Phase Difference Detection Research Articles

Design of a LiDAR ranging system based on dual‐frequency phase modulation

AbstractPhase‐based light detection and ranging (LiDAR) technology is emerging in the fields of industrial mapping, autonomous driving, and robotics, but the traditional phase‐based ranging technology generally suffers from the problem that the ranging accuracy is inversely proportional to the measurement range under a single measurement frequency, the system structure is complicated, and the performance is unstable, and so forth. In this article, a new type of LiDAR system design based on phase ranging is proposed. The system adopts a 100 + 1 MHz double measuring ruler modulation light source, uses the laser to control the phase difference detection method of the same frequency reference, optimizes the structure of the transceiver optical system, and the design of AD8302 high‐resolution signal phase discriminator circuit, builds a high‐precision laser ranging system, and carries out the experiments on the measurement accuracy of the LiDAR ranging system. The experimental results show that the measurement accuracy of the system is millimeter level, which is simple, practical, and can meet the needs of a wide range of practical applications. This study provides a feasible and innovative solution for LiDAR technology in high‐precision distance measurement.

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.

Photoacoustic method for measuring the elasticity of polydimethylsiloxane at various mixing ratios

Measuring elasticity without physical contact is challenging, as current methods often require deconstruction of the test sample. This study addresses this challenge by proposing and testing a photoacoustic effect-based method for measuring the elasticity of polydimethylsiloxane (PDMS) at various mixing ratios, which may be applied on the wide range of applications such as biomedical and optical fields. A dual-light laser source of the photoacoustic (PA) system is designed, employing cross-correlation signal processing techniques. The platform systems and a mathematical model for performing PDMS elasticity measurements are constructed. During elasticity detection, photoacoustic signal features, influenced by hardness and shapes, are analyzed using cross-correlation calculations and phase difference detection. Results from phantom tests demonstrate the potential of predicting Young's modulus using the cross-correlation method, aligning with the American Society for Testing and Materials (ASTM) standard samples. However, accuracy may be affected by mixed materials and short tubes. Normalization or calibration of signals is suggested for aligning with Young's coefficient.

Clinical efficacy of femtosecond laser-assisted phacoemulsification in diabetic cataract patients.

Diabetic patients with cataracts encounter specific difficulties during cataract surgery due to alterations in microcirculation, blood supply, metabolism, and the microenvironment. Traditional phacoemulsification may not fully tackle these issues, especially in instances with substantial preoperative astigmatism. The utilization of femtosecond laser-assisted phacoemulsification, in conjunction with Toric intraocular lens (IOL) implantation, offers a potentially more efficient strategy. This research seeks to evaluate the efficacy and possible complications of this approach in diabetic cataract patients. To investigate the clinical efficacy and complications of femtosecond laser-assisted phacoemulsification combined with Toric IOL implantation in diabetic cataract patients, comparing it with traditional phacoemulsification methods. This retrospective study enrolled 120 patients with diabetes cataract from May 2019 to May 2021. The patients were divided into two groups: the control group underwent traditional phacoemulsification and Toric IOL implantation, while the treatment group received Len Sx femtosecond laser-assisted treatment. Outcome measures included naked eye vision, astigmatism, high-level ocular phase difference detection, clinical efficacy, and complication. There were no significant preoperative differences in astigmatism or naked eyesight between the two groups. However, postoperative improvements were observed in both groups, with the treatment group showing greater enhancements in naked eye vision and astigmatism six months after the procedure. High-level corneal phase difference tests also indicated significant differences in favor of the treatment group. This study suggests that femtosecond laser-assisted phacoemulsification combined with Toric IOL implantation appears to be more effective in enhancing postoperative vision in diabetic cataract patients compared to traditional methods offering valuable insights for clinical practice.

