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Journal articles on the topic 'Frequency filters'
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1
Trantham, E. Clark. "Minimum uncertainty filters for pulses." GEOPHYSICS 58, no. 6 (June 1993): 853–62. http://dx.doi.org/10.1190/1.1443469.
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The objective of this paper is to calculate filters with a minimum uncertainty, the product of filter length and bandwidth. The method is applicable to producing minimum uncertainty filters with time or frequency domain constraints on the filter. The calculus of variations is used to derive the conditions that minimize a filter’s uncertainty. The general solution is a linear combination of Hermite functions, where the Hermite functions are summed from low to high order until the filter’s constraints are met. Filters constrained to have zero amplitude at zero hertz have an uncertainty at least three times greater than expected from the uncertainty principle, and the minimum uncertainty filter is a first derivative Gaussian. For the previous filter, the minimum uncertainty high cut filter is a Gaussian function of frequency, but the minimum uncertainty low cut filter is a linear function of frequency.
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Bader, Milad, Robert G. Clapp, and Biondo Biondi. "Denoising for full-waveform inversion with expanded prediction-error filters." GEOPHYSICS 86, no. 5 (August 31, 2021): V445—V457. http://dx.doi.org/10.1190/geo2020-0573.1.
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Low-frequency data of less than 5 Hz are essential to the convergence of full-waveform inversion (FWI) toward a useful solution. They help to build the velocity model low wavenumbers and reduce the risk of cycle skipping. In marine environments, low-frequency data are characterized by a low signal-to-noise ratio (S/N) and can lead to erroneous models when inverted, especially if the noise contains coherent components. Often, field data are high-pass filtered before any processing step, sacrificing weak but essential signal for FWI. We have denoised the low-frequency data using prediction-error filters that we estimate from a high-frequency component with a high S/N. The constructed filter captures the multidimensional spectrum of the high-frequency signal. We expand the filter’s axes in the time-space domain to compress its spectrum toward the low frequencies and wavenumbers. The expanded filter becomes a predictor of the target low-frequency signal, and we incorporate it in a minimization scheme to attenuate noise. To account for data nonstationarity while retaining the simplicity of stationary filters, we divide the data into nonoverlapping patches and linearly interpolate stationary filters at each data sample. We apply our method to synthetic stationary and nonstationary data, and we find that it improves the FWI results initialized at 2.5 Hz using the Marmousi model. We also demonstrate that the denoising attenuates nonstationary shear energy recorded by the vertical component of ocean-bottom nodes.
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Li, Luping, Lijuan Dong, Peng Chen, and Kai Yang. "Multi-band rejection filters based on spoof surface plasmon polaritons and folded split-ring resonators." International Journal of Microwave and Wireless Technologies 11, no. 08 (April 17, 2019): 774–81. http://dx.doi.org/10.1017/s1759078719000369.
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AbstractA dualband rejection filter and a triband rejection filter are proposed in this letter, both of which are implemented by cascading spoof surface plasmon polaritons (SSPPs) of the same structure but with diverse rejection bands. Compared with traditional ones, the proposed filters provide more compact structures, wider rejection bands, and better independent tunability. In the proposed filters, the rejection bandwidth, the center frequency of the rejection band and the filter's cutoff frequency can be adjusted independently. And the different rejection bands in the same filter also can be independently controlled. Agreements between the dispersion of SSPP units and the S21 of filters are also presented. Measurement results demonstrate that both filters load multiple rejection bands on the 27.7 GHz wide low-pass band and all the rejection bands locate in Ku and K bands. The average rejection bandwidth and the average rejection depth of the two filters are 1.49 GHz and 42.1 dB, respectively.
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Abdolvand, Reza, and Farrokh Ayazi. "High-frequency monolithic thin-film piezoelectric-on-substrate filters." International Journal of Microwave and Wireless Technologies 1, no. 1 (February 2009): 29–35. http://dx.doi.org/10.1017/s175907870900004x.
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A class of micromachined acoustic filters is presented in which the number of individual resonant structures is reduced to 1 (monolithic filter). This resonant structure is comprised of a stack of thin-film piezoelectric-on-silicon. Symmetric and anti-symmetric resonance modes (dual modes) of the silicon structure are piezoelectrically excited and coupled to realize a 2-pole narrowband filter. High-order lateral bulk acoustic resonance modes of a rectangular plate are utilized to design dispersed-frequency UHF filters fabricated on a single substrate. Thickness mode filters are also realized at GHz frequencies using a new interdigitated electrode design. Additionally, it is shown that the filter bandwidth can be controlled by changing the dimensions of the resonant structure and the electrode pattern. Narrowband lateral mode filters with filter Q’s larger than 300 at ~440 MHz and thickness mode filters with filter Q’s in the range of 150–900 at ~3.1 GHz are demonstrated.
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Smirnov, A. V. "Optimization of digital filters performances simultaneously in frequency and time domains." Russian Technological Journal 8, no. 6 (December 18, 2020): 63–77. http://dx.doi.org/10.32362/2500-316x-2020-8-6-63-77.
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Wide used method of digital filters design consists in transformation of analog filter-prototype with required performances into digital filter. This method is applicable if the transformation preserves optimality of filter performances under specified set of quality indexes (QI). It was denoted earlier that such situation is possible when gain-frequency response (GFR) and phase-frequency response are optimized simultaneously. The task of simultaneous optimization of digital filters GFR and step response (SR) is also important but yet a little explored. Alternative method of this problem solving consists in search of digital filter transfer function (TF) which is optimal under GFR and SR QI’s. To investigate capabilities of the first method we found examples of analog filters Pareto-optimal under rise time and transient duration. Other QI’s of these filters fulfilled specified constraints. Then these filters were transformed into digital filters. Bilinear transformation and transformation with invariant impulse response were applied. Further we did the search of digital filters optimal under the same set of QI’s. In either method the hybrid heuristic algorithm was applied for search optimal solutions in the space of TF poles and zeroes coordinates. The results of investigation demonstrated that digital filters developed via search are superiorly under specified set of QI’s then digital filters developed via transformation of analog filters. Accordingly Pareto-optimality for QI of GFR and SR is not preserved during such transformation and direct search must be applied to optimized digital filters simultaneously in frequency and time domains. Further in some cases analog filters developed via reverse bilinear transformation of the found optimal digital filters are superiorly under the same set of QI’s then analog filters developed using search. In such cases using of digital filter-prototypes for design of analog filters is practical.
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GUSTAFSSON, OSCAR, HÅKAN JOHANSSON, and LARS WANHAMMAR. "SINGLE FILTER FREQUENCY-RESPONSE MASKING FIR FILTERS." Journal of Circuits, Systems and Computers 12, no. 05 (October 2003): 601–30. http://dx.doi.org/10.1142/s0218126603001094.
