Channel Filter Research Articles

A Leakage-Based MMSE Beamforming Design for a MIMO Interference Channel

We propose a low complexity design of the linear transmit filters for a MIMO interference channel. This design is based on a minimum mean squared error (MMSE) approach incorporating the signal and the interference leakage for each transmitter. Unlike the previous methods, it allows a closed-form expression of the regularization factor for the MMSE transmit filter. Hence, it requires a lower computational complexity compared to the conventional MMSE approach that is optimally achieved by solving a polynomial equation to find the regularization factor. Furthermore, the mean squared error (MSE) performance of the proposed design is verified by simulations to have nearly no loss compared to the conventional MMSE approach.

A Novel Approach for Turbo Decoding In ISI Channel

codes are family of forward error correcting codes, whose performance is near Shannon limit. Turbo decoding is based on the maximum a-posterior algorithm (MAP) algorithm. In this paper, the problem of turbo decoding in ISI channel is studied. A Super-trellis structure method has been presented and modified turbo decoding is suggested. Two methods have been suggested for turbo decoding in ISI channel. In the first method, we take all possible combinations of output of encoder-2 and in method-2, output of each encoder is passed through channel filter independently. Method-2 performs better than method-1 but requires higher bandwidth. The improvement in performance is demonstrated through simulations. Keywordscode, Intersymbol interferance, ISI channel, Iterative decoding, Turbo code.

TIME DELAYS IN QUASI-PERIODIC PULSATIONS OBSERVED DURING THE X2.2 SOLAR FLARE ON 2011 FEBRUARY 15

We report observations of quasi-periodic pulsations (QPPs) during the X2.2 flare of 2011 February 15, observed simultaneously in several wavebands. We focus on fluctuations on time scale 1-30 s and find different time lags between different wavebands. During the impulsive phase, the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) channels in the range 25-100 keV lead all the other channels. They are followed by the Nobeyama RadioPolarimeters at 9 and 17 GHz and the Extreme Ultra-Violet (EUV) channels of the Euv SpectroPhotometer (ESP) onboard the Solar Dynamic Observatory (SDO). The Zirconium and Aluminum filter channels of the Large Yield Radiometer (LYRA) onboard the Project for On-Board Autonomy (PROBA2) satellite and the SXR channel of ESP follow. The largest lags occur in observations from the Geostationary Operational Environmental Satellite (GOES), where the channel at 1-8 {\AA} leads the 0.5-4 {\AA} channel by several seconds. The time lags between the first and last channels is up to 9 s. We identified at least two distinct time intervals during the flare impulsive phase, during which the QPPs were associated with two different sources in the Nobeyama RadioHeliograph at 17 GHz. The radio as well as the hard X-ray channels showed different lags during these two intervals. To our knowledge, this is the first time that time lags are reported between EUV and SXR fluctuations on these time scales. We discuss possible emission mechanisms and interpretations, including flare electron trapping.

Temperature-Dependent Tunable Photonic Channel Filter

In the present communication, we studied the 1-D photonic quantum-well (PQW) structure for the photonic channel filter. The PQW structure consists of a defect layer in Si/air multilayered regular 1-D photonic crystal. The extension of the work shows the temperature-dependent tuning in the channel filter.

Design of Almost Symmetric Orthogonal Wavelet Filter Bank Via Direct Optimization

It is a well-known fact that (compact-support) dyadic wavelets [based on the two channel filter banks (FBs)] cannot be simultaneously orthogonal and symmetric. Although orthogonal wavelets have the energy preservation property, biorthogonal wavelets are preferred in image processing applications because of their symmetric property. In this paper, a novel method is presented for the design of almost symmetric orthogonal wavelet FB. Orthogonality is structurally imposed by using the unnormalized lattice structure, and this leads to an objective function, which is relatively simple to optimize. The designed filters have good frequency response, flat group delay, almost symmetric filter coefficients, and symmetric wavelet function.

