Phase Difference Of Signals Research Articles

Implementing the procedure of measurement phase difference of the model signals using a virtual laboratory practicum

As this virtual laboratory practicum, which is a tool for mastering theoretical principles and practical skills in digital signal processing, was developed, users (mainly students) were given the possibility to parameterize harmonic signals. It includes the determination of the number of samples, sampling rate, amplitudes, initial phases, and other characteristics necessary for accurate metrological measurements. This publication presents the structure of the virtual workshop and the mathematical model underlying it, with an emphasis on aspects of analyzing the procedures for measuring the phase difference of harmonic signal models using the Discrete Fourier Transform. Particular attention is focused on the phase correction algorithm, which is aimed at improving the accuracy of measurements of the phase difference of signals. The presented methodology describes in detail the measurement process, estimation of errors arising from limited measurement time due to non-synchronization, the influence of the initial phase values of signals, and shows how the synchronization process contributes to a significant increase in the accuracy of measuring informative parameters.

Application of Artificial Intelligence Technology in Optimizing Control Parameters of Traffic Signal Group Systems

On the basis of introducing the concept of intersection signal state phase difference, the author proposes a proportional signal phase difference design scheme for traffic signal system control, on the basis of the HCM signal delay calculation formula, a standardized signal cycle and effective green signal ratio optimization design model were compiled, thus forming a complete set of optimization design modes for the control parameters of the urban main road traffic signal group system. The experimental results indicate that, the entire simulation experiment took 6000 seconds to compare the traditional fuzzy algorithm with the controller implemented by the author's fuzzy neural network, each case was simulated 5 times, the data in the Table is the average of 5 times, compared with traditional fuzzy algorithms, the author's method shows an improvement of 20.8% to 45.67% in average vehicle delay time, especially when the traffic flow is different in the east-west and north-south directions, the improvement is more significant.

The ambiguity of frequency determination in digital microwave frequency discriminators

Instantaneous frequency measurement devices are designated for very fast measurements of the current frequency value of microwave signals, even if they are very short in the time domain. Fast measurements of frequency temporary values may be based on the evaluation of the phase difference of signal propagating through the microwave transmission lines with unequal, but known, lengths. This paper presents the principle of determination of temporary values of the microwave signal frequency using the digitalized signals and the binary value of them eventually. In the purpose of increase the frequency discrimination resolution, additional tracks with lines with a larger length are proposed. For the system with elements with analytical model transmission characteristics it is typical that bands of ambiguity of frequency measurement occurs. To tackle this problem in addition to 4 x 4 Butler matrix implementation the method of using combination sine and cosine signals is proposed.

Photonic-assisted RF phase difference detector with full 0° to 360° phase detection capability

A microwave photonic structure for detecting the phase difference of two radio frequency (RF) signals is presented. It is capable of determining the RF signal phase difference unambiguously over the full 0° to 360° range, which overcomes the 0° to 180° phase detection range limitation in the reported structures. The proposed RF phase detector is designed to generate two DC voltages with amplitudes depending on the phase difference of the two input RF signals. An RF signal phase difference in the 0° to 360° range can be obtained from the ratio of the two system output DC voltages. The proposed RF phase detector has a wide operating frequency range, as it is free of microwave components. It overcomes the drawbacks of complex structures, large phase detection errors, limited phase detection range, and limited operating frequency range in the reported photonics-based RF phase detectors. Experimental results are presented that demonstrate 0° to 360° phase difference detection with errors below ±3∘ for different input RF signal frequencies.

A fringe jump counting method for the phase measurement in the HCN laser interferometer on EAST and its FPGA-based implementation

Electron density in fusion plasma is usually diagnosed using laser-aided interferometers. The phase difference signal obtained after phase demodulation is wrapped, which is also called a fringe jump. A method has been developed to unwrap the phase difference signal in real time using FPGA, specifically designed to handle fringe jumps in the hydrogen cyanide (HCN) laser interferometer on the EAST superconducting tokamak. This method is designed for a phase demodulator using the fast Fourier transform (FFT) method at the front end. The method is better adapted for hardware implementation compared to complex mathematical analysis algorithms, such as field programmable gate array (FPGA). It has been applied to process the phase measurement results of the HCN laser interferometer on EAST in real time. Electron density results show good confidence in the fringe jump unwrapping method. Further possible application in other laser interferometers, such as the POlarimeter-INTerferometer (POINT) system on EAST tokamak is also discussed.