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In this work filter structures that decrease the required number of multipliers and adders for implementation of linear-phase FIR filters using frequency-response masking techniques are introduced. The basic idea of the proposed structures is that identical subfilters are used. This leads to the same arithmetic structure can be multiplexed in the implementation, reducing the number of required multipliers and adders. The subfilters are mapped using the folding transformation to obtain an area-efficient time-multiplexed (or pipeline/interleaved) implementation. Both narrow-band and wide-band frequency-response masking as well as arbitrary bandwidth frequency-response masking techniques are considered. The filter design is discussed and for each filter structure the limits on the specifications are derived. Designed examples show the usefulness of the proposed structures.
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Schlecht, Sebastian J. "Frequency-Dependent Schroeder Allpass Filters." Applied Sciences 10, no. 1 (December 25, 2019): 187. http://dx.doi.org/10.3390/app10010187.
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Since the introduction of feedforward–feedback comb allpass filters by Schroeder and Logan, its popularity has not diminished due to its computational efficiency and versatile applicability in artificial reverberation, decorrelation, and dispersive system design. In this work, we present an extension to the Schroeder allpass filter by introducing frequency-dependent feedforward and feedback gains while maintaining the allpass characteristic. By this, we directly improve upon the design of Dahl and Jot which exhibits a frequency-dependent absorption but does not preserve the allpass property. At the same time, we also improve upon Gerzon’s allpass filter as our design is both less restrictive and computationally more efficient. We provide a complete derivation of the filter structure and its properties. Furthermore, we illustrate the usefulness of the structure by designing an allpass decorrelation filter with frequency-dependent decay characteristics.
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Milic, Ljiljana, and Tapio Saramaki. "Power-complementary IIR filter pairs with an adjustable crossover frequency." Facta universitatis - series: Electronics and Energetics 16, no. 3 (2003): 295–304. http://dx.doi.org/10.2298/fuee0303295m.
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This paper introduces two classes of power-complementary recursive low-pass/high-pass filter pairs with an adjustable crossover frequency in such a way that the stopband attenuation of both filters remains the same. For each class, the filter pair is constructed using two all-pass sub-filters as building blocks. Based on the properties elliptic minimal Q-factors transfer functions, simple expressions are derived for evaluating the coefficients in all-pass sections in order to achieve the desired crossover frequency. The design procedures are developed for synthesizing power-complementary filter pairs implemented as a parallel connection of two all-pass sub-filters and for the tapped cascaded interconnections of two identical all-pass sub-filters. The direct parallel connection has both the power-complementary and all-pass complementary property. The second class of filters constructed using several identical copies of the two all-pass filters possesses the power-complementary property.
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Smirnov, A. V. "The analysis of conditions for preservation of gain-frequency and phase-frequency characteristics optimality under analog and digital filters transformation." Russian Technological Journal 8, no. 2 (April 14, 2020): 43–58. http://dx.doi.org/10.32362/2500-316x-2020-8-2-43-58.
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Prototype filters have wide usage for the design of filters with required quality indexes (QI) of gain-frequency response (GFR). The designed filter is obtained from a prototype filter b means of frequency transformation, which preserves these QI. But most of employed frequency transformations result in variations of QI of phase-frequency response (PFR). In this paper we proposed to use prototype filters that are Pareto-optimal for QI of GFR and PFR. Transfer functions of these filters may be found by means of heuristic optimization algorithms. This method will be efficient if the frequency transformation preserves the optimality of filters. It was shown that frequency transformation has this feature if it preserves the result of QI comparison (more or less) for filters with equal orders. Compliance of this criterion was checked for bilinear transformation of analog low pass filters (LPF) into digital LPF and for Konstantinidis transformation of digital LPF into other digital LPF. The analysis showed that Pareto-optimality for QI of GFR and PFR is preserved if the delay-frequency characteristic of the filter has a minimum at zero frequency and has a maximum at the upper boundary of the pass band. These conditions are complied for LPF with sufficiently small unevenness of GFR in the pass band and sufficiently fast decline of GFR at higher frequencies. Examples confirming these conclusions are given.
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Sessions, Deanna, Alexander Cook, Kazuko Fuchi, Andrew Gillman, Gregory Huff, and Philip Buskohl. "Origami-Inspired Frequency Selective Surface with Fixed Frequency Response under Folding." Sensors 19, no. 21 (November 5, 2019): 4808. http://dx.doi.org/10.3390/s19214808.
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Filtering of electromagnetic signals is key for improved signal to noise ratios for a broad class of devices. However, maintaining filter performance in systems undergoing large changes in shape can be challenging, due to the interdependency between element geometry, orientation and lattice spacing. To address this challenge, an origami-based, reconfigurable spatial X-band filter with consistent frequency filtering is presented. Direct-write additive manufacturing is used to print metallic Archimedean spiral elements in a lattice on the substrate. Elements in the lattice couple to one another and this results in a frequency selective surface acting as a stop-band filter at a target frequency. The lattice is designed to maintain the filtered frequency through multiple fold angles. The combined design, modeling, fabrication, and experimental characterization results of this study provide a set of guidelines for future design of physically reconfigurable filters exhibiting sustained performance.
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Chung, Daewon, Woon Cho, Inyeob Jeong, and Joonhyeon Jeon. "Design of Cut Off-Frequency Fixing Filters by Error Compensation of MAXFLAT FIR Filters." Electronics 10, no. 5 (February 26, 2021): 553. http://dx.doi.org/10.3390/electronics10050553.
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Maximally-flat (MAXFLAT) finite impulse response (FIR) filters often face a problem of the cutoff-frequency error due to approximation of the desired frequency response by some closed-form solution. So far, there have been plenty of efforts to design such a filter with an arbitrarily specified cut off-frequency, but this filter type requires extensive computation and is not MAXFLAT anymore. Thus, a computationally efficient and effective design is needed for highly accurate filters with desired frequency characteristics. This paper describes a new method for designing cutoff-frequency-fixing FIR filters through the cutoff-frequency error compensation of MAXFLAT FIR filters. The proposed method provides a closed-form Chebyshev polynomial containing a cutoff-error compensation function, which can characterize the “cutoff-error-free” filters in terms of the degree of flatness for a given order of filter and cut off-frequency. This method also allows a computationally efficient and accurate formula to directly determine the degree of flatness, so that this filter type has a flat magnitude characteristic both in the passband and the stopband. The remarkable effectiveness of the proposed method in design efficiency and accuracy is clearly demonstrated through various examples, indicating that the cutoff-fixing filters exhibit amplitude distortion error of less than 10−14 and no cut off-frequency error. This new approach is shown to provide significant advantages over the previous works in design flexibility and accuracy.
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Tüzün, Reşat, and Nursel Akçam. "Design of Microstrip Low Pass Filters." Academic Perspective Procedia 1, no. 1 (November 9, 2018): 47–55. http://dx.doi.org/10.33793/acperpro.01.01.13.
