Channel Filter Research Articles

Widely interval-adjustable multiwavelength erbium-ytterbium doped fiber laser based on micro-air cavity

We propose a widely interval-adjustable multiwavelength erbium-ytterbium doped fiber laser (EYDFL) based on a micro-air cavity (MAC). The fabricated MAC functions as a selective channel filter for multiwavelength generation with adjustable wavelength interval. By adjusting the MAC length from 0.10 to 2.40 mm, the wavelength interval can be continuously tuned from 8.61 to 0.47 nm, respectively. When the MAC length is set at 2.40 mm and erbium-ytterbium doped fiber amplifier at 300 mW, 12 multiple wavelength lasers with 0.47 nm spacing are obtained. The generated channels have an average optical signal-to-noise ratio of 40 dB and an average peak power of −35 dBm. The proposed laser introduces the advantages of a relatively simple structure and ease of operation at any wavelength band for potential applications including optical communication systems and sensing.

A practical de‐embedding technique based on the network theory for the filters in a 2‐channel multiplexer

A novel approach to de-embed the frequency response of filters connected to a 2-channel multiplexer without the need for unplugging is proposed. The technique to manifold coupled multiplexers with arbitrary number of filters is also theoretically generalised. In multiplexer tuning, there are practically important circumstances in which it is advantageous to de-embed the frequency response of filters in multiplexers without detaching them. The authors show that using a novel technique and reasonable approximations, all filters of a multiplexer can be modelled by simple microwave networks, and then, the equivalent rational function of the channel filters can be estimated appropriately by the rational H 2 approximation; extraction of this model facilitates tuning of the filters using the coupling matrix method. The impact of mechanical tolerances on the accuracy of the proposed technique is also studied. Next, this method is examined on a 2-channel multiplexer and its application in de-embedding and tuning of its connected filters is verified. Provided that the mechanical tolerances of the structure are sufficiently small, this technique is a powerful engineering solution towards tuning of manifold-coupled multiplexers.

Quantitative assessment of hydraulic tortuosity of oil and gas reservoirs in Western Siberia based on capillarimetric studies

It is known that a capillary model with a given size pore channels distribution does not allow estimating the absolute reservoir permeability with sufficient accuracy. In this case, it is necessary to introduce a certain correction factor into the formula, which is called either the lithological factor or hydraulic tortuosity. The paper shows that the need for a correction factor appears mainly due to the capillary model inconsistency to the real geometry of the reservoir void space. In this regard, we propose to use the dumbbell model when calculating the absolute permeability, in which the filtering channels are represented by alternating pores and interporous narrowings. This paper presents a methodology for calculating the hydraulic tortuosity for reservoirs of Western Siberia based on the results of capillary studies, as well as based on the data from the capacitive properties study. Hydraulic tortuosity is explained by the process of expansion of current lines in the pores and their contraction in the interporous tubules of the rock. It is noted that the residual water leads to a narrowing of the pores’ open area and, accordingly, to a certain decrease in the hydraulic tortuosity.

Multi-band planar diplexers with sub-sets of frequency-contiguous transmission bands

AbstractA class of multi-band planar diplexer with sub-sets of frequency-contiguous transmission bands is reported. Such a radio frequency (RF) device is suitable for lightweight high-frequency receivers aimed at multi-band/multi-purpose mobile satellite communications systems. It consists of two channelizing filters, each of them being made up of the in-series cascade connection of replicas of a constituent multi-passband/multi-embedded-stopband filtering stage. This building filtering stage defines a multi-passband transfer function for each channel, in which each main transmission band is split into various sub-passbands by the multi-stopband part. In this manner, each split passband gives rise to several sub-passbands that are imbricated with their counterpart ones of the other channel. The theoretical RF operational principles of the proposed multi-band diplexer approach with sub-sets of imbricated passbands are detailed by means of a coupling–routing–diagram formalism. Besides, the generation of additional transmission zeros in each channelizing filter for higher-selectivity realizations by exploiting cross-coupling techniques into it is also detailed. Furthermore, for experimental demonstration purposes, a microstrip proof-of-concept prototype of second-order octo-band diplexer in the frequency range of 1.5–2.5 GHz that consists of two quad-band channelizing filters with pairs of imbricated passbands is developed and characterized.

