Relative Phase Shift Research Articles

Interlimb coordination is not strictly controlled during walking

In human walking, the left and right legs move alternately, half a stride out of phase with each other. Although various parameters, such as stride frequency and length, vary with walking speed, the antiphase relationship remains unchanged. In contrast, during walking in left-right asymmetric situations, the relative phase shifts from the antiphase condition to compensate for the asymmetry. Interlimb coordination is important for adaptive walking and we expect that interlimb coordination is strictly controlled during walking. However, the control mechanism remains unclear. In the present study, we derived a quantity that models the control of interlimb coordination during walking using two coupled oscillators based on the phase reduction theory and Bayesian inference method. The results were not what we expected. Specifically, we found that the relative phase is not actively controlled until the deviation from the antiphase condition exceeds a certain threshold. In other words, the control of interlimb coordination has a dead zone like that in the case of the steering wheel of an automobile. It is conjectured that such forgoing of control enhances energy efficiency and maneuverability. Our discovery of the dead zone in the control of interlimb coordination provides useful insight for understanding gait control in humans.

Electro-optically tunable optical delay on a lithium niobate photonic chip.

An approach for continuous tuning of on-chip optical delay with a microring resonator is proposed and demonstrated. By introducing an electro-optically tunable waveguide coupler, the bus waveguide to the resonance coupling can be effectively tuned from the under-coupling regime to the over-coupling regime. The optical delay is experimentally characterized by measuring the relative phase shift between lasers and shows a large dynamic range of delay from -600 to 600 ps and an efficient tuning of delay from -430 to -180 ps and from 40 to 240 ps by only a 5 V voltage.

Intensified Impact of Spring Tibetan Plateau Snow Cover on Summer Compound Heat Waves in Western Europe after 1998

Abstract This study revealed a significant interdecadal change in the impact of spring western Tibetan Plateau (TP) snow cover (TPSC) on subsequent summer compound heat waves (CHWs) in western Europe (WE) after 1998. This interdecadal change is attributed to a change in a western Europe high–western TP low (WEH–TPL) atmospheric circulation pattern. This pattern arises due to both the inherent variability of TPSC and the phase transition of the Atlantic multidecadal oscillation (AMO) after 1998. The increased magnitude and persistence of western TPSC from spring to summer after 1998 enhanced the snow–atmosphere coupling effect, intensifying ascent and decent motion over the TP and WE, respectively, and strengthening the WEH–TPL pattern. In addition, the post-1998 positive AMO phase favors continuous and stable downstream Rossby wave propagation, enhancing the WEH–TPL pattern and the TPSC–CHWs relationship. Further analyses reveal that the interdecadal changes in the TPSC and the AMO around 1998 contribute to the presence of “double jets” over the North Atlantic–central Eurasian sectors. The TPSC–related anomalous atmospheric circulation and AMO phase shift contribute to the southern and northern branches of the intensified westerly jet, respectively. These conditions create a favorable environment for the formation and persistence of summer CHWs in WE. Numerical modeling experiments with a linear baroclinic model confirm these findings. Our findings suggest that in the context of a changing climate, TPSC plays a pivotal role in the genesis of summer CHWs in WE and may serve as a valuable predictor for CHWs. Significance Statement This study discovered that starting from 1998 there was a significant change in how spring snow cover on the western Tibetan Plateau affects summer compound heat waves in western Europe. After 1998, the snow cover on the western Tibetan Plateau increased in size and lasted longer from spring to summer, intensifying the interaction between the snow and the atmosphere. This led to more rising and sinking air over the Tibetan Plateau and western Europe, respectively. Also, after 1998 a positive phase of the Atlantic multidecadal oscillation (AMO) was favorable for the circulation connection between western Europe and the Tibetan Plateau. Further analysis showed that these changes in snow cover and the AMO after 1998 caused “double jets” in the North Atlantic and central Eurasia that created better conditions for summer heat waves in western Europe. Numerical models are used to confirm these findings. Our research indicates that, in a changing climate, the snow cover on the western Tibetan Plateau plays a crucial role in the development of summer heat waves in western Europe and can be a useful predictor for these heat waves.

