Crosstalk Coefficients Research Articles

Accurate calibration for crosstalk coefficient based on orthogonal color phase-shifting pattern.

The crosstalk coefficient calibration of de-crosstalk in color fringe projection profilometry is an essential step for the high-accuracy measurement. In this paper, a novel approach for calibrating crosstalk matrix of color camera is proposed. The wrapped phase error model introduced by color crosstalk in orthogonal pattern is established. Compared with the existing calibration methods depending on calculating the modulation of the crosstalk channel, the crosstalk coefficients are obtained from phase error in our method. By projecting the designed color orthogonal phase-shifting fringe patterns onto a white plate, the phase-shifting fringe patterns in both horizontal and vertical directions can be separated from captured images. The coefficients between different channels are calibrated by fitting the error relationship between the wrapped phase containing crosstalk and the standard ones. Coefficient fitting simulations and experimental validations including shape measurement of a white plate and distance measurement of a step block are carried out to verify the effectiveness of the proposed method.

Error Calibration for Crosstalk of SQUIDs in Full Tensor Magnetic Gradiometer Based on Moore–Penrose Inverse and Helmholtz Coil

In order to calibrate crosstalk error between superconducting quantum interference device (SQUID) magnetometers in a multichannel SQUID system, we propose an innovative error calibration method for crosstalk of SQUID magnetometers based on the Moore–Penrose inverse method and Helmholtz coil in this article and successfully apply it to an eight-channel SQUID magnetometers based full tensor magnetic gradiometer (FTMG). We first analyze the causes of crosstalk through working principle of the SQUID readout circuit and build the crosstalk error model of the eight-channel FTMG. Then, we introduce the solution method of 56 crosstalk coefficients based on the Moore–Penrose inverse method and the construction method of matrix needed for solution based on Helmholtz coil. The effect of nonuniformity of Helmholtz coil on the calibration of crosstalk is analyzed and calculated. The effectiveness of the proposed method is proved by repetitive simulation and comparative experiments. Compared with the traditional direct measurement method, this method has the advantage of high efficiency, and the more the channels of SQUID, the more obvious is the superiority.

Trajectory of a massive localized wave function in a curved spacetime geometry

Propagation of a localised wave function of a massive scalar field is investigated in its rest frame. The complete orthogonal Hermite-Gauss basis is presented, and the Gouy phase and Rayleigh scale notions are adapted. The leading and sub-leading gravitational corrections to a localised quantum wave function propagating in a general curved spacetime geometry are calculated within the Fermi coordinates around the time-like geodesic of its rest frame, and cross-talk coefficients among the modes are derived. It is observed that spherically symmetric modes propagate along the geodesic. However, non-spherical modes are found to experience a mode-dependent residual quantum force at the sub-leading order. It is shown that the residual force does not generate an escape velocity for in-falling wave functions but leads to a mode-dependent deflection angle for the scattered ones.

Numerical estimation of calibration matrices for 241Am measurements using HPGe based in-vivo monitoring system

In-vivo measurements of 241Am using HPGe detectors become complicated when the active adjacent source organs interfere with the target organ measurements. It is important to calculate the contribution of confounding organs to estimate the activity of the target organ accurately. In the current study, numerical simulations were performed using FLUKA Monte Carlo code and International Commission on Radiological Protection (ICRP) computational reference phantoms to determine the calibration matrices consisting of the calibration and cross-talk coefficients for three interfering organs namely, lungs, liver and skeleton. It was found that the interference from adjacent organs contaminated with 241Am was found to be significant in the case of lungs and liver. Knee monitoring was least influenced by the activity possessed by other source organs due to their anatomical distance from the knee. A comparison between lung and liver coefficients obtained from the Lawrence Livermore National Laboratory (LLNL) torso phantom and thorax phantom derived from ICRP adult male voxel phantom was performed. It was found that variations in coefficients obtained from simulations and experiments range between 2% and 48%. The differences were attributed to the uncertainties arising from the composition of the phantoms and detectors, size and shape of organs, positional errors, and source distribution. A comparison of calibration matrices of adult male and adult female thorax voxel phantoms revealed that all the coefficients except knee as the target organ were larger for the female thorax phantom owing to the lesser bulk of attenuating tissues on its chest. The coefficients obtained from simulations for different phantoms also showed that the organ activity estimation can be significantly affected by the subject morphology.

Crosstalk suppression for high-density traveling-wave MZM array based on static and dynamic combined analysis and circuit-level designs.