Tangential Thomson scattering diagnostic for the KSTAR tokamak

A Thomson scattering diagnostic system has been developed for electron density and temperature measurements in KSTAR. The KSTAR Thomson scattering diagnostic system has a 90 degree scattering configuration with the tangential laser-beam input optics and the horizontal collection optics. In the KSTAR 4th campaign, measuring spatial points of the Thomson scattering system was 5 ea for core with 120 mm, 60 mm spacing and 12 ea for edge with 20 mm, 10 mm spacing, respectively. For KSTAR Thomson scattering system, we used the commercial 10 Hz, 2 J, 1064 nm Nd:YAG laser that was installed through the Korea-Japan collaboration. To get the Thomson scattering spectrum, we equipped the core and edge polychromators. And the edge polychromators were developed by Korea-Japan collaboration and manufactured by NIFS, Japan. The measurable range of core polychromator was 500 eV to 20 KeV and edge was 10 eV to 1.8 KeV. To evaluate the electron density and electron temperature, we measure the Rayleigh scattering signals by using polychromator's 1064 nm filter channels and relative calibration by using a tungsten (W) lamp with monochromator system. The measurement result of Rayleigh scattering signal with nitrogen (N2) gas was clearly proportional to the nitrogen density rate. We use the QDC(Charge-to-Digital Conversion) system with signal amplifier ( × 4) to get Thomson scattering signal. In this paper, we report the first result of electron temperature and density by using the tangential Thomson scattering system on KSTAR 4th campaign.

Image Reconstruction Research on Color Filter Array

According to the physical structure of color image sensor in camera, cameras acquire images using image sensors overlaid with a color filter array (CFA) from different channels filters, so we can only achieve a single color component at each pixel position. In order to reconstruct a color image, color demosaicing is required to reconstruct the other two color components. General interpolation method may blur the image edge and introduce visible artifacts near edges. An image reconstruction algorithm based on adaptive region demosaicing is put forward in Bayer format to reduce the color artifacts. Experiment results show that the algorithm can improve the image quality and PSNR, sharpen texture and edge of the image and enhance image quality.

A MODIFIED CAUCHY METHOD SUITABLE FOR DUPLEXER AND TRIPLEXER RATIONAL MODELS EXTRACTION

Abstract—A modified Cauchy method which generates accurate duplexer and triplexer rational models from either measurements or electromagnetic analysis is presented in this paper. The modified Cauchy method has some advantages over the conventional Cauchy method because it takes into account the relationship between the transmission coefficients of each channel filter and reflection coefficient. It is suitable for duplexer and triplexer whose channel filters are connected through resonating junction. The total least square method is used to solve the system matrix. Synthesized numerical duplexer and triplexer examples verify the method successfully.

Dual-core optofluidic chip for independent particle detection and tunable spectral filtering

We present the first integration of fluidically tunable filters with a separate particle detection channel on a single planar, optofluidic chip. Two optically connected, but fluidically isolated liquid-core antiresonant reflecting optical waveguide (ARROW) segments serve as analyte and spectral filter sections, respectively. Ultrasensitive detection of fluorescent nanobeads with high signal-to-noise ratio provided by a fluidically tuned excitation notch filter is demonstrated. In addition, reconfigurable filter response is demonstrated using both core index tuning and bulk liquid tuning. Notch filters with 43 dB rejection ratio and a record 90 nm tuning range are implemented by using different mixtures of ethylene glycol and water in the filter section. Moreover, absorber dyes and liquids with pH-dependent transmission in the filter channel provide additional spectral control independent of the waveguide response. Using both core index and pH control, independent filter tuning at multiple wavelengths is demonstrated for the first time. This extensive on-chip control over spectral filtering as one of the fundamental components of optical particle detection techniques offers significant advantages in terms of compactness, cost, and simplicity, and opens new opportunities for waveguide-based optofluidic analysis systems.

Preliminary Results on Irradiance Measurements from Lyra and Swap

The first and preliminary results of the photometry of Large Yield Radiometer (LYRA) and Sun Watcher using Active Pixel system detector and Image Processing (SWAP) onboard PROBA2 are presented in this paper. To study the day-to-day variations of LYRA irradiance, we have compared the LYRA irradiance values (observed Sun as a star) measured in Aluminum filter channel (171 Å–500 Å) with spatially resolved full-disk integrated intensity values measured with SWAP (174 Å) and Ca II K 1 Å index values (ground-based observations from NSO/Sac Peak) for the period from 01 April 2010 to 15 Mar 2011. We found that there is a good correlation between these parameters. This indicates that the spatial resolution of SWAP complements the high temporal resolution of LYRA. Hence SWAP can be considered as an additional radiometric channel. Also the K emission index is the integrated intensity (or flux) over a 1 Å band centered on the K line and is proportional to the total emission from the chromosphere; this comparison clearly explains that the LYRA irradiance variations are due to the various magnetic features, which are contributing significantly. In addition to this we have made an attempt to segregate coronal features from full-disk SWAP images. This will help to understand and determine the actual contribution of the individual coronal feature to LYRA irradiance variations.