MRI Radiomics Signature as a Potential Biomarker for Predicting KRAS Status in Locally Advanced Rectal Cancer Patients.

Background and PurposeLocally advanced rectal cancer (LARC) is a heterogeneous disease with little information about KRAS status and image features. The purpose of this study was to analyze the association between T2 magnetic resonance imaging (MRI) radiomics features and KRAS status in LARC patients.Material and MethodsEighty-three patients with KRAS status information and T2 MRI images between 2012.05 and 2019.09 were included. Least absolute shrinkage and selection operator (LASSO) regression was performed to assess the associations between features and gene status. The patients were divided 7:3 into training and validation sets. The C-index and the average area under the receiver operator characteristic curve (AUC) were used for performance evaluation.ResultsThe clinical characteristics of 83 patients in the KRAS mutant and wild-type cohorts were balanced. Forty-two (50.6%) patients had KRAS mutations, and 41 (49.4%) patients had wild-type KRAS. A total of 253 radiomics features were extracted from the T2-MRI images of LARC patients. One radiomic feature named X.LL_scaled_std, a standard deviation value of scaled wavelet-transformed low-pass channel filter, was selected from 253 features (P=0.019). The radiomics-based C-index values were 0.801 (95% CI: 0.772-0.830) and 0.703 (95% CI: 0.620-0.786) in the training and validation sets, respectively.ConclusionRadiomics features could differentiate KRAS status in LARC patients based on T2-MRI images. Further validation in a larger dataset is necessary in the future.

On the performance of concentrating fluid-based spectral-splitting hybrid PV-thermal (PV-T) solar collectors

Concentrating fluid-based spectral-splitting hybrid PV-thermal (SSPVT) collectors are capable of high electrical and thermal efficiencies, as well as high-temperature thermal outputs. However, the optimal optical filter and the maximum potential of such collectors remain unclear. In this study, we develop a comprehensive two-dimensional model of a fluid-based SSPVT collector. The temperature distributions reveal that these designs are effective in thermally decoupling the PV module from the high-temperature filter flow-channel, improving the electrical performance of the module. For a Si solar cell-based SSPVT collector with optical filter #Si400-1100, the filter channel is able to produce high-temperature thermal energy (400 °C) with an efficiency of 19.5%, low-temperature thermal energy (70 °C) with an efficiency of 49.5%, and electricity with an efficiency 17.5%. Of note is that the relative fraction of high-temperature thermal energy, low-temperature thermal energy and electricity generated by such a SSPVT collector can be adjusted by shifting the upper- and lower-bound cut-off wavelengths of the optical filter, which are found to strongly affect the spectral and energy distributions through the collector. The optimal upper-bound cut-off always equals the bandgap wavelength of the solar cell material (e.g., 1100 nm for Si, and 850 nm for CdTe), while the optimal lower-bound cut-off follows more complex selection criteria. The SSPVT collector with the optimal filter has a significantly higher total effective efficiency than an equivalent conventional solar-thermal collector when the relative value of the high-temperature heat to that of electricity is lower than 0.5. Detailed guidance for selecting optimal filters and their role in controlling SSPVT collector performance under different conditions is provided.

Inhibited effect of an RGD peptide hydrogel on the expression of β1-integrin, FAK, and Akt in Tenon's capsule fibroblasts.