Electrical crosstalk severely degrades the performance of Mach-Zehnder modulator (MZM) array. However, conventional crosstalk suppression techniques incur losses of large amounts of chip area for signal isolation, which becomes a bottleneck of high-density electronic-photonic integrated circuit. In this paper, the electrical crosstalk of Traveling-Wave MZM array is originally analyzed with static and dynamic combined crosstalk coefficients. Circuit-level suppression techniques of differential dual-drive electrode schemes with tightly coupled electrode pairs and a virtual ground structure with full-matching termination circuit are investigated for noise-removing effects. Simulation results show that the dynamic electrical crosstalk coefficient between two adjacent modulators is reduced to below 1.5%, which is five times lower than the baseline. The electro-optical link measurements show that the BER is significantly reduced from 1E-3 to 1E-12 for multi-channel operation, which confirms the effectiveness of the crosstalk suppression techniques.

Fast and in-situ correction of camera channel crosstalk based on Fourier transform of carrier fringes in multi-colour interferometry

To deal with the light intensity crosstalk between R, G and B channels of colour camera in multi-colour interferometry, we present a fast and in-situ correction method based on Fourier transform of carrier fringes. The crosstalk coefficients of camera channels are obtained in the Fourier frequency domain of captured colour carrier fringes, and the crosstalk is corrected by matrix inverse operation. Simulations and experiments verify that this method has advantages of simple implementation, fast correction speed and high measurement accuracy, and it effectively achieves in-situ correction without removing the camera.

Development and feasibility of quantitative dynamic cardiac imaging for mice using μSPECT

BackgroundDespite growing interest in coronary microvascular disease (CMVD), there is a dearth of mechanistic understanding. Mouse models offer opportunities to understand molecular processes in CMVD. We have sought to develop quantitative mouse imaging to assess coronary microvascular function. MethodsWe used 99mTc-sestamibi to measure myocardial blood flow in mice with MILabs U-SPECT+ system. We determined recovery and crosstalk coefficients, the influx rate constant from blood to myocardium (K1), and, using microsphere perfusion, constraints on the extraction fraction curve. We used 99mTc and stannous pyrophosphate for red blood cell imaging to measure intramyocardial blood volume (IMBV) as an alternate measure of microvascular function. ResultsThe recovery coefficients for myocardial tissue (RT) and left ventricular arterial blood (RA) were 0.81 ± 0.16 and 1.07 ± 0.12, respectively. The assumption RT = 1 − FBV (fraction blood volume) does not hold in mice. Using a complete mixing matrix to fit a one-compartment model, we measured K1 of 0.57 ± 0.08 min−1. Constraints on the extraction fraction curve for 99mTc-sestamibi in mice for best-fit Renkin–Crone parameters were α = 0.99 and β = 0.39. Additionally, we found that wild-type mice increase their IMBV by 22.9 ± 3.3% under hyperemic conditions. ConclusionsWe have developed a framework for measuring K1 and change in IMBV in mice, demonstrating non-invasive µSPECT-based quantitative imaging of mouse microvascular function.

Evolution Properties and Spatial-Mode UWOC Performances of the Perfect Vortex Beam Subject to Oceanic Turbulence

The perfect optical vortex (POV) beam with the characteristic of the topological charge (TC)- independence radial profile is first considered to improve the spatial-mode-based underwater wireless optical communication (UWOC) performance. The evolution model of POV beams is proposed on the basis of Rytov approximation and the mutual coherence function to explore the impact of wave parameters on the orbital angular momentum (OAM) detection probability spectrum. The instantaneous crosstalk coefficients describing the POV-based UWOC systems are simulated by the multiple phase screen method with the signal coefficient modeled by a mixture Gamma-Gamma and normal distribution. A discrete and memoryless channel and a set of noncollaborative channels are modeled to obtain the capacity performances of the spatial-mode modulating and multiplexing systems, respectively. Results show the transmission quality of POV beams in oceanic turbulence is most related to the beam radius, while it is nearly free from the wavelength, TC, and radius-thickness ratio. Enjoying the advantage of the TC-independence beam radius, POV beams-based UWOC systems could achieve better bit error rate and capacity performances than the widely used Laguerre-Gauss beams when the higher-order TCs are adopted to modulate and multiplex information, which also confirms the superiority of POV beams in spatial-mode-based UWOC systems.

