Channel Filter Research Articles

CIR Samples and Channel Taps Based WindowedDFT Channel Estimation for MIMOOFDM System

For high capacity demand for 4G broadband multimedia and internet services with high quality of service (QoS), multiple input multiple output (MIMO) transmission methods are exploited for high speed machine to machine communication. In order to mitigate the fast fading multipath effects, orthogonal frequency division multiplexing (OFDM) is used as modulation technique for MIMO systems. Time-domain channel characteristics are used to make efficient channel state information (CSI) available at the transmitter side. In this paper Windowed-DFT technique is optimized for channel estimation and the performance and complexity are determined. Computer Simulations are used to show the effect of channel filter length and the number of multipath channel taps.

Tunable multichannel drop filters based on the two-dimensional photonic crystal with oval defects

Light propagation through the channel filter based on the two-dimensional photonic crystals with oval-rod defects is studied by the finite-difference time-domain method. In addition to the traditional size tuning, shape alteration of the defects from the usual circle to the ellipse offers a powerful approach to tune the resonant frequency of channel-drop filters based on two-dimensional photonic crystals. It is found that the resonant frequency can be flexibly adjusted only by changing the orientation angle of the oval defects. The sensitivity of the resonant frequency to the alteration of the oval rods’ rotation angle is systematically studied. Because the rotation angles of the ellipse can be continuously adjusted, so the channel drop filter based on this kind of defects with different rotation angles is more suitable to the occasion where a large number of output channel filters is need.

Penggunaan Zeolit Sebagai Media Penyaring Pada Pengolahan Air LimbahDomestik

<p>Sand filter is frequentlyused to treat contaminated water. Channel filter system is a modification of sand filter where the channel is shaped thus the land requirement could be minimized, water is flowed horizontallyfrom intial tank to finaltank through sand filter. Employing the channel filter to treat domestic wastewateris capable of reducing E. Coli up to 98.14%, increasing DO up to 27% and decreasing BOD5 up to 27%. Unfortunately, the final content of E.Coli after treatment process completed is still unacceptable for drinking water. Several options are available to improve the performance of the channel filter system. One of the promising alternativesis modifying the filter medium. Zeolite is natural material that has been utilized to improvewater quality based on several parameters such as Fe, Mn, organic materials, CO and others. Application of zeolite to diminish E. Coli is a challenge. This paper will investigate the effectiveness of zeolite to lower E. Coli contained in domestic wastewater . Zeolite was added to sand filter where thefraction of zeolite is about 5%. Two kind of zeolite-sand combination was implemented that is arranged and mixed zeolite-sand. Wastewater containing E.Coli was then put in the initial tank. Through the hole createdin the tank, wastewater then flowed passing through the combined zeolite-sand filter and accumulated in the final tank. Both E. Coli from initial and final tank was measured to compute treatment efficiency. The result showsE. Coli decreases up to99.99%, BOD5and DO decrease more than 71% and 66% respectively. It can be concluded that 5% addition ofzeolite is able to improve treatment efficiency ofsand filter.</p>

Multiple Fading Factors Kalman Filter for SINS Static Alignment Application

To solve the problem that the standard Kalman filter cannot give the optimal solution when the system model and stochastic information are unknown accurately, single fading factor Kalman filter is suitable for simple systems. But for complex systems with multi-variable, it may not be sufficient to use single fading factor as a multiplier for the covariance matrices. In this paper, a new multiple fading factors Kalman filtering algorithm is presented. By calculating the unbiased estimate of the innovation sequence covariance using fenestration, the fading factor matrix is obtained. Adjusting the covariance matrix of prediction error Pk|k-1 using fading factor matrix, the algorithm provides different rates of fading for different filter channels. The proposed algorithm is applied to strapdown inertial navigation system (SINS) initial alignment, and simulation and experimental results demonstrate that, the alignment accuracy can be upgraded dramatically when the actual system noise characteristics are different from the pre-set values. The new algorithm is less sensitive to uncertainty noise and has better estimation effect of the parameters. Therefore, it is of significant value in practical applications.

Water Vapor Interference Correction in a Non Dispersive Infrared Multi-Gas Analyzer

We demonstrate an effective method to eliminate the interfering effect of water vapor in a non-dispersive infrared multi-gas analyzer. The response coefficients of water vapor at each filter channel are measured from the humidity of the ambient air. Based on the proposed method, the water vapor interference is corrected with the measured response coefficients. By deducting the absorbance of each filter channel related to water vapor, the measuring precision of the analyzer is improved significantly and the concentration retrieval correlation accuracy of each target gas is more than 99%.

