Velocity filters for multiple interference attenuation ingeophysical array data

The problem of velocity filtering a record of seismic data with the objective of extracting a desired signal by attenuating the coherent interferences traveling at different velocities is considered. A two-dimensional (N-input (N-M+1)-output) processing scheme is used where the (N-M+1) output traces are generated from the N-input traces by multichannel processing of overlapping subsets of M-input races. Each output is generated by using a vector of multichannel arrays filters designed to attenuate multiple coherent interference and random noise. The two-dimensional frequency-wavenumber expression corresponding to the proposed multiple-input-multiple-output processing scheme is derived so that it can be implemented using the two-dimensional fast Fourier transform. Two illustrative examples are included     

Weyl filters for linear array data

The Weyl transform, which is closely connected to the Wigner distribution, allows one to reconstruct (temporally and spatially) localized frequency-wavenumber spectral components. Such filters were suggested in time-frequency analysis by Kozek and Hlawatsch (1992). The theory can be naturally extended to signals recorded in space and time. Thereby, wavefield components with predefined varying spectral properties like, for example, wavefront curvature, can be synthesized. The numerical implementation of such filters is in the most general case a computationally expensive task. We present a simplified implementation, which assumes a specially shaped filter pass region. The assumption resembles a ray approximation and allows one to track a temporally and spatially unidimensional wavefield recording for curved wavefronts in reasonable computation times. The suitability of the method is demonstrated by synthetic data and seismic field data, although it is quite general and not restricted to seismic applications.     

Sensitivity evaluation for multiple feedback active filters

A systematic approach based on signal flow graph analysis to the evaluation of multiple feedback active filter sensitivity is presented. Its merits are discussed and compared with those of other known techniques.     

New multicomponent filters for geophysical data processing

As multicomponent processing is a challenge in many fields such as geophysics, seismology, remote sensing, or electromagnetics, a method that could be used to filter multispectral, multicomponent, or multidimensional data is proposed. In this paper, the method, called multicomponent wideband spectral-matrix filtering (MC-WBSMF), is applied on geophysical data to separate interfering wavefields. The technique is based on the decomposition of a special multicomponent spectral matrix and could extract a given wavefield from a multicomponent dataset. MC-WBSMF is compared to two classical single-component seismic methods (the 2D-Fourier transform or f-k filter and the Radon transform) and to a fully multicomponent method based on singular value decomposition. Finally, MC-WBSMF is tested on a real geophysical subsurface dataset in order to remove surface waves and to enhance reflected waves.     

Design tables for partial-response data transmission filters

Practical design tables are presented for partial-response class 1 data transmission filters. These tables give the pole and zero locations and the main sample point of several filters. This information can be used to analyse the performance of the filters, both in the time domain and frequency domain, thus assisting the user in the choice of a filter to meet the requirements. The filters given in the tables can be syntheised in either active or passive form.     

大数据量计算全息相关滤波器

本文扼要地介绍了一种利用不很复杂的计算绘图系统,获取用于汉字字符识别的大数据量计算全息相关滤波器的技术.     

Design method for optimal data transmission filters

A data transmission filter design method is introduced. The method yields filters that are optimal in the sense that for given pole locations the intersymbol interference error is minimum. The prescribed loss requirements in the stopband are met and the eye diagrams are wide open.<>     

Single-phase active power filters for multiple nonlinear loads

This paper presents active power filters for single-phase power systems which are comprised of multiple nonlinear loads. The paper provides background on the operation of the filter, the details of the power circuit, the details of the control design, representative waveforms, and spectral performance for a filter which supports a 384 W AC controller and a 900 W uncontrolled bridge rectifier. Experimental data indicate that the active filter typically consumes 3% or less of the average load power, suggesting that a parallel filter is an efficient compensation approach. The spectral performance shows that the active filter brings the system into compliance with IEC-555 for decision frequencies in excess of 30 kHz. A discussion is presented outlining an alternative single-phase active filter which uses two controllable switches and is based on a half-bridge topology     

Optimal data transmission filters

In the letter new closed-form formulas (in terms of the poles) for a class of optimal data transmission filters are derived. These formulas always put the main sample point at the peak value of the impulse response.     

Velocity selective filters recursively implemented in the spatiotemporal domain.

Energy-based methods for motion estimation in image sequences process the input data either in the spatiotemporal or in the frequency domain. In both cases, the algorithms already described in the literature often require a huge number of elementary operations. In this paper, we describe a class of velocity selective filters which yield an accurate detection of the edges moving in the sequence. We first present a filtering scheme based on a convolution operation computed on a finite size neighborhood and describe its properties in the spatiotemporal and frequency domains. Then, we show that filters with similar properties can be implemented recursively, i.e., as convolutions computed on infinite-size neighborhoods. As an example, we finally show the filters' responses in the case of two superimposed translational motions.     

