Channel Filter Research Articles

A Millimeter Wave High-Isolation Diplexer Using Selectivity-Improved Dual-Mode Filters

This letter presents an alternative method to realize millimeter wave waveguide diplexers based on high selectivity bandpass filters. A small perturbation is implemented in a dual-mode circular cavity to expand the bandwidth and significantly enhance the selectivity of the channel filter. The location of a transmission zero can be easily adjusted by properly changing the angle of a perturbing notch etched at sidewall of the cavity. A V-band diplexer prototype has been fabricated and tested. The experiment results showed good agreement with simulation results. The designed diplexer has the advantages of simple design process, quasi-planar structure, high isolation, and improved selectivity without any additional mechanical tuning element.

Rotation invariant texture classification using extended wavelet channel combining and LL channel filter bank

In this paper, a simple and effective method for rotation invariant texture classification is proposed. The suggested feature vector is small as compared to other state-of-the-art methods. The proposed method is the development of wavelet combining channels approaches that have been introduced for extraction of rotation invariant features. These methods have two big problems with textures with strong directionality and textures with similar spatial frequency and different directionality. Therefore, these methods have not attracted much attention for texture classification. Our method introduces several extensions on the wavelet combining channels idea: first, it changes the combining scheme, second, it applies a rescaling scheme, third, it changes the method of calculating the energy features and forth, it uses low horizontal and low vertical frequency (LL) channel features in each level of decomposition. We also apply a filter bank on the first level of decomposition for extracting the edge features and different texture features. To illustrate the impact of these developments, we applied the proposed method on four different databases, from the Outex, Brodatz, and VisTex, consisting of 24, 25, 54, and 87 different classes of textures, respectively. The results show that the proposed method has comparable and even better performance than the other state-of-the-art methods. The results show that by increasing the number of classes from 25 to 87, maximum classification accuracy has dropped by only 2.4%. For more comparisons, the method is applied on two different illumination textures and it obtains an average of almost 10.9% increase in accuracy than the traditional wavelet channel combining method.

Architecture and Implementation of OpenPET Firmware and Embedded Software.

OpenPET is an open source, modular, extendible, and high-performance platform suitable for multi-channel data acquisition and analysis. Due to the flexibility of the hardware, firmware, and software architectures, the platform is capable of interfacing with a wide variety of detector modules not only in medical imaging but also in homeland security applications. Analog signals from radiation detectors share similar characteristics - a pulse whose area is proportional to the deposited energy and whose leading edge is used to extract a timing signal. As a result, a generic design method of the platform is adopted for the hardware, firmware, and software architectures and implementations. The analog front-end is hosted on a module called a Detector Board, where each board can filter, combine, timestamp, and process multiple channels independently. The processed data is formatted and sent through a backplane bus to a module called Support Board, where 1 Support Board can host up to eight Detector Board modules. The data in the Support Board, coming from 8 Detector Board modules, can be aggregated or correlated (if needed) depending on the algorithm implemented or runtime mode selected. It is then sent out to a computer workstation for further processing. The number of channels (detector modules), to be processed, mandates the overall OpenPET System Configuration, which is designed to handle up to 1,024 channels using 16-channel Detector Boards in the Standard System Configuration and 16,384 channels using 32-channel Detector Boards in the Large System Configuration.

Channel Estimation and Equalization in Multiuser Uplink OFDMA and SC-FDMA Systems Under Transmitter RF Impairments

Single-carrier frequency-division multiple access (SC-FDMA), which is a modified form of orthogonal frequency-division multiple access (OFDMA), has been adopted as the uplink physical-layer radio access technique for the Third-Generation Partnership Project Long-Term Evolution (3GPP-LTE) and LTE-Advanced. Radio transceiver implementations for such OFDM-based systems with the direct-conversion architecture are desirable to enable small-size, low-cost, and low-power-consumption terminals. However, the associated circuit impairments stemming from the processing of analog radio frequency (RF) signals, such as in-phase and quadrature-phase (I/Q) imbalance and carrier frequency offset errors, can severely degrade the obtainable link performance. In this paper, we analyze the effects of these radio impairments in a multiuser SC-FDMA uplink system and present digital-signal-processing-based methods for the joint estimation and equalization of impairments and channel distortions on the receiver side with an arbitrary number of receiver antennas. For the equalization, linear equalizers such as the zero-forcing (ZF) and the minimum mean square error (MMSE) equalizers that utilize pairs of mirror subcarriers are formulated, and the MMSE equalizer is developed to effectively handle mirror subband users with different power levels. Furthermore, for reduced computational complexity, the joint channel and impairment filter responses are efficiently approximated with polynomial-based basis function models. The parameters of the basis functions are then estimated by exploiting the time-multiplexed reference symbols in the LTE uplink subframe structure. The performance of the proposed estimation and equalization methods is assessed with extensive multiuser link simulations, with both single-antenna and dual-antenna base-station receivers, and the results show that the proposed algorithms are able to significantly reduce the impact of channel distortions and radio impairments. The resulting receiver implementation with the proposed techniques enables improved uplink link performance, even when the mobile terminals fulfill their emission requirements, in terms of I/Q images, with no changes in the LTE standard's frame and pilot structures.

