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In order to analyze the impact of multisource vibration on the imaging quality of aerospace optical payload during camera scanning, a dynamic imaging quality degradation model fused with satellite vibration filter templates is established. Firstly, according to the motion scanning process of the TDI camera, a filter template combining the amplitude and frequency of the vibration source is designed; Secondly, a piecewise function of satellite vibration with a frequency range of 1 Hz to 1000 Hz is obtained by curve fitting, and the amplitudes of different frequency ranges are brought into the image filter template to simulate the output image affected by the vibration. Finally, the output degraded image is analyzed through structural similarity and mean square error. The simulation results show that during the imaging process of the aerospace scanning mirror, the line frequency of the camera changes regularly with the scanning speed. When platform vibration frequency is similar to the camera’s exposure frequency, it will have a large impact on image quality. Therefore, when the camera’s exposure frequency is 110 Hz, vibration at a frequency of 110 Hz will further degrade the image quality. This article is expected to provide guidance for spatial vibration suppression and image quality degradation assessment in the imaging process of aerospace scanning mirrors.

In this paper, a universal biometric system based on human vision is proposed. From recent biological and physiological results, A human identification system that approximates the natural vision and recognition of individuals is conceived. Liquid state machine (LSM), as a recurrent spiking neural network, is highly inspired by the brain neural architecture with low training cost. However, input dimension of large scale images requires efficient processing at the cost of performance or resource overhead. This paper propose a new neural input coding for images based on frequency signals rather than pixels. Each image is filtered and fragmented then the LSM liquid (or reservoir) will receive, first, high frequency signals, then low frequency signals from each fragment. The two sets of output neurons states corresponding to each type of filter will be matched to the entire enrollment database. A weighted sum rule between the matching results will determine the right class of a biometric image. The system was tested on three different biometric datasets: face, palmprint and off-line signature, results show the reliability of the proposed approach.

We discuss the possibility that the contours or details of images can be obtained by using the low-spatial-frequency or high-spatial-frequency parts of the reference beam in ghost imaging. The influence of the threshold selection which is used to divide the reference pattern into low-frequency and high-frequency parts is quite different. With the increase of the threshold, the signal-to-noise ratio (SNR) of low-frequency ghost imaging increases firstly and then decreases, while SNR of high-frequency ghost imaging decreases gradually. Under a suitable threshold, the results are compared with those by directly filtering ghost-image from the traditional ghost imaging. It is shown that better imaging quality can be obtained by using our scheme. To further improve imaging quality, the method of subtracting background before correlation calculation is also presented.

Speech intelligibility improvement is a major field of recent research with in audiology and hearing domain. Speech signal usually gets affected due to various environmental and background...

A new zonal two-dimensional method for wavefront retrieval from a surface under test using lateral shearing interferometry is presented. A modified Saunders method and phase shifting techniques are combined to generate a method for wavefront reconstruction. The result is a wavefront with an error below 0.7 λ and without any global high frequency filtering. A zonal analysis over square cells along the surfaces is made, obtaining a polynomial expression for the wavefront deformations over each cell. The main advantage of this method over previously published methods is that a global filtering of high spatial frequencies is not present. Thus, a global smoothing of the wavefront deformations is avoided, allowing the detection of deformations with relatively small extensions, that is, with high spatial frequencies. Additionally, local curvature and low order aberration coefficients are obtained in each cell.

This paper presents a new filter-based algorithm to estimate the fundamental phasor of fault currents, using the proposed complex frequency filter. The presence of decaying dc component (ddc) in fault currents causes large error in discrete Fourier transform (DFT)-based phasor estimation methods. The proposed filter discriminates the ddc from dc and sinusoidal signals. In this algorithm, first, the ddc is filtered out by the proposed filter. Then, the fundamental phasor can be precisely extracted by applying DFT. Second and fourth order of the complex frequency filter and their design method are presented. To evaluate the performance of the proposed algorithm, several test signals are used. The algorithm is also compared with recent DFT-based and mimic-DFT methods, using four performance indices. The simulation results demonstrate the robustness of the proposed algorithm against harmonics, noise, multiple ddc components, and off-nominal frequency. It also offers faster convergence speed. The proposed complex frequency filter can also be used for the phasor estimation of harmonic components in the presence of ddc with no need to readjust its parameters.

