A method of optimal linear systems for following filtration of active spectrum of non-stationery process

It is shown a necessity of improve of known method of optimally matched filtering for following the spectrum of non-stationery processes. The essence of improvement lies in expansion of the conception of signals active spectrum, taking into account specificities of known following filters with self-tuning and application of known following filters with two integrators. It is proven that selecting of gain coefficients of three amplifies, which are contained in this filter, we can use them as separate section of band-pass filter for synthesis of optimal linear systems for following filtration the active spectrum itself for different signals type.     

Structural-spectral following filters for hardware analysis of non-stationery processes active spectrum

It is noted usefulness degree of application of hardware spectral analysis of real physical processes in different fields of science and technology. So, it is necessary to obtain adequate general following filters (FF) with self-tuning. On a basis of physical-mathematical analysis of non-stationery processes we show clearly its specificities, and, hence, this fact allows to prove required criteria of adequacy of known FF to active spectrum components.     

Simulation of following self-tuning filters with VisSim system

It is noted that usefulness of application of known second-order following filters (FF) and their main drawbacks, which are absent in general FFs. For these FFs research now the most efficient is simulation in VisSim system. It is shown, that basic principles of construction in VisSim filter transfer function (TF) of known simulation block diagram of linear stationery systems. As a result, we obtain TF with variable coefficients that allows to define auxiliary controlled units in simulation bock diagram of different higher-order self-tuning FF, which are adequate to active spectrum of non-stationery processes.     

About principal possibility of automated following by active frequency of non-stationery processes spectrum by means of active filter

It is underlined explicit usefulness and efficiency of hardware analysis of active spectrum of non-stationery processes, necessity of automated following by frequency of input signal filters (AFFF) application as analyzing filters. It is mentioned drawbacks of analysis methods of such filters and necessity of approval possibility of frequency self-tuning of any type filters (FSAF) of high order. Possibility of FSAF and, hence, AFFF is proven in terms of application of some known features of manual regulation of electrical filters. By means of computer mathematical modeling in system VisSim/com it is proven AFFF possibility. It is underlined possibilities of some useful their application.     

Calculation of self-tuning process of frequency filters in Mathcad system

Ona basis of theory of automated following the frequency of input signal systems in dynamic mode we have obtained analytical expression for transient frequency of general frequency filters tuning. As a result we have proved a possibility of MathCAD application for filter self-tuning process. Taking into account known features of non-stationery process active spectrum, we have obtained another possibility of mentioned calculations. We propose an algorithm for these calculations for general filters. We note that known problem of mathematical analysis of general following filters is solved.     

Estimation of the energy spectrums of reflections in pulse doppler weather radars. Part 1. Modifications of the spectral estimation algorithms

This is the first paper in a series of papers devoted to the peculiarities of estimation of the continuous energy spectra of random processes of different nature, which are defined by their samples at discrete moments of time. In the paper we consider two kinds of the generalized spectrum analyzers (GSA), whose structure fits the majority of classical (nonparametric) and modern noneigenstructured spectral estimation (SE) methods. It has been demonstrated that a number of known superresolution SE methods may be considered as particular cases of parametric GSA based on whitening or inversing filters of the input process. We focus on the autoregressive models of analyzed processes with continuous energy spectrums, for which the whitening or inversing filters are the transversal filters of various structures with proper parameters. The utilized interpretation allows one to modify the well-known superresolution SE methods for the problem of continuous spectrums reconstruction and, what is more important, to establish their new varieties with practically useful properties, that are going to be explored in the following two papers.     

Correlation background of the concept of active spectrum of nonstationary processes

The need of developing the known concept of active spectrum of nonstationary processes has been shown using its correlation background. Expressions for the input and response signals in complex form of the so-called active filter were derived in terms of the second known definition of this concept. A two-dimensional correlation function similar to the known uncertainty function was obtained using the known autocorrelation function of complex signals. In conclusion, some directions of the beneficial use of the correlation relationships obtained were noted, especially in solving the topical synthesis problem of optimal active filters for the specified signals.     