Fiber-optic parametric amplifier-based all-optical format conversion enabling optical networks interconnection with different modulation formats

A fiber-optic parametric amplifier (FOPA)-based all-optical format conversion (AOFC) scheme is proposed and numerically simulated to achieve optical networks interconnection with different modulation formats. In this scheme, the power transfer function (PTF) and the relative phase shift (RPS) functions between the input and output optical signals for the single-pump FOPA are derived and numerically analyzed. For the input 20 Gbps bipolar 4-ary pulse amplitude modulation (PAM4) signal, it can be converted into a BPSK signal (BPSK1) based on the power saturation characteristic of the PTF. By adjusting the input power of the input PAM4 signal, it can also be converted into a level-swapping PAM4 signal based on the single-pump FOPA. When the level-swapping PAM4 signal is sent into the single-pump FOPA with suitable power again, another BPSK signal (BPSK2) could also be generated. When the PAM4-to-BPSK format converter based on the single-pump FOPA is combined with the dual-pump FOPA (namely phase-sensitive amplifier, PSA), the 16-ary quadrature amplitude modulation (16QAM) signal can also be de-aggregated into four BPSK signals or two quadrature phase shift keying (QPSK) signals. The constellation diagrams, the power waveforms, the error vector magnitude (EVM) and the bit error rate (BER) of the relevant optical signals are measured to evaluate the scheme performance. The scheme can be deployed at the optical gateway to realize optical networks interconnection using different modulation formats.

Synthesis and design of miniaturized poly-phase differential phase shifters with filtering function

In this paper, a class of miniaturized poly-phase differential phase shifters with filtering function is proposed, synthesized and developed. The proposed design is constructed by using parallel-coupled microstrip lines as the phase-shifting element in all branches. Operational mechanisms for these parallel-coupled microstrip lines are given. Closed-form formulas of insertion phase and phase slope are derived to guide a practical design procedure for phase shifters with arbitrary shifted phases and minimized phase errors. Benefitting from the compact size of those parallel-coupled microstrip lines, the proposed design is much smaller when compared with state-of-the-art works. To validate the proposed concept and synthesis method, a class of five-way poly-phase (ΔΦ = 45°, 90°, 135°, and 180°) differential phase shifter centered at 3 GHz is designed, fabricated, and measured. Measured results indicate that, achieved relative phase shifts are 45° ± 2.7°, 91° ± 2.9°, 135° ± 3.2°, and 181° ± 3.9° within a 33 % fractional bandwidth, with amplitude imbalances smaller than 0.2 dB among different ways.

Measuring axion gradients with photon interferometry

We propose a novel search technique for axions with a CP-violating monopole coupling g˜Q to bulk Standard Model charges Q∈{B,L,B−L}. Gradients in the static axion field configurations sourced by matter induce achromatic circular photon birefringence via the axion-photon coupling gϕγ. Circularly polarized light fed into an optical or (open) radio-frequency (RF) Fabry-Pérot (FP) cavity develops a phase shift that accumulates up to the cavity finesse: the fixed axion spatial gradient prevents a cancellation known to occur for an axion dark-matter search. The relative phase shift between two FP cavities fed with opposite circular polarizations can be detected interferometrically. This time-independent signal can be modulated up to nonzero frequency by altering the cavity orientations with respect to the field gradient. Multiwavelength co-metrology techniques can be used to address chromatic measurement systematics and noise sources. With Earth as the axion source, we project reach beyond current constraints on the product of couplings g˜Qgϕγ for axion masses mϕ≲10−5 eV. If shot-noise-limited sensitivity can be achieved, an experiment using high-finesse RF FP cavities could reach a factor of ∼105 into new parameter space for g˜Qgϕγ for masses mϕ≲4×10−11 eV. Published by the American Physical Society 2024

Edelstein Effect Induced Superconducting Diode Effect in Inversion Symmetry Breaking MoTe2 Josephson Junctions