Unbalanced Current Identification of Three-Core Power Cables Based on Phase Detection of Magnetic Fields

Identifying unbalanced phase currents is crucial for control and fault alarm rates in power grids, especially in urban distribution networks. The zero-sequence current transformer, specifically designed for measuring unbalanced phase currents, offers advantages in measurement range, identity, and size, compared to using three separate current transformers. However, it cannot provide detailed information on the unbalance status beyond the total zero-sequence current. We present a novel method for identifying unbalanced phase currents based on phase difference detection using magnetic sensors. Our approach relies on analyzing phase difference data from two orthogonal magnetic field components generated by three-phase currents, as opposed to the amplitude data used in previous methods. This enables the differentiation of unbalance types (amplitude unbalance and phase unbalance) through specific criteria and allows for the simultaneous selection of an unbalanced phase current in the three-phase currents. In this method, the amplitude measurement range of magnetic sensors is no longer a critical factor, allowing for an easily attainable wide identification range for current line loads. This approach offers a new avenue for unbalanced phase current identification in power systems.

Coriolis mass flowmeter signal processing system based on time-varying signal model

In order to improve the signal processing effect and efficiency of Coriolis mass flowmeter, a signal processing system of Coriolis mass flowmeter based on time-varying signal model is designed. Based on the analysis of the structure and working principle of Coriolis mass flowmeter, the environmental factors affecting the performance of Coriolis mass flowmeter are discussed. Based on the above analysis, the signal processing environment is designed, including serial signal processing environment and dual core parallel signal processing environment. Then the effective signal processing of Coriolis mass flowmeter is completed from three aspects: initial processing, phase calculation and frequency tracking. The experimental results show that after the time-varying signal model is applied, a complete signal frame can be collected in less than 50 ms in the pre-processing process, and the signal processing frame can be completed in less than 80 ms in the post-processing process. This shows that the signal processing time of the system is short, and the phase difference detection accuracy of the signal processing system based on the time-varying signal model is high, which is of great value to further improve the application effect of Coriolis mass flowmeter.

Phase Difference Detection Method for Frequency Tracking in the WPT Systems Using ICST

Phase Difference Detection Method for Frequency Tracking in the WPT Systems Using ICST

Microwave Phase Detector Based on Optical Frequency Translation and Downconversion

A new techniqueto detect the phase difference of two high-frequency RF signals is presented. It is based on downconverting the two high-frequency input RF signals into two low-frequency signals via Serrodyne optical frequency translation and optical frequency downconversion. The phase difference of the two low-frequency downconverted signals is the same as the two high-frequency input RF signal phase difference. Hence a low-cost low-frequency electronic phase detector can be used after photodetection to generate a DC voltage with a value depending on the two input RF signal phase difference. The technique is simple, novel, and innovative. It utilises the advantage of ultra-wide operating frequency range in microwave photonics and the input RF power independent phase detection characteristic in electronic phase detectors. It overcomes the limitations of the input RF signal power and frequency need to be known prior to phase detection in the reported microwave photonic based phase detectors. Experimental results demonstrate 0°-180° RF signal phase difference detection with 1° resolution and less than ±2.6° errors for different RF signal frequencies (10 GHz, 14 GHz and 18 GHz) and different RF modulation indexes (0.2, 0.4 and 0.7). Results also demonstrate the proposed phase detector has excellentrepeatability.

Control strategy for seamless switching of virtual synchronous generators based on secondary frequency and voltage regulation

In microgrid, virtual synchronous generators can enhance the system stability by simulating the operation mechanism of synchronous generators. However, a large impact current could be triggered during the grid-access of VSG inverters, resulting in switching failure. Aiming at this problem, based on real-time digital simulator (RTDS), this paper proposes a complete and simple pre-synchronization control strategy based on secondary frequency modulation and voltage regulation. Firstly, the grid-access structure of VSG was defined, and a mathematical model of VSG was constructed, followed by the design of power-frequency and excitation regulators. Next, secondary frequency and voltage regulation was performed on the microgrid in islanded mode to eliminate the frequency and voltage bias induced by load changes. On this basis, the grid phase was collected by phase-locked loop, the phases were synchronized through phase difference detection, and the grid-access synchronization was completed, realizing the seamless switching between islanded and grid-connected modes. Compared with the universality of applying matlab simulation software, real-time digital simulator (RTDS) has great advantages compared with physical simulation and general simulation software. Finally, the proposed strategy was proved effective with a self-designed RTDS simulation model.