Tenon's capsule fibroblasts are the main cellular components of filtration tract scar that limit the success rate of glaucoma filtration surgery. Scar formation results from infiltration and proliferation of fibroblasts into damaged areas, meanwhile synthesis of extracellular matrix glycoproteins. Integrins are cell surface receptors for extracellular molecules that mediate cell adhesion, spreading, migration, and invasion. They bind their ligands often through recognition of short amino-acid sequences-arginine-glycine-aspartic acid (RGD). Peptides that contain RGD sequence can compete with RGD containing insoluble matrix proteins for binding to the integrin receptor and thus prevent the downstream signaling pathway. Increasing evidence supports that β1-integrin/focal adhesion kinase (FAK)/Akt signal pathway plays an important role in fibrogenesis and scar formation in different tissues. In consideration of advantages of peptide hydrogel, that is well biocompatibility, gel state, degradability, good drug loading, we designed and fabricated an RGD peptide hydrogel, and hypothesized that it could inhibit the expression of β1-integrin, FAK, and Akt in Tenon's capsule fibroblasts. Rheology results showed that 1% wt Fmoc-FFGGRGD peptide solution could self-assemble into hydrogel. Western blot analysis revealed that there were statistical differences between control group and 1% wt group in β1-integrin/β-actin, FAK/β-actin, Akt/β-actin respectively (*p < .05). The relative mRNA expression of β1-integrin, FAK, Akt in control group and 1% wt group were also statistically different respectively (*p < .05). We proved that 1% wt Fmoc-FFGGRGD self-assembly peptide hydrogel could inhibit the expression of β1-integrin, FAK and Akt in Tenon's capsule fibroblasts. It is a promising way to solve scar formation of glaucoma filter channel.

A Switchless Quad Band Filter Bank Based on Ferroelectric BST FBARs

An intrinsically switchable ferroelectric barium strontium titanate (Ba <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(x)</sub> Sr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(1-x)</sub> TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , BST)-based film bulk acoustic resonator (FBAR) quad channel filter bank is presented for the first time. The design incorporates a matching network free of tunable elements and provides a high isolation >30 dB across all four filter paths when the resonators are switched off. The measured insertion loss for the four 2.5 stage BST FBAR filters range from 6 to 7 dB with an out-of-band rejection >30 dB, which is an improvement over previously reported BST ladder-type structure. The filter bank, realized through T-networks, occupies an area of 840 μm × 340 μm and operates across four different bands solely through the BST-based acoustic resonators.

A new approach for designing and implementing ADF equalization for 5G frequency selective channel based on two operating phases of LS and RLS algorithms

In this paper, a new approach is proposed for implementing an adaptive decision feedback equalizer (ADFE) for the 5G channel. The proposed equalizer works in two phases. In the first phase, a least-squares (LS) algorithm with a variable-length training sequence is used to estimate the coefficients of the channel and the equalizer. In the second phase, the recursive least-squares algorithm estimates the channel and adapts the equalizer, jointly. According to the channel quality, a variable-length training sequence is used to estimate the channel vector and the coefficients of the equalizer. The feed-forward equalizer (FFE) compensates the effects of the transmitting filter and the channel filter. No matched filter is used in the receiver. The noise samples at the input of the proposed FFE are independent. The noise enhancement of the proposed FFE is less than the noise enhancement of its corresponding one in the conventional ADFE. The overall filtering response (OFR) from the input of the transmitting filter to the output of the FFE is calculated and used to estimate the coefficients of the feedback equalizer (FBE). The channel model, the FFE coefficients, the OFR vector, and the FBE coefficients are continuously updated every symbol period. Using a variable training sequence increases the bandwidth efficiency of the transmitted signal. Simulation results and real-time implementation measurements show that the convergence time and the steady-state error at the output of the proposed equalizer are smaller than their corresponding values in the conventional ADFE.

