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For the time and frequency signals of Beidou satellites, a high-accuracy phase frequency detection technology based on phase group synchronization is proposed. Using the Beidou receiver and satellite signals as the frequency standard and the measured signals, respectively. The Beidou receiver and the satellite signals are sent to the phase coincidence detector of the different frequencies to generate a phase coincidence point pulse, which is sent to the different frequency phase detector as a control signal to generate the phase differences between the Beidou receiver and satellite signals, and then complete the high-accuracy phase synchronization between the Beidou receiver and satellite signals. Experimental results show that when the delay resolution reaches ps level, the phase synchronization accuracy of the system can reach 10 ps, which has the characteristics of small phase noise, low development cost, simple circuit structure, and high synchronization accuracy compared with the traditional phase synchronization technologies. Therefore, it would be widely used in satellite positioning, astrometry, precision navigation, aerospace, satellite launch, power transmission, communications, radar, and other high-tech fields. [ABSTRACT FROM AUTHOR]

We investigate the utilization of advanced single photons produced by quantum dots (QDs) in a microcavity for quantum metrology. Through the integration of lateral excitation and the Purcell effect in an Fabry–Perot microcavity, we realized single-photon emission with an extraction efficiency of 46.39%, high purity of 96.91%, and high indistinguishability of 98.32%. Our QD-generated single photons enabled the creation of high-quality NOON states (N = 2) for phase measurement, yielding an interference contrast of 79.79% and surpassing the standard quantum limit (SQL) with phase super-sensitivity. Our results underscore the immense potential of QD-derived single photons for propelling quantum metrology forward, facilitating enhanced precision measurements across diverse applications. [ABSTRACT FROM AUTHOR]

This article focuses on the optimal traffic control strategy for a tandem intersection with presignals. First, the impact of a lane assignment scheme at presignals on the operational performance of the tandem intersection is analyzed. An improved lane assignment method is thus proposed to avoid setting the lanes with the same traffic flow direction adjacent to each other as far as possible. Second, vehicle delay models behind the presignals and in the sorting area are established, respectively. Third, considering green times of presignal phases and sorting area lengths on all approaches as variables, an optimization model is proposed to minimize the average vehicle delay. Finally, a case study is conducted on a congested intersection in Changchun, China, to validate the proposed method. The effects of the proposed improved lane assignment scheme on the tandem intersection are analyzed compared with the traditional lane assignment scheme. The results show that the former can decrease average vehicle delay by 22.9% and increase intersection capacity by 18.6%. [ABSTRACT FROM AUTHOR]

In unmanned aerial vehicle (UAV)-based time difference of arrival (TDOA) positioning technique, baselines are limited due to communication constraints. In this case, the accuracy is highly sensitive to the TDOA measurements' error. This article primarily addresses the problem of short-baseline high-precision time synchronization and TDOA measurement. We conducted a detailed analysis of error models in TDOA systems, considering both the time and phase measurement. We utilize the frequency division wireless phase synchronization technique in TDOA systems. Building upon this synchronization scheme, we propose a novel time delay estimation method that relies on phase measurements based on the integer least squares method. The performance of this method is demonstrated through Monte Carlo simulations and outdoor experiments. The standard deviations of synchronization and TDOA measurements in experiments are 1.12 ps and 1.66 ps, respectively. Furthermore, the circular error probable (CEP) accuracy is improved from 0.33%R to 0.02%R, offering support for the practical application of distributed short-baseline high-precision passive location techniques. [ABSTRACT FROM AUTHOR]

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For the time and frequency signals of Beidou satellites, a high-accuracy phase frequency detection technology based on phase group synchronization is proposed. Using the Beidou receiver and satellite signals as the frequency standard and the measured signals, respectively. The Beidou receiver and the satellite signals are sent to the phase coincidence detector of the different frequencies to generate a phase coincidence point pulse, which is sent to the different frequency phase detector as a control signal to generate the phase differences between the Beidou receiver and satellite signals, and then complete the high-accuracy phase synchronization between the Beidou receiver and satellite signals. Experimental results show that when the delay resolution reaches ps level, the phase synchronization accuracy of the system can reach 10 ps, which has the characteristics of small phase noise, low development cost, simple circuit structure, and high synchronization accuracy compared with the traditional phase synchronization technologies. Therefore, it would be widely used in satellite positioning, astrometry, precision navigation, aerospace, satellite launch, power transmission, communications, radar, and other high-tech fields.

We investigate the utilization of advanced single photons produced by quantum dots (QDs) in a microcavity for quantum metrology. Through the integration of lateral excitation and the Purcell effect in an Fabry–Perot microcavity, we realized single-photon emission with an extraction efficiency of 46.39%, high purity of 96.91%, and high indistinguishability of 98.32%. Our QD-generated single photons enabled the creation of high-quality NOON states (N = 2) for phase measurement, yielding an interference contrast of 79.79% and surpassing the standard quantum limit (SQL) with phase super-sensitivity. Our results underscore the immense potential of QD-derived single photons for propelling quantum metrology forward, facilitating enhanced precision measurements across diverse applications.