Arduino Mega Based System Design for Sequence and Phase Difference Detection of Three-Phase Systems

In a three-phase system, the difference in the angle between the phases and the phase sequence of the system is very important to ensure the system functions normally and does not cause damage to the three-phase equipment connected to the system. Trigonometric formulas in multiphase systems are used to obtain the angle difference between the phases and the sequence of phases in the system. The trigonometric formula was tested in a simulation using MATLAB software, then applied to an Arduino Mega-based system. In the simulation, the data are two voltages vs. time with a certain phase angle difference, then using the trigonometric formula in the MATLAB program, the data is recovered from the phase angle difference and the direction of rotation of the two voltages. Based on the valid MATLAB simulation test results, the program algorithm is embedded in an Arduino Mega-based system equipped with 2 voltage sensors and a 2.4-inch TFT LCD. The Arduino Mega-based system has succeeded in detecting and visualizing in the form of a graph the angle difference between the phases and the direction of rotation of the three-phase system.

Sensitive detection of radio-frequency field phase with interacting dark states in Rydberg atoms.

An efficient scheme of phase measurement of a radio-frequency (RF) field is proposed by interacting dark states. Under the condition of electromagnetically induced transparency (EIT), the four-level Rydberg atom exhibits two windows. Compared with the transmission spectrum on resonance, the linewidths of absorption peaks off resonance are very narrow due to the interaction of double dark states. It is interesting to find that the distance of absorption peaks shifts approximately linearly with the phase of an RF field, which can be used to measure the RF field phase. Simulation results show that the linewidth of an absorption peak can be narrowed by more than one order of magnitude, and a narrow linewidth improves the detectable minimum phase difference by more than six times. It helps to reduce analyzation complexity and increase sensing resilience. The dependence of phase measurement on the control field and RF field is also investigated.

A linear range extension phase frequency detector and charge pump for frequency hopping acceleration and cycle slips elimination

AbstractThis paper presents a phase‐locked loop (PLL) with a novel phase frequency detector (PFD) and charge pump (CP) which can extend the linear phase difference detection range and eliminate cycle slips. Thus, the frequency settling time can be effectively reduced compared with the conventional PFD and CP during the frequency acquisition process. The proposed PLL with linear range extension PFD and CP (LEPFD/CP) is designed in 180 nm BiCMOS technology and occupies 3.61 mm2 area. As the LEPFD/CP is disabled when the PLL is locked, the PLL is robust enough and the extra power consumption can be ignored. The measurement results show that a 50 MHz reference frequency acquisition process with 10 μs has been accelerated 3.7 times compared with the conventional PFD/CP PLL with the same 200 kHz loop bandwidth.

Dynamic range enhancement of the roll angle displacement measurement with birefringence using a polarization camera.

A roll angle displacement measurement technique with high resolution for large-range measurement is presented. The proposed technique is based on the birefringence effect and phase detection of polarization interferometry with a polarization camera. The phase difference variation between the s- and p-polarized light induced by a rolling birefringent crystal can be obtained by a polarization camera. The roll angle displacement of the birefringent crystal can be determined from the detected phase difference variation. Several experiments were performed to evaluate the feasibility and performance of the proposed technique. The experimental results demonstrate that the resolution of the system can reach 0.003° with a 10° measurement range. The nonlinear and periodic errors of the system are also analyzed.

Automation of multi-modal beam focusing of an MeV sub-microprobe for ion beam analysis

We have developed an automatic beam-focusing system to reduce the experimental configuration time for a sub-micrometer-scaled beam probe of MeV ions with various analytical applications. Parasitic aberration due to misalignment and astigmatism must be eliminated or minimized to obtain an ideal beam spot size of less than 1 × 1 µm2, because astigmatism from excitation error and axial misalignment broaden the beam. The system involves a two-stage process of contrast and phase-difference detection that includes an automated minimization algorithm for astigmatism. The process can identify misalignments of axial rotation by measuring the line profiles of a fine mesh grid. The contrast method focused a proton microprobe to approximately 1 μm2 within 30 min, without the need for manual control when rotational misalignment was not present, while the phase-difference method successfully reduced the rotational error of lenses.

Photonics-Based RF Signal Phase Detector With Wide Operating Frequency Range and High Resolution

A new topology that generates a DC voltage whose value is depending on the phase difference of two input RF signals is presented. It is implemented by the mixer concept. With the use of microwave photonics, the mixer-based phase detector can be operated over a very wide frequency range. It also has the advantages of high phase detection resolution, small phase detection error, and small DC offset and phase offset. The phase detector can be constructed using off-the-shelf components including a single integrated optical modulator and a low-speed balanced detector. Measured results on the phase detector demonstrate a 0° to 180° RF signal phase difference detection range for 3.5 GHz to 18 GHz input RF signal frequencies, less than ±3° phase detection error and 2° phase detection resolution.

