Filter Concept Research Articles

Time-Varying IIR Notch Filter with Reduced Transient Response Based on the Bézier Curve Pole Radius Variability

In this paper a concept of the second order digital infinite impulse response narrow band-reject filter with reduced transient response is proposed. In order to suppress the transient response of the considered infinite impulse response (IIR) notch filter its pole radius is temporarily varied in time using the Bézier parametric curve. Computer simulations verifying the effectiveness of the proposed pole-radius-varying notch filter are presented and compared to the performance of the traditional time-invariant filter using ECG signals distorted by unwanted powerline interference.

Critical examination of critical bands

The concept of the critical band has driven the design and interpretation of psychophysical experiments for decades. The critical band was initially proposed by Fletcher [Rev. Mod. Phys. 12, 47 (1940)] to describe results of masking experiments, and it is generally interpreted as evidence for a filter that limits the signal-to-noise ratio in stimulus representations that are provided to the central nervous system. This filter-based interpretation of masked-detection thresholds has been extended and applied to numerous tasks, including many without masking. The concept of a bank of critical-band filters also forms the basis for signal-processing strategies used for hearing aids and cochlear implants. This talk will review both psychophysical and physiological results that challenge the concept of the critical-band filter. For example, the minimal effect of roving-level paradigms on masked-detection thresholds directly refutes the critical-band based power-spectrum model. Furthermore, most auditory neurons have receptive fields that are much broader than critical bands at the moderate to high sound levels used in most psychophysical tasks, with or without masking. Alternative concepts that are robust across a wide range of levels and in roving-level paradigms, such as fluctuation profiles, explain the original masked-detection results and related experiments, such as psychophysical tuning curves.

Mixed-technology quasi-reflectionless planar filters: bandpass, bandstop, and multi-band designs

AbstractThe design of mixed-technology quasi-reflectionless planar bandpass filters (BPFs), bandstop filters (BSFs), and multi-band filters is reported. The proposed quasi-reflectionless filter architectures comprise a main filtering section that determines the power transmission response (bandpass, bandstop, or multi-band type) of the overall circuit network and auxiliary sections that absorb the reflected radio-frequency (RF) signal energy. By loading the input and output ports of the main filtering section with auxiliary filtering sections that exhibit a complementary transfer function with regard to the main one, a symmetric quasi-reflectionless behavior can be obtained at both accesses of the overall filter. The operating principles of the proposed filter concept are shown through synthesized first-order BPF and BSF designs. Selectivity-increase techniques are also described. They are based on: (i) cascading in-series multiple first-order stages and (ii) increasing the order of the filtering sections. Moreover, the RF design of quasi-reflectionless multi-band BPFs and BSFs is discussed. A hybrid integration scheme in which microstrip-type and lumped-elements are effectively combined within the filter volume is investigated for size miniaturization purposes. For experimental validation purposes, two quasi-reflectionless BPF prototypes (one- and two-stage architectures) centered at 2 GHz and a second-order BSF prototype centered at 1 GHz were designed, manufactured, and measured.

An agent-based approach to power system dynamic state estimation through dual unscented Kalman filter and artificial neural network

This paper proposes a novel approach to the power system dynamic state estimation by using the concepts of dynamic artificial neural networks and dual unscented Kalman filter. A dynamic artificial neural network is applied for developing a discrete-time state transition model of power system which is used for one-step-ahead prediction of the state vector. The model is also applicable for the generation of pseudo-measurements while it is needed. The dual unscented Kalman filter estimates the state vector of power system and calculates the weights of the dynamic artificial neural network simultaneously. A multi-agent-based model is utilized to structure the computational architecture of the proposed approach. The autonomous agents are designed to carry out the complex computations needed in the power system dynamic state estimation. The agents distribute multiple execution tasks among themselves, and they share information interactively. The agent-based modeling of the proposed method enhances the computing efficiency through decomposition of the computations among several autonomous agents. The effectiveness of the proposed method is examined through comprehensive simulations. The results guarantee the performance of the proposed approach as a practical solution for the power system dynamic state estimation.

