Effects Of Signal Interference Research Articles

Input-Reflectionless Quasi-Elliptic-Type Single- and Dual-Band Bandpass Filters Based on Passive Channelized Principles

An approach to design quasi-elliptic-type planar filters with single- and dual-band bandpass transfer functions and input-absorptive capabilities is presented. Two-branch channelized passive circuit configurations are exploited for this purpose, in which the low-order reflective-type filtering profile of their branches is converted into the desired sharp-rejection input-reflectionless filtering action in the overall circuit. This is achieved by means of fully-destructive and frequency-selective transversal signal-interference effects at the total input and output accesses of the channelized filter, respectively. The theoretical operational principles of the proposed concept of single/dual-passband input-reflectionless two-branch channelized filter are detailed, along with design considerations for their RF transmission-line-based implementation. Besides, its generalization to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\boldsymbol {N}$ </tex-math></inline-formula> -channel architectures is also analyzed. Furthermore, as the fundamental elements of the devised channelized filtering philosophy to increase selectivity, alternative solutions to realize their output phase-delay sections for a more-flexible control of the transmission zeros in the overall transfer function are discussed. For experimental-demonstration purposes, two microstrip proof-of-concept prototypes are developed and measured. They consist of 3-GHz single-band and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.58/3.43$ </tex-math></inline-formula> -GHz dual-band designs with input-quasi-reflectionless spectral ratio above 2.5:1 and 3:1, respectively.

On-Chip Millimeter-Wave Integrated Absorptive Bandstop Filter in (Bi)-CMOS Technology

A millimeter-wave passive-integrated bandstop filter (BSF) with absorptive/reflectionless behavior is reported. It avoids the creation of RF-power reflections for filtered signals which can deteriorate earlier active stages in integrated RF front-end chains. It exploits a two-path transversal configuration in a multi-layer structure. Specifically, it is composed of a direct transmission line for the main path (top layer) and two lossy edge-grounded spiral-shaped resonators for the secondary path (bottom layer) that are coupled between them and to the main path. Thus, a sharp second-order stopband is created through destructive signal-interference effects between the two signal paths with intrinsic RF-power absorption within the volume of the lossy resonators. As practical validation, a 24.5-GHz on-chip millimeter-wave absorptive BSF circuit is built in a 0.13- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> SiGe bipolar complementary metal-oxide-semiconductor [(Bi)-CMOS] technology and tested. Close agreement between simulated and measured results for this on-chip BSF circuit is achieved.

The Rhodamine Isothiocyanate Analogue as a Quorum Sensing Inhibitor Has the Potential to Control Microbially-Induced Biofouling.

Quorum sensing inhibitors (QSIs) have been proven to be an innovative approach to interfering with biofilm formation, since this process is regulated by QS signals. However, most studies have focused on single-species biofilm formation, whereas studies of the effects of signal interference on the development of multispecies biofilm, especially in the natural environment, are still lacking. Here we develop and evaluate the anti-biofilm capability of a new QSI (rhodamine isothiocyanate analogue, RIA) in natural seawater. During the experiment, biofilm characteristics, microbial communities/functions and network interactions were monitored at 36, 80, and 180 h, respectively. The results showed that the biomass and 3D structure of the biofilm were significantly different in the presence of the QSI. The expression of genes involved in extracellular polysaccharide synthesis was also downregulated in the QSI-treated group. Dramatic differences in microbial composition, β-diversity and functions between the RIA-treated group and the control group were also observed, especially in the early stage of biofilm development. Furthermore, co-occurrence model analysis showed that RIA reduced the complexity of the microbial network. This study demonstrates that rhodamine isothiocyanate analogue is an efficient QS inhibitor and has potential applications in controlling biofouling caused by multispecies biofilm, especially in the early stage of biofouling formation.

Mass cytometry panel optimization through the designed distribution of signal interference.