Unbalanced Two-Way Filtering Power Splitter for Wireless Communication Systems

A compact unbalanced two-way filtering power splitter with an integrated Chebyshev filtering function is presented. The design is purely based on formulations, thereby eliminating the constant need for developing complex optimization algorithms and tuning, to deliver the desired amount of power at each of the two output ports. To achieve miniaturization, a common square open-loop resonator (SOLR) is used to distribute energy between the two integrated channel filters. In addition to distributing energy, the common resonator also contributes one pole to each integrated channel filter, hence, reducing the number of individual resonating elements used in achieving the integrated filtering power splitter (FPS). To demonstrate the proposed design technique, a prototype FPS centered at 2.6 GHz with a 3 dB fractional bandwidth of 3% is designed and simulated. The circuit model and layout results show good performances of high selectivity, less than 1.7 dB insertion loss, and better than 16 dB in-band return loss. The common microstrip SOLR and the microstrip hair-pin resonators used in implementing the proposed integrated FPS ensures that an overall compact size of 0.34 λg × 0.11 λg was achieved, where λg is the guided-wavelength of the 50 Ω microstrip line at the fundamental resonant frequency of the FPS passband.

Multiscale Modeling and Analysis of Pressure Drop Contributions in Catalytic Filters

Catalytic monolith filters with a honeycomb structure represent a key component of modern automotive exhaust gas aftertreatment systems. In this paper, we present and validate a multiscale modeling methodology for the prediction of filter pressure loss depending on the monolith channel geometry as well as the microscopic structure of the wall including catalytic coating. The approach is based on the combination of a 3D pore-scale model of flow through the wall reconstructed from X-ray tomography and a 1D+1D model of the filter channels. Several cordierite and SiC filter samples with varying substrate pore sizes and catalyst distributions are examined. A series of experiments are performed at different gas flow rates and filter lengths in order to validate the model predictions and to distinguish individual pressure drop contributions (inlet and outlet, channel, and wall). The predicted pressure drop shows a strong impact of the coating location and agrees well with the experiments.

Multivariate intrinsic chirp mode decomposition

A multivariate intrinsic chirp mode decomposition (MICMD) algorithm is proposed to process multivariate/multichannel signals. In contrast to most existing multivariate time-frequency decomposition techniques, the proposed MICMD can efficiently extract time-varying signals by solving a multivariate linear system. In this paper, we first define a multivariate intrinsic chirp mode (MICM) by assuming the presence of a joint or common instantaneous frequency (IF) among all channels. Then the IFs and instantaneous amplitudes (IAs) are modeled as Fourier series. IFs can be estimated using the framework of the general parameterized time-frequency transform and then the corresponding MICMs are reconstructed by solving multivariate linear equations through an extended least square method. MICMD can characterize a set of multivariate modes without requiring more user-defined parameters than the original ICMD. Its properties and advantages, including mode-alignment, computational complexity, filter bank structure, quasi-orthogonality, channel number and noise robustness, are investigated successively. MICMD outperforms both multivariate empirical mode decomposition (MEMD) and multivariate variational mode decomposition (MVMD) in extracting time-varying components. The computational complexity of the proposed MICMD is proven to be O(N), thus much faster than MNCMD, which is of O(N3) complexity. In the end, we highlight the utility and superiority of MICMD in three real-world cases, including the periodicity analysis in meteorology (three-channel), the α-rhythm separation in electroencephalogram (EEG) (four-channel), and the plant-wide oscillation detection in industrial control system (eleven-channel).

Observation of Nociceptive Processing: Effect of Intra-Epidermal Electric Stimulus Properties on Detection Probability and Evoked Potentials

Monitoring nociceptive processing is a current challenge due to a lack of objective measures. Recently, we developed a method for simultaneous tracking of psychophysical detection probability and brain evoked potentials in response to intra-epidermal stimulation. An exploratory investigation showed that we could quantify nociceptive system behavior by estimating the effect of stimulus properties on the evoked potential (EP). The goal in this work was to accurately measure nociceptive system behavior using this method in a large group of healthy subjects to identify the locations and latencies of EP components and the effect of single- and double-pulse stimuli with an inter-pulse interval of 10 or 40 ms on these EP components and detection probability. First, we observed the effect of filter settings and channel selection on the EP. Subsequently, we compared statistical models to assess correlation of EP and detection probability with stimulus properties, and quantified the effect of stimulus properties on both outcome measures through linear mixed regression. We observed lateral and central EP components in response to intra-epidermal stimulation. Detection probability and central EP components were positively correlated to the amplitude of each pulse, regardless of the inter-pulse interval, and negatively correlated to the trial number. Both central and lateral EP components also showed strong correlation with detection. These results show that both the observed EP and the detection probability reflect the various steps of processing of a nociceptive stimulus, including peripheral nerve fiber recruitment, central synaptic summation, and habituation to a repeated stimulus.