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Microstrip filters have a significant role in Radio Frequency/Microwave applications. Microstrip filters are common on microwave circuits, satellite communications, radars, test equipments and so on. Because microstrip filters are compact, cheap and easy to produce, they are highly preferred for microwave applications. Microwave filter; microwave system is a two-ported element used to control the frequency response at a certain point by attenuating the frequencies in the stop band by transmitting in the frequency band. Typical frequency responses are low pass, high pass, band pass and band stop. Also approaches such as Butterworth, Chebyshev, and Elliptic are defining filter characteristics. In this paper, microstrip filters havign Chebyshev, Elliptic and Maximally Flat approaches were designed. For example Chebyshev filter of design filters having 6 GHz cut frequency and having 46,34 dB at 6,6 GHz. The insertion loss is -3,66 dB at 6 GHz. AWR Sonnet is used for the simulation and analysis of this filters.
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SARAMÄKI, TAPIO, JUHA YLI-KAAKINEN, and HÅKAN JOHANSSON. "OPTIMIZATION OF FREQUENCY-RESPONSE MASKING BASED FIR FILTERS." Journal of Circuits, Systems and Computers 12, no. 05 (October 2003): 563–91. http://dx.doi.org/10.1142/s0218126603001070.
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A very efficient technique to drastically reduce the number of multipliers and adders in implementing linear-phase finite-impulse response (FIR) digital filters in applications demanding a narrow transition band is to use the frequency-response masking (FRM) approach originally introduced by Lim. The arithmetic complexity can be even further reduced using a common filter part for constructing the masking filters originally proposed by Lim and Lian. A drawback in the above-mentioned original FRM synthesis techniques is that the subfilters in the overall implementations are separately designed. In order to further reduce the arithmetic complexity in these two FRM approaches, the following two-step optimization technique is proposed for simultaneously optimizing the subfilters. At the first step, a good suboptimal solution is found by using a simple iterative algorithm. At the second step, this solution is then used as a start-up solution for further optimization being carried out by using an efficient unconstrained nonlinear optimization algorithm. An example taken from the literature illustrates that both the number of multipliers and the number of adders for the resulting optimized filter are less than 80% compared with those of the FRM filter obtained using the original FRM design schemes in the case where the masking filters are separately implemented. If a common filter part is used for realizing the masking filters, then an additional reduction of more than 10% is achieved compared with the optimized design with separately implemented masking filters.
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Ragani, Taoufik, N. Amar Touhami, and M. Agoutane. "Designing a Microstrip coupled line bandpass filter." International Journal of Engineering & Technology 2, no. 4 (September 6, 2013): 266. http://dx.doi.org/10.14419/ijet.v2i4.1173.
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Bandpass filters play a significant role in wireless communication systems. Transmitted and received signals have to be filtered at a certain center frequency with a specific bandwidth, in this paper, a coupled-line bandpass Filter at the center frequency 6 GHz with the wide bandwidth of 2 GHz. this type of filter can be used in WLAN and other applications for the frequency range of 5-7 GHz.
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Chervinskiy, Evgeniy N. "DESIGN OF BAND-PASS FILTERS WITH NON-EQUIRIPPLE FREQUENCY RESPONSES." Journal of the Russian Universities. Radioelectronics 22, no. 3 (July 2, 2019): 5–23. http://dx.doi.org/10.32603/1993-8985-2019-22-3-5-23.
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Introduction. Band-pass filters circuit elements can be calculated by converting low-pass filter (LPF) parameters, which is the prototype of the designed band-pass filter. The conversion causes problems in case calculated values of circuit elements (resistors and capacitors) are out of standard values determined by the GOST standard. Obviously, frequency characteristics of band-pass filters are distorted when replacing the calculated values of circuit elements by the standard ones. The number of circuit elements with values different from standard can be reduced to zero by solving an additional system of equations that connects parameters of designed and reintroduced non-equiripple frequency responses. Objective. The objective of this work is to develop a calculation method of band-pass ladder filters with values of circuit elements corresponding to standard ones. Materials and methods. The filter design process includes two stages. The first stage is a parameters calculation of a polynomial LPF prototype. The calculated parameters are determined as a system of equations solution set. The equations are formed by equating coefficients of variables raised to the same powers in transfer function (TF) expressions of designed and realized filters. Initial characteristics are the filter order and frequency response unevenness. The transition to the standard values of circuit elements can be done when solving another system of equations that connects LPF converted parameters with unknown parameters of reintroduced non-equiripple frequency response. Results. TF of LPF prototypes up to the fifth order and frequency responses of band-pass filters (BPF) and bandrejection filters up to the tenth order are presented. Analytical expressions of non-equiripple and equiripple frequency responses are used to estimate distortions of the latter when a band-pass filter center frequency is tuned by using variable inductors or capacitors. The integral quadratic function of a variable is taken as a measure of real frequency response distortions. The tenth order BPF calculation example is given. Conclusion. The presented calculation methods of band-pass filters and given example demonstrate possibilities of the filter design method based on the systems of non-linear equations solution. In contrast to approximation methods of ideal filter frequency response by using special functions and tabular filters design, the presented method allows high-order filter calculation for any initial requirements without using reference data.
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RAMACHANDRAN, V., and V. NINOV. "2D ZERO-PHASE FIR FILTER DESIGN WITH NONUNIFORM FREQUENCY SAMPLING." Journal of Circuits, Systems and Computers 10, no. 05n06 (October 2000): 239–77. http://dx.doi.org/10.1142/s0218126600000172.
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In this paper, nonuniform frequency sampling techniques used in the design of two-dimensional zero-phase FIR filters are proposed and investigated. The design problem is treated as a bivariate interpolation problem with unevenly spaced data. The main idea is to select (find) sampling locations in the (ω1, ω2) frequency plane and corresponding sample values Hd(ω1k, ω2k) of the desired filter frequency response such that the designed filter performance is high. Although the filters designed with the proposed techniques are not optimal, the methods are conceptually simple and produce filters with high degree of shape regularity and approximation error comparable and sometimes even smaller than the "conventional" 2D FIR filter design methods.
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Gopinathan, S., Radhakrishnan Kokila, and P. Thangavel. "Wavelet and FFT Based Image Denoising Using Non-linear Filters." International Journal of Electrical and Computer Engineering (IJECE) 5, no. 5 (October 1, 2015): 1018. http://dx.doi.org/10.11591/ijece.v5i5.pp1018-1026.
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We propose a stationary and discrete wavelet based image denoising scheme and an FFTbased image denoising scheme to remove Gaussian noise. In the first approach, high subbands are added with each other and then soft thresholding is performed. The sum of low subbands is filtered with either piecewise linear (PWL) or Lagrange or spline interpolated PWL filter. In the second approach, FFT is employed on the noisy image and then low frequency and high frequency coefficients are separated with a specified cutoff frequency.Then the inverse of low frequency components is filtered with one of the PWL filters and the inverse of high frequency components is filtered with soft thresholding. The experimental results are compared with Liu and Liu's tensor-based diffusion model (TDM) approach.
