Frequency Response Of Filter Research Articles

Compact cross‐coupled filters based on isosceles right triangular and equilateral triangular SIW cavities

Two kinds of classical triangular metric resonant cavities including the isosceles right triangular and equilateral triangular metric cavities are investigated carefully. A comprehensive and rigorous derivation process of these two resonant cavities is proposed. Based on this, the mode function and the transverse field components for the modes in the triangular substrate-integrated waveguide (SIW) cavities can be provided. Then the resonant frequency of both kinds of triangular SIW cavities can be calculated. Combined it with the coupling matrix, a fourth-degree filter implemented of isosceles right triangular SIW cavities and a sixth-degree filter formed by equilateral triangular SIW cavities are designed, fabricated and measured in detail. The measured results are in line with the simulated ones. The frequency responses of both filters show a pair of transmission zeroes at each side of the pass band due to the cross-coupling structure. It also verifies the validity of the derivation in this study. Compared with the rectangular and circular resonant ones, the construct of the triangular cavity has the advantage of much more compact. Besides, the proposed filters based on the triangular cavity also have their own advantages of low cost, good selectivity and easy integration with other planar circuits.

A Novel 2-D FIR Filter Design Methodology Based on a Gaussian-Based Approximation

This letter presents a novel design method for multidimensional finite-impulse response (FlR) filters based on the representation of the desired frequency response by using a Gabor system generated by a Gaussian function. A direct synthesis of the desired filter frequency response is obtained from standard design specifications. Further, we report some comparative tests with the well known Parks–McClellan's methodology in order to illustrate the concrete advantages of the novel design approach that we have proposed. With such an approach, the design procedure turns out to be especially simple to implement, as it employs closed design formulas which directly link filter coefficients to design specifications, and moreover, affords a better pass-band flatness than any known design approach. It also yields stop-band attenuations and grants control over critical frequencies, which turn out being very close to those obtainable with Parks–McClellan method. The enhanced performance of the 2-D filters thus obtained are well suited for space applications.

MONITORING THE AFR OF THE INFORMATION SIGNAL FILTER OF A FLUX-GATE MAGNETOMETER ON THE EXAMPLE OF A SINGLE LINK BUTTERWORTH FILTER

The content of this paper relates to the field of monitoring the parameters of a magnetic field (MF) meter with a MF a fluxgate sensor. The article directly discusses the control method for the amplitude frequency response (AFR) of the second harmonic filter of an EMF fluxgate meter. The purpose of the work is to minimize the workplace (WP) equipment for magnetometer monitoring. We suggest an AFR monitoring method based on three readings. As an input signal source, while monitoring an AFR filter, we suggest the use of a WP fluxgate meter. The fluxgate meter is installed in a magnetic screen. The method consists in generating the filter input signal using the magnetometer. The essence of the suggested method is to analyze the AFR symmetry. As the base filter, we use a second-order Butterworth filter with a narrowband symmetric AFR. The effect of the electrical element filter ratings is systematized in the form of a correspondence table: an electric element – an AFR parameter. We present the AFR sufficiency control analysis in terms of its symmetry. The AFR monitoring, in terms of its symmetry, has been supplemented with the Kр(f0) monitoring using the personal computer. We demonstrate the peculiarities of using a fluxgate meter as an input signal source. We derived the ratio of the magnetometer electronic part parameters that affect the accuracy (discreteness) of the filter’s input signal generation. We present an algorithm with a description of the magnetometer operation in the AFR monitoring mode.

Meander Microwave Bandpass Filter on a Flexible Textile Substrate

This paper presents an alternative process to fabricate flexible bandpass filters by using an embroidered yarn conductor on an electronic textile. The novelty of the proposed miniaturized filter is its complete integration on the outfit, with benefits in terms of compressibility, stretchability, and high geometrical accuracy opening the way to develop textile filters for wearable applications in sport and medicine. The proposed design consists of a fully embroidered microstrip topology with a length equal to quarter wavelength (λ/4) to develop a bandpass filter frequency response. A drastic reduction in the size of the filter was achieved by taking advantage of a simplified architecture based on meandered-line stepped impedance resonator. The e-textile microstrip filter was designed, simulated, fabricated, and measured with experimental validation at a 7.58 GHz frequency. The insertion loss obtained by simulation of the filter was substantially small. The return loss was greater than 20 dB for bands. To explore the relations between the physical parameters and filter performance characteristics, a theoretical equivalent circuit model of the filter constituent components was studied. The bending effect of the e-textile filter was also studied. The results showed that by raising the radius of bending to 40 mm, the resonance frequency was raised to 4.25 MHz/mm.