The aim of this study is to examine the influence of the variation of the intrinsic impedance on the phase of a Gaussian pulse during propagation through a biological tissue. This paper describes a method for varying the intrinsic impedance while retaining the characteristics of the propagation medium. The propagation medium is considered as the superposition of four semi-infinite layers each characterized by their thickness, their conductivity, and their dielectric constant. These last parameters, on which the intrinsic impedance depends, are functions of the pulsation of the medium. In this work, we will test the continuity of the phase shift of the signal at the level of interfaces of biological layers with respect to that of the starting point as the function of the excitation pulsation. Next, we are going to vary the intrinsic. Next, we examine the influence of the variation of the intrinsic impedance at the interface on the phase shift of the signal at that level. We will adopt the Finite Difference Time Domain (FDTD) method to simulate the propagation of a Gaussian pulse. This method which is validated in previous work showed robustness to obtained signals very close to the reality at the interfaces. For these two tests, we will notice that the variation of intrinsic impedance has no influence on the variation of the phase at the interfaces. [ABSTRACT FROM AUTHOR]

Large-aperture space telescopes have played an important role in space gravitational wave detection missions. Overcoming the influence of the space environment on interstellar laser distance measurement and realistic high-concentration laser distance measurement is one of the topics that LISA and Taiji are working hard on. It includes solar temperature, spatial stress relief, pointing shake and tilt, etc. However, when considering the impact of vibration on the telescope, both LISA and Taiji only consider the resonance impact of vibration on structural parts, which greatly ignores the impact of high-frequency micro-vibration on space ranging. This paper first considers space gravitational wave detection. Then, we establish the heterodyne interference model and demodulation algorithm of the optical phase-locked loop, and then introduce the vibration component for theoretical analysis. The results show that, although the resonance effect of low-frequency vibration on the system structure is avoided in space gravitational wave detection, the influence of high-frequency micro-vibration on heterodyne interference cannot be ignored. At the same time, we quantitatively analyze the influence efficiency of amplitude and frequency; in the premise of small amplitudes, the influence of vibration frequency is related to the frequency of the heterodyne signal, which has important guiding significance in engineering. [ABSTRACT FROM AUTHOR]

With growing interest in EUV attenuated phase-shift masks due to their superior image quality for applications such as dense contact and pillar arrays, it is becoming critical to model, measure, and monitor the intensity and relative phase of multilayer and absorber reflections. We present a solution based on physical modeling of reflectometry data, which can achieve single picometer phase precision and sensitivity to changes in average film thickness below one atomic monolayer. We measure absorber and multilayer reflectivity to determine thin-film parameters with a multidimensional optimization and then acquire a new measurement of either multilayer or absorber to determine perturbations in surface contamination thickness. While it is difficult to assess the accuracy of the first step, the simplicity of the second step allows us to characterize our sensitivity to changes in contamination thickness. We apply this analysis using an initial set of measurements and repeated measurements after a period of storage. For the multilayer, the total contamination growth was 1068 pm, which occurred almost exclusively during storage (1085 pm) and decreased very slightly during repeated measurements (-17 pm). For the absorber, the behavior was quite different, with a total growth of 126 pm, which occurred much less during storage (28 pm) and primarily during repeated measurements (98 pm). Ultimately, the change in relative phase (absorber minus multilayer) was -0.86 deg for the multilayer and -1.12 deg for the absorber. We estimate the precision of the surface contamination measurement to be 3σ < 6 pm for measuring thickness and 3σ < 0.2 deg for measuring phase.

In unmanned aerial vehicle (UAV)-based time difference of arrival (TDOA) positioning technique, baselines are limited due to communication constraints. In this case, the accuracy is highly sensitive to the TDOA measurements’ error. This article primarily addresses the problem of short-baseline high-precision time synchronization and TDOA measurement. We conducted a detailed analysis of error models in TDOA systems, considering both the time and phase measurement. We utilize the frequency division wireless phase synchronization technique in TDOA systems. Building upon this synchronization scheme, we propose a novel time delay estimation method that relies on phase measurements based on the integer least squares method. The performance of this method is demonstrated through Monte Carlo simulations and outdoor experiments. The standard deviations of synchronization and TDOA measurements in experiments are 1.12 ps and 1.66 ps, respectively. Furthermore, the circular error probable (CEP) accuracy is improved from 0.33%R to 0.02%R, offering support for the practical application of distributed short-baseline high-precision passive location techniques.

Aiming at the problems of high system cost, complex ranging process, low ranging accuracy, and limited measurement distance in commonly used methods for ground fixed point distance measurement journals, a variable frequency microwave ranging system based on a dual transponder architecture is proposed in this letter. The system uses carrier dual transponder as an active forwarding architecture, utilizing the digital phase‐locked loop to obtain the high‐precision phase difference between two signals, and resolving the ambiguity through microwave frequency sweep within a certain range. The simulation results show that the system can quickly obtain the unambiguous distance between two fixed points, besides, driven by a high‐stability crystal oscillator, submillimetre accuracy can be achieved in km‐level ranging. [ABSTRACT FROM AUTHOR]

This article presents the first demonstration of navigation with cellular signals of opportunity (SOPs) on a high-altitude aircraft. An extensive flight campaign was conducted by the Autonomous Systems Perception, Intelligence, and Navigation Laboratory in collaboration with the U.S. Air Force to sample ambient downlink cellular SOPs in different regions in Southern California, USA. Carrier phase measurements were produced from these signals, which were subsequently fused in an extended Kalman filter along with altimeter measurements to estimate the aircraft’s state (position, velocity, and time). Three flights are performed in three different regions: 1) rural, 2) semiurban, and 3) urban. A multitude of flight trajectories and altitudes above ground level (AGL) was exercised in the three flights: 1) a 51-km trajectory of grid maneuvers with banking and straight segments at about 5,000 ft AGL, 2) a 57-km trajectory of a teardrop descent from 7,000 ft AGL down to touchdown at the runway, and 3) a 55-km trajectory of a holding pattern at about 15,000 ft AGL. The estimated aircraft trajectory is computed for each flight and compared with the trajectory from the aircraft’s onboard navigation system, which utilized a GPS receiver coupled with an inertial navigation system and an altimeter. The cellular SOPs produced remarkable sustained navigation accuracy over the entire flight trajectories in all three flights, achieving a 3D position root mean-squared error of 10.53 m, 4.96 m, and 15.44 m, respectively. [ABSTRACT FROM AUTHOR]