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Hu, Dan Hua, Zhao Xiong Zeng, Jing Song Meng, and Chang Hua Zhang. "Implementation of the Variable Center Frequency Band-Pass Filter Based on FPGA." Advanced Materials Research 1049-1050 (October 2014): 642–45. http://dx.doi.org/10.4028/www.scientific.net/amr.1049-1050.642.
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Digital band-pass filters play a very important role in instrument design. For some special applications, such as corrosion inspection of buried oil or gas pipeline, more than one band-pass filter with different center frequencies are needed to process different frequency signals. FPGA (Field-Programmable Gate Array) are widely used in these applications because of its high compute velocity and flexibility. For low cost and high reliability purposes, it is expected that one digital filter with a fixed configuration parameters can serve as multi different center frequency digital filter. In this paper a design method is proposed to realize two different center frequency band-pass filters which have the same filtering effect. Through analysis of design process for FIR band-pass filter, it’s easy to find that if the ratios (filter’ sample rate of input data to its cut-off frequency) of two filters keep equal, the normalized frequency will also equal. Thus according to this, two band-pass filters can have the same coefficients only if they have the same ratio of sample rate to cut-off frequency. This relationship is discussed here and MATLAB experiment is used to prove its effectiveness. This method is already used to design filters in pipeline current mapper instrument to inspect pipeline corrosion.
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Mezaal, Y. S., H. H. Saleh, and H. Al-saedi. "New Compact Microstrip Filters Based on Quasi Fractal Resonator." Advanced Electromagnetics 7, no. 4 (September 3, 2018): 93–102. http://dx.doi.org/10.7716/aem.v7i4.883.
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This paper presents new microstrip devices as single band bandpass and multi band bandstop filters. The proposed filters use slotted patch microstrip resonator based on quasi fractal geometry, simulated by AWR12 software package. Both filters have quasi elliptic frequency response, designed at centre frequency of 2.437 GHz for bandpass filter and at band frequencies of 2.434, 4.032, 4.976 and 5.638 GHz GHz respectively, for multi bandstop filter. All filters are employed using RT/Duroid 6010.8 LM substrate of dielectric constant and 1.27 mm dielectric thickness. Simulation results show that the designed quasi fractal bandpass filter has very narrow fractional bandwidth of 0.38 % which is very rare in microstrip filter design. On the other hand, the projected bandstop filter offers multi narrow rejection bands that is useful in broadband wireless schemes influencing from fixed interferences. Both filters present satisfactory S11 and S21 responses besides smallness properties that stand for interesting features of the newest wireless applications. The simulated and measured frequency responses for both designed filters are in good agreement.
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Jiang, Lei, Haijian Zhang, Shuai Cheng, Hengwei Lv, and Pandong Li. "An Overview of FIR Filter Design in Future Multicarrier Communication Systems." Electronics 9, no. 4 (March 31, 2020): 599. http://dx.doi.org/10.3390/electronics9040599.
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Future wireless communication systems are facing with many challenges due to their complexity and diversification. Orthogonal frequency division multiplexing (OFDM) in 4G cannot meet the requirements in future scenarios, thus alternative multicarrier modulation (MCM) candidates for future physical layer have been extensively studied in the academic field, for example, filter bank multicarrier (FBMC), generalized frequency division multiplexing (GFDM), universal filtered multicarrier (UFMC), filtered OFDM (F-OFDM), and so forth, wherein the prototype filter design is an essential component based on which the synthesis and analysis filters are derived. This paper presents a comprehensive survey on the recent advances of finite impulse response (FIR) filter design methods in MCM based communication systems. Firstly, the fundamental aspects are examined, including the introduction of existing waveform candidates and the principle of FIR filter design. Then the methods of FIR filter design are summarized in details and we focus on the following three categories—frequency sampling methods, windowing based methods and optimization based methods. Finally, the performances of various FIR design methods are evaluated and quantified by power spectral density (PSD) and bit error rate (BER), and different MCM schemes as well as their potential prototype filters are discussed.
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Pollock, D. S. G. "Improved frequency selective filters." Computational Statistics & Data Analysis 42, no. 3 (March 2003): 279–97. http://dx.doi.org/10.1016/s0167-9473(02)00228-1.
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Gallant, A. J., M. A. Kaliteevski, S. Brand, D. Wood, M. Petty, R. A. Abram, and J. M. Chamberlain. "Terahertz frequency bandpass filters." Journal of Applied Physics 102, no. 2 (July 15, 2007): 023102. http://dx.doi.org/10.1063/1.2756072.
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Joelianto, Endra. "On Minimal Second-order IIR Bandpass Filters with Constrained Poles and Zeros." Journal of Engineering and Technological Sciences 53, no. 4 (August 3, 2021): 210401. http://dx.doi.org/10.5614/j.eng.technol.sci.2021.53.4.1.
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In this paper, several forms of infinite impulse response (IIR) bandpass filters with constrained poles and zeros are presented and compared. The comparison includes the filter structure, the frequency ranges and a number of controlled parameters that affect computational efforts. Using the relationship between bandpass and notch filters, the two presented filters were originally developed for notch filters. This paper also proposes a second-order IIR bandpass filter structure that constrains poles and zeros and can be used as a minimal parameter adaptive digital second-order filter. The proposed filter has a wider frequency range and more flexibility in the range values of the adaptation parameters.
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Borges, Vinícius S., Erivelton G. Nepomuceno, Carlos A. Duque, and Denis N. Butusov. "Some Remarks about Entropy of Digital Filtered Signals." Entropy 22, no. 3 (March 23, 2020): 365. http://dx.doi.org/10.3390/e22030365.
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The finite numerical resolution of digital number representation has an impact on the properties of filters. Much effort has been done to develop efficient digital filters investigating the effects in the frequency response. However, it seems that there is less attention to the influence in the entropy by digital filtered signals due to the finite precision. To contribute in such a direction, this manuscript presents some remarks about the entropy of filtered signals. Three types of filters are investigated: Butterworth, Chebyshev, and elliptic. Using a boundary technique, the parameters of the filters are evaluated according to the word length of 16 or 32 bits. It has been shown that filtered signals have their entropy increased even if the filters are linear. A significant positive correlation (p < 0.05) was observed between order and Shannon entropy of the filtered signal using the elliptic filter. Comparing to signal-to-noise ratio, entropy seems more efficient at detecting the increasing of noise in a filtered signal. Such knowledge can be used as an additional condition for designing digital filters.
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Linville, A. Frank. "Single‐channel digital filter design for seismic applications." GEOPHYSICS 59, no. 10 (October 1994): 1584–92. http://dx.doi.org/10.1190/1.1443547.