Optimization of the FIR Filter Structure in Finite Residue Field Algebra

This paper introduces a method for optimizing non-recursive filtering algorithms. A mathematical model of a non-recursive digital filter is proposed and a performance estimation is given. A method for optimizing the structural implementation of the modular digital filter is described. The essence of the optimization is that by using the property of the residue ring and the properties of the symmetric impulse response of the filter, it is possible to obtain a filter having almost a half the length of the impulse response compared to the traditional modular filter. A difference equation is given by calculating the output sample of modules p1 … pn in the modified modular digital filter. The performance of the modular filters was compared with the performance of positional non-recursive filters implemented on a digital signal processor. An example of the estimation of the hardware costs is shown to be required for implementing a modular digital filter with a modified structure. This paper substantiates the expediency of applying the natural redundancy of finite field algebra codes on the example of the possibility to reduce hardware costs by a factor of two. It is demonstrated that the accuracy of data processing in the modular digital filter is higher than the accuracy achieved with the implementation of filters on digital processors. The accuracy advantage of the proposed approach is shown experimentally by the construction of the frequency response of the non-recursive low-pass filters.

INVESTIGATION OF EXHAUSTING PHENOMENA OF GAS TURBINE ENGINE ON THE BASIS OF WAVELET ANALYSIS

The method for research of a gas turbine engine (GTE) surging phenomena based on wavelet analysis was developed. GTE DG-90 was chosen for research. A wavelet decomposition of the air pressure signal was carried out using a high pressure compressor and Dobeski, Symlet, Coffle and Meyer's discrete wavelet. The advantages and disadvantages of filtering properties of these wavelets were graphically represented in the form of amplitude-frequency characteristics. Based on the results obtained, a wavelet transform parameter selection scheme based on the analysis of the frequency response of wavelet filters was constructed, and the optimum sampling time of the wavelet filtering of the investigated signal was calculated for determination of the propagation and rotational breakdown in the GTE turbocompressor. According to this scheme, among the wavelets of Dobeski, Simlet, Koefleta, and Meyer's discrete wavelet, for studying the air pressure signal at the compressor during bursting processes, the first were selected by the Dobeches and Symmetes wavelets of the 2nd order according to their filtration rate. Considering high speed and characteristics of the description of the occurrence of excite phenomena by means of a fast Fourier transform to the distribution of the wavelet coefficients of the air pressure signal by turbocompressor, for the diagnosis of unstable flows occurring in the gas path of the gas turbine trajectory (surging and rotary breakdown), the Dobeski wavelet was selected 2nd order. At the same time, to monitor the wavelet coefficients behavior, the detail of the investigated signal is necessary at the 7th level of decomposition. Thus, the obtained results allow to carry out further analysis of breakdown processes using low-order wavelets.

Design of a new low power MISO multi-mode universal biquad OTA-C filter

ABSTRACTIn this article, a new low-power multiple-input, single-output (MISO) multi-mode universal biquad operational transconductance amplifier-capacitor (OTA-C) filter with a minimum number of active and passive components is proposed. The proposed filter employs three OTAs, one inverter and two grounded capacitors. The proposed filter can realise all filter frequency responses including low-pass (LP), band-pass (BP), high-pass (HP), band-stop (BS) and all-pass (AP) in all operation modes including voltage, current, tranasresistance and transconductance modes using the same topology. Furthermore, sensitivity analysis is done which shows that the proposed filter has a low sensitivity to the values of the active and passive elements. The proposed filter is simulated in HSPICE using 0.18 µm CMOS technology. The HSPICE simulation results demonstrate that the proposed filter consumes only 35 μW at 2.5 MHz from a ±0.5 V supply voltage, while all of the transistors are biased in strong inversion region. Also, the simulation results are in a close agreement with the theoretical analysis which is done in MATLAB. Furthermore, the process, voltage and temperature variation simulations are done to study the effect of non-idealities on the performance of the proposed filter. It is shown that the simulation results justify a 4.8%, 0.8% and 20% variations of the centre frequency for process, voltage and temperature, respectively. Finally, Monte-Carlo, noise and transient simulations are done to justify the good performance of the proposed filter performance.