Modal analysis of ultra-compact channel filters based on race-track photonic crystal ring resonators

A new channel drop filter (CDF) is proposed based on a race-track photonic crystal ring resonator composed of square-lattice cylindrical silicon rods in air. By using a two-dimensional finite-difference, time-domain numerical technique, the modal behavior of two representative CDFs, parallel and perpendicular, has been analyzed. The analyses include the impact of additional scatterer size, scatterer amount and their position on the performance of proposed CDFs, such as drop efficiency and quality factor (Q). For the parallel CDF, about 130 spectral Q and 99% drop efficiency can be optimally achieved at 1363 nm channel with 0.145 periodicity scatterer size, whereas for the perpendicular one, about 180 spectral Q and 99% drop efficiency can be optimally obtained at 1366 nm channel with 0.165 periodicity scatterer size. By increasing the number of scatterers, the efficiency of both configurations can be enhanced. No obvious variation is obtained by changing the scatterer position.

Radar Sensor Wireless Channel Modeling in Foliage Environment: UWB Versus Narrowband

In this paper, we study the radar sensor wireless channel modeling in foliage environment, a rich scattering and time-varying environment, based on extensive data collected using ultra-wideband (UWB) and narrowband (200 and 400 MHz) radar sensors. We apply two approaches to the wireless channel modeling: Saleh and Valenzuela (S-V) method for UWB channel modeling and CLEAN method for narrowband and UWB channel modeling. We validated that UWB echo signals (within a burst) do not hold self-similarity, which means the future signals cannot be forecasted based on the received signals and channel modeling is necessary from statistical point of view. Based on the S-V method for UWB channel modeling, in foliage UWB channel, the multipath contributions arriving at the receiver are grouped into clusters. The time of arrival of clusters can be modeled as a Poisson arrival process, while within each cluster, subsequent multipath contributions or rays also arrive according to a Poisson process. At different distance (near distance, medium distance, and far distance), we observe that the Poisson process parameters are quite different. We also observe that the amplitude of channel coefficient at each path follows Rician distribution for medium and far distance, and it is non-stationary for paths from short distance (one of two Rician distributions), and these observations are quite different with the IEEE indoor UWB channel model and S-V indoor channel model. Based on the CLEAN method, the narrowband (200 and 400 MHz) and UWB channel impulse responses have many similarities: both can be modeled as linear time-variant filter channel. We also studied the large-scale fading using path-loss and log-normal shadowing model for foliage enviroment, and observed that the path-loss exponent is very high because it has rich scattering.

Novel multi-channel fiber-optic filters based on step-chirped sampled Bragg grating

A new kind of multi-channel–channel filter, based on the strongly discretely chirped sampled Bragg grating, has been proposed and studied. Compared with the previous methods, the step-chirp number is much smaller or the nonlinearity chirp inherent in the strongly chirped holographic phase mask can be avoided. Based on the analysis and numerical simulations, it has been shown that high-performance multi-channel comb filter can be realized in such a simple structure.

Using spiking onset neurons and a recurrent neural network for sound identification.

Physiological evidence suggests that specific neurons within the cochlear nucleus specialize in sound onset detection. These are innervated by type 1 spiral ganglion fibers covering a relatively wide spectrum. Sudden increases in sound energy (e.g., during the initial portion of a sound) result in an increased firing rate in a downstream onset neuron. Onset timing and spectral location are thought to play a role both in auditory stream separation and sound identification and interpretation. Onset neurons are modeled using leaky integrate‐and‐fire units innervated by spiking data streams produced using a passive gammatone filterbank followed by positive‐going zero‐crossing detection. Signal level is coded using multiple spike trains per filter channel. The model is presented with a succession of 607 musical samples selected from the McGill dataset and the pattern of onset spikes recorded for each sound. Groups of onset spikes occur close to the beginning of each note. The objective is to use the pattern of...

Channel-Robust Classifiers

A key assumption underlying traditional supervised learning algorithms is that labeled examples used to train a classifier are drawn i.i.d. from the same distribution as test samples. This assumption is violated when classifying a test sample whose statistics differ from the training samples because the test signal is the output of a noisy linear time-invariant system, e.g., from channel propagation or filtering. We assume that the channel impulse response is unknown, but can be modeled as a random channel with finite first and second-order statistics that can be estimated from sample impulse responses. We present two kernels, the expected and projected RBF kernels, that account for the stochastic channel. Compared to the strategy of virtual examples, an SVM trained with the proposed kernels requires dramatically less training time, and may perform better in practice. We also extend the joint quadratic discriminant analysis (joint QDA) classifier, which also accounts for a stochastic channel, to a local version that reduces model bias. Results show the proposed methods achieve state-of-the-art performance and significantly faster training times.