An affine combination of adaptive filters for channels with different sparsity levels

An affine combination of adaptive filters for channels with different sparsity levels

Design of hexa‐channel triplexer with modified manifold‐coupled structure

ABSTRACTIn this article, a novel hexa‐channel triplexer with modified manifold‐coupled structure is presented. Three asymmetrical coupling shorted stub loaded stepped‐impedance resonator dual‐band bandpass filter is used to replace the single‐band channel filters in the conventional manifold‐coupled triplexer. The proposed modified manifold‐coupled structure is constructed by two different three‐element lowpass Π‐networks for achieving the required phase shift and filtering performance. Good agreements can be observed between the simulated and measured results. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:279–283, 2016

Design Analysis of Channel Filter for Digital Down Converter in WiMAX Application

filter has been designed for Digital Down converter (DDC),that meets the standard of WiMAX in wireless communication. WiMAX is a technology emerging in the wireless communication system, in order to enhance the broadband wireless internet access. Digital Up Converter (DUC) and Digital Down Converter (DDC) are integral part of WiMAX system, that results in efficient low cost WiMAX system. In order to fulfill the spectral requirement of bandwidth reduction, effective spectral leakage and eliminating interference from adjacent channels, in WiMAX system, DDC and DUC utilizes a channel filter for pulse shaping. Channel Filter in DDC applies pulse shaping to attenuate any out of band energy in the baseband data after decimation. The raised cosine filter and Gaussian filters are the most common pulse-shaping filters in communications systems. In present paper raised cosine filter technique and Gaussian filter is utilizes and compared for designing and analysis of channel filter using MATLAB.

Automatic classification of seismic events within a regional seismograph network

This paper presents a fully automatic method for seismic event classification within a sparse regional seismograph network. The method is based on a supervised pattern recognition technique called the Support Vector Machine (SVM). The classification relies on differences in signal energy distribution between natural and artificial seismic sources. We filtered seismic records via 20 narrow band-pass filters and divided them into four phase windows: P, P coda, S, and S coda. We then computed a short-term average (STA) value for each filter channel and phase window. The 80 discrimination parameters served as a training model for the SVM. We calculated station specific SVM models for 19 on-line seismic stations in Finland. The training data set included 918 positive (earthquake) and 3469 negative (non-earthquake) examples. An independent test period determined method and rules for integrating station-specific classification results into network results. Finally, we applied the network classification rules to independent evaluation data comprising 5435 fully automatic event determinations, 5404 of which had been manually identified as explosions or noise, and 31 as earthquakes. The SVM method correctly identified 94% of the non-earthquakes and all but one of the earthquakes.The result implies that the SVM tool can identify and filter out blasts and spurious events from fully automatic event solutions with a high level of accuracy. The tool helps to reduce the work-load and costs of manual seismic analysis by leaving only a small fraction of automatic event determinations, the probable earthquakes, for more detailed seismological analysis. The self-learning approach presented here is flexible and easily adjustable to the requirements of a denser or wider high-frequency network.

Techniques for Constructing Biorthogonal Bipartite Graph Filter Banks

The processing of data defined on irregular discrete domains, i.e., graph signals, is becoming an emerging area with great application potential. Using spectral graph theory, Narang and Ortega (2013) laid the framework for two channel filter banks with critical sampling for bipartite graph signals. The bipartite graph filter bank can be extended to any arbitrary graph using the notion of separable filtering. The design of the biorthogonal filter banks by Narang and Ortega (2013) is based on the factorization of a maximally flat polynomial. The factorization technique does not allow much control of the spectral response of the graph filters, resulting in response asymmetry. In this paper, we present a generic framework for constructing biorthogonal graph filter banks that does not require factorization. We introduce the notion of polyphase representation and ladder structures for graph filter banks. We show that filters having virtual spectral symmetry and almost energy preservation can be constructed without any sophisticated optimization. Fine control of the spectral response can also be achieved with ease.

