Phase Deviation Research Articles

Generation and transmission of phase-stable coherent multi-band linear frequency modulated signals.

We present a coherent multi-band linear frequency modulated (LFM) signal generation and transmission system based on dual optical frequency combs (OFCs). In the proposed scheme, the two OFCs are phase-locked to ensure high coherence of the generated multi-band LFM signals. A round-trip phase correction is adopted to stabilize the time delay of the fiber transmission and enable the system to resist temperature variation. In the demonstration experiment, the generated multi-band LFM signals across L, S, and C frequency bands has a bandwidth of 200 MHz in each band. The root-mean-square (RMS) phase deviation of the multi-band signal is below 4×10-3rad after 1.2 km fiber transmission. During 1°C temperature variation, the RMS phase drift is suppressed from 1 rad to 0.1 rad. The high signal coherence between different bands and the capability of resisting temperature variation are highly desired for a multi-band distributed radar system.

Effects of motor skill level and speed on movement variability during running

Variability in movement is an informative biological feature. This study aimed to examine the effects of motor skill level and running speed on movement variability. Twenty-nine male college students (fourteen athletes and fifteen non-athletes) participated in this study. All participants performed three motor tasks: 3 m/s running, 5 m/s running, and sprint running. Lower-limb kinematic data were acquired using a 16-camera infrared motion capture system. Lower-limb coordination during the stance phase was quantified using a continuous relative phase (CRP) method for interlimb (hip-hip, knee-knee, ankle-ankle) and intralimb (hip-knee, knee-ankle). The variabilities of stride length, stride cadence, joint angles, intralimb CRP, and interlimb CRP were calculated as standard deviations of each measurement. The results revealed that there were significant interaction effects between motor skill level and speed on movement variability for stride length (p = 0.047), ankle angle during propulsive phase (p = 0.001), knee-ankle CRP during propulsive phase (p = 0.007) and knee-knee CRP during propulsive phase (p = 0.009). Athletes showed greater angle variability, coordination variability and lower stride length variability during sprinting (all p < 0.05). In contrast, no between groups variability difference was observed when jogging at fixed lower speeds (all p > 0.05). Movement variability was greater for sprinting compared to jogging. Skill level was found to differentially affect the role of coordination variability in sprint performance. For athletes, hip-knee deviation phase and hip-hip deviation phase during braking phase were negatively correlated with sprinting speed (r = -0.563 and −0.642, respectively; both p < 0.05). For non-athletes, hip-knee deviation phase was positively correlated with sprinting speed (r = 0.581, p = 0.023). In conclusion, stride length become more stable, joint angle and coordination become more variable with long-term training. Results of this study also suggest that the relationship between coordination variability and performance is complicated and may depend on motor skill level. More longitudinal studies are needed to definitively determine the relationship between movement variability and performance.

A Broadband 90° Balun With Low-Phase-Imbalance Performance Based on Periodic Slow Wave Structure

We propose a method to construct the broadband 90° balun with low-phase-imbalance performance based on a U-shaped periodic slow wave structure (PSWS) transmission line (TL), whose dispersion curve has a linear region in a wide frequency band. By introducing meander lines and U-shaped TLs, the linearity, cutoff frequencies and slope of dispersion curves of PSWS can be controlled flexibly. Simulated and measured results show good agreements. Both reflection coefficient and isolation of the proposed balun are below -15 dB from 1.5 to 2.0 GHz. The phase deviation is within ±3°, covering a fractional bandwidth of 28.6%. Compared with that based on the traditional corrugated periodic slow wave TL unit, the operating bandwidth of the proposed balun is increased by more than six times. Moreover, the proposed PSWS keeps excellent ability of field confinement and therefore improves the isolation between the output ports. In a word, based on the proposed method, the microwave devices and circuits which realize the function of phase shifting can be designed.