Two-dimensional phase unwrapping (PU) is an essential step in interferometric synthetic aperture radar (InSAR) analysis. Although the $L^{0}$ -norm PU method is desired, it is nondeterministic polynomial (NP)-hard. Thus, many PU methods have been proposed to find near-optimal solutions of the $L^{0}$ -norm. As PU is an ill-posed problem, it is difficult to choose the method with the most accurate solution unless reference data are available. In this letter, we prove that the NP-hardness of the $L^{0}$ -norm is weak, suggesting that the $\alpha $ -approximation algorithm of the $L^{0}$ -norm can be devised, that is, the obtained near-optimal solutions can be within a factor of $\alpha $ of the $L^{0}$ -norm optimal value. The primary contribution of the proof is that the $\alpha $ value of each obtained PU solution can be considered as a new index to assess the PU performance without using reference data. The validity and effectiveness of the $\alpha $ -based index have been verified using simulated and acquired interferometric datasets and three PU methods. [ABSTRACT FROM AUTHOR]

We propose a new single-shot digital holography that measures the complex amplitude high precisely using a single image sensor. In this technology, a signal beam passes through a diamond-shaped low-pass filter, and a reference beam passes through a chessboard pattern phase-shift plate, where the phase difference between adjacent pixels is π/2. The signal and reference beams interfere, and the interference fringe is captured by a single image sensor. In a computer, an image is acquired by extracting the phase-dependent component from the interference fringe. The real and imaginary parts were obtained separately from the inside and outside of the diamond shape in the Fourier plane of the acquired image, respectively. Subsequently, the real and imaginary parts were combined to reconstruct the complex amplitude. This method can obtain the signal light in the diamond-shaped band of the Fourier plane, where the information of the signal light is concentrated generally, so this method can measure high precisely. Numerical analysis showed that the signal-to-noise ratio of the intensity and phase of this method were more than 4.8 and 2.8 dB higher, respectively, than two-step parallel phase-shift digital holography, and more than 7.3 and 4.8 dB higher, respectively, than Fourier fringe analysis, an off-axis digital holography technique. Moreover, the range of the reference intensity that maintains high-precision measurements was clarified, and the reconstruction accuracy against noise in the interference fringe or reference beam intensity was investigated. [ABSTRACT FROM AUTHOR]

Distance measurement based on the accumulated phase of intensity-modulated continuous-wave lasers is an established approach for pointwise geometry acquisition in uncontrolled conditions, enabling some of the most accurate Lidar/laser-scanning solutions. Inherently affected by cycle ambiguities due to the modulo 2 π phase observations, several modulation wavelengths are typically used in practical implementations to extend the measurement range. One of the main limitations of these systems arises from their inability to decouple mixed signals affected by different delays. This is especially relevant when the laser beam illuminates simultaneously two or more surfaces at significantly different distances, producing mixed-pixel measurements in which the estimated distance does not reliably correspond to any of the involved scatterers. Algorithms for detection and filtering of mixed pixels within point-cloud data have been proposed based on analyzing consistency across local neighborhoods. The resolution of multiple scatterers on individual measurements, however, has not been yet reported nor is provided by undisclosed commercial implementations. In this work, we analyze the problem of signal mixing in multi-wavelength phase-based distance estimation, and propose an algorithm for joint phase ambiguity resolution and mixed pixel detection based on mixed integer linear programming. We first analyze theoretically the performance limits of the proposed solution, demonstrating unbiasedness in the presence of noise and robustness in the presence of multiple scatterers. In addition, we investigate empirically the impact of noise, mixed measurements and choice of modulation wavelengths on the performance of the proposed algorithm. The results demonstrate the capacity of the presented approach, given an adequate wavelength selection, to provide unambiguous distance estimates under realistic noise conditions and to identify measurements affected by mixed pixels while approximating the position of the dominant scatterer. Aside from contributing to improving the reliability and resolution capability of Lidar and laser-scanning data, the proposed solution sets a promising step towards fully resolved multi-target distance measurement. [ABSTRACT FROM AUTHOR]

In a recent work, a technique was proposed to recover the absolute phase maps of fringe patterns with two or three selected fringe wavelengths with the aim to improve anti-error capability. To further increase the anti-error capability associated with the phase unwrapping operation, multiple fringe patterns with different wavelengths may also be used. In this paper, we present a general rule to select the wavelengths and the strategy to increase phase error tolerance bound. Based on this rule, it is concluded that to maximize the error tolerance, four-wavelength method should be selected, where the maximum upper bound of the tolerable phase error is π/6. To minimize the required number of fringe patterns, three-wavelength method with three-step PSP should be selected, that is exactly the case the previous paper has demonstrated. These theoretical conclusions are verified by experimental results. [ABSTRACT FROM AUTHOR]