In this paper we propose a method for extracting the fundamental frequency fo from degraded speech signals using single frequency filtering SFF approach. The SFF of frequency-shifted speech signal gives high signal-to-noise ratio SNR segments at some frequencies and hence the SFF approach can be exploited for fo extraction using autocorrelation function of those segments. Since the fo is computed from the envelope of a single frequency component of the signal, the vocal tract resonances do not affect the fo extraction. The use of the high SNR frequency component in a given segment helps in overcoming the effects of degradations in the speech signal, without explicitly estimating the characteristics of noise. The proposed method of fo extraction is shown to give better performance for several types of real and simulated degradations, in comparison with some of the methods reported recently in the literature.

There are a number of characteristics that make metamaterial has wide applications and has been researched at present, such as negative phase, negative index of refraction, super resolution, and reverse of Doppler's effects. This paper investigates a hexagonal metamaterial structure with a split and a double concentric rings so-called split ring resonator hexagonal (SRR-H) for frequency filtering application. SRR-H is designed structurally and operated computationally for frequency range of 1 to 120 GHz. The simulation results showed that SRR-H size will affect the resonant frequency significantly. The resonant frequency tends to shift the lower frequency when the size of the structure is enlarged. The properties of the structure SRR-H, such as permeability, permittivity and the refractive index have a similarity because it is dominated by the properties of permeability. Metamaterial SRR-H successfully responded to double negative and agreed with Lorentz's model.

An improved method of physical activity accelerometer data processing, involving a wider frequency filter than the most commonly used ActiGraph filter, has been shown to better capture variations in physical activity intensity in a lab setting. The aim of the study was to investigate how this improved measure of physical activity affected the relationship with markers of cardiometabolic health. Accelerometer data and markers of cardiometabolic health from 725 adults from two samples, LIV 2013 and SCAPIS pilot, were analyzed. The accelerometer data was processed using both the original ActiGraph method with a low-pass cut-off at 1.6 Hz and the improved method with a low-pass cut-off at 10 Hz. The relationship between the physical activity intensity spectrum and a cardiometabolic health composite score was investigated using partial least squares regression. The strongest association between physical activity and cardiometabolic health was shifted towards higher intensities with the 10 Hz output compared to the ActiGraph method. In addition, the total explained variance was higher with the improved method. The 10 Hz output enables correctly measuring and interpreting high intensity physical activity and shows that physical activity at this intensity is stronger related to cardiometabolic health compared to the most commonly used ActiGraph method. Mätning av det dagliga aktivitetsmönstret SCAPIS

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.

The paper presents proposal of the 2nd-order universal frequency filter. The presented filter operates in the current-mode and it is designed in the single-ended and fully-differential form. Signal-flow graphs (SFG) method has been used in the proposal. The proposed filter is employing multi-output current followers (MO-CFs) and digitally adjustable current amplifiers (DACAs) as active elements. The pole frequency of the filter can be controlled without disturbing its quality factor. Functionality of the proposed filter in both S-E and F-D form has been verified by PSpice simulations using available models of used active elements and also by experimental measurements. A comparison of simulation and experimental results of the S-E and F-D form of the presented filter is made. Subsequently, a comparison of experimental results of both forms of the filter is also included.

Filter banks on spectrums play an important role in many audio applications. Traditionally, the filters are linearly distributed on perceptual frequency scale such as Mel scale. To make the output smoother, these filters are often placed so that they overlap with each other. However, fixed-parameter filters are usually in the context of psychoacoustic experiments and selected experimentally. To make filter banks discriminative, the authors use a neural network structure to learn the frequency center, bandwidth, gain, and shape of the filters adaptively when filter banks are used as a feature extractor. This paper investigates several different constraints on discriminative frequency filter banks and the dual spectrum reconstruction problem. Experiments on audio source separation and audio scene classification tasks show performance improvements of the proposed filter banks when compared with traditional fixed-parameter triangular or gaussian filters on Mel scale. The classification errors on LITIS ROUEN dataset and DCASE2016 dataset are reduced by 13.9% and 4.6% relatively.

International audience; We propose and numerically demonstrate a novel simple method to produce optical Nyquist pulses based on pulse shaping in a passively mode-locked fiber laser with an in-cavity flat-top spectral filter. The proposed scheme takes advantage of the nonlinear in-cavity dynamics of the laser and offers the possibility to generate high-quality sinc-shaped pulses with widely tunable bandwidth directly from the laser oscillator. We also show that the use of a filter with a corrective convex profile relaxes the need for large nonlinear phase accumulation in the cavity by offsetting the concavity of the nonlinearly broadened pulse spectrum.