AbstractSuperconducting diode effect (SDE) with nonreciprocal supercurrent transport has attracted intense attention recently, not only for its intriguing physics, but also for its great application potential in superconducting circuits. It is revealed in this work that planar Josephson junctions (JJs) based on type‐II Weyl semimetal (WSM) MoTe2 can exhibit a prominent SDE due to the emergence of asymmetric Josephson effect (AJE) in perpendicular magnetic fields. The AJE manifests itself in a very large asymmetry in the critical supercurrents with respect to the current direction. The sign of this asymmetry can also be effectively modulated by the external magnetic field. Considering the special noncentrosymmetric crystal symmetry of MoTe2, this AJE is understood in terms of the Edelstein effect, which induces a nontrivial phase shift in the current phase relation of the junctions. Besides these, it is further demonstrated that the rectification of supercurrent in such MoTe2 JJs with the rectification efficiency up to 50.4%, unveiling the great application potential of WSMs in superconducting electronics.

On‐Chip Light Polarization Management by Mapping the Polarization Information to Phase Shift

AbstractThe comprehensive management of light polarization states has significantly advanced various fields into a new era. With the advent of photonic integration, there has been a persistent desire to replace the bulky optical components with compact chip‐scale circuits. Nonetheless, the complete integration of polarization‐dependent systems has not yet been accomplished due to the absence of a mature polarization management scheme that possesses a tiny form factor and high foundry process compatibility meanwhile maintaining low operation complexity. Here, to overcome these limitations a novel concept called polarization phase mapping, which encodes the information between the light polarization in one waveguide and the relative light phase shift in another two waveguides, is proposed. With this bi‐directional mapping approach, the fundamental basis of polarization management has shifted from polarization adjustment to phase regulation. All essential polarization‐related functions including synthesizing, stabilizing, measuring, rotating, splitting, and mixing are demonstrated with the standard process in foundries. The size of the polarization rotating unit is pushed down to a few light wavelengths while keeping a competitive performance. Moreover, the proposed concept can be readily applied to other integrated photonics platforms. It is expected to unlock new opportunities for complex polarization‐related applications.

Flexible All-Optical 8QAM Signal Format Conversion Using Pump Assisted Nonlinear Optical Loop Mirror

A flexible all-optical format interconversion scheme based on a pump assisted nonlinear optical loop mirror (NOLM) is proposed and numerically simulated for the first time to our knowledge. In this scheme, input multi-Gbps 8QAM signals are divided into clockwise (CW) and counter-clockwise (CCW) components by a 3-dB optical coupler (OC), which also couples light from the input pump into the NOLM from the CCW direction. The numerical model of the pump assisted NOLM with CW and CCW optical paths is simplified using a nonlinear Mach-Zehnder interferometer (MZI). Optical signals in the upper MZI arm will be mainly affected by the self-phase modulation (SPM) effect when traversing the highly nonlinear fiber (HNLF) and those in the lower MZI arm are impacted by cross-phase modulation (XPM) in addition to SPM when they experience the HNLF with the input pump light. When the upper-arm optical signal with SPM phase shift and the lower arm optical signal with SPM and XPM phase shifts are coherently mixed, a new converted 8QAM signal can be obtained. The power transfer function (PTF) of the pump assisted NOLM and the relative phase shift (RPS) between the input and the output optical signals are theoretically provided and verified. By only changing the input power of the 8QAM signal and the pump light, all-optical format interconversion of square-, standard- and star-shaped 8QAM signals can be achieved. Furthermore, the proposed scheme can achieve format conversion from the 30 Gbps square-shaped 8QAM signal to a 20 Gbps quadrature phase shift keying (QPSK) signal. The scheme performance is analyzed via constellation diagrams, eye diagrams, the error vector magnitude (EVM) and the bit error rate (BER) of the optical signals. The scheme developed can be deployed in optical gateways to connect different optical networks by dynamically selecting their appropriate modulation formats.