In case of in-line inspection of optical functional micro-structured surfaces with phase response as well as amplitude response, higher resolution than the diffraction limit and phase measurability are needed. We proposed a novel coherent super-resolution method named complex-amplitude-response SIM (structured illumination microscopy). An equation is derived that enables extraction of frequencies higher than the diffraction limit of the complex-amplitude response distribution of a sample from multiple acquired images, which had not been obtained previously. This equation was validated through theoretical analysis by using images calculated by numerical optical simulation that were assumed to be acquired. Numerical analyses using the derived equation and simulations of image acquisition revealed that the proposed method is able to measure phase- and amplitude-response distributions of samples with a resolution higher than the diffraction limit. It was demonstrated that the proposed method is able to separate two points at a submicron distance of 500 nm under conditions of visible light and long W.D. (NA 0.2) and measure the phase difference with a maximum error of approximately 0.03 rad (∼π/100). When the amplitude response distribution of a sample is uniform and consists only of phase responses, the structure of the sample cannot be observed by standard optical microscopy. Numerical simulations revealed that the proposed method is able to visualise such samples with fine periodic phase responses on the submicron scale (∼500 nm) beyond the diffraction limit. Furthermore, we have shown that the proposed method is able to detect phase defects in ultra-fine optical functional structures with periods of less than 100 nm, which is expected to characterise the next generation metasurfaces. • Long working distance optical measurement of submicron-structured surfaces with amplitude and phase response distributions. • The proposed method enables extraction of high frequencies of a sample beyond the diffraction limit not only for amplitude but also phase response measurement. • Visualisation of fine periodic phase structures under constant amplitude distribution condition beyond the diffraction limit. • Phase defect of 20 nm in ultra-fine periodic phase structures can be detected in long working distance measurement. [ABSTRACT FROM AUTHOR]

This article presents a method for calculating all the proportional–integral/proportional–derivative controllers with a low-pass filter of a given order, which satisfy gain–phase margins and sensitivity (or complementary sensitivity) specifications. The method is explicit and requires solving a set of a polynomial and two linear equations. It is shown how to extend the method to design all the proportional–integral–derivative or cascaded controllers with a low-pass filter assuming that a minimum value of one of the controller components is given. [ABSTRACT FROM AUTHOR]

A novel radio frequency (RF) phase measurement method that uses optical modulation was proposed. The mathematical model of Mach–Zehnder modulator (MZM) characterization was reviewed. By measuring the output sideband power of the optical modulator, the phase difference of the electric signals fed to the modulator was experimentally measured, and picosecond-level accuracies were achieved. This technique is expected to be useful for radio-over-fiber-based antenna array systems. [ABSTRACT FROM AUTHOR]

Ellipsometric Surface Plasmon Resonance (SPR) sensors are known for their relatively simple optical configuration compared to interferometric and optical heterodyne phase interrogation techniques. However, most of the previously explored ellipsometric SPR sensors based on intensity measurements are limited by their real-time applications because phase or polarization shifts are conducted serially. Here we present an ellipsometric SPR sensor based on a Kretschmann–Raether (KR) diverging beam configuration and a pixelated microgrid polarization camera. The proposed methodology has the advantage of real-time and higher precision sensing applications. The short-term stability of the measurement using the ellipsometric parameters tan ψ and cos (Δ) is found to be superior over direct SPR or intensity measurements, particularly with fluctuating sources such as laser diodes. Refractive index and dynamic change measurements in real-time are presented together with Bovine Serum Albumin (BSA)–anti-BSA antibody binding to demonstrate the potential of the developed sensor for biological sensing applications with a resolution of sub-nM and down to pM with additional optimization. The analysis shows that this approach may provide the ultimate detection limit for SPR sensors. [ABSTRACT FROM AUTHOR]

Abstract Aiming at the problems of high system cost, complex ranging process, low ranging accuracy, and limited measurement distance in commonly used methods for ground fixed point distance measurement journals, a variable frequency microwave ranging system based on a dual transponder architecture is proposed in this letter. The system uses carrier dual transponder as an active forwarding architecture, utilizing the digital phase‐locked loop to obtain the high‐precision phase difference between two signals, and resolving the ambiguity through microwave frequency sweep within a certain range. The simulation results show that the system can quickly obtain the unambiguous distance between two fixed points, besides, driven by a high‐stability crystal oscillator, submillimetre accuracy can be achieved in km‐level ranging.

Indoor air movement affects many functions of buildings, including ventilation and air quality, comfort and health of occupants, fire safety, and building energy use. Accurately measuring air movement has been difficult and expensive over extended periods of time, especially for velocities below 1 m/s. A new type of high frequency ultrasonic transceiver provides high sensitivity measurements and low cost through microelectromechanical systems (MEMS) manufacturing. However, at high frequencies, conventional ultrasonic signal processing algorithms function only over small ranges of ambient temperature and velocity. In this paper, we describe three algorithms that use the complex phase angle of an ultrasonic pulse to measure velocity and temperature over extended ranges of temperature and velocity. They employ heuristics to track the vibration cycle of the measured phase angle. These methods are applied in a pulse-based anemometer whose 176kHz MEMS transceivers both transmit and receive. In wind tunnel tests between 0-4 m/s, the tracking algorithm with a low-pass filter measured air speed with high sensitivity and accuracy (0.026 m/s mean absolute error). The ability to monitor to this accuracy with such low power draw and low cost is currently unprecedented in the industry.

The article presents the results of experimental studies of mutual high-precision navigation methods for unmanned and specialized transport systems. The proposed methods are based on the application of the relative operating modes of two or more angle-measuring receivers of global navigation satellite systems signals. To conduct research, a software and hardware complex has been developed, consisting of two angle-measuring receivers of global navigation satellite systems signals, a turntable and a computer model of the navigation system of unmanned and specialized transport systems. It provides the positioning error of the antenna system in angular coordinates less than 1 arc minute, which allows it to be used as a reference when measuring the angular displacements of the receiver of global navigation satellite systems signals antenna system. The results of measurements of planar and angular coordinates both in autonomous and relative phase modes of operation of goniometric receivers global navigation satellite systems signals are presented and analyzed. It has been established that the root-mean-square error of measuring relative coordinates was 0,019 meter. A further increase in the relative position measurement accuracy is possible by taking measures to reduce the multipath reception error, which is the most significant uncorrelated position measurement error by two sets of receivers of global navigation satellite systems signals. Thus, the methods of mutual high-precision navigation using angle-measuring receivers of global navigation satellite systems signals have high accuracy without the use of external information about differential corrections. This will allow the operation of unmanned or special transport systems in hard-toreach and northern regions, in conditions of lack of communication and other adverse factors.