Optimal number of baseline sessions before changing phases within single-case experimental designs

Recommendations vary considerably for the minimum or optimal number of baseline sessions to conduct within single-case experimental design clinical analyses or research studies. We examined the optimal number of baseline sessions that produced minimal bias. First, we examined the relation between the number of baseline sessions and the degree of bias in calculating estimates of treatment effect size. As the number of baseline sessions increased, the bias in effect size estimates decreased, r = -0.36, p < 0.001. s, we examined what would be the minimum number of baseline sessions associated with varying levels of bias. Bias of approximately ten percent was associated with four to five baseline sessions. Bias of about five percent was associated with six to seven baseline sessions. Third, we examined the relation between standard deviation and varying levels of bias. As the number of baseline sessions increases, the standard deviation for the phase decreased, r = -0.89, p < 0.001. Fourth, we examined what value of standard deviation in the baseline phase was associated with equal to or more than five versus ten percent bias. When considering five or ten percent bias, the optimal level of standard deviation was 0.59 or less.

Precise control of squeezing angle to generate 11 dB entangled state.

The strength of the quantum correlations of a continuous-variable entangled state is determined by several relative phases in the preparation, transmission, and detection processes of entangled states. In this paper, we report the first experimental and theoretical demonstrations of the precision of relative phases associated with the strength of quadrature correlations. Based on the interrelations of the relative phases, three precisely phase-locking methodologies are established: ultralow RAM control loops for the lengths and relative phases stabilization of the DOPAs, difference DC locking for the relative phase between the two squeezed beams, and DC-AC joint locking for the relative phases in BHDs. The phase-locking loops ensure the total phase noise to be 9.7±0.32/11.1±0.36 mrad. Finally, all the relative phase deviations are controlled to be in the range of -35 to 35 mrad, which enhances the correlations of the amplitude and phase quadratures to -11.1 and -11.3 dB. The entanglement also exhibits a broadband squeezing bandwidth up to 100 MHz. This paves a valuable resource for experimental realization and applications in quantum information and precision measurement.

Research on methods of measuring extinction angle and measures to suppress repetitive commutation failures through equivalent DC input resistance

Accurate, simple identification and suppression of repetitive commutation failures are of great significance to the safe and stable operation of the line-commutated converter-based high-voltage direct current (LCC-HVDC). Through the analysis of mathematical models of inverter side converter and DC transmission system. This paper proposes a variable that has an important influence on commutation failure: equivalent DC input resistance. Therefore, a measurement method is proposed, which takes into account the phase deviation of the fundamental commutation line voltage and uses equivalent DC input resistance as the input of the established mathematical model to measure the extinction angle. Meanwhile, according to the characteristics of equivalent DC input resistance, a method based on constant equivalent DC input resistance (EDCIR) to suppress repetitive commutation failures is proposed. Finally, several simulations are conducted on the CIGRE HVDC benchmark and GuiguangII model to validate the effectiveness of the proposed measurement method(TPMM) in the accuracy and suppression of commutation failure. The simulation results show that the proposed measurement method has the same accuracy as the measured extinction angle method and is higher than that of the minimum voltage drop method commonly used in practical engineering in judging commutation failure. At the same time, the proposed method to suppress can effectively reduce the number of commutation failures under single-phase and three-phase ground faults comparing with voltage-dependent current order limiter (VDCOL) and commutation failure prevention and control (CFPREV).

Оценивание точности восстановления абсолютной фазы при интерферометрической обработке данных радиолокаторов с синтезированной апертурой.

The problem of accuracy estimation of the absolute phase recovery in interferometric synthesized aperture radars (InSAR) data processing is considered. A method for accuracy estimation based on the calculation of the standard deviation of the reference phases and the absolute phases measured by the interferometric system in the radar image coordinate system "azimuth – slant range" is developed. The method includes converting the coordinates of the reference topographic height marks from the geographical coordinate system to the radar image coordinate system and then calculating of the transformation parameters between the reference heights and the measured absolute phases using the least squares method. The latter allows one to evaluate the performing effectiveness of individual stages of interferometric processing (multilooking, phase noise suppression, phase unwrapping) and experimentally determine the most effective processing algorithms that provide the best accuracy of the phase recovery and their optimal parameters. The method is tested using the ALOS PALSAR radar images obtained under various imaging conditions.