Mass cytometry is capable of measuring more than 40 distinct proteins on individual cells making it a promising technology for innovating biomarker discovery. However, in order for this potential to be fully realized, best practices in panel design need to be further defined in order to achieve consistency and reproducibility in data analysis. Of particular importance are controls that reveal, and panel design principles that mitigate the effects of signal interference or overlap. We observed a disparity between the staining profiles of two noncompeting anti- integrin β7 mAbs and hypothesized that signal interference was responsible. A mass-minus-one (MMO) control was applied and demonstrated that signal overlap caused the perceived interclonal discrepancy in β7 expression. Panel redesign in consideration of mass-cytometry specific interference dynamics dramatically improved concordance between both mAbs by redistributing background signals caused by overlap. These studies visualize how signal overlap can complicate mass cytometry data interpretation and demonstrate how the rational distribution of interference can greatly improve panel design and data quality. © 2016 International Society for Advancement of Cytometry.

Femtocell interference analysis based on the development of system-level LTE simulator

Abstract Although femtocell can confer various benefits to both operators and users, many technical issues, such as interference coordination, network synchronization, self-configuration, and self-optimization must be considered to effectively deploy femtocells in real environments. In this article, we develop a system-level simulator in order to evaluate performance of long-term evolution (LTE)-femtocell systems. The simulator consists of five functional modules which realize packet scheduling and call admission control functionalities and model various wireless channel effects, real and non-real time traffics, and user mobility. These modules are managed by operational modules that follow event-driven programming. In addition, the simulator adopts a graphical user interface (GUI) that facilitates configuration, management, and observation of simulations in real time. Based on the simulator, we analyze effects of signal interference between macro- and femtocells under four scenarios. From the results, we confirm that the developed LTE-femtocell simulator can effectively support performance evaluation and analysis on various femtocell deployment scenarios.

Correlation between liver histology and novel magnetic resonance imaging in adult patients with non‐alcoholic fatty liver disease – MRI accurately quantifies hepatic steatosis in NAFLD

Conventional magnetic resonance imaging (MRI) techniques that measure hepatic steatosis are limited by T1 bias, T(2)* decay and multi-frequency signal-interference effects of protons in fat. Newer MR techniques such as the proton density-fat fraction (PDFF) that correct for these factors have not been specifically compared to liver biopsy in adult patients with non-alcoholic fatty liver disease (NAFLD). To examine the association between MRI-determined PDFF and histology-determined steatosis grade, and their association with fibrosis. A total of 51 adult patients with biopsy-confirmed NAFLD underwent metabolic-biochemical profiling, MRI-determined PDFF measurement of hepatic steatosis and liver biopsy assessment according to NASH-CRN histological scoring system. The average MRI-determined PDFF increased significantly with increasing histology-determined steatosis grade: 8.9% at grade-1, 16.3% at grade-2, and 25.0% at grade-3 with P ≤ 0.0001 (correlation: r(2) = 0.56, P < 0.0001). Patients with stage-4 fibrosis, when compared with patients with stage 0-3 fibrosis, had significantly lower hepatic steatosis by both MRI-determined PDFF (7.6% vs. 17.8%, P < 0.005) and histology-determined steatosis grade (1.4 vs. 2.2, P < 0.05). NAFLD patients with grade 1 steatosis were more likely to have characteristics of advanced liver disease including higher average AST:ALT (0.87 vs. 0.60, P < 0.02), GGT (140 vs. 67, P < 0.01), and INR (1.06 vs. 0.99, P < 0.01), higher stage of fibrosis and hepatocellular ballooning. MRI-determined proton density-fat fraction correlates with histology-determined steatosis grade in adults with NAFLD. Steatosis is non-linearly related to fibrosis progression. In patients with NAFLD, a low amount of hepatic steatosis on imaging does not necessarily indicate mild disease.