A Low-Complexity Delayless Selective Subband Adaptive Filtering Algorithm

Adaptive filters of significant order, requiring high computational complexity, are necessary in many applications such as acoustic echo cancellation and wideband active noise control. Successful approaches to lessen the computational complexity of such filters are subband methods, and partial updating schemes where only a part of the filter is updated at each instant. To avoid the time delay introduced by the subband-splitting, delayless structures which reconstructs a fullband filter, producing delayless output, from the adaptive subband filters have been proposed. This paper proposes a delayless subband adaptive filter partial updating scheme, where the general idea is to only update the most misadjusted subband filter(s). Analysis in terms of mean square deviation is presented and shows that the fullband filter convergence speed is significantly increased, even for flat spectrum signals, as compared to traditional periodic subband filter update with the same computational complexity. Echo cancellation simulations with an artificial system to verify the analysis, using both flat spectrum signals and speech, is also presented, as well as offline calculations using signals from a real system.      

稳定分布多项式自回归有色噪声及其白化方法

本文提出了一种稳定分布白噪声的概念及其判断标准,对传统意义上的白噪声进行了广义化,提出了一种非线性系统中稳定有色的噪声概念并建立其非线性PAR模型,提出EIRLP算法对多项式自回归稳定有色噪声的模型参数进行估计,并探讨了其白化方法.计算机模拟表明,这种算法是一种在高斯和分数低阶稳定分布噪声条件下具有良好韧性的白化滤波方法.     

Reference current computation methods for active power filters: accuracy assessment in the frequency domain

This paper focuses on the steady-state response of existing methods for computing the reference current of active power filters. For each class of methods, the main source of discrepancy between the load harmonic current and the computed reference current is identified and the frequency spectrum of the resulting error is analytically determined. Although this topic has been partially addressed in previous publications, the proposed frequency-domain approach provides valuable qualitative information about how the errors are produced and distributed, which is masked when the analysis is carried out in the time domain. First, the frequency-domain formulation is separately presented for each method. Then, a comparison of the resulting errors is performed on a case study. Finally, some experimental results are given to validate the proposed frequency-domain analysis.     

Theory and design of two-parallelogram filter banks

It is well known that the analysis and synthesis filters of orthonormal DFT filter banks can not have good frequency selectivity. The reason for this is that each of the analysis and synthesis filters have only one passband. Such frequency stacking (or configuration) in general does not allow alias cancellation when the individual filters have good stopband attenuation. A frequency stacking of this nature is called nonpermissible and should be avoided if good filters are desired. In a usual M-channel filter bank with real-coefficient filters, the analysis and synthesis filters have two passbands. It can be shown that the configuration is permissible in this case. Many designs proposed in the past demonstrate that filter banks with such configurations can have perfect reconstruction and be good filters at the same time. We develop the two-parallelogram filter banks, which is the class of 2-D filter banks in which the supports of the analysis and synthesis filters consist of two parallelograms. The two-parallelogram filter banks are analyzed from a pictorial viewpoint by exploiting the concept of permissibility. Based on this analysis, we construct and design a special type of two-parallelogram filter banks, namely, cosine-modulated filter banks (CMFB). In two-parallelogram CMFB, the analysis and synthesis filters are cosine-modulated versions of a prototype that has a parallelogram support. Necessary and sufficient conditions for perfect reconstruction of two-parallelogram CMFB are derived     

Coherently Controlled Multifunctional Active Optical Filters

In this paper, we propose multifunctional active optical filters using coherent nonlinear effects and quantum interference in quantum-well structures. Based on the application demand, in the absence of a control laser field, these filters can be either completely opaque or transparent. However, in the presence of such a control laser, the filter structure is activated, allowing transmission of a single frequency. We show that the amplitude and linewidth of these filters can be optically controlled, demonstrating various functionalities and performances including attenuation, amplification, and switching processes. We also show that, with proper design of such active filters, one can tune the wavelength of the filtered signal by varying the intensity of the control field.     