Design of Microstrip Triplexer with High Isolation Based on Parallel Coupled-Line Filters Using T-Shaped Short-Circuited Resonators

Design approach for simultaneously achieving impedance matching and enhancing the isolation of multiplexer has been proposed. The channel filters constituting the multiplexer utilize the T-shaped short-circuited resonators as resonant components and short-circuited parallel-coupled lines as interstage couplings. The embedded open-ended stubs of resonators intentionally placed along the main transmission path of each channel contribute the virtual-shorts by creating transmission zeros thereby making the matching and isolation improvement possible. A triplexer with satisfactorily high output isolation is designed and implemented to validate the concept.

A METHODOLOGY FOR DEVELOPING VIDEO PROCESSING SYSTEM

The data is exploding day by day in digital technology. Now a day’s multimedia data is also handled by the database, multimedia data contains data like images, text and video. The video processing plays a tremendous role in the multimedia but all the videos are not same, it can exists number of settings and different number of formats. By This video processing system the video is processed for enhancement, analysis, dividing the channels and binarization by using different image processing techniques. In this system different color system like YCBR, HSL, and RGB color systems are considered for processing any type of video. For this system, the input video can be from a stored file or continuous stream of video sequences from the web camera (or) any type of camera by this video processing system we can improve the quality of the video and we can also apply some special effects to the video by applying various image processing techniques and filters. The enhancement techniques considered in his system are filtering with correlation and convolution, adaptive smoothing, conservative smoothing and median filtering. The analysis techniques like edge detection, histogram and statistical analysis are considered for this system. Binarization methods implemented in this system are Custom Threshold, Order Dither. The Color filters like converting RGB to Grayscale, Grayscale to RGB ,Sepia, invert, rotate, Custom Color filter, Euclidean color filter, channel filter, red, green, blue, cyan, magenta and yellow, they are so many other filters are also implemented in this system.

Structural implications of weak Ca2+ block in Drosophila cyclic nucleotide-gated channels.

Calcium permeability and the concomitant calcium block of monovalent ion current ("Ca(2+) block") are properties of cyclic nucleotide-gated (CNG) channel fundamental to visual and olfactory signal transduction. Although most CNG channels bear a conserved glutamate residue crucial for Ca(2+) block, the degree of block displayed by different CNG channels varies greatly. For instance, the Drosophila melanogaster CNG channel shows only weak Ca(2+) block despite the presence of this glutamate. We previously constructed a series of chimeric channels in which we replaced the selectivity filter of the bacterial nonselective cation channel NaK with a set of CNG channel filter sequences and determined that the resulting NaK2CNG chimeras displayed the ion selectivity and Ca(2+) block properties of the parent CNG channels. Here, we used the same strategy to determine the structural basis of the weak Ca(2+) block observed in the Drosophila CNG channel. The selectivity filter of the Drosophila CNG channel is similar to that of most other CNG channels except that it has a threonine at residue 318 instead of a proline. We constructed a NaK chimera, which we called NaK2CNG-Dm, which contained the Drosophila selectivity filter sequence. The high resolution structure of NaK2CNG-Dm revealed a filter structure different from those of NaK and all other previously investigated NaK2CNG chimeric channels. Consistent with this structural difference, functional studies of the NaK2CNG-Dm chimeric channel demonstrated a loss of Ca(2+) block compared with other NaK2CNG chimeras. Moreover, mutating the corresponding threonine (T318) to proline in Drosophila CNG channels increased Ca(2+) block by 16 times. These results imply that a simple replacement of a threonine for a proline in Drosophila CNG channels has likely given rise to a distinct selectivity filter conformation that results in weak Ca(2+) block.