Study on Correlation of Angstrom Turbidity Coefficient (β) with Aerosol Optical Depth (τ) over a Period of Two Years (2004-2006) for the Special Mangrove Ecosystem of Sun-darbans

A study on the correlation of the angstrom turbidity coefficient (β) with aerosol optical depth (τ) have been studied on the basis of field measurements carried out at Kaikhali (22.022°N & 88.614°E) lying in the east coast of India inside the Sundarbans. The angstrom turbidity coefficients have been calculated with respect to the filter channels at 340 nm, 500 nm, 870 nm, 936 nm and 1020 nm of a Sunphotometer. Assessment of the possible influx of the fine particulate concentrations to the total aerosol loading in the area have been made with respect to the calculated angstrom turbidity values for the summer and winter seasons over a period of two years from 2004 to 2006. Substantially high angstrom turbidity coefficient values exceeding 0.2 and indicative of a relatively hazy atmosphere for both the summer and winter periods over these two years from 2004-2006 have been observed. Considering the importance of this fragile mangrove ecosystem of the Sundarbans and also the vulnerability of the area to severe impacts of climate changes, this is indeed a thought provoking issue as far as the policy makers of the country are concerned. In fact, the study has confirmed positive correlation of β with τ.

Letter to the Editor

The authors wish to correct an error made in a publication submitted to the sixth Argentine School of Micro-Nanoelectronics, Technology and Applications (EAMTA 2011). The paper entitled “Analysis of time delay difference due to parametric mismatch in matched filter channels” has a mistake in the results of the theorem proposed.

A hyperparameter consensus method for agreement under uncertainty

This paper addresses the problem of information consensus in a team of networked agents by presenting a generic consensus method that permits agreement to a Bayesian fusion of uncertain local parameter estimates. In particular, the method utilizes the concept of conjugacy of probability distributions to achieve a steady-state estimate consistent with a Bayesian combination of each agent’s local knowledge, without requiring complex channel filters or being limited to normally distributed uncertainties. It is shown that this algorithm, termed hyperparameter consensus, is adaptable to many local uncertainty distributions within the exponential family, and will converge to a Bayesian fusion of local estimates with some standard assumptions on the network topology.

Rugate filter with multi-channel grown by glancing angle deposition

Glancing angle deposition (GLAD) is an effective technique to fabricate thin films with desired nanoscale porosity variations in three dimensions. GLAD can be used to grow rugate filters characterized by a sinusoidal refractive index profile from one single source material through control of film porosity. A multi-stopband rugate filter can be achieved either by introducing a layer of constant index into the center of sinusoidal refractive index profile or by embedding discrete layers of constant refractive index to sinusoidal index profile with the GLAD technique. Transmittance measurements of the one channel filter, formed with titanium dioxide, revealed this method is one of the most valid technologies to fabricate multi-band filters.

Optimization of colorimetric DET technique for the in situ, two-dimensional measurement of iron(II) distributions in sediment porewaters

The recently developed colorimetric diffusive equilibration in thin films (DET) technique for the in situ, high-resolution measurement of iron(II) in marine sediments is optimized to allow measurement of the higher iron concentrations typical of freshwater sediment porewaters. Computer imaging densitometry (CID) is used to analyze the retrieved samplers following exposure to ferrozine, a colorimetric reagent selective for iron(II). The effect of ferrozine concentration, image processing parameters and ionic strength are investigated to improve the applicability of this technique to a wider range of aquatic systems than reported in the first publications of this approach. The technique was optimized to allow detection of up to 2000μmolL−1 iron(II), a four-fold increase on the previous upper detection limit of 500μmolL−1. The CID processing of the scanned color image was also optimized to adjust the sensitivity of the assay as required; by processing the image with different color channel filters, the sensitivity of the assay can be optimized for lower concentrations (up to 100μmolL−1) or higher concentrations (up to 2000μmolL−1) of iron(II), depending on the specific site characteristics. This process does not require separate sampling probes or even separate scans of the DET gels as the color filter and grayscale conversion is done post-image capture. The optimized technique is very simple to use and provides highly representative, high-resolution (1mm) two-dimensional distributions of iron(II) in sediment porewaters. The detection limit of the optimized technique was 4.1±0.3μmolL−1 iron(II) and relative standard deviations were less than 6%.