Realization of current-mode high-order filters employing multiple output OTAs

Current-mode linear transformation (CMLT) high-order filters with minimum number of multiple output operational transconductance amplifiers (MOOTAs) are presented. Based on proposed design methods, we can synthesize current-mode high-order all-pole filters with minimum number of MOOTAs and all grounded capacitors efficiently. Moreover, high-frequency canonical CMLT elliptic filters with minimum number of MOOTAs and floating capacitors are also presented. Our proposed filters have the following merits: simplified design procedures, minimum number of active elements and simple design equations. Two design examples are demonstrated in this paper. Experimental results that confirm the theoretical analysis are provided.     

Inductorless filters: a survey II. Linear active and digital filters

In this two-part survey the author has attempted to review the main methods of inductorless filter design being pursued at the present time. These filters are of particular interest because they may provide the replacement for the LC filters that are being eliminated from electronic equipment as a result of the trend toward microminiaturization. This month's installment discusses inductorless filters of both the linear active and digital types.     

The method for dispersion and dispersion-and-tracking instrumentation analysis of the active spectrum of nonstationary processes

The need for refining the known methods of dispersion analysis of radio signal spectrum has been demonstrated. A new method was proposed on the basis of using the known peculiarities of the active spectrum of nonstationary processes. This method makes it possible to enhance the accuracy of spectral analysis and its informativeness about a brief malfunction of normal continuous operation of real physical entities, perform the synthesis of measured signals, and reduce the dispersion coefficient of the stationary dispersive delay line (DDL) about two times, while that of the tracking DDL about 15 times as compared with the DDL dispersion coefficient of the known methods.     

Noise characteristics of spectrum sliced microwave photonic filters

An analysis of the noise properties of spectrum sliced microwave photonic filters is presented. It reveals that the excess intensity noise in spectrum sliced filters is around 46 dB higher than the shot noise. This is verified by experimental noise measurements, which are presented for the first time. This extremely high excess noise poses the dominant limitation to the filter performance, and requires effective suppression techniques.     

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.     

Digital filter approach for Simulation of a complex integrated laser diode based on the traveling-wave model

The traveling-wave model is commonly used in the simulation of semiconductor laser diodes and photonic integrated circuits. When the laser diode is cascaded with other passive elements of relatively large optical dimension or complicated structure such as a sophisticated distributed Bragg reflector section, the conventional approach by tracing the forward and the backward traveling waveform along the entire passive section in the time domain becomes time consuming or technically impossible. To overcome this difficulty, a split-step approach is proposed in this study. Since the spectral characteristics of the passive sections are known from analytical/numerical calculations or experimental measurement, the effective time-domain digital filters are introduced for the passive components. Therefore, in the simulation, the laser diode part is still modeled by the traveling-wave approach, but the digital filters are used to model the passive components butted at the end of the active part, which interact with the optical field of the laser diode at the interface.     

Spectrally-filtered electroluminescence of vertical-cavitysurface-emitting lasers

We show that spontaneous emission from the mirror layers (λ=780 nm) of a vertical cavity surface emitting laser (VCSEL) is a significant component of the spectrum. By using bandpass filters, we are able to distinguish the electroluminescence (or “near-field”) pattern of the mirror layers from the active region pattern. We show that in some lasers, these patterns are irregular, possibly due to the presence of absorbing doping or defect clusters in the p-mirror that absorb light from the active region, and re-radiate the light at the shorter wavelength characteristic of the mirror layers. In addition, we show that dark areas appear, both in the active regions and the mirrors, as the device degrades     

Phase retrieval from impedance amplitude measurement

In this letter, we propose a numerical method for computing the phase spectrum of impedance. The developed method is based on the maximum entropy model (MEM) and enables one to retrieve the phase spectrum directly from an impedance amplitude spectrum. The validity of the method is tested with an input impedance measurement of a distribution transformer in the frequency band 100 kHz-30 MHz, where both the amplitude and the phase spectrum of the impedance are measured. According to the tests carried out, the method is useful and it may be applied, for example, in the research of active filters, power line communication, and electromagnetic interference.