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A general least‐squares, time‐domain filter design methodology has been developed that is easy to use for a variety of seismic filtering applications. The 1-D finite‐impulse response frequency filter can efficiently provide the noise attenuation and selectivity needed in modern data processing. Flexibility of design allows a choice of all basic types of single‐channel filters commonly used in processing. These include low‐pass, high‐pass, band‐pass, band‐reject, and notch filters. In addition, multiple bands may be passed or rejected using a single operator design without increasing the length of the filter. The ability to reject multiple noise bands with one filter is convenient and also reduces data processing costs. The filter can be viewed as a minimum‐phase Wiener‐Levinson predictive deconvolution filter designed to reject specified frequency bands. The filter is designed from an exact mathematical description of the specified stop bands that provide an explicit expression for the required autocorrelation lags in the normal equations. The filter’s desired frequency response (transition zone width and rejection level) is simply related to two input parameters—operator length and white noise level.
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Sharma, Pavan, Veerendra Jadaun, Devesh Mahor, and Atal Verma. "Designing Microstrip Low Pass Filter In ISM Band For Rectenna System." International Journal of Engineering & Technology 1, no. 4 (August 26, 2012): 356. http://dx.doi.org/10.14419/ijet.v1i4.287.
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The filter is required in all RF-communication techniques. Low Pass Filters play an important role in wireless power transmission systems. Transmitted and received signals have to be filtered at a certain frequency with a specific bandwidth. In this paper the design of filter is done in the ISM (Industrial, Scientific and Medical) band whose frequency lies between 1.55GHz- 3.99GHz. After getting the specifications required, we realized the filter structure with the help of CST-MW software.
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Novira, Ayu. "Filtering Sinyal Menggunakan Band Pass Filter." JTIM : Jurnal Teknologi Informasi dan Multimedia 1, no. 1 (May 15, 2019): 66–69. http://dx.doi.org/10.35746/jtim.v1i1.16.
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Sound is a signal or wave that propagates with a certain frequency and amplitude through intermediary media that are delivered such as water, air and solid objects. Humans can communicate with other humans with sound. But the sound that is released by humans, musical instruments, or other objects does not always sound clear and good, some of the recorded sound has a lot of noise which makes the sound quality is disturbed and not good. The solution for making sound in an object better and cleaner is filtering. [2]. Filters can be interpreted as a circuit that passes a certain frequency band desired and dampens other frequency bands. Filters are divided into two types, namely analog filters and digital filters. According to the impulse response the digital filter is divided into two, namely the Infinite Impulse Filter (IIR) filter and the Finite Impulse Filter (FIR) filter. In this study a filtering process will be carried out on the sound of the guitar. The filter used is the Band Pass Filter, a filter that can be used to isolate or filter certain frequencies in a particular band or frequency range.
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Sayed, Inayatullah S., and Siti S. Ismail. "Comparison of Low-Pass Filters for SPECT Imaging." International Journal of Biomedical Imaging 2020 (April 1, 2020): 1–9. http://dx.doi.org/10.1155/2020/9239753.
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In single photon emission computed tomography (SPECT) imaging, the choice of a suitable filter and its parameters for noise reduction purposes is a big challenge. Adverse effects on image quality arise if an improper filter is selected. Filtered back projection (FBP) is the most popular technique for image reconstruction in SPECT. With this technique, different types of reconstruction filters are used, such as the Butterworth and the Hamming. In this study, the effects on the quality of reconstructed images of the Butterworth filter were compared with the ones of the Hamming filter. A Philips ADAC forte gamma camera was used. A low-energy, high-resolution collimator was installed on the gamma camera. SPECT data were acquired by scanning a phantom with an insert composed of hot and cold regions. A Technetium-99m radioactive solution was homogenously mixed into the phantom. Furthermore, a symmetrical energy window (20%) centered at 140 keV was adjusted. Images were reconstructed by the FBP method. Various cutoff frequency values, namely, 0.35, 0.40, 0.45, and 0.50 cycles/cm, were selected for both filters, whereas for the Butterworth filter, the order was set at 7. Images of hot and cold regions were analyzed in terms of detectability, contrast, and signal-to-noise ratio (SNR). The findings of our study indicate that the Butterworth filter was able to expose more hot and cold regions in reconstructed images. In addition, higher contrast values were recorded, as compared to the Hamming filter. However, with the Butterworth filter, the decrease in SNR for both types of regions with the increase in cutoff frequency as compared to the Hamming filter was obtained. Overall, the Butterworth filter under investigation provided superior results than the Hamming filter. Effects of both filters on the quality of hot and cold region images varied with the change in cutoff frequency.
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Zhang, Shuai, Yong Xiang Zhang, and Jie Ping Zhu. "Rolling Bearing Feature Extraction Based on Wavelet Filtering with Optimal Combination Bands." Applied Mechanics and Materials 599-601 (August 2014): 434–40. http://dx.doi.org/10.4028/www.scientific.net/amm.599-601.434.
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In order to select the band-pass filter parameters reasonably, a new method of rolling bearing feature extraction based on wavelet filtering with optimal combination bands is proposed. Filter banks with different number of filter/octave are constructed by Morlet wavelet, which are used to filter the signal. The filters with the optimal frequency-band are selected according to the kurtosis of the filtered signal. Then, the optimal band filters in each filter bank are combined to filter the signals and the feature extraction is available. Through simulation and experimental verification, results show that the proposed method is more effective than the common one.
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Chen, Zhimin, and Lenan Wu. "Design of Special Impacting Filter for Multicarrier ABPSK System." Mathematical Problems in Engineering 2013 (2013): 1–7. http://dx.doi.org/10.1155/2013/921932.
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A rather intuitive technique known as pole-zero placement is introduced to illustrate the frequency response of the special impacting filters (SIFs) with a pair of conjugate zero-poles and deduce the equation of the pole radii. Based on that, the paper proposes an iterative scheme to derive the parameters of the cascade notch filter. The cost function is determined by the cascading notch filter’s influence on impacting filters, converting the cost function’s least square problem to a filter parameters’ standard quadratic programming problem. Finally, a cascading notch SIF (CNSIF) designed to demodulate the ABPSK signals is realized.
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Беляев, Б. А., С. А. Ходенков, И. В. Говорун, and А. М. Сержантов. "Микрополосковые фильтры с широкими полосами пропускания." Письма в журнал технической физики 47, no. 7 (2021): 30. http://dx.doi.org/10.21883/pjtf.2021.07.50796.18581.
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New microstrip designs of bandpass filters based on a low-pass filter was developed. Several or all the sections of high-impedance microstrip lines of the designed filters were connected to the ground by stubs. The filters have high frequency-selective properties, and their fractional bandwidths are in the range of 30 % –150 %. An experimental sample of a filter with a 2 GHz central frequency of the passband and 70% fractional bandwidth was made on an alumina substrate 1 mm thick. The filter has a substrate area of 46 × 21 mm2. Good agreement of the measured frequency response of the filter with the characteristics calculated by the numerical electrodynamic analysis of its 3D model was shown.
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Duda, Krzysztof, and Tomasz P. Zieliński. "Fir Filters Compliant with the IEEE Standard for M Class PMU." Metrology and Measurement Systems 23, no. 4 (December 1, 2016): 623–36. http://dx.doi.org/10.1515/mms-2016-0055.