Complex coefficient data transmission filters

The author shows how to design filters with asymmetric amplitude and group delay properties, while maintaining low intersymbol interference. The asymmetry gives independent control of the lower and upper stopband rolloff rates. Examples are given to illustrate the method, and its results     

Concurrent nulling and locations of multiple interferences inadaptive antenna arrays

An approach for concurrent nulling and location (CANAL) of multiple interferences impinging on an array antenna is presented. It is based on the principle of constructing the signal and the noise subspaces from the nulling weights which correspond to different steering directions. In this respect, the data snapshots and their estimated covariance matrix are not required. As in the MUSIC algorithm, the basis of the noise subspace is then used to form a spectrum in which the peak locations define the estimated angles of arrivals. Applebaum optimum weights are employed to delineate the properties of the proposed approach under the assumption of narrowband uncorrelated jamming sources, and providing that the number of steering directions exceeds the number of interferences. CANAL is presented for the general case of unknown noise power. The effect of the desired signal presence on the performance Is discussed     

Design and analysis of receiver filters for multiple chip-rateDS-CDMA systems

As multimedia applications proliferate, there is a desire to provide wireless transport to information streams with inherently different data rates. Direct-sequence code division multiple access (DS-CDMA) is a natural multiple-access strategy for multiple data-rate systems. Previous work on multirate DS-CDMA receivers has focused on signal-processing techniques, which detect all users of all rates simultaneously. In the current work, multirate users have multiple bandwidths. Thus, it is proposed to exploit bandwidth differences to achieve frequency-based rate separation followed by single-rate detection schemes. Such a methodology enables a tradeoff between receiver complexity and performance. The performance of the proposed filters and receivers are derived for both a modified matched filter and modified decorrelator employing rate separation. The performance of a multirate CDMA overlay system is evaluated. In addition, chip pulse shaping for wide-band users is developed to improve performance for narrow-band users for the overlay system     

Potential efficiency of data transmission systems in channels with non-Gaussian quasi-pulsed interferences

The potential efficiency of data transmission systems in channels with quasi-pulsed radio interferences of the natural and industrial type has been estimated. The lognormal model of pulsed interference components has been used.     

MOS switched capacitor sample data filters

Thin paper presents a configuration for realizsing second-order switched capacitor filters. The basic building blocks ore switched capacitor integrator and first-order networks. The integrator and the first-order networks are free from parasitic capacitances. The design of filters is achieved by using bilinear Z-transform.     

Color-scale morphological filters with multiple structuring elements

With the wide use of color in many areas, the interest on the color perception and processing has been growing rapidly. An important topic in color image processing is the development of efficient tools capable of filtering images without blurring them and without changing their original chromatic contents. In this paper, a new technique reducing noise of color image is developed. A class of color-scale morphological operations is introduced, which extend mathematical morphology to color image processing, representing a color image as a vector function. The correlation between color components is utilized to perform noise removal. Color-scale morphological niters with multiple structuring elements (CSMF-MSEs) are proposed. Their properties are discussed and proved. Experimental results show that CSMF-MSEs are suitable and powerful to eliminate noise and preserve edges in color image because of efficient utilization of inherent correlation between color components, and they perform better than vector med     

Implementation of digital matched filters in data receivers

It is shown that analogue-filter and analogue-detector circuits in data receivers can be replaced by simple digital networks designed from truth-table specifications. A method of compiling truth tables from given received-signal probabilities is presented. An example illustrates an application to the reception of binary raised cosine signals in the presence of Gaussian noise.     

A network of adaptive Kalman filters for data channel equalization

The aim of this paper is to revisit the Kalman filtering-based approach of channel equalization. Indeed, Kalman equalizers have already been proposed in the literature as an alternative to more classical structures. However, these Kalman solutions are based on the assumption of Gaussian signals that is not valid in the context of data channel equalization. From an approximation of the density functions of the data signals by a weighted sum of Gaussian probability density functions, we here propose a new structure of an equalizer that is based on a network of Kalman filters operating in parallel. An adaptive version of this network is investigated. It includes the on-line estimation of the channel and of the noise variance     

Design of transmit FIR filters for FDM data transmission systems

The design of transmit finite-impulse response (FIR) filters with few coefficients in frequency division multiplexing data transmission systems is considered. In these systems, quality objectives are imposed for transmission over channels affected by additive white Gaussian noise (AWGN) and over channels affected by AWGN plus adjacent channel interference (ACI). The goal of this letter is: given that an adaptive receive filter, possibly cooperating with an adaptive decision feedback equalizer, is used for the AWGN channel and for the AWGN plus ACI channel, what is the best fixed FIR transmit filter to use for both channel cases? This goal is achieved by optimizing the compromise between the performance of the system on the two mentioned channels. Also, the advantages of the proposed design over a rival method based on a fixed receive filter are demonstrated.     

Error probability of coherent PSK and FSK systems with multiple cochannel interferences

The symbol error probability of binary and quaternary CPSK and binary CPSK systems with multiple cochannel interferences and Gaussian noise is investigated. Numerical results obtained by using the Monte Carlo method are presented as an example.<>