A Compact Broadband Phase Shifter Based on HMSIW Evanescent Mode

A compact broadband phase shifter based on the half-mode substrate-integrated waveguide (HMSIW) is proposed in this letter. By etching interdigital capacitor or adding blind holes and patches into the HMSIW, the width of the HMSIW can be reduced. Moreover, based on the complementary phase responses of series capacitance and shunt capacitance loading on the HMSIW, a broadband phase shifter is designed with a small phase deviation. To validate the proposed design approach, two phase shift channels and the reference channel are fabricated and measured. Phase shifts of 86° ± 2.5° (and 43.5° ± 2.5°) with fractional bandwidths of 53.3% (and 35.7%) covering central frequencies of 7.5 GHz (and 8.4 GHz) are achieved. The insertion losses of the three channels are 0.76-1.32, 0.40-0.63, and 0.87-1.40 dB, respectively. Besides, the area of each branch is only 0.343λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ; λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> is the guided wavelength at the center frequency in the dielectric.

Exogenous melatonin decreases circadian misalignment and body weight among early types.

Shift workers experience chronic circadian misalignment, which can manifest itself in reduced melatonin production, and has been associated with metabolic disorders. In addition, chronotype modulates the effect of night shift work, with early types presenting greater circadian misalignment when working night shift as compared to late types. Melatonin supplementation has shown positive results reducing weight gain in animal models, but the effect of exogenous melatonin in humans on body weight in the context of shift work remains inconsistent. The aim of this study was thus to evaluate the effects of exogenous melatonin on circadian misalignment and body weight among overweight night shift workers, according to chronotype, under real-life conditions. We conducted a double-blind, randomized, placebo-controlled, crossover trial where melatonin (3mg) or placebo was administered on non-night shift nights for 12weeks in 27 female nurses (37.1 yo, ±5.9 yo; BMI 29.9kg/m2 , ±3.3kg/m2 ). Melatonin (or placebo) was only taken on nights when the participants did not work night shifts, that is, on nights when they slept (between night shifts and on days off). Composite Phase Deviations (CPD) of actigraphy-based mid-sleep timing were calculated to measure circadian misalignment. The analyses were performed for the whole group and by chronotype. We found approximately 20% reduction in circadian misalignment after exogenous melatonin administration considering all chronotypes. Moreover, melatonin supplementation in those who presented high circadian misalignment, as observed in early chronotypes, reduced body weight, BMI, waist circumference, and hip circumference, without any change in the participants' calorie intake or physical activity levels.

Design of wideband phase shifter with edge-coupled semi-elliptical lines

The analysis and design of a wideband phase shifter using semi-elliptical edge-coupled structure is presented. An elliptical defected ground plane at the bottom layer is also incorporated to increase the coupling coefficient and operating bandwidth. Even and odd mode analysis has been performed and sets of design graphs are formulated to facilitate the design of the phase shifter on substrate with dielectric constant of 2.2 and 3.38. The differential phase shift is controlled by the coupling factor while the operating frequency is determined by the physical dimensions. Both simulation and measurement results show that the proposed design exhibits wideband characteristic with a phase deviation within ±4°, an insertion loss less than 1 ​dB and a return loss better than 10 ​dB. The achievable bandwidth is more than 2.4 : 1 for coupling factor of 5 ​dB which gives a differential phase shift of 80°.

Using Mendelian Randomisation methods to understand whether diurnal preference is causally related to mental health