Laser Phase Rangefinders: Ways to Improve Accuracy

Scientific and technological progress in the field of geodetic and industrial measurements in terms of the use of laser rangefinders operating in ranges up to 5000 meters has led to a reduction in the error of such measuring instruments over the past ten years by two or more times. Such rapid development of high-precision rangefinder technologies has led to a significant revision of the requirements for their metrological support, as well as to the need to develop a new generation of length standards, the stock of metrological accuracy of which would provide an assessment of the metrological characteristics of all types of existing and promising length measuring instruments with a laser rangefinder. To solve this problem, the Institute’s staff conducted research within the framework of a number of thematic research and development works in terms of developing the appearance of a new generation of length standards operating in the range up to 5000 meters in an open atmosphere. Within the framework of this article, one of the developed models of a high-precision complex of measuring instruments for length and coordinate increments is considered, which is a serial high-precision laser phase light meter, modified by the institute’s staff in terms of the system for receiving and processing measuring signals. At the same time, in order to increase the accuracy of length measurements using the developed range finder layout, it is proposed to investigate ways to reduce the errors of the model components of the boundaries of its error. To ensure the smallest error in determining the hardware correction of the rangefinder layout, it is proposed to use funds from the state primary special standard of the unit of length. As promising ways to reduce the error in determining the phase difference of signals, it is proposed to use digital recording and signal processing devices that implement a method for calculating the phase difference of signals by mathematically processing the recorded data using a specially developed computational algorithm based on Fourier analysis. For the most accurate determination of the values of the pulse repetition frequency of signals and the values of the speed of light on the measured track, it is proposed to improve the means of determining these indicators. The use of the proposed methods to improve the accuracy of measuring the length of laser phase rangefinders allows you to provide the necessary margin of metrological accuracy.

Measuring the speed of gravity at short distances: Sensitivity estimate

AbstractAn experimental set up was proposed to determine the speed of gravitational signals traveling in air or in some other medium. It involves two vibrating masses—the emitters, which will be the sources of periodic tidal gravitational signals—and one sapphire‐made mass that will act as a detector, positioned between the two emitters. The detector is planned to be suspended in vacuum and cooled down to 4.2 K, and its vibrational amplitude should be measured by a microwave signal (with ultra‐low phase‐noise) that is expected to resonate with the whispering gallery modes inside the detector. The mechanical and electrical quality factors of sapphire are quite high, yielding a very narrow detection band that reduces the detector sensitivity while amplifying the phase difference of the emitters' signals. The frequencies of the normal modes of the detector were previously determined using a finite element program. In this work, these frequencies are applied to the calculation of a first estimate of the sensitivity of the experiment.

Coherent beam combining of 7 fiber amplifiers based on all-fiber internal phase-locking technique

An all-fiber internal phase-locking coherent beam combining (CBC) system is experimental demonstrated. Without the need for any external sampling elements, the relative phase difference signals among the laser channels are detected and compensated before the lasers being emitted into free space. A 7-channel fiber laser array is built to verify the technique experimentally. When the system is in closed loop, the far-field pattern is stable with the fringe contrast of ∼ 95 % and the phase deviation is ∼λ/21. The impacts of phase error, power inconsistency and tilt error to the combining efficiency are analyzed. The all-fiber internal phase-locking system is compact and easy-extending, which could provide a reference for the design of the high-power massive laser array system.