A New Iterative FIR Filter Design Approach Using a Gaussian Approximation

The letter presents a novel iterative methodology for the design of FIR filters based on an approximation of the desired filter frequency response using a Gabor system generated by the Gaussian function. The proposed method exhibits simplicity of implementation, comparable to that of window-based design methods and ensures accuracy in the fulfillment of design requirements, comparable to the one achieved by the Parks–McClellans method. Furthermore, two other advantages of this method are: closed-form formula for the tap coefficients of the filter and the smooth, monotonically decreasing behavior of the frequency response from dc to infinite frequency.

Reconfigurable multilayer dual-mode bandpass filter based on memristive switch

A novel memristor-based multilayer dual-mode resonator is presented, which is suitable for the design of reconfigurable multi-band filters. The memristor is used as an RF/microwave switch. A dual-band bandpass filter is realized with the proposed memristor-based dual-mode resonators. The corresponding memristor setup circuitry is optimized in order to minimize the circuitry influence on the desired filter frequency response.

Planar tunable graphene based low-pass filter in the terahertz band.

In this paper, design and analysis of planar graphene-based low-pass filters in the terahertz band are proposed. Using the proposed approach, it is possible to design plasmonic low-pass filters with the desired properties in the form of open stubs. The transfer matrix method is used based on the transmission line model for analyzing filters. The propagation constant and characteristic impedance required for this method are obtained according to the electrostatic scaling law and power-current approach, respectively. A typical fifth-degree low-pass filter is designed and analyzed according to the mentioned process. The frequency response of the low-pass filter indicates insertion loss of less than 2dB, roll-off rate of 17dB/THz, return loss higher than 10dB, and constant group delay of 0.3ps. The results of the full-wave simulation confirm the analytical ones. Also, the theory of graphene equivalent circuit variation to the different chemical potentials is expressed so the filter frequency response can be explicitly predicted for any bias value. These filters, due to their compact structure and integrated electrical and physical shape, are the suitable choice for use in full-integrated planar circuits of terahertz systems.

Performance optimization methods for switched-capacitor biquadratic filters

Abstract A class of computer-aided optimization methods based on Differential Evolution (DE), Particle Swarm Optimization (PSO) and Nelder Mead algorithms applied to a switched-capacitor (SC) filter circuit design are investigated. Comparisons of these algorithms applied to a 4th order biquadratic two-channel filter bank CMOS design on 0.35 µm technology are made. The frequency responses of the biquadratic filters must match ideal responses in a finite number of iterations with a limited number of “particles”. The original and derived methods are evaluated on the base of their convergence progress and their reliability over different starting populations. An optimal design approach based on combining algorithms is derived as a more suitable and more reliable method for SC circuit optimization.

CPW based Band Pass Filter Using DGS for ISM Band Applications

The design and simulation of coplanar waveguide (CPW) bandpass filter (BPF) has been described in this paper. It mainly focuses on Defected Ground Structure (DGS), where U-shaped DGS with open stub in transmission line has been introduced. By etching the DGS pattern in ground and transmission will change the distribution of inductance and capacitance to produce filtering effect. This paper also discusses about the influence of geometrical parameter l for the improvement in the frequency response of bandpass filter. As increasing the dimension of the geometric parameter l shift the center frequency to the higher frequencies. This filter offers a bandwidth of 1.65 GHz with passband ranging from 2.1 GHz to 3.75 GHz with a stopband rejection is about -28 dB.