Control of dual-wavelength laser emission via optical feedback phase tuning

We propose and demonstrate a technique to control the balance between the two amplitudes of a dual-wavelength laser based on a phase-controlled optical feedback. The feedback cavity length is adjusted to achieve a relative phase shift between the desired emission wavelengths, introducing a boost in gain for one wavelength while the other wavelength experiences additional losses. Tuning the optical feedback phase proves to be an effective way to control the gain and losses, and, thus, to select one or balance the amplitude of the two emission wavelengths. This concept can be easily adapted to any platform, wavelength range and wavelength separations providing that a sufficient carrier coupling and gain can be obtained for each mode. To demonstrate the feasibility and to evaluate the performance of this approach, we have implemented two dual-wavelength lasers with different spectral separations together with individual optical feedback loops onto a InP generic foundry platform emitting around 1550 nm. An electro-optical-phase-modulator is used to tune the feedback phase. With this single control parameter, we successfully achieved extinction ratios of up to 38.6 dB for a 10 nm wavelength separation and up to 49 dB for a 1 nm wavelength separation.

All-optical wavelength and format conversion of DQPSK-to-PAM4 using DLI and pump assisted NOLM

An all-optical wavelength and format conversion scheme of 20 Gbps differential quadrature phase shift keying (DQPSK)-to-4-ary pulse amplitude modulation (PAM4) signals based on the delay line interferometer (DLI) and the pump assisted nonlinear optical loop mirror (NOLM) is proposed and numerically simulated. The input DQPSK signal is converted into two star-16-ary quadrature amplitude modulation (star-16QAM) signals (namely, star-16QAM-I and star-16QAM-Q) using DLI with the time delay of 1-symbol and different linear phase shifts of π/4 and −π/4, respectively. The star-16QAM signals are converted into the on-off keying (OOK) signals (namely, OOK-I and OOK-Q) using the pump assisted NOLM based on the self-phase modulation (SPM) and the cross-phase modulation (XPM) in the highly nonlinear fiber (HNLF). The two OOK signals can be aggregated into different types of PAM4 signals by adjusting their power ratio (PR) and relative phase shift (RPS) flexibly. Error vector magnitude (EVM) and bit error rate (BER) for the input and output optical signals are calculated to verify the scheme performance. Compared to the DQPSK signal with an input optical signal-to-noise ratio (OSNR) of 30 dB, there are about 2.5 dB penalty of receiver OSNR for the converted OOK-I and OOK-Q signals. For the corresponding aggregated equidistant PAM4 and equiamplitude PAM4 signals, they have about 6.3 dB and 12.1 dB penalty of receiver OSNR. The proposed scheme of DQPSK-to-PAM4 can be deployed at the all-optical gateway to bridge the long-hual and short-reach optical networks.

Antenna Combiner for Periodic Broadcast V2V Communication Under Relaxed Worst-Case Propagation

The performance of a previously developed analog combining network (ACN) of phase shifters for periodic broadcast vehicle-to-vehicle (V2V) communication is investigated. The original ACN was designed to maximize the sum of signal-to-noise ratios (SNRs) for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$</tex-math> </inline-formula> consecutive cooperative awareness messages (CAMs). The design was based on the assumption of a dominant propagation path with an angle of arrival (AOA) that is constant for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$</tex-math> </inline-formula> messages. In this work, we relax this assumption by allowing the AOA and path-loss (PL) of the dominant path to be time-variant. Assuming a highway scenario with a line of sight (LOS) propagation between vehicles, we use affine approximations to model the time variation of different path quantities, including the PL, the relative distance-dependent phase shift between antennas, and the AOA-dependent far-field function of the antennas. By leveraging these approximations, we analytically derive the ACN sum-SNR as each one of these quantities varies over <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$</tex-math> </inline-formula> CAMs. Moreover, we suggest a design rule for a phase slope that is robust against time variation of the dominant path and optimal under time-invariant conditions. Finally, we validate this design rule using numerical computations and an example of vehicular communication antenna elements.

Female meiotic drive shapes the distribution of rare inversion polymorphisms in Drosophila melanogaster.