Фазовый компаратор спиновых волн

The principle of operation of a spin waves phase comparator, made on the basis of ferromagnetic film, is described. Mathematical model of equivalent electrical scheme is investigated. The dependence of the output voltage on the comparator on the phase difference of the input microwave signals is obtained. Micromagnetic modelling of conversion of spin waves propagating in a ferromagnetic film into an output microwave signal was carried out.

Fiber Optic Sensor Based on Linear Sagnac Interferometer for Branch Localization

One of the challenges of distributed fiber optic sensors is to monitor objects that have multiple branches, such as pipelines or power grids. Existing sensors require multiple sensing systems to cover each branch, which increases the cost and complexity of the monitoring. We propose a fiber optic sensor based on linear Sagnac interferometer for branch localization for practical environments where branch paths exist. The system is based on a dual-wavelength single-core Sagnac interferometer, which can extend multiple branches in the sensing cable part. The phase difference signals caused by external disturbances are demodulated and go through different signal processing. By using time delay estimation and null frequency method, we can determine the exact location of the disturbance on the main or branch path. Moreover, we propose a new method to reduce interference with null frequencies of the spectrum by subtracting the phase difference signal at one wavelength from the other. We demonstrate the feasibility and performance of our proposed system through theoretical analysis and experimental results. Our proposed system offers a simple and effective solution for branch localization in distributed fiber optic sensing applications.

A differential phase spectropolarimeter for measuring optical rotatory dispersion

This paper considers the features of polarimetric methods used for the analysis of optically active substances. It presents a design of a differential spectropolarimeter operating by analyzing the phase difference between two harmonical signals received when splitting a laser beam from a common source into separate reference and object beams. The expediency of using the Fourier transform to calculate the phase difference of differential spectropolarimeter signals is noted. The results of calculating the parameters of the measuring method and the results of an experimental study of reference polarimetric plates at various wavelengths are presented. The error in measuring the optical rotation angle in the wavelength range 405–780 nm did not exceed ±0.005°.

An all-digital built-in-self-test scheme for duty cycle corrector with de-skew circuit in NAND Flash memory

This paper presents an all-digital built-in-self-test (BIST) scheme to quickly test the duty cycle corrector (DCC) with de-skew circuit in NAND Flash memory. The proposed BIST circuit adopts an adjustable duty cycle module to generate the input signal of DCC, then it utilizes a high-resolution vernier time-to-digital converter to quantify the pulse widths related to duty cycle and phase difference into digital codes. The proposed BIST scheme can quickly obtain accurate measurement results of the input/output duty cycle of DCC and the phase difference of signals without using high-precision test equipment, it is a low-cost built-in testing solution for NAND Flash memory. The test chip is fabricated using 130 nm CMOS process. The area occupies 0.0425 mm2, and the proposed circuit consumes 2 mW when supply voltage is 1.2 V and clock frequency is 1 GHz. The experimental results show that the measurement error of duty cycle is in the range of −0.85% to 1.5% and the measurement error of phase difference is within ±6 ps.

A High-Gain Dual-Band Multibeam Antenna System for MIMO Wi-Fi Application

A compact dual-band multibeam antenna system with high gain is presented for multiple-input-multiple-output (MIMO) Wi-Fi application. The antenna system is composed of four rotationally symmetric antenna panels occupying a compact size of 60 × 200 × 7.2 mm3. Two series-fed microstrip patch antenna (MPA) arrays are proposed to operate at the 5-GHz band. They are fed with ±90° phase difference signals for two directional radiation patterns with about 45° horizontal 3-dB beamwidth and distinct radiation directions. Two dual-function metasurface based on periodically loaded parallel lines is designed and compactly placed between the two MPA arrays. The metasurface works as a 2.4-GHz antenna with about 90° 3-dB beamwidth in the azimuth. Besides, the application of metasurface improves the gains at the 5-GHz band. Then, four antenna panels are placed in a rotating arrangement with an electric size of 0.59λL × 0.59λL × 1.57λL (λL is the free-space wavelength at the lowest operating frequency). The antenna system was manufactured and demonstrated the characteristics of 360° pattern coverage in azimuth and high gain. The measured average gains are respectively higher than 8 dB and 12 dB at the 2.4-and 5-GHz bands.