Design and Research of Key Technology of Coriolis Flowmeter’s Signal Processing System

This paper innovatively presents DSP processor- TMS320F28335 and CYCLONE series FPGA-EP3C16F484 as a dual-core processor to design Coriolis flowmeter’s signal processing system. This paper introduces key techniques of Coriolis flowmeter’s signal processing system in details from hardware to software, using phase difference based on DTFT with negative frequency and sliding DTFT to detect phase difference, then give then give Cumulative mass flow measurement results.

Detection of tower bolt looseness and its influence of wind level

Taking the wind turbine tower as the research object, based on the finite element software, a simplified beam-shell hybrid element model was first established; through the simulation, the phase difference between the loose position and the unloose position was compared to verify the feasibility of the phase difference detection method; Secondly, the influence of the number of loose bolts, the position of loosening, and the magnitude of the wind force on the phase of the flange bolt connection structure and the response characteristics of the system are analyzed. The research results show that the number of loose bolts, the position of loosening, and the magnitude of the wind have certain effects on the phase difference and response characteristics of the flange. With the increase in the number of loose bolts, the connection stiffness of the bolt connection continues to decrease. The linear characteristic is enhanced; the closer the loosening is to the excitation force loading position, the greater the detected phase difference; as the wind increases, the phase of the upper flange of the tower changes, and the phase of the lower flange remains unchanged, and the wind is on the flange The disc connection strength has little effect.

An improved phase difference detection method for a Coriolis flowmeter

To detect the phase difference of two vibration signals in a Coriolis flowmeter, the commonly used methods include the zero crossing phase detection method, the correlation function method and the Fourier transform method. However, these methods are subject to low accuracy, entire-cycle sampling and excessive calculation. To solve these problems, a Coriolis flowmeter experimental system was initially modeled, and then a phase difference detection method was built based on least squares and curve fitting. The results showed that this method could reduce the amount of calculation significantly without reducing the detection accuracy or adjusting the entire-cycle sampling. A simulation and a single-phase flow experiment indicated that this method was simple, practical and efficient, and it provided a new method for data processing with a Coriolis flowmeter.

Effects of age and tinnitus: Limited physiological evidence and no perceptual consequence of cochlear synaptopathy

Evidence from animal models and human temporal bones has shown that cochlear synaptopathy is associated with aging. Previous work from our lab has suggested that a weakened middle-ear-muscle-reflex (MEMR) in individuals with tinnitus and normal hearing may reflect the presence of cochlear synaptopathy. In this study, we investigated effects of age and tinnitus on the MEMR strength. We also investigated the relationship between the MEMR strength and amplitudes of auditory brainstem responses (ABRs) as well as several perceptual measures that rely on precise temporal neural coding, such as amplitude-modulation detection, the detection of envelope interaural phase difference, and spatial release from speech-on-speech masking. Younger (20–30 yrs) and older (55–69 yrs) listeners with and without tinnitus and with normal or near-normal hearing were tested. We found that aging and tinnitus were associated with significant reductions in MEMR strength and ABR-based measures. However, only the MEMR-strength reduction was significant after accounting for group differences in high-frequency hearing sensitivity. No significant group differences between the older, tinnitus and control groups were found in the perceptual measures obtained in this study. Results will be discussed in terms of sensitivity of these measures to cochlear synaptopathy in humans. [Work supported by NIH grant R01 DC015987.]

Visualization of ultrasonic wave field by stroboscopic polarization selective imaging.

A stroboscopic method based on polarization selective imaging is proposed for dynamic visualization of ultrasonic waves propagating in a transparent medium. Multiple independent polarization parametric images were obtained, which enabled quantitative evaluation of the distribution of the ultrasonic pressure in quartz. In addition to the detection of optical phase differences δ in conventional photo-elastic techniques, the azimuthal angle φ and the Stokes parameter S2 of the polarized light are found to be highly sensitive to the wave-induced refraction index distribution, opening a new window on ultrasonic field visualization.