Calibration of Flux Crosstalk in Large-Scale Flux-Tunable Superconducting Quantum Circuits

Magnetic flux tunability is an essential feature in most approaches to quantum computing based on superconducting qubits. Independent control of the fluxes in multiple loops is hampered by crosstalk. Calibrating flux crosstalk becomes a challenging task when the circuit elements interact strongly. We present a novel approach to flux crosstalk calibration, which is circuit model independent and relies on an iterative process to gradually improve calibration accuracy. This method allows us to reduce errors due to the inductive coupling between loops. The calibration procedure is automated and implemented on devices consisting of tunable flux qubits and couplers with up to 27 control loops. We devise a method to characterize the calibration error, which is used to show that the errors of the measured crosstalk coefficients are all below 0.17%.

Optical section structured illumination-based Förster resonance energy transfer imaging.

Förster resonance energy transfer (FRET) microscopy is an important tool suitable for studying molecular interactions in living cells. Optical section structured illumination microscopy (OS-SIM), like confocal microscopy, has about 200 nm spatial resolution. In this report, we performed quantitative 3-cube FRET imaging in OS-SIM mode and widefield microscopy (WF) mode, respectively, for living cells expressing FRET constructs consisting of Cerulean (C, donor) and Venus (V, acceptor). OS-SIM images exhibited higher resolution than WF images. Four spectral crosstalk coefficients measured under OS-SIM mode are consistent with those measured under WF mode. Similarly, the system calibration factors G and k measured under OS-SIM mode were consistent with those measured under WF mode. The measured FRET efficiency (E) values of C32V and C17V as well as C5V constructs, standard FRET plasmids, in living Hela cells were , and , and the measured acceptor-to-donor concentration ratios ( ) were , , and , consistent with the reported values. Collectively, our data demonstrates that OS-SIM can be integrated into FRET microscopy to build an OS-SIM-FRET with confocal microscopy-like resolution.

Determination of calibration matrix for HPGe-based in vivo monitoring system for estimation of 241Am in lungs and liver

The detection of internal contamination may be carried out by direct or indirect methods. The lung counting technique using an array of High Purity Germanium (HPGe) detectors is one of such direct detection methods. It is known from the literature that the estimation of activity by organ counting can lead to erroneous results if an amount of activity is possessed by an adjacent organ. In the case of HPGe-based lung monitoring, the estimation could be misleading if the activity is possessed by the liver, which is a proximal organ. In such cases the measured activity should be modified using cross-talk coefficients which account for the contribution from adjacent organs. The determination of cross-talk coefficients for 241Am was carried out by placing the detectors over inactive lungs of an Lawrence Livermore National Laboratory phantom when the source activity was contained in the liver and vice versa. A calibration matrix was formulated with calibration coefficients as diagonal elements and cross-talk coefficients as off-diagonal elements. The measured activities may be modified by matrix multiplication with the inverse of the calibration matrix to nullify the contribution from adjacent organs. The current work has empirically determined the fitting equations which relate calibration and cross-talk coefficients for lungs and liver measurement geometries with muscle-equivalent chest wall thickness (MEQ-CWT) values. The values of these coefficients were determined for an average MEQ-CWT of 1.77 cm for lungs and 1.33 cm for liver. The calculations showed that the activity contribution from liver to lungs was 29% higher than that of lungs to liver. A verification exercise was conducted to demonstrate this method. For the given calibration source, the percent overestimation was reduced for lung activity, while the liver activity was slightly underestimated. In the case of old exposure follow-up monitoring cases, the 241Am activity built up in liver could interfere with the lung monitoring results and this method using the calibration matrix may be used for estimation of more accurate results.

Aqua MODIS Electronic Crosstalk Survey: Mid-Wave Infrared Bands

The Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Aqua polar-orbiting satellite has long been known to be subjected to electronic crosstalk. Its signatures are clearly visible in images of the lunar disk by various bands, which are routinely obtained during scheduled roll maneuvers. Electronic crosstalk can potentially impact Level 1B products, causing image artifacts such as striping and radiometric bias. However, a comprehensive effort in mapping the sending/receiving bands and detectors, deriving the crosstalk coefficients, and assessing the impact of the crosstalk contamination on the Level 1B product for Aqua’s mid-wave IR bands (3.75– 4.52 $\mu \text{m}$ ) had been lacking. In this work, we surveyed lunar images by the Aqua MODIS bands that are connected to electronic output 2 of the SWIR/MWIR FPA, identifying all detectors affected by electronic crosstalk contamination and determined which bands and detectors are sending the contaminating signal. By assuming a linear model to describe the contamination, we derived linear crosstalk coefficients for the bands/detectors concerned from lunar images and used these to generate corrected Earth Level 1B images for the mid-wave IR bands and assessed the impact of the electronic crosstalk on the Level 1B imagery.