On-Chip Mach-Zehnder-Like Interferometer for Atomic Spin Precession Detection

At present, most atomic spin precession detection schemes use discrete optical elements, which leads to bulky detection systems. However, chip-based spin precession detection schemes lack modulation, resulting in lower detection sensitivity. In this paper, we propose and simulatively demonstrate an integrated atomic spin precession detection scheme using an on-chip Mach-Zehnder-like interferometer. An on-chip polarization sorter is designed, with contrast ratio of 24dB and coupling efficiency of 16.8% at 795 nm. With this device, linearly polarized probe light that experienced optical rotation can be split and coupled into two waveguide arms of the interferometer. To avoid the effect of low frequency noise, our scheme uses a micro-heater to modulate the phase difference signal, allowing for high sensitivity detection. The whole detection system can reach micron size, which provides a practical new technique for high precision atomic sensors that can be integrated into chips.

Precise RF Phase Measurement by Optical Sideband Generation Using Mach–Zehnder Modulators

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.

ANALYSIS OF MODELS AND PARAMETERS OF SENSORS BASED ON BREGG GRIDS AND THE INFLUENCE OF PHYSICAL PARAMETERS ON THE SPECTRAL CHARACTERISTICS OF GRIDS

The results of the project have a wide practical application in various industries, such as medical institutions and healthcare facilities, large industrial enterprises, in the automotive industry, food, agricultural and livestock industries, as well as in industrial technology, the metallurgical industry; oil and gas industry. In phase interferometric sensors (PID) based on arrays, the optical element itself acts as a sensitive element, which leads to a significant reduction in cost. The OB segment between two gratings is a Fabry-Perot interferometer. Under the influence of deformation and acoustic vibrations, the phase difference of signals from two adjacent Bragg gratings changes. Interferometric sensors are most sensitive to changes in the length of a fiber segment under the influence of external factors. The principle of operation of distributed fiber-optic measuring complexes based on PID in the simplest case (in the case of one PID) is shown in Figure 3.6 and is as follows [4]. Each of the Bragg gratings RB1 and RB2 of the sensor reflects the pulse coming to it from the pulsed laser at the same Bragg wavelength. In this case, the time delay between the reflected pulses is equal to twice the propagation time of light in the sensitive element of the sensor – a fiber enclosed between the gratings. The reflected pulses enter the compensating interferometer (CI), which, in turn, also bifurcates each of them. The delay introduced into the propagation of pulses by the arm 2 of the CI with respect to arm 1 ensures the overlap in time of the pulse reflected from the grating RB1 at the output of arm 2 and the pulse reflected from the grating RB2 at the output of arm 1 and their phase shift by ϕ 0 =π/2.

Backscattering Statistics of Indoor Full-Polarization Scatterometric and Synthetic Aperture Radar Measurements of a Rice Field

The backscattering coefficient σ0 of a rice field is closely related to the amplitude, power, and phase of its radar backscattered signals. An investigation of the statistics of indoor full-polarization scatterometric and synthetic aperture radar (SAR) measurements on rice fields in the Laboratory of Target Microwave Properties (LAMP) is implemented in terms of the amplitude, power, and phase difference of backscattered signals. The validity and accuracy of LAMP measured data are studied and confirmed for the first time. The Rayleigh fading model and phase difference statistical model are both validated by the experimental data. Continuous microwave spectrum is obtained after spatial and frequency averaging over N independent scatterometric samples and full-polarization images are generated by applying a focusing algorithm to the SAR data. Comparisons between scatterometric results and SAR images with three resolutions of rice field scene are conducted with respect to amplitude and co-pol phase difference (CPD) statistics, as well as backscattering coefficients. The results show that the measured statistics of a rice field scene are in good agreement with those calculated by theoretical formulas. Spatial and frequency averaging of scatterometric data can increase N and thus improve the estimation accuracy of the backscattering coefficients. SAR images show a shift to the near range due to the intrinsic height of the rice plants and the probable existence of the double bounce scattering between vertical rice stems and the water surface considering the measurement geometry. The measured amplitude statistics of the SAR images approach a Rayleigh distribution with reduction of the resolution cell size while the size has little effect on the CPD statistics. The differences between backscattering coefficients extracted from the scatterometric data and SAR images confirm a 1-dB calibration accuracy in power of the LAMP measurement system.