Tracking the myotendinous junction (MTJ) motion in consecutive ultrasound images is essential to assess muscle and tendon interaction and understand the mechanics’ muscle-tendon unit and its pathological conditions during motion. However, the inherent speckle noises and ambiguous boundaries deter the reliable identification of MTJ, thus restricting their usage in human motion analysis. This study advances a fully automatic displacement measurement method for MTJ using prior shape knowledge on the Y-shape MTJ, precluding the influence of irregular and complicated hyperechoic structures in muscular ultrasound images. Our proposed method first adopts the junction candidate points using a combined measure of Hessian matrix and phase congruency, followed by a hierarchical clustering technique to refine the candidates approximating the position of the MTJ. Then, based on the prior knowledge of Y-shape MTJ, we finally identify the best matching junction points according to intensity distributions and directions of their branches using multiscale Gaussian templates and a Kalman filter. We evaluated our proposed method using the ultrasound scans of the gastrocnemius from 8 young, healthy volunteers. Our results present more consistent with the manual method in the MTJ tracking method than existing optical flow tracking methods, suggesting its potential in facilitating muscle and tendon function examinations with in vivo ultrasound imaging. [ABSTRACT FROM AUTHOR]

Fourier phase retrieval is a classical problem of restoring a signal only from the measured magnitude of its Fourier transform. Although Fienup-type algorithms, which use prior knowledge in both spatial and Fourier domains, have been widely used in practice, they can often stall in local minima. Convex relaxation methods such as PhaseLift and PhaseCut may offer performance guarantees, but these algorithms are usually computationally expensive for practical use. To address this problem, here we propose a novel unsupervised feed-forward neural network for Fourier phase retrieval which generates high quality reconstruction immediately. Unlike the existing deep learning approaches that use a neural network as a regularization term or an end-to-end blackbox model for supervised training, our algorithm is a feed-forward neural network implementation of physics-driven constraints in an unsupervised learning framework. Specifically, our network is composed of two generators: one for the phase estimation using PhaseCut loss, followed by another generator for image reconstruction, all of which are trained simultaneously without matched data. The link to the classical Fienup-type algorithms and the recent symmetry-breaking learning approach is also revealed. Extensive experiments demonstrate that the proposed method outperforms all existing approaches in Fourier phase retrieval problems. [ABSTRACT FROM AUTHOR]

Accurate and real-time measurement of water cut (WC) and flowrate of oil–water flow is a critical factor in achieving intelligent digital oil field. In this article, a dual-parameter (WC and water flowrate) measurement method for oil–water flow is proposed based on a Venturi embedded with microwave transmission line sensor (V&MS). Dynamic experiments of horizontal fine dispersed oil–water flow are conducted. A two-dimensional finite element simulation model for V&MS under the fine dispersed flow is developed to simulate microwave phase outputs at 0%–100% WC. The simulation results agree with the experiments, providing a low-cost alternative to expensive oil–water dispersed flow tests. Furthermore, it is found that the flow patterns for 0%–10% WC and 40%–100% WC are water-in-oil and oil-in-water flows, respectively, but the flow patterns for 10%–40% WC are dispersions of water-in-oil and oil-in-water flow, and 20% WC is the transition point of the dominant continuous phase. When the water phase is continuous, V&MS has a higher sensitivity to phase signals. Finally, a WC prediction model (40%–100%) is developed by combining a modified Bruggeman model with microwave transmission line theory. Then, a discharge coefficient model is developed and the water flowrate is obtained by combining the pressure drop and the predicted WC. The absolute average relative deviation (AARD) of the predicted WC and water flowrate is 1.49% and 1.54%, respectively. The results suggest that appropriate sensing technology integration can offer a powerful solution for accurate and real-time determination of dual-parameter in oil–water flow systems. [ABSTRACT FROM AUTHOR]

NOON states are entangled states of great interest in the development of quantum technologies, because they enable high‐precision phase measurements in interferometric schemes relevant to quantum metrology and sensing. This study shows that two degenerate modes of a cavity field coupled to an atom or molecule that can be modeled as a two‐level system through two‐photon interactions, initially prepared in a (generalized) NOON state, experience a dynamical evolution that distinctly depends on the parity of the photon number. When the total photon number is even, the system dynamics is characterized by a time range in which the state of the system evolves near maximally entangled states that may be fed to an optical interferometer to make phase measurements essentially at the Heisenberg limit. Such entangled states cannot be achieved for odd photon numbers instead. The parity effect thus emerges as a potential control factor in quantum metrology, sensing, and lithography. [ABSTRACT FROM AUTHOR]

In phase-contrast magnetic resonance imaging (PC-MRI), spin velocity contributes to the phase measured at each voxel. Therefore, estimating velocity from potentially wrapped phase measurements is the task of solving a system of noisy congruence equations. We propose Phase Recovery from Multiple Wrapped Measurements (PRoM) as a fast, approximate maximum likelihood estimator of velocity from multi-coil data with possible amplitude attenuation due to dephasing. The estimator can recover the fullest possible extent of unambiguous velocities, which can greatly exceed twice the highest venc. The estimator uses all pairwise phase differences and the inherent correlations among them to minimize the estimation error. Correlations are directly estimated from multi-coil data without requiring knowledge of coil sensitivity maps, dephasing factors, or the actual per-voxel signal-to-noise ratio. Derivation of the estimator yields explicit probabilities of unwrapping errors and the probability distribution for the velocity estimate; this, in turn, allows for optimized design of the phase-encoded acquisition. These probabilities are also incorporated into spatial post-processing to further mitigate wrapping errors. Simulation, phantom, and in vivo results for three-point PC-MRI acquisitions validate the benefits of reduced estimation error, increased recovered velocity range, optimized acquisition, and fast computation. A phantom study at 1.5T demonstrates 48.5% decrease in root mean squared error using PRoM with post-processing versus a conventional “dual-venc” technique. Simulation and 3T in vivo results likewise demonstrate the proposed benefits. [ABSTRACT FROM AUTHOR]