Turbulence-induced optical loss and cross-talk in spatial-mode multiplexed or single-mode free-space communication channels

Single-mode or mode multiplexed free-space atmospheric optical channels draw increasingly more attention in the last decade. The scope of their possible applications spans from the compatibility with the telecom WDM technology, fiber amplifiers, and modal multiplexing for increasing the channel throughput to various quantum communication related primitives such as entanglement distribution, high-dimensional spatially encoded quantum key distribution, and relativistic quantum cryptography. Many research papers discuss application of specific mode sets, such as optical angular momentum modes, for communication in the presence of atmospheric turbulence. At the same time some basic properties and key relations for such channels exposed to the atmospheric turbulence have not been derived yet. In the current paper we present simple analytic expressions and a general framework for assessing probability density functions of channel transmittance as well as modal cross-talk coefficients. Under some basic assumptions the presented results can be directly used for estimation of the Fried parameter of the turbulent channel based on the measured statistics of the fundamental mode transmittance coefficient.

Crosstalk Effect in SNPP VIIRS

An investigation has been carried out to examine the crosstalk contamination in the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (SNPP) spacecraft. Prior to this study, the cause of the pronounced striping in Earth View (EV) images and obvious discontinuity in the EV brightness temperature (BT) of the thermal emissive bands (TEB) during black body (BB) warm-up cool-down (WUCD) calibration observed since launch has not been identified. Meanwhile, it has been recently demonstrated in the MODerate-resolution Imaging Spectroradiometer (MODIS) long-wave infrared (LWIR) photovoltaic (PV) bands that the crosstalk effect induces the same erroneous features. In this investigation, it is shown that the established lunar imagery analysis indeed verifies the existence of crosstalk contamination in SNPP VIIRS TEB. The crosstalk effect is quantitatively characterized by deriving the crosstalk coefficients from the scheduled lunar observations. The magnitude of the effect is comparatively smaller than that in MODIS LWIR PV bands, but is of a large enough magnitude to induce the aforementioned artificial features. Among all SNPP VIIRS TEB, Band M14 has the largest crosstalk contamination from Band M15, while Bands M13, M15, M16, and I5 have pronounced crosstalk effects as well. One new detail of the crosstalk effect specific to SNPP VIIRS, differing from the MODIS result, is the distinctive two-group pattern of odd and even detectors for each affected band due to the arrangement of the detector on the focal plane assembly (FPA). This is fully consistent with the earlier finding that this odd-even detector arrangement contributes to striping in the sea surface temperature (SST) products. Our analyses additionally suggest an explanation of the large temperature anomalies appearing during the WUCD time periods. The parallel effort examining the potential crosstalk contamination in SNPP VIIRS reflective solar bands, however, reveals no observable effect.

Crosstalk Reduction on 6-line Suspension Assembly Interconnect Trace in Head Gimbal Assembly by using Guard Technique

The guard technique is proposed by adding the stainless steel at backing layer to reduce the crosstalk on 6 lines suspension assembly interconnect trace (SAIT). The Near-End and Far- End crosstalk coefficients (NEXT and FEXT) are used to analyze the crosstalk on the SAIT in the frequency of 0-20GHz. The finite integration technique (FIT) is used in the simulation based on CST microwave studio. The space between heat and read pairs is modified and guard addition at the space is also varied. From the results, it is found that the varying of space cannot reduce the crosstalk. However, the additional guard can reduce the crosstalk by monitoring the NEXT and FEXT. The lowest crosstalk is at 100% of the space with 100% of guard that can attenuate the noise around 4.7 and 3.2dB for NEXT and FEXT, respectively. The 80% of space with 80% of additional guard has the crosstalk less than or equal to the conventional SAIT. In addition, it can also decrease the dimension of SAIT about 11.87% of the conventional SAIT. Hence, this technique can reduce the crosstalk and can decrease the dimension of the SAIT which is useful for the robustness for future SAIT design.

Investigation of the Electronic Crosstalk in Terra MODIS Band 28

The Moderate Resolution Imaging Spectroradiometer (MODIS) is a whisk broom scanning radiometer, which is onboard the Terra and Aqua spacecraft. Both MODIS instruments have successfully completed more than 12 years of on-orbit flight. The long-wave infrared (LWIR) photovoltaic bands (bands 27–30, 6.72–9.73 μm) on the LWIR focal plane assembly in Terra MODIS have contamination due to electronic crosstalk. In this paper, we examine Terra MODIS band 28 (7.33 μm) crosstalk effects, their impact, and mitigation. The crosstalk signal is identified and characterized using the regular lunar observations acquired by MODIS. It is evident from the derived crosstalk coefficients that the contamination was mainly from bands 27 (6.72 μm), 29 (8.55 μm), and 30 (9.73 μm). The crosstalk coefficients are generally a small positive quantity in the early to middle part of the mission with a few exceptions, and then changing directions. A linear correction algorithm is applied to both L1B calibration and retrieval to qualitatively and quantitatively assess the impact and improvements in this paper. It is shown that the crosstalk correction improved the imagery and radiometric fidelity of this band.