Micromachined Filters at 450 GHz With 1% Fractional Bandwidth and Unloaded <italic>Q</italic> Beyond 700

This letter presents two silicon-micromachined narrowband fourth-order waveguide filter concepts with center frequency of 450 GHz, which are the first narrowband submillimeter-wave filters implemented in any technology with a fractional bandwidth as low as 1%. Both filters designs are highly compact and have axial port arrangements, so that they can be mounted directly between two standard waveguide flanges without needing any split-block interposers. The first filter concept contains two TM110 dual-mode cavities of circular shape with coupling slots and perturbations arranged in two vertically stacked layers, while the second filter concept is composed of four TE101 series resonators arranged in a folded, two-level topology without crosscouplings. Prototype devices are fabricated in a multilayer chip platform by high-precision, low-surface roughness deep-silicon etching on silicon-on-insulator wafers. The measured passband insertion loss of two prototype devices of the dual-mode circular-cavity filters is 2.3 dB, and 2.6 dB for three prototypes of the folded filter design. The corresponding extracted unloaded quality factors of the resonators are 786 ± 7 and 703 ± 13, respectively, which are the best so far reported for submillimeter-wave filters in any technology. The presented filters are extremely compact in terms of size; their footprints have areas of only 0.53 and 0.55 mm2, respectively, and the thickness between the waveguide flanges is 0.9 mm.

A Study on Three-Phase FLLs

Contrary to the phase-locked loop (PLL), which has almost reached a mature stage of development in power and energy applications (particularly in three-phase systems), the frequency-locked loop (FLL) is not a mature technique yet. This is probably because of the implementation of FLLs in the stationary reference frame, which makes their modeling, tuning, and performance enhancement more complicated than PLLs. The aim of this paper is conducting a research on three-phase FLLs. Providing a review of recent advances, introducing the concept of inloop filters for designing more advanced FLLs, demonstrating the FLL modeling and tuning in the presence of an inloop filter, analyzing the advantages and disadvantages of using an inloop filter in the FLL structure, and establishing a connection between FLLs and PLLs are the main parts of this research.

Switched <img width="58" height="55" src="http://article.sciencepublishinggroup.com/journal/248/2481135/image001.png" /> Detection Filter Design for Nonlinear Systems

This paper presents the application of the concept of detection filters to the detection of faults in nonlinear systems. The nonlinear dynamics in specific meaningful points of the operation is approximated by means of a matched array of linear systems. Then, linear filters are designed for each particular subsystem and a switching scheme is applied to carefully choose the most suitable filter regarding the operational characteristics of the plant in real time. Stability of the switching process is guaranteed by keeping the switching time between two consecutive switching large enough to ensure a proper falloff of filter transients. Therefore, apart from the solution of the standard linear-quadratic optimization problem represented by the detection filter design problem one has to derive sufficient conditions for the observation error dynamics to be globally asymptotically stable during switching. The goal is to find a common minimum of the switching time to each specific level calculated separately for every single filter that can be used as a restriction for the switching signal. The idea is demonstrated with the application to the detection of faults in the air path of a diesel engine. The results can be considered as the extension of the standard linear fault detection filtering problem to nonlinear systems.

Development concept of CRRT filter by Nipro Corporation

Development concept of CRRT filter by Nipro Corporation

Study on synchronisation capability enhancement of optoelectronic oscillator using dynamic control bandpass filter

This study introduces the concept of dynamic controlled bandpass filter (BPF) to achieve improved synchronisation capability of a single-loop optoelectronic oscillator (OEO) under the effect of externally applied angle modulated signal. The governing equation for synchronisation ability of an OEO using dynamic control BPF has been derived. Theoretical study and comparison of locking capability enhancement using this dynamic BPF over a conventional static BPF are provided which is properly validated by simulation. Finally, the ability of frequency modulation to amplitude modulation conversion has been compared by measuring the total harmonic distortion values of the reconstructed signals.