Innovative Filter Topology for Power Grid Protection from Switching Ripple Harmonics Produced by Matrix Converter

This article presents an innovative CLCR filter topology for protecting power grid from switching ripple harmonics produced by AC drives based on a direct matrix converter. The filter as an intermediate link between the power grid and the matrix drive is an essential part. Choosing the correct filter topology and filter components value would reduce filter weight, size and cost. This is especially important for high-power matrix matric converter-based AC drives. Depending on the composition of the harmonics generated by the matrix converter and the frequency response of the filters, the traditional LCR filter is supplemented with a small capacity capacitor. This changed the filter frequency response and increased the filter attenuation rate at the frequency range of switching ripple harmonics generated by the matrix converter. The effectiveness of the innovative CLCR topology has been demonstrated through simulations using MATLAB and MATLAB/Simulink and experimental results on a laboratory prototype.

Unsupervised selection of the singular spectrum components based on information theory for bioacoustic signal filtering

In this work, we present a comprehensive study of Singular Spectrum Analysis (SSA) applied to bioacoustics signal enhancement. The SSA method decomposes the signal into oscillatory components with physical meaning, allowing us to analyze different sound frequencies. One of the major SSA's challenges is how to choose those oscillatory components that will result in a better signal reconstruction, with less noise and distortion. We thus examine three entropy-based criterions for choosing such components. The quantifiers evaluated are: Amplitude Entropy, Spectral Entropy, and Permutation Entropy. The convergence of these quantifiers for different contamination conditions is provided. We then propose a grouping algorithm to arrange these components according to their entropy values. With the proposed rule, it is possible to identify the predominantly deterministic inner structure of the signal, in an unsupervised manner. We perform two different evaluations. First, we test a synthetic amplitude modulated signal contaminated with white, blue, pink, red, and violet color noises at 0 dB. Second, we analyze three audio calls of different anuran species recorded in the rainforest. The best quality of the recovered signal assessed through the Mean Square Error and the Signal-to-Distortion Ratio are 0.21 and 7.23 respectively for a white noise contamination applying the Permutation Entropy-based rule. Therefore, we conclude that our criterion is suitable for real scenarios under severe noise conditions, easily identifying trends and low-frequency components with a narrow band spectrum. Furthermore, we show how to derive an optimal FIR filter from SSA's components to build a specific filter bank for each species. We then present the magnitude–frequency response of the FIR filters of a bioacoustic anuran call.

Method of the out-of-band rejection improvement of the AlN based surface acoustic wave filters

AlN based surface acoustic wave (SAW) filters with an acoustic wavelength (λ) of 8 µm have been fabricated based on sputtered AlN films on sapphire. The acoustic velocity of 1-µm-AlN/Sapphire bilayer structure is 5536 m/s, 60% higher than that of LiNbO3. The central frequency, insertion loss, out-of-band rejection, and bandwidth of fabricated AlN based two-port type SAW filters with a delay gap of λ are 692 MHz, 25.58 dB, 35.40 dB, and 2.7 MHz, respectively. The impact of delay gap on the performance of AlN based filters have been studied experimentally. By the analysis of frequency response of SAW filters with delay gaps of λ, 15λ, and 30λ with and without time gating technique, we find that increase the delay gap of AlN based SAW resonators can improve the out-of-band rejection effectively because of the reduction of electromagnetic coupling, with a cost of a little degradation of insertion loss due to the small propagation loss of AlN/Sapphire bilayer. When the delay gap is increased from λ to 15λ, out-of-band rejection of AlN based filters is increased by 4.75 dB, while the insertion loss is only increased by 0.81 dB. When the delay gap is further increased from 15λ to 30λ, the suppression of out-of-band rejection is not obvious.

Novel configuration of a HTS filter with adjustable transmission zeros based on a modified cascaded quartet structure

A novel configuration for adjusting the relative position of transmission zeros (TZs) based on the cascaded quartet (CQ) structure filter is proposed. By simply introducing joint cross coupling (JCC) between two adjacent CQ units of the filter and changing its coupling strength, the relative position of TZs produced by the conventional CQ units can be altered easily so as to achieve better selectivity and out-of-band rejection. The filter with the proposed configuration is named a quasi-CQ (QCQ) configuration filter in this paper. The symmetrical QCQ configuration filter can obtain the frequency response of the asymmetrical filter, so the design difficulty of filters with multiple pairs of separated TZs is greatly reduced. A series of prototypes of QCQ configuration filters is given and analyzed to provide design guidance for designers in the future. Finally, the correctness and feasibility of the proposed approach are verified by fabricating and measuring a symmetrical high-temperature superconducting QCQ configuration filter, and the test results accord well with the simulated ones.