This article proposes an online diagnosis scheme for transistor faults of asymmetric half-bridge converter (AHBC) in switched reluctance motor (SRM) drives. In order to extract more information from the phase current to identify faults, based on the conventional current measurement method, two novel current measurement methods are presented by reconstructing current sensors. According to the novel current measurement methods, a current prediction method is raised. The phase current at the kth sampling time is available so that the estimated current can be calculated. The fault can be detected and located by analyzing the given and actual switching states, which are deduced by comparing the measured and estimated currents. Compared with existing methods, the proposed scheme can be applied to diagnosis of multiple faults in n-phase AHBC, which can operate at various control strategies and chopping modes. With a single current sensor in each phase, the scheme will not increase the cost and complexity of the SRM drive. Furthermore, the scheme does not require complicated computation, making it easy to implement online. The experimental results confirm the effectiveness and flexibility of the proposed scheme. [ABSTRACT FROM AUTHOR]

From the actual development and testing requirements of horizontal wells in domestic oilfields, according to the problems that the common sensors have relatively low resolution during the water cut measurement for the oil–water flow in the horizontal wells with medium and low production, a trielectrode capacitance sensor (TECS) is designed and a water cut measurement system based on TECS is developed for different conditions of horizontal oil–water flow. Specifically, the electrostatic field distribution of the annular measurement region is investigated under different conditions of horizontal stratified flow. Then, its equivalent capacitance on the electrodes is analyzed. Based on the simulated results, the effects of structural parameters on sensitivity distribution are analyzed, including the electrode length, the radius of the flow channel, and the thickness of the insulation, determining its optimal structure. Moreover, the static and dynamic experiments, as well as the field testing, validate the designed TECS, indicating that the TECS enables measuring the water cut of horizontal oil–water flow, especially under low flow rate and oil–water stratified conditions. The developed TECS could realize the water cut measurement with a wide flow rate range (3–60 m $^3$ /d) and the full water cut range (0%–100%) for the horizontal oil–water flow. [ABSTRACT FROM AUTHOR]

Wireless telecommunication technology is evolving fast. Driven by an insatiable demand for higher data rates, the modulated signals that are being transmitted and received over the air and through space are growing in bandwidth and use ever higher carrier frequencies. The 6G visionaries are setting goals of 30 GHz of modulation bandwidth at a carrier frequency of 300 GHz and achieving a mind-boggling data rate of 11 Gb/s. At the heart of this technological evolution of the wireless telecommunications industry are billions of high-frequency active components: amplifiers, mixers, and frequency converters. These active components are necessary for the amplification and frequency conversion of the modulated signals. These components are not perfect, and the modulated signal deteriorates as it passes through the active component semiconductor core. [ABSTRACT FROM AUTHOR]

This letter presents a scalable multipolarized planar phased array for the low earth orbit satellite communication application. A dual-polarized aperture-coupled patch element antenna is proposed for designing the array, which can provide dual-linear polarization (LP) and dual-circular polarization (CP). The rotated feed technique is adopted to reduce the cross-polarization level. By using 8-channel beamformer chips and the multilayer printed circuit board technology, a phased array prototype with good electromagnetic shielding performance, high integration, and low cost is designed, fabricated, and measured. For dual-LP radiation, it steers up to the scan angles (±50°) with a scan loss less than 3.5 dB, and a cross-polarization level lower than −30 dB in azimuth/elevation plane and −15 dB in diagonal plane. For dual-CP radiation, it steers up to the scan angle (±50°) with a scan loss less than 3 dB and an axial ratio less than 3 dB. The phased array developed in this letter can be scaled to larger arrays and provides feasibility for the production of low-cost phased arrays. [ABSTRACT FROM AUTHOR]

This article presents a novel built-in test equipment (BITE) for phase measurements in millimeter-wave integrated circuits (ICs). The BITE targets 5G New Radio (NR) applications. It is able to measure the phase in good agreement with $\mathbf {S_{21}}$ measurements and has a relative rms phase error lower than 6° over the frequency band of interest. Aside from the relative phase, this BITE also addresses the absolute phase difference of all ICs on the same phased array. To the authors’ best knowledge, this is the first BITE and built-in self-test (BIST) to do so. The BITE is able to reduce the absolute phase discrepancy by a factor of 3. To reduce the measurement complexity, the BITE is implemented as a homodyne architecture to output a dc voltage relative to the phase of the channel. A built-in algorithm is used, mitigating the impairments normally associated with a homodyne receiver. This reduces the design complexity and hence the area overhead. The BITE occupies an area of 480 $\mathbf {\mu m} \times 135\,\,\mathbf {\mu m}$ , facilitating easy integration. [ABSTRACT FROM AUTHOR]