A neurocognitive model of recognition and pitch segregation

This paper describes a neurocognitive model of pitch segregation in which it is proposed that recognition mechanisms initiate early in auditory processing pathways so that long-term memory templates may be employed to segregate and integrate auditory features. In this model neural representations of pitch height are primed by the location and pattern of excitation across auditory filter channels in relation to long-term memory templates for common stimuli. Since waveform driven pitch mechanisms may produce information at multiple frequencies for tonal stimuli, pitch priming was assumed to include competitive inhibition that would allow only one pitch estimation at any time. Consequently concurrent pitch information must be relayed to short-term memory via a parallel mechanism that employs pitch information contained in the long-term memory template of the chord. Pure tones, harmonic complexes and two pitch chords of harmonic complexes were correctly classified by the correlation of templates comprising auditory nerve excitation and off-frequency inhibition with the excitation patterns of stimuli. The model then replicated behavioral data for pitch matching of concurrent vowels. Comparison of model outputs to the behavioral data suggests that inability to recognize a stimulus was associated with poor pitch segregation due to the use of inappropriate pitch priming strategies.

A Cochlear Implant Signal Processing Lab: Exploration of a Problem-Based Learning Exercise

This paper presents an introductory signal processing laboratory and examines this laboratory exercise in the context of problem-based learning (PBL). Centered in a real-world application, a cochlear implant, the exercise challenged students to demonstrate a working software-based signal processor. Partnering in groups of two or three, second-year electrical and computer engineering and biomedical engineering students used MATLAB graphical user interface programs, complemented with their own original MATLAB code, to design filters suitable for achieving a filter bank decomposition of an audio signal. Rather than using the envelope-detected output for direct electrical stimulation of auditory nerve fibers as in an implant, the students reconstructed the signal by modulating sinusoids to yield an acoustic simulation. To appreciate the impact of filter order on sound intelligibility, students were asked to reconstruct signals using 4-16 filter channels for both speech and music and to examine the results critically. The lab served as a substrate upon which to solidify fundamental signal processing concepts such as the distinction between time and frequency domains, constructing and interpreting spectrograms, sampling, spectral decomposition, filtering, and reconstruction. In the spirit of PBL, the students examined engineering tradeoffs and discussed implementations when they were asked to consider realizing a significantly higher channel count (128-channel) device. To determine how the laboratory exercise impacted student learning and comprehension, as well as the level of student engagement achieved with this compelling application, an anonymous online survey was administered at the end of the course. The survey outcomes, as well as the components of the lab, are discussed in the context of PBL pedagogy.

Light propagation properties of two-dimensional photonic crystal channel filters with elliptical micro-cavities

Light propagation through a channel filter based on two-dimensional photonic crystals with elliptical-rod defects is studied by the finite-difference time-domain method. Shape alteration of the defects from the usual circle to an ellipse offers a powerful approach to engineer the resonant frequency of channel filters. It is found that the resonant frequency can be flexibly adjusted by just changing the orientation angle of the elliptical defects. The sensitivity of the resonant wavelength to the alteration of the oval rods' shape is also studied. This kind of multi-channel filter is very suitable for systems requiring a large number of output channel filters.

Multilayered LTCC triplexer with star-junction topology

A 3D structure for the realisation of a triplexer with star-junction topology is proposed using low-temperature co-fired ceramic (LTCC) technology. By properly locating the resonators in different layers, a triplexer with three fourth-order filter channels (30.5–31, 31.75–32.25, 33–33.5 GHz) for Ka-band applications is designed and fabricated. Good agreement is achieved between simulation and measurement.

Protein interactions central to stabilizing the K + channel selectivity filter in a four-sited configuration for selective K + permeation

The structural and functional conversion of the nonselective NaK channel to a K(+) selective channel (NaK2K) allows us to identify two key residues, Tyr and Asp in the filter sequence of TVGYGD, that participate in interactions central to stabilizing the K(+) channel selectivity filter. By using protein crystallography and channel electrophysiology, we demonstrate that the K(+) channel filter exists as an energetically strained structure and requires these key protein interactions working in concert to hold the filter in the precisely defined four-sited configuration that is essential for selective K(+) permeation. Disruption of either interaction, as tested on both the NaK2K and eukaryotic K(v)1.6 channels, can reduce or completely abolish K(+) selectivity and in some cases may also lead to channel inactivation due to conformational changes at the filter. Additionally, on the scaffold of NaK we recapitulate the protein interactions found in the filter of the Kir channel family, which uses a distinct interaction network to achieve similar stabilization of the filter.