In all species, new chromosomal inversions are constantly being formed by spontaneous rearrangement and then stochastically eliminated from natural populations. In Drosophila, when new chromosomal inversions overlap with a pre-existing inversion in the population, their rate of elimination becomes a function of the relative size, position, and linkage phase of the gene rearrangements. These altered dynamics result from complex meiotic behavior wherein overlapping inversions generate asymmetric dyads that cause both meiotic drive/drag and segmental aneuploidy. In this context, patterns in rare inversion polymorphisms of a natural population can be modeled from the fundamental genetic processes of forming asymmetric dyads via crossing-over in meiosis I and preferential segregation from asymmetric dyads in meiosis II. Here, a mathematical model of crossover-dependent female meiotic drive is developed and parameterized with published experimental data from Drosophila melanogaster laboratory constructs. This mechanism is demonstrated to favor smaller, distal inversions and accelerate the elimination of larger, proximal inversions. Simulated sampling experiments indicate that the paracentric inversions directly observed in natural population surveys of Drosophila melanogaster are a biased subset that both maximizes meiotic drive and minimizes the frequency of lethal zygotes caused by this cytogenetic mechanism. Incorporating this form of selection into a population genetic model accurately predicts the shift in relative size, position, and linkage phase for rare inversions found in this species. The model and analysis presented here suggest that this weak form of female meiotic drive is an important process influencing the genomic distribution of rare inversion polymorphisms.

Demonstration of the Nonlocal Josephson Effect in Andreev Molecules.

We perform switching current measurements of planar Josephson junctions (JJs) coupled by a common superconducting electrode with independent control over the two superconducting phase differences. We observe an anomalous phase shift in the current-phase relation of a JJ as a function of gate voltage or phase difference in the second JJ. This demonstrates the nonlocal Josephson effect, and the implementation of a φ0-junction which is tunable both electrostatically and magnetically. The anomalous phase shift is larger for shorter distances between the JJs and vanishes for distances much longer than the superconducting coherence length. Results are consistent with the hybridization of Andreev bound states, leading to the formation of an Andreev molecule. Our devices constitute a realization of a tunable superconducting phase source and could enable new coupling schemes for hybrid quantum devices.

An 8-18 GHz 90° Switched T-Type Phase Shifter.

This paper proposes a novel 8-18 GHz 90° switched T-type phase shifter (TPS). In contrast to the conventional TPS, the proposed TPS adds a compensation capacitance to greatly enhance the phase shifting capacity. Moreover, the designed structure also integrates a filtering compensation network, which can effectively achieve a flat relative phase shift in a wide band. The proposed 90° TPS is fabricated using 0.15 μm GaAs pHEMT technology. The TPS achieves homogeneous phase shift at 8-18 GHz, with the measured phase error of less than ±1.5°. The insertion loss of the proposed phase shifter is 1.3-2.6 dB, and the chip size is merely 0.53 × 0.86 mm2. Thanks to these excellent performance characteristics, the designed phase shifter is well-suited for ultra-wideband wireless communication and radar systems.

Post‐Sunset Field‐Line Resonances at Equatorial Latitudes Observed by Swarm

AbstractIn this study employing data from the Swarm satellites at an altitude of ≈500 km, we present evidence of field‐line resonances (FLRs) in the Pc2‐3 (0.02–0.2 Hz) frequency band in the undisturbed post‐sunset region of the equatorial ionosphere. We identify 26 events extending to magnetic latitudes as low as 2°, which was previously thought to be too low for FLRs to exist due to ionospheric damping. Identification of FLRs is supported by a narrow‐band fundamental and first harmonics, an oscillating field‐aligned Poynting vector, a relative phase shift between E and δB of ≈90°, and in one case observation of one wave in conjugate hemispheres by two satellites separated by 4 min. We show that, contrary to the non‐uniform trend of ground‐based observations, the fundamental frequencies of these occurrences decline monotonically with increasing field‐line length. Their frequencies differ from those of ground‐based magnetometer observations reported in the literature.