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Abstract In this paper it is shown that M class PMU (Phasor Measurement Unit) reference model for phasor estimation recommended by the IEEE Standard C37.118.1 with the Amendment 1 is not compliant with the Standard. The reference filter preserves only the limits for TVE (total vector error), and exceeds FE (frequency error) and RFE (rate of frequency error) limits. As a remedy we propose new filters for phasor estimation for M class PMU that are fully compliant with the Standard requirements. The proposed filters are designed: 1) by the window method; 2) as flat-top windows; or as 3) optimal min-max filters. The results for all Standard compliance tests are presented, confirming good performance of the proposed filters. The proposed filters are fixed at the nominal frequency, i.e. frequency tracking and adaptive filter tuning are not required, therefore they are well suited for application in lowcost popular PMUs.
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Fridolfsson, Jonatan, Mats Börjesson, Christoph Buck, Örjan Ekblom, Elin Ekblom-Bak, Monica Hunsberger, Lauren Lissner, and Daniel Arvidsson. "Effects of Frequency Filtering on Intensity and Noise in Accelerometer-Based Physical Activity Measurements." Sensors 19, no. 9 (May 11, 2019): 2186. http://dx.doi.org/10.3390/s19092186.
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In objective physical activity (PA) measurements, applying wider frequency filters than the most commonly used ActiGraph (AG) filter may be beneficial when processing accelerometry data. However, the vulnerability of wider filters to noise has not been investigated previously. This study explored the effect of wider frequency filters on measurements of PA, sedentary behavior (SED), and capturing of noise. Apart from the standard AG band-pass filter (0.29–1.63 Hz), modified filters with low-pass component cutoffs at 4 Hz, 10 Hz, or removed were analyzed. Calibrations against energy expenditure were performed with lab data from children and adults to generate filter-specific intensity cut-points. Free-living accelerometer data from children and adults were processed using the different filters and intensity cut-points. There was a contribution of acceleration related to PA at frequencies up to 10 Hz. The contribution was more pronounced at moderate and vigorous PA levels, although additional acceleration also occurred at SED. The classification discrepancy between AG and the wider filters was small at SED (1–2%) but very large at the highest intensities (>90%). The present study suggests an optimal low-pass frequency filter with a cutoff at 10 Hz to include all acceleration relevant to PA with minimal effect of noise.
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Simas, Maria Lúcia De Bustamante, and Natanael Antonio Dos Santos. "Narrow-Band 1, 2, 3, 4, 8, 16, 24, 32, 48, 64, and 96 Cycles/360° Angular Frequency Filters." Spanish Journal of Psychology 9, no. 2 (November 2006): 240–48. http://dx.doi.org/10.1017/s1138741600006144.
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We measured human frequency response functions for eleven angular frequency filters using a forced-choice procedure in a supra-threshold summation paradigm. Each of the eleven functions of 17 experimental conditions was measured 4-9 times among 12 observers. Results show that, for the arbitrarily selected filter phases, maximum summation effect occurred at test frequency for all filters. These results lead to the conclusion that there are narrow-band angular frequency filters operating in human visual system mostly through summation surrounded by inhibition at the specific test frequency ranges. Our previous suggestion (Simas & Santos, 2002), arguing that summation for the higher angular frequency filters should occur if background angular frequency contrast were set to a maximum of 5 times the test frequency threshold, was supported.
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Bittanti, Sergio, Marco Campi, and Sergio M. Savaresi. "Notch Filters Versus Funnel Filters in Frequency Estimation." IFAC Proceedings Volumes 31, no. 22 (August 1998): 379–84. http://dx.doi.org/10.1016/s1474-6670(17)35972-4.
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Hyde, Elizabeth M., and Laura W. Lackey. "The impact of loading frequency and copper as a biocide on biosand filter performance." Journal of Water, Sanitation and Hygiene for Development 3, no. 3 (March 22, 2013): 355–64. http://dx.doi.org/10.2166/washdev.2013.084.
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Biological sand filters (BSFs) can appropriately serve as point-of-use water treatment in developing nations. This study examined the benefit of adding copper to a BSF, and evaluated the impact of its addition in relation to extended pause times. Four 70-L BSFs were created – copper was incorporated in the packing of the two BSFs labeled Filter 1 and Filter 3. Filters 1 and 2 were loaded daily while Filters 3 and 4 were watered every third day. Source water was taken from the Ocmulgee River in Macon, Georgia. To investigate variation due to watering frequency and biocidal addition, BSF performance was quantified using coliforms, turbidity, solids, dissolved oxygen, pH, and copper analyses. E. coli removal efficiencies for Filters 1, 2, 3, and 4 averaged 90, 77, 87, and 80%, respectively. Paired t-tests at α = 0.05 indicate that effluent coliform concentrations from filters watered daily were significantly impacted by the presence of copper. Filters loaded every third day showed no significant performance effect from copper addition on coliform removal efficiency. Similar paired t-tests at α = 0.05 for turbidity, solids, and COD showed no significant difference between filter performance.
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Cheng, Fei, Ping Lu, and Kama Huang. "Center frequency and bandwidth switchable substrate integrated waveguide filters." International Journal of Microwave and Wireless Technologies 12, no. 4 (October 16, 2019): 282–87. http://dx.doi.org/10.1017/s1759078719001363.
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AbstractThis paper presents center frequency and bandwidth switchable substrate integrated waveguide filters loaded with PIN diodes. The diodes are added in the slot on the surface of the resonators to switch the resonant frequencies and the coupling coefficients. Although the introduction of the slot causes extra radiation loss, it is small and acceptable. The proposed center frequency switchable filter has four center frequency switchable states of 1.78, 1.82, 1.88, and 1.91 GHz, while the bandwidth only changes ±0.64%. The bandwidth switchable filter has two states with 3 dB bandwidths of 70 and 103 MHz at a center frequency of 2.08/2.09 GHz. The measured performance of the fabricated filters shows good agreement with the simulation.
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Babochkin, Mikhail A., Oleg S. Kolosov, and Anna A. Kuznetsova. "Reducing the High-Frequency Noise Power in the Automatic Control System Signal by Using Comb Filters." Vestnik MEI 6, no. 6 (2020): 91–100. http://dx.doi.org/10.24160/1993-6982-2020-6-91-100.