Reconfigurable Low Area Complexity Filter Bank Architecture Based on Frequency Response Masking for Nonuniform Channelization in Software Radio Receivers

The most computationally demanding block in the digital front-end of a software defined radio (SDR) receiver is the channelizer which operates at the highest sampling rate. Channelizers are employed in the SDR receivers for extracting individual channels (frequency bands) from the digitized wideband input signal. Reconfigurability and low complexity are the two key requirements in an SDR channelizer. A new reconfigurable filter bank (FB) architecture based on frequency response masking (FRM) for SDR channelizers is proposed. The proposed FB offers reconfigurability at the architectural level and at the channel filter level and is capable of extracting channels of nonuniform bandwidths corresponding to multiple wireless communication standards from the digitized wideband input signal. Design examples show that the proposed FB offers multiplier complexity reduction of 84% over the conventional per-channel (PC) approach, which is best suitable for the extraction of channels of nonuniform bandwidth. The proposed FB has been synthesized on 0.18 μm complementary metal oxide semiconductor (CMOS) technology and compared with the PC approach. Synthesis results show that the proposed FB offers area reduction of 85%, power reduction of 48.5%, and improvement in speed of 56.7% over the PC approach. The proposed FB has been implemented on Xilinx Virtex 2v3000ff1152-4 FPGA and tested using real-time inputs from a vector signal generator.

Synthesis of an Optimal Wavelet Based on Auditory Perception Criterion

A method is proposed for synthesizing an optimal wavelet based on auditory perception criterion for dyadic filter bank implementation. The design method of this perceptually optimized wavelet is based on the critical band (CB) structure and the temporal resolution of human auditory system (HAS). The construction of this compactly supported wavelet is done by designing the corresponding optimal FIR quadrature mirror filter (QMF). At first, the wavelet packet (WP) tree is obtained that matches optimally with the CB structure of HAS. The error in passband energy of the CB channel filters is minimized with respect to the ideal QMF. The optimization problem is formulated in the lattice QMF domain and solved using bounded value global optimization technique. The corresponding wavelet is obtained using the cascade algorithm with the support being decided by the temporal resolution of HAS. The synthesized wavelet is maximally frequency selective in the critical bands with temporal resolution closely matching with that of the human ear. The design procedure is illustrated with examples, and the performance of the synthesized wavelet is analyzed.

Fabrication of Micro-Silicon Filter and Separating of Blood Cells

This research developed a micro-silicon cell filter using MEMS fabricating technology, which has constant filtering channel size, uniformed distribution, and good surface quality. Blood cell filtering experiment was carried out by applying pressure injection and the filtering quality was studied via cell counting. The experimental results demonstrates that flat plate filter can implement blood cells filtering separation, and erythrocyte recycling rate reaches 90% with the 4～5m in filtering size and 0.1L/min injection flow-rate fulfilling the requirement of blood cells separation. Increasing the flow-rate can improve filtering efficiency to a certain degree but has little effect on erythrocyte recycling rate, because micro array filter is insensitive to back pressure in contract to the filled filter.

Tree Image Growth Analysis Using Instantaneous Phase Modulation

We propose the use of Amplitude-Modulation Frequency-Modulation (AM-FM) methods for tree growth analysis. Tree growth is modeled using phase modulation. For adapting AM-FM methods to different images, we introduce the use of fast filterbank filter coefficient computation based on piecewise linear polynomials and radial frequency magnitude estimation using integer-based Savitzky-Golay filters for derivative estimation. For a wide range of images, a simple filterbank design with only 4 channel filters is used. Filterbank specification is based on two different methods. For each input image, the FM image is estimated using dominant component analysis. A tree growthmodel is developed to characterize and depict quarterly and half-seasonal growth of trees using instantaneous phase. Qualitative evaluation of inter- and intraring reconstruction is performed on 20 aspen images and a mixture of 12 tree images of various types. Qualitative scores indicate that the results were mostly of good to excellent quality (4.4/5.0 and 4.0/5.0 for the two databases, resp.).