Reproducibility of MRI‐determined proton density fat fraction across two different MR scanner platforms

To evaluate magnetic resonance imaging (MRI)-determined proton density fat fraction (PDFF) reproducibility across two MR scanner platforms and, using MR spectroscopy (MRS)-determined PDFF as reference standard, to confirm MRI-determined PDFF estimation accuracy. This prospective, cross-sectional, crossover, observational pilot study was approved by an Institutional Review Board. Twenty-one subjects gave written informed consent and underwent liver MRI and MRS at both 1.5T (Siemens Symphony scanner) and 3T (GE Signa Excite HD scanner). MRI-determined PDFF was estimated using an axial 2D spoiled gradient-recalled echo sequence with low flip-angle to minimize T1 bias and six echo-times to permit correction of T2* and fat-water signal interference effects. MRS-determined PDFF was estimated using a stimulated-echo acquisition mode sequence with long repetition time to minimize T1 bias and five echo times to permit T2 correction. Interscanner reproducibility of MRI determined PDFF was assessed by correlation analysis; accuracy was assessed separately at each field strength by linear regression analysis using MRS-determined PDFF as reference standard. 1.5T and 3T MRI-determined PDFF estimates were highly correlated (r = 0.992). MRI-determined PDFF estimates were accurate at both 1.5T (regression slope/intercept = 0.958/-0.48) and 3T (slope/intercept = 1.020/0.925) against the MRS-determined PDFF reference. MRI-determined PDFF estimation is reproducible and, using MRS-determined PDFF as reference standard, accurate across two MR scanner platforms at 1.5T and 3T.

Super-Orthogonal Block Codes with Multichannel Equalisation and OFDM in Frequency Selective Fading

Super-orthogonal block codes in space-time domain (i.e., Super-orthogonal space-time trellis codes (SOSTTCs)) were initially designed for frequency nonselective (FNS) channels but in frequency selective (FS) channels these super-orthogonal block codes suffer performance degradation due to signal interference. To combat the effects of signal interference caused by the frequency selectivity of the fading channel, the authors employ two methods in this paper, namely, multichannel equalization (ME) and orthogonal frequency division multiplexing (OFDM). In spite of the increase complexity of the SOSTTC-ME optimum receiver design scheme, the SOSTTC-ME scheme maintains the same diversity advantage as compared to the SOSTTC scheme in FNS channel. In OFDM environments, the authors consider two forms of the super-orthogonal block codes, namely, super-orthogonal space-time trellis-coded OFDM and super-orthogonal space-frequency trellis-coded OFDM. The simulation results reveal that super-orthogonal space-frequency trellis-coded OFDM outperforms super-orthogonal space-time trellis-coded OFDM under various channel delay spreads.

Effect of signal interference from dosing excipients on pharmacokinetic screening of drug candidates by liquid chromatography/mass spectrometry.

The effect of dosing vehicle excipients such as PEG400, propylene glycol, Tween 80, and hydroxypropyl-beta-cyclodextrin on the accuracy of LC/MS measurements used in pharmacokinetic studies is examined. Using PEG400 as a probe compound, the concentration-time profile of the excipient in plasma from rats dosed both orally and intravenously is determined. These excipient plasma concentrations can result in a 2-5-fold increase in calculated plasma clearance values when the excipient interferes with the quantitation of the dosed compound. This can result in false rejection of a compound in a drug discovery screen. Several plasma purification methods and enhanced chromatographic selectivity are examined as ways to minimize or avoid excipient effects, particularly for very polar compounds. The combination of efficient sample purification and selective chromatography provides an effective way to diminish the significant interference effects of PEG400 and Tween 80. When appropriate, using negative ion mode MS or changing a dosing vehicle excipient, such as substituting propylene glycol for PEG400, provides an alternative approach for eliminating signal interference. The mechanism of excipient-related signal interference is discussed in relation to both competition of gas-phase proton-transfer reactions and high viscosity of dosing excipients.