Late diurnal preference has been linked to poorer mental health outcomes, but the understanding of the causal role of diurnal preference on mental health and wellbeing is currently limited. Late diurnal preference is often associated with circadian misalignment (a mismatch between the timing of the endogenous circadian system and behavioural rhythms), so that evening people live more frequently against their internal clock. This study aims to quantify the causal contribution of diurnal preference on mental health outcomes, including anxiety, depression and general wellbeing and test the hypothesis that more misaligned individuals have poorer mental health and wellbeing using an actigraphy-based measure of circadian misalignment. Multiple Mendelian Randomisation (MR) approaches were used to test causal pathways between diurnal preference and seven well-validated mental health and wellbeing outcomes in up to 451,025 individuals. In addition, observational analyses tested the association between a novel, objective measure of behavioural misalignment (Composite Phase Deviation, CPD) and seven mental health and wellbeing outcomes. Using genetic instruments identified in the largest GWAS for diurnal preference, we provide robust evidence that early diurnal preference is protective for depression and improves wellbeing. For example, using one-sample MR, a twofold higher genetic liability of morningness was associated with lower odds of depressive symptoms (OR: 0.92, 95% CI: 0.88, 0.97). It is possible that behavioural factors including circadian misalignment may contribute in the chronotype depression relationship, but further work is needed to confirm these findings.

Are SPECT MPI measures of dyssynchrony dyssynchronous?

BackgroundAssessment of left ventricular mechanical dyssynchrony (LVMD) from gated SPECT myocardial perfusion imaging (MPI) aims to aid selection of patients for cardiac resynchronization therapy (CRT), using either the standard deviation of left ventricular phase (PSD) ≥ 43° or phase histogram bandwidth (HBW) of > 38° and > 30.6° in males and females, respectively. We observed dyssynchrony parameters might be affected by test type and alignment. MethodsWe reviewed 242 patients who underwent gated SPECT MPI with use of the Emory Cardiac Toolbox comparing PSD and HBW at rest and stress for Pearson correlation, and substitutability with Bland–Altman analysis. ResultsThere is statistically significant difference in the mean PSD and HBW during rest vs stress (33.4 ± 17.4° vs 20.7 ± 13.5° and 97.7 ± 59.6° vs 59.4 ± 45.4°, respectively, P < 0.001). Proper valve plane alignment rendered smaller values (i.e., less dyssynchrony) in both phase SD and HBW (16.8 ± 13.5) vs (22.2 ± 14.7) (P = 0.011), and (47.0 ± 38.2) vs (60.7 ± 48.0) (P = 0.023), respectively. ConclusionProper alignment and test type, particularly low-dose rest vs high-dose stress, should be considered when assessing LVMD using SPECT MPI.

Entropy generation of a nanofluid in a porous cavity with sinusoidal temperature at the walls and a heat source bellow

PurposeThis paper aims to focus on the analysis of the entropy generation in an inclined square cavity filled with a porous media saturated by a nanofluid with sinusoidal temperature distribution on the side walls, adiabatic conditions on the upper wall and a heat source at the lower wall.Design/methodology/approachThe two-phase nanofluid model including the Brownian diffusion and thermophoresis effects has been used for simulation of nanofluid transport inside the porous cavity. The governing equations and the entropy generation owing to fluid friction, heat and mass transfer are transformed in terms of the dimensionless variables, and the results are obtained by using the finite difference method of the second-order accuracy.FindingsThe numerical results of the model are investigated, and the effect of different important parameters, such as inclination angle of the cavity, amplitude ratio of the sinusoidal temperature or phase deviation, is discussed. The results for no inclination of the cavity is compared and successfully validated with previous reported results of the literature. The important findings of the study are focused mainly on the existence of the irreversibility phenomena which are affected by the conditions of the model and the values of the studied parameters.Originality/valueThe originality of this work is given by the presented mathematical model, the numerical solution with new results for entropy generation in an inclined porous cavity filled by a nanofluid and the applications for design of electronic or energy devices.

Design and analysis of 3D-printed hybrid couplers for D-band applications

AbstractThis work focuses on the impact of the build orientation on additively manufactured waveguide-based hybrid couplers for D-band frequency range and relates it to other sources of uncertainty within the overall manufacturing process and measurement instrumentation for the D-band frequency range. The designed specimens are first printed from UV curable photopolymer resin and subsequently metal coated by an electroless silver plating process, which in turn is improved by making use of the slotted waveguide approach. Although the requirements toward geometrical precision to achieve phase errors below 10° are in an order of 0.1 mm, a desktop grade DLP printer is utilized in this work in order to point out the prospects and limitations of additive manufacturing. Furthermore, waveguide paths with bends are part of the model and their impact on the measured attenuation is estimated explicitly.Despite this narrow field of tolerances, one specimen could have been realized, which achieves a measured output magnitude imbalance of 0.7 dB over the frequency range from 120 to 155 GHz while at the same time exhibiting a phase deviation of only &lt;10° from the desired 90°. With these demonstrated results, the proposed approach provides suitability for future applications in the D-band frequency range.