Weighted Orthogonal Vector Rejection Method for Loudspeaker-Based Binaural Audio Reproduction

A method for reproducing binaural audio over an array of loudspeakers is presented. The proposed method is based on spatially-matched filters and is shown to be, in general, more stable than the conventional inverse filter approach. The non-weighted formulation of the method introduces reductions in the reproduced pressure magnitude response at each control point and is therefore inherently lossy. On the other hand, far less error is introduced for frequencies where the Hermitian angle between the row vectors of the plant matrix is close to ninety degrees. For sufficiently dense arrays, little error is introduced at mid-low and high frequencies. The trade-off between reductions in the reproduced target signals and crosstalk cancellation is controlled by introducing frequency-dependent weights to the left and right channel filters. The weights that minimise the error are derived. It is shown that the optimal weight solution emphasises achieved crosstalk cancellation over lossless focusing.

Design of Four-Port Planar Filter Circuits With Multiplexer Operation

This paper presents a design method of four-port microstrip filter circuits that have increased filter passbands for multiplexer operation using a simple feed structure. The proposed circuits can be used as different diplexers or even triplexers according to different application requirements. The stub-loaded resonator is used as the basic element to design each filter channel. A simple feed structure with asymmetrical U-shaped feedlines is deployed using the discriminating coupling method. As a result, for each filter channel, specific transmission zero is introduced in other channel frequency bands, thus achieving high channel isolation. Firstly, a compact four-port filter circuit is proposed with four diplexer functions. By exciting one port as the input while two adjacent ports as the output, two filter passbands can be utilized for duplexing channels. Then, without adding extra ports, a four-port five-passband filter circuit is designed. It features a high integration level since it can be used as either diplexers or triplexers, once the corresponding ports are excited. For proof of concept, two design examples are fabricated. The prototypes show good agreement between the simulated and measured results, verifying the feasibility of the proposed design methodology. In addition, the operating frequency and bandwidth of each filter passband can be tuned to desired values. These characteristics are promising in multi-band base-station antenna array feed systems.

Analysis of a photonic crystal temperature sensor based on Z-shaped ring resonator

A 2D photonic crystal (PC) sensor based on optical filter has been designed using a PC ring resonator (PCRR). The sensor used a 2D-PCRR triangular lattice with circular silicon rods placed in air background. We employed a ring resonator with Z-shaped core in the investigated structure, which is designed as temperature sensor and investigated theoretically along with high quality factor, transmission and sensitivity parameters. For sensing analysis, the 2D finite-difference time-domain method and the plane-wave expansion approach have been applied. A temperature variation from 0 to 20 °C causes a defect mode shifting and the channel filter wavelength shift was used as sensing mechanism. Using the number of the functionalized rods N = 36 at the temperature of 5 °C, the quality factor, the temperature sensitivity, the refractive index sensitivity and the detection limit of the studied structure were found to be 57,104, 96 pm/°C, 400 nm/RIU and 6.16 × 10–6 RIU, respectively.