Inadequate drying and overdrying of grains due to the absence of timely and reliable information on moisture content (MC) aggravates grain postharvest loss. In this study, we investigate the real-time acquisition of MC using microwave free-space transmission measurements. A multifrequency swept signal is used to acquire the attenuation and phase-shift spectrum (2.00–10.00 GHz) of the paddy samples (9.553%–29.633% w.b.) for six thicknesses (1–6 cm). Based on the four rules that are followed in the phase-shift measurement, a phase-shift correction algorithm without any restrictions on the sample thickness is proposed to solve the phase-shift ambiguity that occurs when the sample thickness exceeds the wavelength. To choose the most effective frequencies, 17 candidate frequency subsets are generated by the recursive feature elimination algorithm, and the optimal frequency set, containing eight individual frequencies, is selected by using the Friedman and Nemenyi post hoc tests. The sample thickness and microwave characteristics are used as the input variables to establish the prediction models to achieve a thickness-independent measurement of the MC, and the support vector machine model yielded the best performance ($R^2$ = 0.992, RMSE = 0.555%, and MAE = 0.398%). The results of this study should encourage future research on the real-time acquisition of reliable MC information in food processing and agriculture-related industries. [ABSTRACT FROM AUTHOR]

Conventional sparse phase retrieval schemes can recover sparse signals from the magnitude of linear measurements only up to a global phase ambiguity. This work proposes a novel approach that instead utilizes the magnitude of affine measurements to achieve ambiguity-free signal reconstruction. The proposed method relies on two-stage approach that consists of support identification followed by the exact recovery of nonzero signal entries. In the noise-free case, perfect support identification using a simple counting rule is guaranteed subject to a mild condition on the signal sparsity, and subsequent exact recovery of the nonzero signal entries can be obtained in closed-form. The proposed approach is then extended to two noisy scenarios, namely, sparse noise (or outliers) and non-sparse bounded noise. For both cases, perfect support identification is still ensured under mild conditions on the noise model, namely, the support size for sparse outliers and the power of the bounded noise. Under perfect support identification, exact signal recovery can be achieved using a simple majority rule for the sparse noise scenario, and reconstruction up to a bounded error can be achieved using linear least-squares (LS) estimation for the non-sparse bounded noise scenario. The obtained analytic performance guarantee for the latter case also sheds light on the construction of the sensing matrix and bias vector. In fact, we show that a near optimal performance can be achieved with high probability by the random generation of the nonzero entries of the sparse sensing matrix and bias vector according to the uniform distribution over a circle. Computer simulations using both synthetic and real-world data sets are provided to demonstrate the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

In the phase retrieval problem one seeks to recover an unknown $n$ dimensional signal vector $\mathbf {x}$ from $m$ measurements of the form $y_{i} = |(\mathbf {A} \mathbf {x})_{i}|$ , where $\mathbf {A}$ denotes the sensing matrix. Many algorithms for this problem are based on approximate message passing. For these algorithms, it is known that if the sensing matrix $\mathbf {A}$ is generated by sub-sampling $n$ columns of a uniformly random (i.e., Haar distributed) orthogonal matrix, in the high dimensional asymptotic regime ($m,n \rightarrow \infty, n/m \rightarrow \kappa $), the dynamics of the algorithm are given by a deterministic recursion known as the state evolution. For a special class of linearized message-passing algorithms, we show that the state evolution is universal: it continues to hold even when $\mathbf {A}$ is generated by randomly sub-sampling columns of the Hadamard-Walsh matrix, if the signal is drawn from a Gaussian prior. [ABSTRACT FROM AUTHOR]

Phase unwrapping is the prerequisite to obtain the true phase in interferometric fiber sensing. This article proposes a method based on an unscented Kalman filter (UKF) for interferometric fiber sensors. This method can break the limitation that the traditional phase unwrapping methods fail with a high probability when the differences in phase change are more than $\pi $ radians according to the Itoh criterion. Then, the measurement range of the phase signal can be expanded. This method combines the true phase and the phase gradient into the state vector estimation for UKF. The feasibility of this method is verified theoretically and experimentally. In the specific experiment, the phase signal with a maximum absolute phase difference of $1.5\pi $ (about 4.705) between adjacent sampling points can be recovered perfectly. The time and frequency domain results using this method show better performance. This method can effectively improve the detection range of the system and reduce the sampling rate to a certain extent, which is suitable for large-scale array systems. [ABSTRACT FROM AUTHOR]

We present measurements and analysis of self-interference in multi-panel millimeter wave (mmWave) full-duplex communication systems at 28 GHz. In an anechoic chamber, we measure the self-interference power between the input of a transmitting phased array and the output of a colocated receiving phased array, each of which is electronically steered across a number of directions in azimuth and elevation. These self-interference power measurements shed light on the potential for a full-duplex communication system to successfully receive a desired signal while transmitting in-band. Our nearly 6.5 million measurements illustrate that more self-interference tends to be coupled when the transmitting and receiving phased arrays steer their beams toward one another but that slight shifts in steering direction (on the order of one degree) can lead to significant fluctuations in self-interference power. We analyze these measurements to characterize the spatial variability of self-interference to better quantify and statistically model this sensitivity. Our analyses and statistical results can be useful references when developing and evaluating mmWave full-duplex systems and motivate a variety of future topics including beam selection, beamforming codebook design, and self-interference channel modeling. [ABSTRACT FROM AUTHOR]

Ground-based positioning systems (GBPSs), such as cellular networks and pseudolites, can provide high-precision positioning services through carrier phase positioning (CPP). Most existing methods are based on having accurate coordinates of all transmitters (TXs). In some applications, however, it could be too expensive and time-consuming to measure the coordinates of all TXs accurately, and requiring precise manual measurements severely degrades the flexibility of GBPSs. In this paper, we propose a carrier phase based autonomous coordinate evolution (CPACE) method for GBPSs, which uses the observations of multiple users to continuously improve the accuracy of TX coordinates. We first propose a Batch CPACE (B-CPACE) method and analyze its theoretical advantages over traditional single-point positioning (SPP). In the case of a large number of users, to avoid heavy burden on data transmission and calculation, we propose two distributed CPACE (D-CPACE) methods which have the same asymptotic performance with B-CPACE. Our numerical simulations prove that both B-CPACE and D-CPACE have better accuracy than SPP and reach the Cramer-Rao lower bounds. A real-world experiment shows that the proposed method can achieve centimeter-level accuracy. [ABSTRACT FROM AUTHOR]

