appropriate selection of scale parameters and appropriate normalization of filter responses, the filter responses are then extracted and fused in the scale production domain. The experimental results demonstrate that the proposed method works well for accurately segmenting vessels with good width estimation.

- by Jane You
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- Computer Science, Mathematical Sciences, Matched Filter

to a lock-in amplifier. Reference spectra were measured using the same evaporated gold film.

- by Aleksa Zejak
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- Signal Processing, Matched Filter, Pulse Compression, Linear Equations

In radar signal detection, the problem is to automatically detect a target in a nonstationary noise and clutter background while maintaining a constant probability of false alarm. Classical detection using a matched filter receiver and a fixed threshold is not applicable due to the nonstationary nature of the background noise. Therefore, adaptive threshold techniques are needed to maintain a constant false-alarm rate (CFAR). One approach to adaptive detection in nonstationary noise and clutter background is to compare the processed target signal to an adaptive threshold. In the cell-averaging CFAR processing, an estimate of the background noise from the leading and the lagging reference windows is used to set the adaptive threshold. A threshold multiplier (or scaling factor) is used to scale the threshold to achieve the desired probability of false alarm. In the first part of this report, we have proposed two modified cell-averaging detectors for multiple target situations. The firs...

- by Mourad Barkat
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- Probability Theory, Probability, Adaptive Systems, Signals

The types of circuits in which analog design techniques are employed typically differ from those in which digital design methods are used, with analog circuits being commonly applied to high speed, low precision functional blocks such as mixers and RF modulators, while digital circuits are chosen for high precision, high complexity blocks that operate at frequencies well below the f T of the transistors from which the circuits are comprised. Yet there still exist applications for which the superior circuit implementation-analog or digital-is unclear. The recent birth of commercial interest in spread-spectrum communications provides the motivation for investigating one such application, that of the parallel programmable matched filter. In this paper, analog and digital circuit realizations of a parallel programmable matched filter are examined. Through wide variations of the design space parameters, the general trend that is observed is that short, fast circuits tend to favor an analog implementation, while longer, slower circuits make a digital implementation more appropriate. A methodology is provided for choosing the preferable circuit-implementing technology when power consumption-as a function of data precision, filter length, operating frequency, technology scaling, and the maturity of the fabrication process-is used as the primary metric of comparison. It is shown that neither the analog nor the digital matched filter implementation is universally more power efficient than the other. Rather, a surface is mapped in the multidimensional design space where, on one side of this surface, a digital solution is preferable, while on the other side of the surface, an analog circuit is appropriate. Equations are given which delineate the position of this transitional surface in terms of the design space parameters, and example calculations and plots depicting the regions of dominance for the digital and analog matched filters for specific process and system parameters are presented.

- by Eby Friedman
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- Analog Circuits, Digital Circuits, Power Consumption, Low Power

This paper presents the design and implementation of a novel multi-antenna receiver front-end, which is capable of accommodating various multi-antenna schemes including spatial multiplexing (SM), spatial diversity (SD), and beamforming (BF). The use of orthogonal code-modulation at the RF stage of multi-antenna signal paths enables linear combination of all mutually orthogonal code-modulated RF received signals. The combined signal is then fed to a single RF/baseband/ADC chain. In the digital domain, all antenna signals are fully recovered using matched filters. Primary advantages of this architecture include a significant reduction in area and power consumption. Moreover, the path-sharing of multiple RF signals mitigates the issues of LO routing/distribution and cross-talk between receive chains. System-level analyses of variable gain/dynamic range, bandwidth/area/power trade-off, and interferers are presented. Designed for the 5-GHz frequency and fabricated in 0.18 m CMOS, the 76 mW 2.3 mm 2 two-antenna receiver front-end prototype achieves a 10 2 symbol error rate (SER) at 64, 77, and 78 dBm of input power for SM, SD, and BF, respectively, while providing 21-85 dB gain, 6.2 dB NF, and 10.6 dBm IIP3.