Explore Benefits of Distributed Fiber Optic Sensing for Optical Network Service Providers

We review various applications of distributed fiber optic sensing (DFOS) and machine learning (ML) technologies that particularly benefit telecom operators' fiber networks and businesses. By leveraging relative phase shift of the reflectance of coherent Rayleigh, Brillouin and Raman scattering of light wave, the ambient environmental vibration, acoustic effects, temperature and fiber/cable strain can be detected. Fiber optic sensing technology allows optical fiber to support sensing features in addition to its conventional role to transmit data in telecommunications. DFOS has recently helped telecom operators by adding multiple sensing features and proved feasibility of co-existence of sensing and communication systems on same fiber. We review the architecture of DFOS technique, and show examples where optical fiber sensing helps enhance network operation efficiency and create new services for customers on deployed fiber infrastructures, such as determination of cable locations, cable cut prevention, perimeter intrusion detection and networked sensing applications. In addition, edge AI platform allows data processing to be conducted on-the-fly with low latency. Based on discriminative spatial-temporal signatures of different events of interest, real-time processing of the sensing data from the DFOS system provides results of the detection, classification and localization immediately.

Differential Method for the Formation of Relative Phase Shifts between Light Beams in a Two-Arm Interferometer

Differential Method for the Formation of Relative Phase Shifts between Light Beams in a Two-Arm Interferometer

Application of electromagnetic disturbance technology in predicting ventriculoperitoneal shunt dependency after aneurysm-associated subarachnoid hemorrhage.

The aim of this study was to evaluate the predictive power of electromagnetic disturbance technology in patients with hydrocephalus after subarachnoid hemorrhage. This prospective, observational cohort study was conducted at The First Affiliated Hospital of Zhengzhou University and Nanfang Hospital. A total of 155 patients with subarachnoid hemorrhage (SAH) were enrolled in this study. Disturbance coefficients were recorded using a continuous sinusoidal signal in real time after SAH. The patients were divided into two groups: hydrocephalus group (patients who underwent shunt insertion within a month after SAH) and non-hydrocephalus group (patients without need for a ventriculoperitoneal shunt). We used SPSS to draw a ROC Curve to assess the ability of disturbance coefficients to predict the probability of hydrocephalus. Hydrocephalus occurred in 37 patients after SAH. The average disturbance coefficient of patients with hydrocephalus decreased by 25.14±9.78, and the disturbance coefficient of patients with no hydrocephalus decreased by 6.58±10.10 (one aspect of the present invention is a system of non-invasively monitoring hydrocephalus, cerebral edema, and intracranial bleeding comprising of a source emitting electromagnetic waves to brain tissue, a detector detecting said wave that propagates through said tissue, a signal conditioning unit amplifying and filtering said wave, a quadrature detector estimating magnitude and phases of said wave, and a parameter estimator calculating the complex wave number, relative attenuation coefficient (RAC), relative phase shift (RPS), wave speed change (WSC), and travel-time difference (TTD) of said brain, and assessing status of hydrocephalus and cerebral edema). The difference was statistically significant (t=9.825, P<0.001). The decrease in disturbance coefficient can be used to predict the occurrence of hydrocephalus, and if the disturbance coefficient decreases by more than 15.5 (sensitivity, 92.37%; specificity, 86.49%), it can be used to indicate the occurrence of hydrocephalus. The disturbance coefficient can predict the occurrence of hydrocephalus. The greater decline of the disturbance coefficient, the greater probability of occurrence of intracranial hydrocephalus. Hydrocephalus can be early detected. However, the CT scan is necessary to confirm the occurrence of hydrocephalus. Early diagnosis and early treatment may improve the prognosis of patients with hydrocephalus after subarachnoid hemorrhage.

Frictional shakedown of a coupled continuous contact

The plane elastic problem of a circular disc shrink fitted into a hole in an elastically similar plane, with a frictional interface, is studied. The disc is subject to a radial force and torque both of which vary with time. In the steady-state the loads vary harmonically, and a relative phase shift is considered. Frictional slip is accounted for by edge dislocations distributed along the interface. It is shown that the steady-state response, which might, for example, be cyclic slip or full adhesion (shakedown) for a particular loading regime, depends on the loading history before the steady-state loading regime is entered. This contrasts with Melan’s theorem for elastic–plastic shakedown, and is a consequence of the normal–tangential coupling in this frictional system.