Compact Packaged Diplexer Based on Highly Selective Dual-Mode Bandpass Filter

A cost-effective planar packaged diplexer was designed, fabricated and measured for X and Ku-band applications. The miniaturization and selectivity of the diplexer are achieved by using a dual-mode resonator concept. The packaged diplexer has shown a low insertion loss of 2.6 and 2.95 at 10 GHz and 15 GHz center frequencies, respectively. Four transmissions zeros provided by each channel filter allow a high suppression over the stopband. Finally, the proposed diplexer shows a less than 1.5% center frequency shift over room temperature ranging conditions of -25 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ο</sup> C, +25 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ο</sup> C and +40 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ο</sup> C.

Engineering the hERG1 Selectivity Filter into the NaK Pore Domain

Comparison of the hERG1 selectivity filter sequence and pore helix with a variety of prokaryotic ion channels revealed an unusually high sequence identity (63%) with the non-selective cation channel NaK (∼19 amino acids). Taking advantage of this remarkable similarity, we have used NaK as a template to carry out a structural analysis of a hERG1-like NaK selectivity filter in K+. To engineer the NaK filter into that of hERG1, we substituted two critical residues, V59S in the pore helix and D66F at the selectivity filter (equivalent to positions Ser620 and Phe627 in hERG1, respectively). The final construct shares 73% sequence identity with the hERG1 selectivity filter, equivalent to the closest orthologue of hERG1, the bovine ether-a-go-go channel (bEAG1). Crystals of this engineered hERG-NaK diffracted to 2.8 Å resolution and were solved by molecular replacement using closed NaK as template. The crystal structure of hERG1-like NaK in 100 mM K+ revealed a striking similarity to the all canonical K+ channel filters in the conductive conformation (RMSD= 0.5 Å with the KcsA filter) and shows three major differences compared to WT NaK. First, hERG1-like NaK filter revealed four equivalent K+ binding sites. Second, the side chain of Phe66 residue establishes critical packing interactions with the adjacent aromatic residues from the pore helix. Third, hERG1-like NaK shows hydrogen bond interactions through a water molecule behind the selectivity filter, which is absent in WT NaK, but present in KcsA. We suggest that the hERG-NaK construct represents a unique tool to investigate the properties of the hERG1 channel selectivity filter at atomic level.

Corrections to “Current-Mode, WCDMA Channel Filter With In-Band Noise Shaping” [Sep 10 1770-1780

In the above titled paper (ibid., vol. 45, no. 9, pp. 1770-1780, Sep. 10), the authors should have referred to another paper [2] which reports a voltage mode topology that is much like the current-mode filter presented in [1]. This was an unintentional negligence and we sincerely apologize for it.

Enhanced Microwave Multiplexing Network

A new approach for designing a microwave multiplexing network is presented in order to improve channel performance. Through design and optimization of the connecting transmission line structure, the new approach ensures that an extra pole is formed in the passband of each channel. The channel filter order is therefore increased by one without additional resonators. Significant improvement in the performance of the multiplexer is achieved without the penalty of increased size or weight of the hardware, which is extremely important for applications in communication satellite. Simulation and measurement results are used to demonstrate the feasibility of such enhanced microwave multiplexing networks.

Etched beam splitters in InP/InGaAsP

An etched beam splitter (EBS) photonic coupler based on frustrated total internal reflection (FTIR) is designed, fabricated and characterized in the InP/InGaAsP material system. The EBS offers an ultra compact footprint (8x11 μm) and a complete range of bar/cross coupling ratio designs. A novel pre-etching process is developed to achieve sufficient depth of the etched coupling gaps. Fabricated EBS couplers demonstrate insertion loss between 1 and 2.6 dB with transmission (cross-coupling) ≤ 10%. The results show excellent agreement with 3D finite-difference time-domain (FDTD) modeling. The coupling of EBS has weak wavelength dependence in the C-band, making it suitable for wavelength division multiplexing (WDM) or other wide bandwidth applications. Finally, the EBS is integrated with active semiconductor optical amplifier (SOA) and phase-modulator components; using a flattened ring resonator structure, a channelizing filter tunable in both amplitude and center frequency is demonstrated, as well as an EBS coupled ring laser.

一维可调谐非磁化等离子体光子晶体的滤波特性

The piecewise linear current density recursive convolution finite-different time-domain method is applied to study the filtering properties of one dimension tunable unmagnetized plasma photonic crystals with single defect layer.In frequency domain,the transmission coefficients of electromagnetic differential Gaussian pulses are computed,and under the isothermal hypothesis,the plasma relaxation time,plasma temperature and plasma frequency are taken as the tunable parameters to study the effects of filtering properties.The results are as follows:the filter channel can be tuned by changing relaxation time and frequency of plasma,while the resonant frequency can not be tuned by changing plasma temperature.