Generalized Maximum Likelihood for Cross-Polarization Modulation Effects Compensation

We investigate the mitigation of nonlinearities with advanced digital signal processing focusing in particular on cross-polarization effects. Based on a relaxation of an analytical model derived for cross-polarization effects, this paper proposes a novel compensation method called generalized maximum likelihood. It performs a joint blind channel estimation and symbol detection, and it additionally accounts for the statistical prior distributions of the cross-polarization crosstalk coefficients. This avoids an overestimation of these crosstalk coefficients. A practical method for both fast computations and optimal performance is then presented, which allows nonlinear compensation for high-order modulations. Next, we present Monte-Carlo simulations showing that the proposed algorithm performs close to the theoretical limits. Large performance improvement can be obtained and this is particularly emphasized with higher order modulation such as a 16-ary quadrature amplitude modulation. Finally, using Nyquist pulse shaping and polarization-division multiplexed with a quadrature phase-shift keying modulation, the experiments are shown to be in accordance with the simulations and show up to 0.7 dB improvement in Q-factor for the worst-case samples.

Neural network for solving Nash equilibrium problem in application of multiuser power control

In this paper, based on an equivalent mixed linear complementarity problem, we propose a neural network to solve multiuser power control optimization problems (MPCOP), which is modeled as the noncooperative Nash game in modern digital subscriber line (DSL). If the channel crosstalk coefficients matrix is positive semidefinite, it is shown that the proposed neural network is stable in the sense of Lyapunov and global convergence to a Nash equilibrium, and the Nash equilibrium is unique if the channel crosstalk coefficients matrix is positive definite. Finally, simulation results on two numerical examples show the effectiveness and performance of the proposed neural network.

A Unified Method for Crosstalk Reduction in Multiview Displays

The slanted lenticular sheet-based multiview display usually suffers both extrinsic crosstalk resulting from fabrication errors or assembling errors and intrinsic crosstalk originating from the leaked light from the two closest neighboring views. In this paper, a unified method is proposed to eliminate the extrinsic crosstalk and alleviate the intrinsic crosstalk simultaneously by adjusting the predefined view index (i.e., the corresponding viewpoint number) and grayscale intensity of each LCD subpixel. Two sets of patterns are utilized: structured light patterns are applied for building the correspondence between LCD subpixels and the captured photos pixels, and intensity test images are used for determining the brightness of LCD subpixels observed at given viewing points. Then the optimal view index for each LCD subpixel can be obtained for extrinsic crosstalk elimination according to the calculated correspondence and the estimated subpixel brightness. Moreover, the crosstalk coefficients for each subpixel can also be computed according to the correspondence and brightness, which are used for intrinsic crosstalk reduction. Experimental results prove the effectiveness of our method.

Terra MODIS Band 27 Electronic Crosstalk Effect and Its Removal

The Moderate Resolution Imaging Spectroradiometer (MODIS) is one of the primary instruments in the National Aeronautics and Space Administration Earth observing system. The first MODIS instrument was launched in December, 1999 onboard the Terra spacecraft. MODIS has 36 bands, covering a wavelength range 0.4-14.4 μm. MODIS band 27 (6.72 μm) is a water vapor band, which is designed to be insensitive to Earth surface features. In recent Earth view images of Terra band 27, surface feature contamination is clearly seen with pronounced striping. In this paper, it is shown that these band-27 issues are caused by electronic crosstalk from bands 28-30. An algorithm using a linear approximation is developed to correct the crosstalk effect. The crosstalk coefficients are derived from Terra MODIS lunar observations. They show that the crosstalk is strongly detector-dependent and the crosstalk pattern has changed in a noticeable fashion since launch. The crosstalk contributions were positive to the instrument response of band 27 early in the mission but became negative and much larger in magnitude at later stages of the mission for most detectors of the band. The algorithms are applied to both the black body (BB) calibration and the MODIS L1B calibrated products. With the crosstalk effect significantly removed, the calibration coefficients of Terra MODIS band 27 derived from the BB show that the detector differences become smaller. With the algorithms applied to MODIS L1B products, the Earth surface features are significantly removed, thereby restoring the radiometric balance of the band and substantially reducing the striping features in the image.