The Nature of and System Inferences of Delay Distortion Due to Mode Conversion in Multimode Transmission Systems

Quantitative estimates of delay distortion due to mode conversion in a multimode medium are made using an analysis based on modes coupled through power-transfer coefficients. This results in a simple translation from the spatial distribution of mode conversion to delay distortion without an intermediate step in the frequency domain. The expected value of the reconversion magnitude and its delay distribution relative to a driving impulse are found for (i) the case where the undesired mode loss is distributed (helix damped modes and higher-order circular electric modes) and (ii) the case where discrete mode filters are inserted (as in smooth-walled waveguide). Numerical estimates are given for TE 01 in 2-inch I.D. guides at 55 kmc. For both cases the power in the reconversion echo varies directly as the system length, and the shape of the echo is independent of length. For the case of distributed undesired mode loss the echo to impulse-excitation has an exponential shape in relative delay τ, varying as e−τ/τ 0, and for the case of partially absorbing mode filters the echo is a line-segment approximation to an exponential in τ (Fig. 4). The characteristic delay constant τ 0 is about 0.035 nanosecond for helix damped modes in an all-helix line, and is about 0.106 microsecond for TE 02 in either helix or smooth-walled guide. For solid-walled guide with mode filters every 300 feet the characteristic delay constant (similar to τ 0 ) is about 2 nanoseconds. Estimates are made for signal interference effects from such echoes, taking account of the fact that the most limiting requirements on echoes in some system arrangements occur at τ ≫ τ 0 , where the reconversion power is small. For PCM in smooth-walled copper waveguide with mode filters every 300 or 150 feel, it is concluded that pulse rates of 200 or 400 megabits might be used, with up to 20 or 40 miles respectively between regenerators; beat wavelength straightness variation mode conversion is controlling. for PCM in an all-helix waveguide, it is confluded that a pulse rate up to 5000 megabits and up to 746 miles between regenerators is permitted by mode conversion effects; diameter variations (TE02 conversion) are controlling. For transmission of frequency division multiplex multiplex via a frequency-modulated carrier (FDM-FM), estimates based on the discrete-echo theory of Bennett, Curtis and Rice suggest that 4000-mile transmission of 2000 channel groups is possible in all-helix waveguide; diameter variations are controlling. An rms frequency deviations (σ) increase the allowed system length (z) according to z ≈ (σ)2.8 Even in solid-walled waveguide there is a good prospect for 4000-mile FDM-FM using guide toleraces already achievable. Separate consideration is being given to delay distortion due to wave-guide cutoff dispersion, which will be appreciable in some configurations described and will require equalization.

Analysis and prediction of radio signal interference effects due to ionized layer around a re-entry vehicle

Principally this report treats the problem of transmission of electromagnetic waves through the thermally ionized layer of gases in the shock layer around a hypersonic missile. Giving simplified theory, methods and graphic aids for approximate predictions of the problem, it also presents some specific results for a typical hemisphere-cylinder vehicle shape. While details of the theory allowing computation of temperature and the concentration of electrons and neutral particles are not given, a method which has been used is outlined and referenced.

Analysis of radio signal interference effects due to ionized layer around a re-entry vehicle

The theoretical section of this paper discusses the electromagnetic properties of the ionized shock layer about a missile re-entering the atmosphere; a treatment is then given of the problem of predicting the transmission, through the shock layer, of electromagnetic waves originating on the vehicle. The major portion of this section is given to outlining the important quantitative aspects for calculating the extent of the attenuation problem. Theoretical curves are given which allow rapid prediction of the attenuation effects due to air ionization once temperature and density are specified in the shock layer. If other sources of free electrons are significant, e.g. ablation products, separate determination of the density distribution must be made. Specific results are given on certain Polaris configurations and trajectories as computed using this method; these predictions are based upon two specific transmitter frequencies. Although the method utilizes the Lorentz theory and the plane wave-plane homogeneous sheet assumption is made, the resulting estimates are shown to agree satisfactorily with signal strength records of actual re-entry tests. A quantitative discussion is given concerning the approximations inherent with the use of the Lorentz theory of conductivity in view of “strong fields” near a transmitter and the velocity dependence of collision cross-sections. A portion is given to possible solutions of the transmission problem suggested by the parameters available in various ranges of temperature and density; particular attention is given to transmitter frequency and position of the antenna. A method is demonstrated for extrapolating the results of a minimum of predictions for a given combination of radiator and re-entry body to include predictions for a wide range of altitudes and velocities.