ACCOUNTING OF INSTRUMENTAL ERRORS IN THE CONTROL OF WINDINGS OF ELECTRICAL MACHINES WITH THE USE OF QUASI-PERIODIC TEST SIGNALS

The solution of problems of diagnostics of windings of electric machines is associated with the necessity of selection of quasi-periodic test signals against the background noise. In order to highlight useful signals, as a rule, the differences in spectral compositions of signals and noises are used. Ideally, the shape of the optimal filter frequency response should coincide with the shape of the spectrum of the useful signal, which determines the complexity of such a filter. The aim of the research is to increase the accuracy of measurements and simplify the algorithmic support of measuring systems by developing a mathematical tool that makes it possible to uniquely identify and take into account errors caused by the finiteness of the measurement intervals in the processing. Determining a one-to-one relationship between local variations of signal time parameters and alterations in its spectrum parameters is believed to be the reserve of increase of sensitivity of methods of processing of quasi-periodic signals in the conditions of constant growth of computing capabilities of measuring instruments. Variations in the values of the parameters of the signals lead to a violation of the original distribution of the harmonic components, some of the latter being subjected to the greatest alterations changes, and the some other – to the smallest ones. It is proposed to increase the accuracy of measurements due to the replacement the low-sensitivity registration of alterations in the time parameters of signals with the registration of alterations in the parameters of the characteristic harmonic components of the spectrum, which have a maximum sensitivity to deviations of the controlled parameter and a minimum sensitivity to deviations caused by the instability of the measuring equipment. The mathematical tool corresponding to the practice has been developed, that makes it possible to determine unambiguously the errors caused by finiteness of measurement intervals of quasi-periodic signals. Automatic accounting of these errors makes it possible to do without complex correlation processing of quasi-periodic signals that require large computing resources (time and speed of data processing, the amount of RAM) and to ensure the accuracy of measurements.

Full Wave Simulation and Design of Film Bulk Acoustic Wave Filters

In order to simulate the frequency response of thin film bulk acoustic wave filter accurately, the MBVD model of film bulk acoustic wave filter chip and three dimension electro-magnetic model of package were respectively established. And then, the collaborative simulation of acoustic and electro-magnetic components was realized in ADS software. Finally, thin film bulk acoustic wave filter with working frequency of 2.825GHz and 5.6 GHz were designed and fabricated by this method. Insertion loss of 2.825GHz FBAR filter is less than 1.5dB, and rejection is more than 40dB. Insertion loss of 5.6GHz FBAR filter is less than 1.7dB, and rejection is more than 30dB. The simulation and experimental results show that the proposed method has good design precision and can simulate the influence of package on the performance of the filter accurately.

Realization of a recursive digital filter based on penalized splines

In this paper the possibility of development of the recursive digital filter using a P-spline is considered. The frequency and time response of the spline filter for real-time data are analytically obtained and investigated. The influence of the P-spline parameters on effectiveness of interpretation is explored with input metrical data. The patterns obtained during spline filter frequency analysis are confirmed by an example of Doppler function restoration.

Stimulated Brillouin Scattering Enhanced Fibers for Narrow-Band Filtering by Tailoring Brillouin Gain Spectrum

A novel highly nonlinear optical fiber with enhanced stimulated Brillouin scattering for narrow-band filtering is proposed. Herein, we initially discuss the tailoring of the Brillouin gain spectrum in germanium and fluorine co-doped single cladding fibers. By adjusting the fiber structure and the doping concentration, the excitation of optical and acoustic modes, as well as coupling efficiency between them, can be manipulated properly. Then a double cladding structure is introduced in order to mitigate the accompanying undesired four-wave mixing effect. The simulation results show that the Brillouin gain spectrum of the proposed fiber is composed of single peak, corresponding to the fundamental optical mode and fundamental acoustic mode. The Brillouin gain efficiency is ∼2.45 m−1 ·W−1, and the bandwidth is ∼17 MHz. Finally, the experimental and simulated frequency responses of the narrow-band optical filter utilizing the proposed fiber are in good agreement.