A NEW VIEW OF FUZZY ORDERED SEMIGROUPS

fuzzy coding theory, fuzzy finite state machines, and fuzzy languages. In this paper, we introduce the concept of an interval-valued -fuzzy filter of an ordered semigroup, where with. Since the concept of an interval-valued -fuzzy filter is an important and useful generalization of the ordinary interval-valued fuzzy filter, we discuss some fundamental aspects of an interval-valued -fuzzy filters. An interval-valued -fuzzy filter is a generalization of the existing concept of an interval-valued fuzzy filter. We discuss the concept of an interval-valued -fuzzy left (right)-filters and provide some characterization theorems. Finally, we extend the concept of an interval-valued fuzzy subgroup with thresholds to the concept of an interval-valued fuzzy left (right)-filter with thresholds of s.

Active Cancelation of Equivalent Grid Impedance for Improving Stability and Injected Power Quality of Grid-Connected Inverter Under Variable Grid Condition

An active grid impedance cancelator using the concept of series active filter to suppress the effect of the grid disturbance and stabilize the single-phase grid-connected inverters with an inductive–capacitive–inductive filter operating under variable grid condition is presented. Harmonic interaction between the inverter and the grid is thereby avoided owing to the cancelation of equivalent grid impedance. More importantly, the impedance cancelator offers an active damping function to ease the heavy burden of the inverter control, such as power control, phase locked loop, current regulation, impedance shaping, etc. The impedance cancelator is a full-bridge dc–ac converter having no passive inductive–capacitive filter. It is connected in series with the inverter output and is operated as a negative virtual grid impedance. As the volt-ampere rating of the impedance cancelator is low, the efficiency of the entire system is not sacrificed. Starting with the impedance-based analytical modeling method, the basic principle of equivalent grid impedance cancelator is derived and studied. Then, the digital control strategy and the modeling of equivalent grid impedance cancelator are examined. The experimental results of a prototype cancellator for a single-phase inverter are favorably compared with theoretical predictions.

Development and Tests of a Combined Filter for NOx, Particulates, and SO2 Reduction

AbstractThe idea of this innovative filter concept is to combine three individual flue gas technology treatment systems into one product to be more economic and efficient. The central part of the filter is a ceramic filter candle, which is used for common dust separation. The ceramic filter material is activated with modified catalysts to enable selective catalytic reduction at low temperatures (150–200 °C). To reduce acid components while simultaneously increasing dust separation, the activated filter candle surface is precoated with an absorbent. The developed filter is suitable for many applications, especially decentralized applications such as solid biomass combustion or utilization of biofuels in combined heat and power engines, which are target markets. The production of the filter material and the practical test using exhaust gas from a dual fuel engine operating with biofuels are described.

A new generalization of BE-algebras

In this paper we introduce the notion of PSRU-algebras as a generalization of BE-algebras, we investigate its elementary properties. The aim of this paper is to investigate the concept of filters, left ideals (right ideal, ideal) and fuzzy filters in PSRU-algebras. Moreover, we investigate relationships between left ideals and filters in PSRU-algebras. Furthermore, we characterize filters in terms of fuzzy filters. It is shown that if I be a left ideal of a PSRU-algebra X, then Ix is a left ideal of X for all x∈X.

On the Molecular Filters in Cochlea Transduction

The article is devoted to the specific consideration of the cochlear transduction for the low level sound intensities, which correspond to the regions near the perception threshold. The basic cochlea mechanics is extended by the new concept of the molecular filters, which allows discussing the transduction mechanism on the molecular level in the space-time domain. The molecular filters are supposed to be built on the set of the stereocilia of every inner hair cell. It is hypothesized that the molecular filters are the sensors in the feedback loop, which includes also outer hair cells along with the tectorial membrane and uses the zero compensation method to evaluate the traveling wave shape on the basilar membrane. Besides the compensation, the feedback loop, being spatially distributed along the cochlea, takes control over the tectorial membrane strain field generated by the outer hair cells, and implements it as the mechanism for the automatic gain control in the sound transduction.