A widely tunable single-passband microwave photonic filter (MPF) based on a distributed-feedback semiconductor optical amplifier (DFB-SOA) is proposed and experimentally demonstrated in this paper. The fundamental principle is to recover the suppressed optical carrier from a passband optical filter by the wavelength-selective amplification via a DFB-SOA. A microwave signal is then generated by beating the recovered optical carrier with the phase-modulated lower sideband, and thus, an MPF is achieved with the shape of the passband optical filter that is mapped from the optical domain to the electrical domain. By tuning the central wavelength of the passband optical filter, a single-passband MPF with a frequency tuning range from 5 to 35 GHz is obtained. The 3-dB bandwidth and the out-of-band suppression ratio are measured to be 4 GHz and 20 dB, respectively. In addition, the tunability of the MPF that is dependent on the driven current of the DFB-SOA is also experimentally investigated.

The present study suggests a localization method for the first (S1) and the second (S2) feature of heart sounds, based on an algorithm involving frequency filtering, energy detection, and interval regulation. Localization accuracy was evaluated by comparing the algorithm with the traditional Hilbert transform-based localization method. Results show that the sensitivity and the positive predictivity value of proposed method, respectively, were 97.27 % and 99.94 % in S1 detection and 94.99 % and 100 % in S2 detection.

The resonance approximations of phase-shifted Bragg grating (PSBG) reflection and transmission coefficients are obtained as a function of frequency and wave-vector’s tangential components of incident light. The proposed theoretical description is verified using numerical simulations.

This paper presents the synthesis and analysis of reconfigurable frequency filter with differential input and differential output terminals and its experimental verification. The inner structure of the filter has single-ended form, i.e., filter behaves as the so-called pseudo-differential circuit. Filtering function can be electronically reconfigured between low-pass (LP) and band-pass (BP) responses. Active elements of the filter are differential voltage buffer (DVB) as an input stage and modified current differencing unit (MCDU) together with modified current summing unit (MCSU) as the inner and also output stage. Each of the important parameters of the filter (angular pole frequency, quality factor and pass-band gain) is electronically controllable by parameters of these active elements used. Some of the parameters of the filter are controlled by two independent parameters, i.e., are dual-controlled, which enables the extended electronic controllability. The proposed topology operates in the voltage mode and both input nodes have high input impedance. Expected behavior of the filter is analyzed and verified by PSpice simulations using CMOS models of above-mentioned active elements. Moreover, features of the filter in both configurations were successfully verified also by experimental measurements using behavioral models of active elements.

We show that waveguides with a dielectric core and a lossy metamaterial cladding (metamaterial-dielectric guides) can support hybrid ordinary-surface modes previously only known for metal-dielectric waveguides. These hybrid modes are potentially useful for frequency filtering applications as sharp changes in field attenuation occur at tailorable frequencies. Our results also show that the surface modes of a metamaterial-dielectric waveguide with comparable electric and magnetic losses can be less lossy than the surface modes of an analogous metal-dielectric waveguide with electric losses alone. Through a characterization of both slab and cylindrical metamaterial-dielectric guides, we find that the surface modes of the cylindrical guides show promise as candidates for all-optical control of low-intensity pulses., Comment: 15 pages, 11 figures. Accepted by Photonics and Nanostructures - Fundamentals and Applications. This version: Title is extended. Section 3 (Modes) and 4 (Characterization) are revised. The abstract, discussion and summary are also revised accordingly

Application of image frequency filtering to elimination of the noise in scanned photographs caused by the embossing of the photographic paper is considered.

The analog circuit design is very often focused on the design of frequency filters employing different types of active elements. In this paper we present the universal voltage conveyor that is used for the design of the KHN-equivalent filters working in the voltage-mode. Auxiliary voltage inputs of the active elements are used to reduce the number of floating admittances in the structure. Both proposed structures are easily cascadable since the input and output impedances are in theory infinitely high and zero, respectively. The behavior of the filters has been verified through PSpice simulations and furthermore by experimental measurements.

The transmission properties of a two-period structure consisting of dielectric layers and air layers are studied by numeric methods. On the condition of total reflection from dielectric to air layer, the coupling of the evanescent waves in air layers and propagation waves in dielectric layers forms some special transmission bands. Given proper structure parameters, one incident direction only allows one transmission frequency; on the other hand, one transmission frequency only allows one incident direction. This structure can simultaneously achieve frequency filtering and direction filtering.