- by Payam Heydari
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- Routing, Coding, Beamforming, Antenna arrays

The conventional matched filter approach uses the replica of thc transmitted, frequency modulated signal to generate a reference function for the range compression. Phase and amplitude errors occuring in the total transceiver chain before digitalization will be contained in the reference function, which is the complex conjugate of the time reversed replica. The impulse response function in this case has the best achievable signal to noise ratio but high sidelobes or paired echoes will appear for severe phase and amplitude errors. We present here a new method for the generation of the reference function from the replica, which provides both, matched filtering and deconvolution of the amplitude and phase errors. The final impulse response function will be like the ideal one irrespective of the amount of errors present. Several simulation results are shown which are significant for the improvement of the image quality and for relaxation in the amount of allowed amplitude and phase errors in the S A R design for range processing. The proposed method can also be extended to azimuth processing of signals received a t high squint angles.

- by Tapan Misra
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- Signal Processing, Image Quality, Deconvolution, Synthetic Aperture Radar

We develop a linearized imaging theory that combines the spatial, temporal, and spectral aspects of scattered waves. We consider the case of fixed sensors and a general distribution of objects, each undergoing linear motion; thus the theory deals with imaging distributions in phase space. We derive a model for the data that is appropriate for any waveform, and show how it specializes to familiar results when the targets are far from the antennas and narrowband waveforms are used.

- by Margaret Cheney
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- Algorithms, Antennas, Remote Sensing, Imaging

Video images of laser beams imprinted with distinguishable features are used for alignment of 192 laser beams at the National Ignition Facility (NIF). Algorithms for determining the position of these beams enable control systems to perform the task of alignment. Real world beam images suffer from intensity fluctuation or other distortions, making algorithms susceptible to higher position measurement variability. Using matched filtering to identify beam positions results in greater stability of position measurement compared to centroiding techniques. However, this gain is achieved at the expense of extra processing time. This work explores the use of FPGAs to accelerate these computations. Results indicate a performance improvement of 20 times for an FPGA over a 3 GHz Pentium 4 processor.

- by Abdul Awwal
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- Algorithms, Image Processing, Reconfigurable Computing, Pattern Recognition

The estimation of on-off timing of human skeletal muscles during movement is an important issue in surface electromyography (EMG) signal processing with relevant clinical applications. In this paper, a novel approach to address this issue is proposed. The method is based on the identification of single motor unit action potentials from the surface EMG signal with the use of the continuous wavelet transform. A manifestation variable is computed as the maximum of the outputs of a bank of matched filters at different scales. A threshold is applied to the manifestation variable to detect EMG activity. A model, based on the physical structure of the muscle, is used to test the proposed technique on synthetic signals with known features. The resultant bias of the onset estimate is lower than 40 ms and the standard deviation lower than 30 ms in case of additive colored Gaussian noise with signal-to-noise ratio as low as 2 dB. Comparison with previously developed methods was performed, and representative applications to experimental signals are presented. The method is designed for a complete real-time implementation and, thus, may be applied in clinical routine activity.

- by Roberto Merletti
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- Algorithms, Biomedical Engineering, Signal Processing, Skeletal muscle biology

Absfruct-Propagation effects degrade the performance of active sonar systems operating in either deep or shallow water. The ocean medium distorts the transmitted signals by time dispersion and as a result, the performance (signal-to-noise ratio) of correlation receivers is reduced if the receiver does not account for energy spreading. Results from this study demonstrate that the performance of a conventional matched filter can be improved if the reference (replica) channel compensates for the distortion. A model-based matched filter is generated by correlating the received signal with a reference channel that consists of the transmitted signal convolved with the impulse response of the medium. The channel impulse responses are predicted with a broadband propagation model using in situ sound speed measured data and archival bottom loss data. The relative performance of conventional and model-based matched filter processing is compared for large time-bandwidth product linear frequency modulated signals propagating in a dispersive waveguide. From ducted propagation measurements conducted in an area west of Sardinia, the model-based matched filter localizes the depths of both the source and receiving array and the range between them. The peak signal-to-noise ratio for the model-based matched filter is always larger than the conventional. Index Terms-Model-based matched filter, channel adaptive processing, time dispersion.

- by Jean-Pierre Hermand
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- Signal Processing, Impulse response, Fading, Predictive models

Due to the demand for cellular wireless services, recent interests are in techniques, which can improve the capacity of CDMA systems. On such technique is multi-user detection. Multi-user Detection (MUD) is the intelligent estimation/demodulation of transmitted bits in the presence of Multiple Access Interference (MAI). In this paper, we will show the role of matched filter used as pre-processing tool for MUD in DS-CDMA system.

- by Otman Chakkor
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- Matched Filter, Multi-User Detection, Multiple-access Interference