Compact and low loss magneto-optical waveguide isolator for TE mode based on lithium niobate on insulator

A novel optical isolator for fundamental transverse electric (TE) mode light based on asymmetric Mach–Zehnder interferometer (MZI) configuration is proposed. Asymmetric Mach–Zehnder interferometer (MZI) configuration is employed to generate nonreciprocal phase shift (NRPS). The optical isolator is implemented by applying Ce: YIG thin film on lithium niobate on insulator (LNOI). The NRPS of LN/Ce: YIG composite waveguides with different geometric sizes are calculated. The 30 dB isolation bandwidth is larger than 48.3 nm and the total simulated insertion loss is as low as 2.736 dB for NRPS waveguides with a length of 504.5μm at a wavelength around 1550 nm. Considering the state-of-art technology, the fabrication tolerances and a suitable process are discussed. Besides, a wavelength-tuning optical isolator is designed to cancel the phase deviation.

Coherent Integration Loss Due to Nonstationary Phase Noise in High-Resolution Millimeter-Wave Radars

Phase noise refers to the instability of an oscillator, which is the cause of instantaneous phase and frequency deviations in the carrier wave. This unavoidable instability adversely affects the performance of range–velocity radar systems, including synthetic aperture radars (SARs) and ground-moving target indicator (GMTI) radars. Phase noise effects should be considered in high-resolution radar designs, operating in millimeter wavelengths and terahertz frequencies, due to their role in radar capability during the reliable identification of target location and velocity. In general, phase noise is a random process consisting of nonstationary terms. It has been shown that in order to optimize the coherent detection of stealthy, fast-moving targets with a low radar cross-section (RCS), it is required to evaluate the integration gain and to determine the incoherent noise effects for resolving target location and velocity. Here, we present an analytical expression for the coherent integration loss when a nonstationary phase noise is considered. A Wigner distribution was employed to derive the time–frequency expression for the coherent loss when nonstationary conditions were considered. Up to now, no analytical expressions have been developed for coherent integration loss when dealing with real nonstationary phase noise mathematical models. The proposed expression will help radar systems estimate the nonstationary integration loss and adjust the decision threshold value in order to maximize the probability of detection. The effect of nonstationary phase noise is demonstrated for studying coherent integration loss of high-resolution radar operating in the W-band. The investigation indicates that major degradation in the time-frequency coherent integration due to short-term, nonstationary phase noise instabilities arises for targets moving at low velocities and increases with range. Opposed to the conventional model, which assumes stationarity, a significant difference of up to 25 dB is revealed in the integration loss for radars operating in the millimeter wave regime. Moreover, for supersonic moving targets, the loss peaks at intermediate distances and then reduces as the target moves away.

Finite element treatment for nanofluids flow within enclosures filled with hydrodynamically and thermally anisotropic porous media: Impacts of sinusoidal heating

AbstractThe local thermal non‐equilibrium model (LTNEM) in case of a sinusoidal heating is applied to investigate the unsteady nanofluid flow and thermal fields inside an inclined enclosure filled with a thermally and hydrodynamically anisotropic porous medium. The Galerkin finite element method (GFEM) together with the Characteristic‐based Split (CBS) Scheme is used to solve the dimensionless governing equations. Impacts of the controlling parameters are studied in two cases, namely, non‐Darcy Regime in which values of the Darcy number and the Rayleigh number are, respectively, and the Darcy regime where . Parametric studies are performed for wide ranges of the permeability ratio , the Nield number , the inclination angle , the nanoparticles volume fraction , the inclination of the principal axes , the amplitude ratio and the phase deviation . The main outcomes revealed that the sinusoidal heating results in multicellular flow components inside the geometry. Also, the increase in the Nield number causes that the system converts from the LTNE state to local thermal equilibrium (LTE) state. For the non‐Darcy regime, the convective process and the rate of the heat transfer are augmented as the inclination of the principal axes is increased.