Dichroics are key components in the design of quasioptical networks.However, there are many practical issues in designing and fabricating these components. This article presents the design and uncertainty analysis of a dichroic being operated in a two-channel multireflector quasioptical network. The dichroic is designed to work as a frequency filter, which transmits at 54 GHz and reflects at 89 GHz. A low insertion loss is achieved both in simulation and in measurement. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:900–904, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25075

This paper studies the problem of finite frequency filter design for linear time-invariant discrete-time systems with polytopic uncertainties. Generalized Kalman–Yakubovich–Popov lemma is exploited to formulate the filter design problem in finite frequency domain. A design method is presented in terms of solutions to a set of linear matrix inequalities. A numerical example is given to illustrate the effectiveness of the proposed method. Copyright © 2007 John Wiley & Sons, Ltd.

We study theoretically, by means of layer-multiple scattering techniques, the propagation of elastic waves through finite slabs of phononic crystals consisting of metallic spheres in polyester matrix, embedded in air. We focus on the study of modes localized on the surfaces of the structure, investigating the physical parameters which influence and determine their appearance. Our results reveal the existence of absolute phononic frequency gaps in these finite structures, and point out the possibility, under an appropriate choice of the parameters, of tunable regions of frequency free of propagating and/or surface-localized modes. This could be very useful in the design of devices related to frequency filtering, waveguiding, etc.

Bessel illumination is an established method in optical imaging and manipulation to achieve an extended depth of field without compromising the lateral resolution. When broadband or multicolour imaging is required, wavelength-dependent changes in the radial profile of the Bessel illumination can complicate further image processing and analysis. We present a solution for engineering a multicolour Bessel beam that is easy to implement and promises to be particularly useful for broadband imaging applications. A phase-only spatial light modulator (SLM) in the image plane and an iterative Fourier Transformation algorithm (IFTA) are used to create an annular light distribution in the back focal plane of a lens. The 2D Fourier transformation of such a light ring yields a Bessel beam with a constant radial profile for different wavelength.

Broadband frequency filtering and mode-matching transition using finline technology for high-frequency nonlinear electronic applications is proposed. Based on homemade code and full-wave three-dimensional electromagnetic simulations, the validity of the concepts are assessed on a prototype aimed at operation between 18 and 26 GHz. Results show that very good performance (less than −0.5 dB for the insertion loss of the taper, as well as a rejection higher than −20 dB for the filtering action) can be maintained over the 30% bandwidth required for future space applications. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 234–237, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20103

A configuration consisting of a double slit and pipe in conjunction with moving fluid is proposed to manipulate a broadband light source through the interference spectrum. Theoretical analysis shows that, by varying the speed of the fluid, the scheme can act as a special dynamic frequency filter and produce regular dark lines that may serve as an optical frequency ruler.

Plane-wave reflection and transmission by 2D grids formed by Ω-shaped conducting particles connected by their arms and dispersion properties of an infinite set of such grids are studied. Arms of connected Ω-particles are collinear, and every grid can be considered as a mesh of parallel wires periodically loaded by loops. These loops are parallel to one another and lie in planes orthogonal to the grid plane. The grids are bianisotropic and self-resonant. An analytical model of such a grid is proposed and then used so that to study the dispersion properties of 3D lattices. The dispersion and polarization properties of the 3D Ω-lattice (a bianisotropic electromagnetic crystal) are close to those of a lattice from inductively loaded wires. Such structures can be prospective for frequency filtering and antenna reflectors and substrates.

In this paper, we discuss the use of weighted filter bank analysis (WFBA) to increase the discriminating ability of mel frequency cepstral coefficients (MFCCs). The WFBA emphasizes the peak structure of the log filter bank energies (LFBEs) obtained from filter bank analysis while attenuating the components with lower energy in a simple, direct, and effective way. Experimental results for recognition of continuous Mandarin telephone speech indicate that the WFBA-based cepstral features are more robust than those derived by employing the standard filter bank analysis and some widely used cepstral liftering and frequency filtering schemes both in channel-distorted and noisy conditions.