Left-m-filter, Right-n-filter and (m,n)-filter on Ordered Semigroup

In this paper, as a generalization of the concepts of left filters, right filters and filters of ordered semigroups, the concepts, for any positive integers m and n, of left-m-filters, right-n-filters and -filters in ordered semigroups have been introduced and some properties of these generalized notions have been investigated. Finally left-m-filters (resp. right-n-filters, -filters) of -regular (resp. -regular, -regular) ordered semigroups have been characterized in terms of its prime generalized -ideals (resp. -ideals, -ideals).

Transitive and Absorbent Filters of Implicative Almost Distributive Lattices

In this paper, we introduce the concept of transitive and absorbent filters of implicative almost distributive lattices and studied their properties. A necessary and sufficient condition is derived for every filter to become a transitive filter. Some sufficient conditions are also derived for a filter to become a transitive filter. A set of equivalent conditions is obtained for a filter to become an absorbent filter.

Load frequency control strategy via fractional-order controller and reduced-order modeling

This paper proposes a simple approach to design fractional-order (FO) controller via internal model control (IMC) technique for load frequency control (LFC) problem in power systems. The proposed scheme utilizes the concept of CRONE principle, model-order reduction and FO filter in IMC framework to derive a robust controller. Initially, the scheme is applied to single-area power system and then extended to two-area interconnected system. The turbines considered are non-reheated, reheated and hydro type; and physical constraints of turbine and governor are also taken into account to validate the applicability in more realistic environment. Simulation results show that it can bring improved disturbance rejection performance in nominal condition as well as in presence of uncertainties and constraints in plant parameters.

Nanoparticles capture on cellulose nanofiber depth filters

A self-standing filter with a porosity of 80% is prepared from naturally abundant cellulose biopolymer in its native state by water-based cationization and freeze-drying processes. The positive surface charge of the filter in a wide pH range favors its interaction with various nanoparticles (NPs), while its tortuous sheet structure builds a contact between cellulose nanofibers (CNF) and the NPs, and hinders them to pass through the filter. Unlike membranes used for the retention of NPs and viruses, the separation in the CNF filter is not only limited to its surface but occurs also in its interior even when the NPs are orders of magnitude smaller than the filter pores. Additional functionalities added to the filter enlarge the spectrum of NPs it can separate. NPs supported onto the filter can thereafter be utilized for the reduction of harmful chemicals into their benign form. The present filter concept may not only address shortcomings of the current membrane systems, but could offer a disruptive technology for the sustainable and universal water purification.

RF Wide-Band Bandpass Filter With Dynamic In-Band Multi-Interference Suppression Capability

A class of RF multi-functional bandpass filter with multiple frequency-reconfigurable rejected bands that are embedded into its broad transmission frequency range is reported. This filter concept exploits an original tunable multi-band quasi-bandstop section as constituent block. In this manner, unprecedented levels of spectral adaptivity are obtained for its in-band notches. Among them: 1) independent control of center frequency and rejection level; 2) notch-combination capability to conform wider rejected bands and make their number dynamically selectable; and 3) generation of dual-band bandpass responses with adjustable bandwidth and inter-band transmission zeros. This results in controllable in-band stopbands with reconfigurable bandwidth, attenuation level, and filtering-profile type. The devised filter architecture, which is appropriate for dynamic multi-interference mitigation in broad-band RF receivers, is scalable to any number of arbitrary-order in-band notches. For proof-of-concept purposes, a UHF-band microstrip prototype with up to two tunable in-band second-order stopbands is manufactured and measured.

Proper UP-filters in UP-algebra

In this paper we introduce and discus a concept of proper UP-filters in UP-algebras. We present a connection between proper UP-filters and UP-ideals. We expect this concept of filters to play a significant role in research and understanding of algebras.