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The article addresses the matter of reducing the power of high-frequency noise in the control signal produced by industrial automatic systems through the use of algorithms implementing the properties of comb filters in microprocessor controllers. The specific features relating to the frequency responses of open- and closed-loop automatic control systems of industrial facilities are analyzed - both taken alone and in combination with the characteristics of comb filters. The frequency properties of three filter groups that are conventionally used in continuous automatic control systems are compared with three groups of comb filters that implement similar functions. As applied to control tasks, such filters include real differentiating sections or first-order high-pass filters, first-order lag sections or low-pass filters, and proportional sections. The ratios between the parameters of continuous filters and comb filters at which their frequency properties coincide in the operating frequency band are determined. These ratios known, it becomes possible to synthesize the controllers of systems using the existing techniques. It is shown that the amplitude-frequency responses of comb filters have dips in the high-frequency band, due to which the high frequency noise power is finally decreased by up to 30%. The advantage of comb filters in control systems lies in simplicity of implementing them in digital form in a microprocessor controller. The application of comb filters in automatic control systems makes it possible to cut undesirable harmonic noise of large amplitude in the control signal.
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LIAN, YONG. "A MODIFIED FREQUENCY-RESPONSE MASKING STRUCTURE FOR HIGH-SPEED FPGA IMPLEMENTATION OF SHARP FIR FILTERS." Journal of Circuits, Systems and Computers 12, no. 05 (October 2003): 643–54. http://dx.doi.org/10.1142/s0218126603001069.
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This paper presents the design and implementation of high-speed, multiplierless, arbitrary bandwidth sharp FIR filters based on frequency-response masking (FRM) technique. The FRM filter structure has been modified to improve the throughput rate by replacing long band-edge shaping filter in the original FRM approach with two to three cascaded short filters. The proposed structure is suitable for FPGA as well as VLSI implementation for sharp digital FIR filters. It is shown by an example that a near 200-tap equivalent Remez FIR filter can be implemented in a single Xilinx XC4044XLA device that operates at sampling frequency of 5.5 MHz.
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Kuznetsov, Alexey Ivanovich. "Refined calculation of low-frequency filters on direct current locomotives with induction traction drive." Transport of the Urals, no. 3 (2020): 100–103. http://dx.doi.org/10.20291/1815-9400-2020-3-100-103.
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The paper proposes a refined calculation of parameters of low-frequency filters used in direct current locomotives with induction drive. It also provides requirements to setting of filter’s coefficients and equations for constructing frequency characteristics. As a result, the author gives recommendations on improving transient processes in power circuits by optimization of parameters of low-frequency filters.
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Rachman, Rizki Aulia, I. Dewa Gede Hari Wisana, and Priyambada Cahya Nugraha. "Development of a Low-Cost and Effisient ECG devices with IIR Digital Filter Design." Indonesian Journal of electronics, electromedical engineering, and medical informatics 3, no. 1 (February 22, 2021): 21–28. http://dx.doi.org/10.35882/ijeeemi.v3i1.4.
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Measurement of biosignals such as electrocardiograph has the interpretation of noise from other signals. The noise can interfere with the measurement of the heart signal and make the measurement inaccurate, so the purpose of this study is to make a 6-Lead Electrocardiogram module with an Arduino-Based Digital Filter. By using a digital filter. The contribution of this research is the use of digital filters to eliminate noise in electrocardiograph signals. This research uses Infinite Impulse Filter digital filters such as Butterworth, Chebyshev I, Chebyshev II, and Elliptic in order 2, 4, 6, 8, and 10. The study was conducted by providing input from the Function Generator on Arduino which has been applied digital filters with Frequency with 0.5Hz – 100Hz cut-off. The instrument is compared with a factory electrocardiograph. Filter measurements using 460 input data. Butterworth filter with the greatest emphasis on order 8 frequency 0.5Hz produces an emphasis of -5.74298158 dB and a frequency of 100Hz produces an emphasis of -5.93529424 dB. The Chebyshev I filter has the greatest emphasis on order 6 frequency 0.5Hz producing an emphasis of -3.27104076 dB and on order 8 frequency 100Hz producing an emphasis of -5.08730424 dB. Chebyshev II filter the biggest emphasis on the order of frequency 0.5Hz produces a suppression of -44,66011104 dB and 80Hz frequency produces a suppression of -37,3653957 dB. Elliptic filters the greatest emphasis on order 6 frequency 0.5Hz produces an emphasis on -1.55429354 dB and 100Hz frequency on order 8 produces an emphasis on -2.2849115 dB. The results showed that what was appropriate with the cut-off frequency was the Butterworth order 8 filter which was suitable for the application of the Electrocardiograph signal filter because it had bandwidth that suppressed the signal outside the cut-off frequency. The results of this study can be implemented on a 6-Lead ECG module to eliminate noise or interference when tapping ECG signals.
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Gülünay, Necati. "Noncausal spatial prediction filtering for random noise reduction on 3-D poststack data." GEOPHYSICS 65, no. 5 (September 2000): 1641–53. http://dx.doi.org/10.1190/1.1444852.
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A common practice in random noise reduction for 2-D data is to use pseudononcausal (PNC) 1-D prediction filters at each temporal frequency. A 1-D PNC filter is a filter that is forced to be two sided by placing a conjugate‐reversed version of a 1-D causal filter in front of itself with a zero between the two. For 3-D data, a similar practice is to solve for two 2-D (causal) one‐quadrant filters at each frequency slice. A 2-D PNC filter is formed by putting a conjugate flipped version of each quadrant filter in a quadrant opposite itself. The center sample of a 2-D PNC filter is zero. This paper suggests the use of 1-D and 2-D noncausal (NC) prediction filters instead of PNC filters for random noise attenuation, where an NC filter is a two‐sided filter solved from one set of normal equations. The number of negative and positive lags in the NC filter is the same. The center sample of the filter is zero. The NC prediction filters are more center loaded than PNC filters. They are conjugate symmetric as PNC filters. Also, NC filters are less sensitive than PNC filters to the size of the gate used in their derivation. They can handle amplitude variations along dip directions better than PNC filters. While a PNC prediction filter suppresses more random noise, it damages more signal. On the other hand, NC prediction filters preserve more of the signal and reject less noise for the same total filter length. For high S/N ratio data, a 2-D NC prediction filter preserves geologic features that do not vary in one of the spatial dimensions. In‐line and cross‐line vertical faults are also well preserved with such filters. When faults are obliquely oriented, the filter coefficients adapt to the fault. Spectral properties of PNC and NC filters are very similar.
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Zhou, Hongbo, and George A. McMechan. "Parallel Butterworth and Chebyshev dip filters with applications to 3-D seismic migration." GEOPHYSICS 64, no. 5 (September 1999): 1573–78. http://dx.doi.org/10.1190/1.1444661.
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Dip filtering is a necessary part of accurate frequency‐space domain migration, so design and application of reliable and efficient filters are of practical as well as theoretical importance. Frequency‐space domain dip filters are implemented using Butterworth and Chebyshev algorithms. By transforming the product terms of the filter transfer function into summations, a cascaded (serial) Butterworth or Chebyshev dip filter can be made parallel, which improves computational efficiency. For a given order of filter, the cost of the Butterworth and Chebyshev filters is the same. However, the Chebyshev filter has a sharper transition zone than that of a Butterworth filter with the same order, which makes it more effective for phase compensation than a Butterworth filter, but at the expense of some wavenumber‐dependent amplitude ripples. Both implementations have been incorporated into 3-D one‐way frequency‐space depth migration for evanescent energy removal and for phase compensation of splitting errors; a single filter achieves both goals.