We numerically study multiple soliton interactions in a polarization–division multiplexing transmission system. It is found that, unlike the transmission system of solitons with the same polarization, the two soliton interaction is not the strongest compared to the interaction of more than two solitons. Therefore, the maximum transmission distance limited by the interaction of solitons cannot be inferred by the collision distance of two solitons in a polarization–division multiplexing system and the interactions of more solitons must be considered.

A new method for updating the SVD is introduced, based on perturbation formulas. The complexity of the method is O(n/sup 2/). Applications are made to frequency estimation and filtering.

This paper is concerned with the reliable finite frequency filter design for networked control systems (NCSs) subject to quantization and data missing. Taking into account quantization, possible data missing and sensor stuck faults, NCSs are modeled in the framework of discrete time-delay switched systems, and the finite frequency l2 gain is adopted for the filter design of discrete time-delay switched systems, which is converted into a set of linear matrix inequality (LMI) conditions. By the virtues of the derived conditions, a procedure of reliable filter synthesis is presented. Further, the filter gains are characterized in terms of solutions to a convex optimization problem which can be solved by using the semi-definite programme method. Finally, an example is given to illustrate the effectiveness of the proposed method.

International audience; Many technological bottlenecks prevent from realizing a software radio (SR) mobile terminal. The old way of building radio architectures is now over because a single handled terminal has to address various communication standards. This paper exposes a SR receiver: a sampled analog signal processor (SASP) is designed to perform downconversion and channel presorting. The idea is to process analog voltage samples in order to recover in baseband any RF signal emitted from 0 to 5$~$GHz. An analog fast Fourier transform achieves both frequency shifting and filtering. An experimental demonstrator of the SASP using 65$~$nm CMOS technology from STMicroelectronics is here presented and measured. It validates the concept of a new SR receiver with the design of a demonstrator which runs at 1.2 GHz consuming 389 mW.

Systematic lossy error protection (SLEP) is a robust error resilient mechanism based on principles of Wyner-Ziv (WZ) coding for video transmission over error-prone networks. In an SLEP scheme, the video bitstream is separated into two parts: a systematic part consisting of a video sequence transmitted without channel coding, and additional information consisting of a WZ supplementary stream. This paper presents an adaptive SLEP scheme in which the WZ stream is obtained by frequency filtering in the transform domain. Additionally, error resilience varies adaptively depending on the characteristics of compressed video. We show that the proposed SLEP architecture achieves graceful degradation of reconstructed video quality in the presence of increasing transmission errors. Moreover, it provides good performances in terms of error protection as well as reconstructed video quality if compared to solutions based on coarser quantization, while offering an interesting embedded scheme to apply digital video format conversion.

An intracavity wavelength filter formed by a nematic liquid crystal cell is used to tune the wavelength of a fibre laser. The tuning range of the device is 17 nm and the tuning rate is 8 nm/V.

An image-processing algorithm for analysis of migration of vascular endothelial cells in culture is presented. The algorithm correctly detected the cellular regions on either side of an artificial 'wound' made by dragging a sterile pipette tip across the monolayer of cells (scratch wound assay). Frequency filtering and mathematical morphology were used to approximate the boundaries of cellular regions. This allowed measurement of the distance between the regions, and therefore the migration rates, regardless of the orientation of the wound and even in cases where the cells were sparse and not tightly packed.

A simple programmable chirp-transform band-pass and/or band-stop filter has been implemented using ultrasonic strip dispersive delay lines. Experimental results demonstrating the capability of the system are presented. In addition to processing applications, the system may also be employed as a teaching tool for illustrating concepts in spectral analysis.

Two opto-electronic systems for seismic data information treatment are described. The possibilities of directional and frequency filtering and evaluation on the basis of the seismic section correlogram are discussed.

In the literature, use of computer processing of radiographic images for easy and better interpretation has been established. However, in India, the subject is in its infancy. This paper deals with the processing and enhancement techniques such as Gray scale mapping, boundary detection, cycle enhancement, frequency filtering etc. which find application in cancer detection, lung and heart disease identification, lesions in blood vessels etc. and pattern recognition techniques for automatic chromosome analysis. The work done at Indian Institute of Science on some of these aspects is highlighted.

Digital calculation of symmetrical components may be based on simple delay of input signals. However, to avoid errors due to the distortion of signals, some kind of frequency filtering ought to be added. This may be done either as a separate procedure or by an operation which combines phase shifting with band pass filtering. Several digitally efficient algorithms and the results of calculation are presented in the paper.