Phase methods of measuring physical quantities and phase measuring equipment are widely used in various fields of science and technology. The article proposes a signal processing methodology based on a combination of the discrete Hilbert transform (DHT) and deterministic, as well as statistical methods of phase measurement. This methodology makes it possible to more fully use the information resource of the measuring signal phase in a wide range of the signal-to-noise ratio. It can be used both in computerized measurement and testing systems, as well as in the processing of measurement data. The benefits of the DHT are considered. The possibility of using statistics of directional data for phase measurements is shown. Circular statistics, such as the mean ring value, circular variance and the resulting vector length, were proposed for use in the phase measurements. Some examples of the use of this methodology in measurements and non-destructive testing are given.

Abstract The use of nanometre fiso interferometer to measure heterodyne interference signals at the same time for phase and phase element detection and phase‐locked frequency multiplication counting is employed here. After a certain logic mixing, a set of measurement results with a certain degree of redundancy can be obtained; the test results can be measured and resolved. The rate is better than 0.1 nm, and the measurement range is not limited by the λ/2 period, thus overcoming the previous problems that is the measurement range of the phase measurement method is limited to one period and the resolution of the phase‐locked frequency multiplication counting method is not easy to improve.

Large-aperture space telescopes have played an important role in space gravitational wave detection missions. Overcoming the influence of the space environment on interstellar laser distance measurement and realistic high-concentration laser distance measurement is one of the topics that LISA and Taiji are working hard on. It includes solar temperature, spatial stress relief, pointing shake and tilt, etc. However, when considering the impact of vibration on the telescope, both LISA and Taiji only consider the resonance impact of vibration on structural parts, which greatly ignores the impact of high-frequency micro-vibration on space ranging. This paper first considers space gravitational wave detection. Then, we establish the heterodyne interference model and demodulation algorithm of the optical phase-locked loop, and then introduce the vibration component for theoretical analysis. The results show that, although the resonance effect of low-frequency vibration on the system structure is avoided in space gravitational wave detection, the influence of high-frequency micro-vibration on heterodyne interference cannot be ignored. At the same time, we quantitatively analyze the influence efficiency of amplitude and frequency; in the premise of small amplitudes, the influence of vibration frequency is related to the frequency of the heterodyne signal, which has important guiding significance in engineering.

A new far-field valid angle equation for rectilinear planar near-field measurements is derived. The new valid angle equation is derived by viewing the near-field to far-field transformation process as the generation of a pseudo plane wave by a synthetic phased array and subjecting the antenna-under-test (AUT) to the radiation from this synthetic array. The synthetic phased array does not physically exist; rather, the array is formed during the postprocessing of the planar near-field measurements. The resultant valid far-field angle computed with the new equation is compared against previously established and popularly accepted valid angle equations. A brief discussion is offered on the measurement of low-directivity antennas with a planar near-field measurement system and on amplitude tapering of the near-field measurements to improve the quality of the pseudo plane wave inside the test zone. [ABSTRACT FROM AUTHOR]

This communication presents a millimeter-wave wideband dual-polarized low-temperature cofired ceramics (LTCC) antenna array based on metasurfaces (MSs) for beam-scanning applications. Benefiting from the wideband and large-freedom property of MS-based structures, a novel ±45° dual-polarized wideband MS-based antenna (MSA) element with high isolation is designed. The antenna element is fed by two orthogonal striplines on different layers, through a crosslike dog-bone slot and a narrow slot, respectively, to realize the two polarizations. The feeding structure consists of slot–stripline–slot–stripline from top to bottom and is specially designed to improve the polarization isolation of the antenna element. The proposed MSA element is compactly arranged with a small distance ($ < 0.5\lambda$) to construct a 4 $\times $ 4 array integrated in an LTCC package, where via walls with metal ring strips are loaded between adjacent elements to reduce the gain fluctuation. Consequently, the array can achieve a good beam-scanning capability over a wide band of 19.5% with a maximum scanning angle up to ±55° and a small gain variation of less than 3 dB. Meanwhile, the active $S$ parameters almost always remain below −10 dB, enabling good impedance matching when scanning at all angles. With these features, the proposed design has potential for application in 5G base-station systems. [ABSTRACT FROM AUTHOR]

A physics-assisted deep learning framework to perform accurate indoor imaging using phaseless Wi-Fi measurements is proposed. It can image objects that are larger than wavelength and have high permittivity that existing radio frequency (RF) inverse scattering techniques find very challenging. The technique utilizes a Rytov-based inverse scattering model and deep learning. The inverse scattering model is based on an extended Rytov approximation (xRA) that prereconstructs RF measurements. Under strong scattering conditions, this prereconstruction is related to the actual permittivity profile by a nonlinear function, which is learned by a modified U-Net model to obtain the permittivity profile. Thus, our proposed approach both reconstructs the shape of objects and estimates their permittivity values accurately. We demonstrate its performance using simulations and experiment results in actual indoor environments using 2.4 GHz Wi-Fi phaseless measurements. For incident wavelength $\lambda _{0}$ , the framework can reconstruct objects with permittivity as high as 77 and electrical size up to $40~\lambda $ , where $\lambda =\lambda _{0}/\sqrt {77}$ as opposed to existing phaseless techniques, which cannot reconstruct permittivity beyond 3 or 4. Thus, our proposed method is the first inverse scattering-based deep learning framework, which can image large scatterers with high permittivity and achieve accurate indoor RF imaging using phaseless Wi-Fi measurements. [ABSTRACT FROM AUTHOR]