Comparison Between an HVS Inspired Linear Filter and the Bilateral Filter in Performing "Vision at a Glance" through Smoothing with Edge Preservation

We propose that the Magno (M)-channel filter, belonging to the extended classical receptive field (ECRF) model, provides us with "vision at a glance", by performing smoothing with edge preservation. We compare the performance of the M-channel filter with the well-known bilateral filter in achieving such "vision at a glance" which is akin to image preprocessing in the computer vision domain. We find that at higher noise levels, the M-channel filter performs better than the bilateral filter in terms of reducing noise while preserving edge details. The M-channel filter is also significantly simpler and therefore faster than the bilateral filter. Overall, the M-channel filter enables us to model, simulate and arrive at a better understanding of some of the initial mechanisms in visual pathway, while simultaneously providing a fast, biologically inspired algorithm for digital image preprocessing.

Efficient Design of Waveguide Manifold Multiplexers Based on Low-Order EM Distributed Models

In this paper, a new systematic technique to design manifold-coupled multiplexers in waveguide technology is proposed. The new technique uses generalized low-order electromagnetic (EM) distributed models, which constitute a half-way point between the fast, but imprecise, analytical models, and the more accurate, but costly, full-wave EM models. The method can be applied to contiguous and noncontiguous channel multiplexers, in both $ { E}$ -plane or $ { H}$ -plane configurations. This paper covers the complete design procedure for manifold multiplexers, starting from the required specifications and finishing with the physical dimensions. After explaining the general design technique for multiplexers with channel filters based on transmission-line resonators, the method is specialized for the design of classic multiplexers with circular-waveguide dual-mode filters. As a further application example, the same methodology is also used for the design of a nonconventional tuningless wideband multiplexer with a new type of rectangular waveguide filters. This paper is concluded with a comparison between simulation and measurements for the wideband multiplexer. Excellent agreement between measurements and simulations are demonstrated, thereby validating the complete design procedure.

A single conserved basic residue in the potassium channel filter region controls KCNQ1 insensitivity toward scorpion toxins

Although many studies concerning the sensitivity mechanism of scorpion toxin-potassium channel interactions have been reported, few have explored the biochemical insensitivity mechanisms of potassium channel receptors toward natural scorpion toxin peptides, such as the KCNQ1 channel. Here, by sequence alignment analyses of the human KCNQ1 channel and scorpion potassium channel MmKv2, which is completely insensitive to scorpion toxins, we proposed that the insensitivity mechanism of KCNQ1 toward natural scorpion toxins might involve two functional regions, the turret and filter regions. Based on this observation, a series of KCNQ1 mutants were constructed to study molecular mechanisms of the KCNQ1 channel insensitivity toward natural scorpion toxins. Electrophysiological studies of chimera channels showed that the channel filter region controls KCNQ1 insensitivity toward the classical scorpion toxin ChTX. Interestingly, further residue mutant experiments showed that a single basic residue in the filter region determined the insensitivity of KCNQ1 channels toward scorpion toxins. Our present work showed that amino acid residue diversification at common sites controls the sensitivity and insensitivity of potassium channels toward scorpion toxins. The unique insensitivity mechanism of KCNQ1 toward natural scorpion toxins will accelerate the rational design of potent peptide inhibitors toward this channel.

Distribution and Analysis of Milk Fat Globule and Crescent in Murrah Buffalo and Crossbred Cow

India is the largest producer of buffalo milk in the world. Buffalo milk is rich in minerals like calcium and magnesium, containing 100 % more fat and less cholesterol than cow milk. Physio-chemical properties of dairy products depend upon the size and distribution of milk fat globules (MFG). Individual MFG from Murrah buffalo were analysed as a function of size and distribution and comparisons were made with MFG of crossbred (HF X Sahiwal) cows. Crescents associated with MFG could serve as a source of RNA of mammary epithelial cells and that would be a non-invasive method of epithelial cell RNA. Acridine orange staining of fresh milk was visualized by light microscopy under red and green channel filters. MFG and MFG with crescents were analysed using imageJ image analysis software. The percentage of large sized MFG (area >20 µm2) was greater and the percentage of small sized MFG (area <10 µm2) was lower in buffalo milk than that of cow. The percentage of crescents was <1 % of total MFG in both the species. These results indicate that MFG in buffalo milk is larger than MFG of cow milk. RNA isolation from crescents of buffalo MFG and its suitability for microarray analysis remains to be determined.

Atomic filter based on stimulated Raman transition at the rubidium D1 line.