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Fursov, V. A. "Constructing a quadratic-exponential FIR-filter with an extended frequency response midrange." Computer Optics 42, no. 2 (July 24, 2018): 297–305. http://dx.doi.org/10.18287/2412-6179-2018-42-2-297-305.
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This article is concerned with synthesizing filter with finite impulse response (FIR-filters) employed to correct radially symmetric distortions such as defocusing. We propose a new parametric class of finite impulse response filters (FIR-filters) based on a model of the one-dimensional radially symmetric frequency response. In the proposed method, the one-dimensional frequency response is composed of quadratic and exponential functions. The two-dimensional impulse response of the filter is constructed by sampling one-dimensional impulse responses for all directions. The development consists in introducing an extended mid-frequency region of the frequency response, thus increasing the contribution of the frequencies to image correction. Examples are given in order to illustrate the possibility of the high-quality distortion correction. In particular, it is shown that the proposed method provides the restoration quality higher than that obtained when using an optimal Wiener filter (taken from OpenCV).
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Mitić, Darko, Goran Jovanović, Mile Stojčev, and Dragan Antić. "ON DESIGN OF SELF-TUNING ACTIVE FILTERS." Facta Universitatis, Series: Automatic Control and Robotics 19, no. 1 (July 28, 2020): 059. http://dx.doi.org/10.22190/fuacr2001059m.
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In this paper, we present one approach in design of self-tuning all-pass, band-pass, low-pass and notch filters based on phase control loops with voltage-controlled active components and analyze their stability as well. The main idea is to vary signal delay of the filter and in this way to achieve phase correction. The filter phase characteristics are tuned by varying the transconductance of the operational transconductance amplifier or capacitance of an MOS varicap element, which are the constituents of filters. This approach allows us to implement active filters with capacitance values of order of pF, making the complete filter circuit to be amenable for realization in CMOS technology. The phase control loops are characterized by good controllable delay over the full range of phase and frequency regulation, high stability, and short settling (locking) time. The proposed circuits are suitable for implementation as a basic building RF function block, used in phase and frequency regulation, frequency synthesis, clock generation recovery, filtering, selective amplifying etc.
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NEUMANN, JULIA, and GABRIELE STEIDL. "DUAL-TREE COMPLEX WAVELET TRANSFORM IN THE FREQUENCY DOMAIN AND AN APPLICATION TO SIGNAL CLASSIFICATION." International Journal of Wavelets, Multiresolution and Information Processing 03, no. 01 (March 2005): 43–65. http://dx.doi.org/10.1142/s0219691305000749.
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We examine Kingsbury's dual-tree complex wavelet transform in the frequency domain where it can be formulated for standard wavelet filters without special filter design. We prove that the dual-tree filter bank construction leads to wavelets with vanishing negative frequency parts, present numerical examples illustrating the improvement of translation and rotation invariance for various standard wavelet filters and apply the method to the classification of signals.
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Matei, Radu. "Design of Adjustable Square-Shaped 2D IIR Filters." ISRN Signal Processing 2013 (September 11, 2013): 1–10. http://dx.doi.org/10.1155/2013/796830.
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This paper proposes an analytical design method for two-dimensional square-shaped IIR filters. The designed 2D filters are adjustable since their bandwidth and orientation are specified by parameters appearing explicitly in the filter matrices. The design relies on a zero-phase low-pass 1D prototype filter. To this filter a frequency transformation is next applied, which yields a 2D filter with the desired square shape in the frequency plane. The proposed method combines the analytical approach with numerical approximations. Since the prototype transfer function is factorized into partial functions, the 2D filter also will be described by a factorized transfer function, which is an advantage in implementation.
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Cho, John Y. N. "A New Radio Frequency Interference Filter for Weather Radars." Journal of Atmospheric and Oceanic Technology 34, no. 7 (July 2017): 1393–406. http://dx.doi.org/10.1175/jtech-d-17-0028.1.
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AbstractA new radio frequency interference (RFI) filter algorithm for weather radars is proposed in the two-dimensional (2D) range-time/sample-time domain. Its operation in 2D space allows RFI detection at lower interference-to-noise or interference-to-signal ratios compared to filters working only in the sample-time domain while maintaining very low false alarm rates. Simulations and real weather radar data with RFI are used to perform algorithm comparisons. Results are consistent with theoretical considerations and show the 2D RFI filter to be a promising addition to the signal processing arsenal against interference with weather radars. Increased computational burden is the only drawback relative to filters currently used by operational systems.
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HOTA, MALAYA KUMAR, and VINAY KUMAR SRIVASTAVA. "MULTISTAGE FILTERS FOR IDENTIFICATION OF EUKARYOTIC PROTEIN CODING REGIONS." International Journal of Biomathematics 05, no. 02 (March 2012): 1250018. http://dx.doi.org/10.1142/s179352451100160x.
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A class of multistage filters, namely, real narrowband bandpass filter (RNBPF) has been previously used for identification of protein coding regions. This filter passes the frequency component at 2π/3 along with its conjugate. This conjugate frequency component may degrade the identification accuracy. To improve the identification accuracy, two types of multistage filters are proposed in this paper. A complex narrowband bandpass filter (CNBPF) is proposed for suppressing the conjugate frequency component which, in turn, reduces the background noise present in the deoxyribonucleic acid (DNA) spectrum and improves identification accuracy. By cascading RNBPF with moving average filter (RNBPFMA), another type of multistage filter is proposed. As moving average filter smooth out the rapid variations in the DNA spectrum, RNBPFMA improves the identification accuracy. The computational complexity of RNBPFMA is less than that of CNBPF. The RNBPF and proposed multistage filters are compared with previously reported short-time discrete Fourier transform (ST-DFT) method in terms of computational complexity. It is found that multistage filters reduce the computational load to a greater extent compared to ST-DFT method. The identification accuracy of the proposed CNBPF and RNBPFMA methods is compared with existing anti-notch filter and RNBPF methods. The results show that proposed methods outperform existing methods in terms of identification accuracy for benchmark data sets.
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Zinovyev, A. G., and I. A. Shestakov. "CONFIGURABLE HARMONIC FILTERS FOR SHORT-WAVE TRANSMITTERS." RADIO COMMUNICATION TECHNOLOGY, no. 47 (November 23, 2020): 87–97. http://dx.doi.org/10.33286/2075-8693-2020-47-87-97.
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Harmonic filters of short-wave transmitters, tunable in the frequency range using discrete variable capacitors, are presented. A comparison of a harmonic filter based on tunable LC low-pass filters with inductive coupling between the filter inductors is carried out with a similar harmonic filter, each LC low-pass filter of which con-tains an additional capacitive coupling capacitor connected between the two filter links and significantly changed the parameters of the harmonic filter.