Multispacecraft wave analysis of current sheet flapping motions in Earth’s magnetotail

In our work, for the first time, we conducted a comprehensive multispacecraft wave study of flapping current sheet oscillations in Earth’s magnetotail. Measurements taken from the Magnetospheric Multiscale (MMS) mission were analyzed for two flapping events with different morphologies of oscillation behavior: stationary-like and kink-like type. A comparison of the results calculated by the methods of phase difference, wave surveyor, and Multipoint Signal Resonator technique was carried out. For the first time, using observations, it was found that the energy distribution of wavy magnetic field contains complex multi-branch dispersion dependencies on ky and kz. The phase velocities of propagation of flapping oscillations were estimated. The used methods complement each other, and their differences made it possible to assess the presence of non-linear wave packets during kink flapping and the azimuthal asymmetry of the current sheet profile.

Weak-light phase locking aided by frequency division phase meter for intersatellite laser interferometry

Weak light phase locking is an important part of intersatellite laser interference ranging. Phase-locked loop (PLL) is used to track the phase of heterodyne interference optical signal. Owing to shot noise, laser frequency and other kinds of noise, there is a phase difference between the internal PLL local oscillator and the heterodyne signal, while the phase detection range of the PLL is only one period. If the phase difference exceeds the phase detection range at a certain time, the local oscillator may enter the wrong operating point under feedback regulation, resulting in cycle clip, which leads to subsequent phase reconstruction errors. In this paper, a cycle clip diagnosis method based on the detection background of gravitational waves is proposed. Based on the original PLL, an auxiliary frequency phase divider with larger phase detection range is introduced, which can provide a basis for judging whether the cycle clip occurs in the PLL. In this paper, a digital weak-light PLL model is established to evaluate the influence of various noise. The theoretical spectral density of the error phase is given according to the two main kinds of noise (laser phase noise and particle noise). Considering the limited detection range of PLL, large error phase may lead to cycle clip, making the PLL work at the wrong locking point. A phase meter with smaller frequency division phase range can be used to solve this problem. First, the input heterodyne sine signal is converted into in-phase square wave N frequency division. Then the phase difference is determined by comparing the output signal with output signal reduced by 1/<i>N</i> through the time-to-degital converter (TDC) Based on the theory of PLL and noise, the theoretical model of frequency division phase meter is established. The simulation results show that the frequency division phase meter can realize a wide range of phase detection under the current theoretical framework and has the ability to judge the cycle clip of weak light phase locking. It can be used in the weak- light phase locking task represented by LISA.

Analysis of the accuracy of the signal processing algorithm of the differential phase polarimeter

The purpose of this work is to analyze the effect of the polarimeter signal processing algorithm on the results of measurements of the optical rotation angle of the polarization plane to improve the accuracy of measurements in differential polarimetry. Methods. The paper considers the methods of polarimetry used for the analysis of optically active substances, based on the methods of phase measurements used to calculate the optical rotation angle. The expediency of using the Fourier transform to calculate the phase difference of differential polarimeter signals is noted. To analyze the error of the algorithm, mathematical modeling of the measurement information processing for various signal parameters is applied. Results. The results of the study of the effect of the bit depth of the analog-to-digital converter, the number of samples over the period of the signal and the accumulation time on the accuracy of restoring the phase difference are presented. The influence of the ratio of signal amplitudes and the level of amplitude and phase noise caused by the imperfection of the measuring system has also been investigated. Conclusion. The obtained results make it possible to optimize the operating mode and improve the accuracy of the optical rotation angle measurements using a differential phase polarimeter based on the Fourier transform.