We report on a 795 nm atomic filter consisting of a stimulated Raman gain amplifier together with normal Faraday anomalous dispersion optical filtering (FADOF) at the rubidium D1 line. The filter is operated with a single transmission peak. The gain of the filter's transmission light signal is enhanced up to 85-fold compared to case operating without a stimulated Raman transition. Based on atomic coherence, the filter's minimum transmission bandwidth is less than 22 MHz. In each filtering channel, the signal light's frequency can be tuned by changing the detuning of the coupling light. Such a filter with stimulated Raman gain is more efficient in extracting weak signals in the presence of a strong light background compared with the normal FADOF. This expands the range of potential applications in optical communications and lidar technology. This filtering method can also be extended to the lines of other atoms.

헬리콥터의 비행영역제한 알고리즘 설계

This paper presents the algorithm for envelope protection of helicopters. The algorithm consists of two feedback control loops: inner loop and outer loop. As an inner loop control, model following control is designed to meet the ADS-33 handling qualities specification by minimizing the tracking errors between the responses of the actual model and those of the command filter. In order to implement envelope protection, saturation limiter is imposed to command channels in command filter, whose limits are computed corresponding to the envelope limit. Fast model predictive control is designed as an outer loop control to deal with saturation constraints generated by the inner loop envelope protection and also imposed by outer loop envelope protection variables. Simulation results show that the proposed algorithm yields good envelope protection performance.

Noise assisted excitation energy transfer in a linear model of a selectivity filter backbone strand

In this paper, we investigate the effect of noise and disorder on the efficiency of excitation energy transfer (EET) in a sites linear chain with ‘static’ dipole–dipole couplings. In fact, here, the disordered chain is a toy model for one strand of the selectivity filter backbone in ion channels. It has recently been discussed that the presence of quantum coherence in the selectivity filter is possible and can play a role in mediating ion-conduction and ion-selectivity in the selectivity filter. The question is ‘how a quantum coherence can be effective in such structures while the environment of the channel is dephasing (i.e. noisy)?’ Basically, we expect that the presence of the noise should have a destructive effect in the quantum transport. In fact, we show that such expectation is valid for ordered chains. However, our results indicate that introducing the dephasing in the disordered chains leads to the weakening of the localization effects, arising from the multiple back-scatterings due to the randomness, and then increases the efficiency of quantum energy transfer. Thus, the presence of noise is crucial for the enhancement of EET efficiency in disordered chains. We also show that the contribution of both classical and quantum mechanical effects are required to improve the speed of energy transfer along the chain. Our analysis may help for better understanding of fast and efficient functioning of the selectivity filters in ion channels.

TU‐EF‐204‐11: Impact of Using Multi‐Slice Training Sets On the Performance of a Channelized Hotelling Observer in a Low‐Contrast Detection Task in CT

Purpose:To investigate using multiple CT image slices from a single acquisition as independent training images for a channelized Hotelling observer (CHO) model to reduce the number of repeated scans for CHO‐based CT image quality assessment.Methods:We applied a previously validated CHO model to detect low contrast disk objects formed from cross‐sectional images of three epoxy‐resin‐based rods (diameters: 3, 5, and 9 mm; length: ∼5cm). The rods were submerged in a 35x 25 cm2 iodine‐doped water filled phantom, yielding‐15 HU object contrast. The phantom was scanned 100 times with and without the rods present. Scan and reconstruction parameters include: 5 mm slice thickness at 0.5 mm intervals, 120 kV, 480 Quality Reference mAs, and a 128‐slice scanner. The CHO's detectability index was evaluated as a function of factors related to incorporating multi‐slice image data: object misalignment along the z‐axis, inter‐slice pixel correlation, and number of unique slice locations. In each case, the CHO training set was fixed to 100 images.Results:Artificially shifting the object's center position by as much as 3 pixels in any direction relative to the Gabor channel filters had insignificant impact on object detectability. An inter‐slice pixel correlation of &gt;∼0.2 yielded positive bias in the model's performance. Incorporating multi‐slice image data yielded slight negative bias in detectability with increasing number of slices, likely due to physical variations in the objects. However, inclusion of image data from up to 5 slice locations yielded detectability indices within measurement error of the single slice value.Conclusion:For the investigated model and task, incorporating image data from 5 different slice locations of at least 5 mm intervals into the CHO model yielded detectability indices within measurement error of the single slice value. Consequently, this methodology would Result in a 5‐fold reduction in number of image acquisitions.This project was supported by National Institutes of Health grants R01 EB017095 and U01 EB017185 from the National Institute of Biomedical Imaging and Bioengineering.