Measuring sleep regularity: theoretical properties and practical usage of existing metrics.

Sleep regularity predicts many health-related outcomes. Currently, however, there is no systematic approach to measuring sleep regularity. Traditionally, metrics have assessed deviations in sleep patterns from an individual's average; these traditional metrics include intra-individual standard deviation (StDev), interdaily stability (IS), and social jet lag (SJL). Two metrics were recently proposed that instead measure variability between consecutive days: composite phase deviation (CPD) and sleep regularity index (SRI). Using large-scale simulations, we investigated the theoretical properties of these five metrics. Multiple sleep-wake patterns were systematically simulated, including variability in daily sleep timing and/or duration. Average estimates and 95% confidence intervals were calculated for six scenarios that affect the measurement of sleep regularity: "scrambling" the order of days; daily vs. weekly variation; naps; awakenings; "all-nighters"; and length of study. SJL measured weekly but not daily changes. Scrambling did not affect StDev or IS, but did affect CPD and SRI; these metrics, therefore, measure sleep regularity on multi-day and day-to-day timescales, respectively. StDev and CPD did not capture sleep fragmentation. IS and SRI behaved similarly in response to naps and awakenings but differed markedly for all-nighters. StDev and IS required over a week of sleep-wake data for unbiased estimates, whereas CPD and SRI required larger sample sizes to detect group differences. Deciding which sleep regularity metric is most appropriate for a given study depends on a combination of the type of data gathered, the study length and sample size, and which aspects of sleep regularity are most pertinent to the research question.

Polarisation variation of linear polarised Bi‐ISAR system in space targets imaging

A bistatic inverse synthetic aperture radar (Bi-ISAR) system is used to observe space targets through different viewing angles via a bistatic radar configuration. It is seen that the receiver of a linear polarised Bi-ISAR system with a long baseline will encounter energy variation and high-order phase deviation in ISAR imaging due to the polarisation variation of this system. Here, the authors quantitatively analyse the energy variation caused by polarisation mismatch in a linearly polarised Bi-ISAR system by investigating the time-varying bistatic angle and intrinsic variable polarisation effect of targets via the combination of observation geometry and computational electromagnetic. The high-order phase deviation in long-term coherent processing is also presented through the same strategy. The authors conducted simulations for a bistatic system, which is configured with different baseline vectors, to analyse the impact of polarisation variation of the linear polarised Bi-ISAR system on the energy loss and high-order phase terms.

Method of Detecting Radio Signals using Means of Covert by Obtaining Information on the basis of Random Signals Model

The article presents a developed method for determining random radio signals. Random signals can be signals from hidden means of obtaining information. The signal is considered as a random process. The description of such signals is based on probability theory and the theory of random functions. In the practice of analysis of random radio signals, static methods based on the theory of stationary random functions have become widespread. The existing models of a stationary random process are not adequate for a large number of random processes, especially for processes that are dynamic in nature and are observed during a finite time interval. The developed method allows to detect signals from hidden means of obtaining information with greater efficiency. The novelty of the method is to determine the deviation of the main parameters of the signals from the function of the sample. The method is based on determining the function of a sample of signals of a given radio range. The function of the sample is obtained as the implementation of the smoothing function of a random process, by the method of least squares using the principle of sliding smoothing. It is proposed to determine the signals of the means of covert receipt of information by the instantaneous deviation of the parameters of random signals. To determine the signals of the means of covert obtaining information, it is proposed to determine the deviation of the amplitude of the random signals from the amplitude of the signals of the sample function, then, if necessary, to determine the deviation of the signal phases. So, the effectiveness of the method is achieved by determining two parameters of the deviation of the amplitude and phase. This makes it possible to detect random signals with a higher probability. Determining the function of the sample of the required radio band significantly increases the probability of determining random signals, by reducing the scanning time of a given radio band, by excluding known signals from the additional software analysis of a given radio band.