Imaging Evidence for Solar Wind Outflows Originating from a Coronal Mass Ejection Footpoint

Abstract We report on Atmospheric Imaging Assembly observations of plasma outflows originating in a coronal dimming during a 2015 April 28 filament eruption. After the filament started to erupt, two flare ribbons formed, one of which had a well-visible hook enclosing a core (twin) dimming region. Along multiple funnels located in this dimming, a motion of plasma directed outward started to be visible in the 171 and 193 Å filter channels of the instrument. In time–distance diagrams, this motion generated a strip-like pattern, which lasted for more than 5 hr and whose characteristics did not change along the funnel. We therefore suggest the motion is a signature of outflows corresponding to velocities ranging between ≈70 and 140 km s−1. Interestingly, the pattern of the outflows and their velocities were found to be similar to those we observed in a neighboring ordinary coronal hole. Therefore, the outflows were most likely a signature of a coronal mass ejection–induced solar wind flowing along the open-field structures rooted in the dimming region. Further, the evolution of the hook encircling the dimming region was examined in the context of the latest predictions imposed for 3D magnetic reconnection. The observations indicate that the filament’s footpoints were, during their transformation to the dimming region, reconnecting with surrounding canopies. To our knowledge, our observations present the first imaging evidence for outflows of plasma from a dimming region.

Statistical Analysis of Image with Various Noises and Filters

Research displays an extensive investigation for different factual statistical estimates and their practical implementation in picture handling with various noises and filter channel procedures. Noise is very challenging to take out it from the digital images. The purpose of image filtering is to eliminate the noise from the image in such a way that the new image is detectible. We have clarified different calculations and systems for channel the pictures and which calculation is the best for sifting the picture. Signal and maximum Peak proportion parameters are utilized for execution for factual estimating, Wiener channel performs preferred in evacuating clamor over different channels. Wiener channel functions admirably for a wide range of clamors. The exhibition of Gaussian channel is superior to anything Mean channel, Mask Filter and Wiener channel as per MSE results. In picture setting up, a Gaussian fog generally called Gaussian smoothing is the result of darkening an image by a Gaussian limit. We reason that Gaussian separating approach is the best method that can be effectively actualized with the assistance of the MSE of picture. The Gaussian channel is certifiably superior to different calculations at expelling clamor. The outcomes have been looked at for channels utilizing SNR, PSNR and Mean Square Error esteem.

What is “Acute Hearing”? Measures of the Frequency-Resolving Power of Hearing

The current levels of development of diagnostic methods for the sensitivity and frequency resolving power (FRP) of hearing are significantly different. Devices for measuring FRP have not entered clinical practice. Laboratory methods for measuring FRP are not suitable for practical applications. Signals with rippled spectra may provide an effective tool for testing the FRP of hearing both in studies of the basic mechanisms of hearing and in practical audiology. The use of such signals for testing allows measurement not of the acuteness of individual frequency-selective filter channels but directly assesses their ability to analyze sound signals with complex time-spectral patterns. In addition, measurement of FRP using rippled test signals is convenient for practical application. Measurements using rippled test signals yield data on the real ability of the auditory system to discriminate complex sound signals. Furthermore, these measurements demonstrate the roles of a number of basic auditory mechanisms – compressive nonlinearity, lateral suppression, and the frequency- and time-based mechanisms of frequency analysis – in the perception of complex auditory signals. Depending on the discrimination task, either frequency or time analysis is activated, giving fundamentally different evaluations of FRP. There is successful experience of the use of test signals with rippled spectra for assessment of auditory acuity in users of cochlear implants.

Design of Reconfigurable FRM Channelizer using Resource Shared Non-maximally Decimated Masking Filters

This paper presents a reconfigurable frequency response masking (FRM) wideband channelizer architecture which is characterized by low computational and hardware complexity. The proposed hardware efficient architecture is realized by incorporating resource shared non-maximally decimated filter bank in the implementation of the FRM wideband channelizer structure. The coefficients of the proposed architecture are optimized and made multiplier-free using Pareto based meta-heuristic algorithm in the canonic signed digit (CSD) space for reducing the total power consumption of the architecture. The architecture is finally designed and synthesized using Xilinx Vivado and Cadence RTL Encounter compiler for the area and power analysis and is compared with existing channnelizer architectures. The comparison highlights the advantages of the proposed architecture in terms of hardware complexity, power and workload in realizing sharp wideband channel filters.