We present an experimental study on tilt-tip（TT） and phase-locking（PL） control in a coherent beam combination（CBC） system of adaptive fiber laser array.The TT control is performed using the adaptive fiber-optics...We present an experimental study on tilt-tip（TT） and phase-locking（PL） control in a coherent beam combination（CBC） system of adaptive fiber laser array.The TT control is performed using the adaptive fiber-optics collimator（AFOC）,and the PL control is realized by the phase modulator（PM）.Cascaded and simultaneous controls of TT and PL using stochastic parallel gradient descent（SPGD） algorithm are investigated in this paper.Two-fiber-laser-,four-fiber-laser-,and six-fiber-laser-arrays are employed to study the TT and PL control.In the cascaded control system,only one high-speed CMOS camera is used to collect beam data and a computer is used as the controller.In a simultaneous control system one high-speed CMOS camera and one photonic detector（PD） are employed,and a computer and a control circuit based on field programmable gate array（FPGA） are used as the controllers.Experimental results reveal that both cascaded and simultaneous controls of TT using AFOC and PL using PM in fiber laser array are feasible and effective.Cascaded control is more effective in static control situation and simultaneous control can be applied to the dynamic control system directly.The control signals of simultaneous PL and TT disturb each other obviously and TT and PL control may compete with each other,so the control effect is limited.展开更多
The mean climatology and the basic characteristics of the ENSO cycle simulated by a coupled model FGCM-1.0 are investigated in this study. Although with some common model biases as in other directly coupled models, FG...The mean climatology and the basic characteristics of the ENSO cycle simulated by a coupled model FGCM-1.0 are investigated in this study. Although with some common model biases as in other directly coupled models, FGCM-1.0 is capable of producing the interannual variability of the tropical Pacific, such as the ENSO phenomenon. The mechanism of the ENSO events in the coupled model can be explained by “delayed oscillator” and “recharge-discharge” hypotheses. Compared to the observations, the simulated ENSO events show larger amplitude with two distinctive types of phase-locking： one with its peak phase-locked to boreal winter and the other to boreal summer. These two types of events have a similar frequency of occurrence, but since the second type of event is seldom observed, it may be related to the biases of the coupled model. Analysis show that the heat content anomalies originate from the central south Pacific in the type of events peaking in boreal summer, which can be attributed to a different background climatology from the normal events. The mechanisms of their evolutions are also discussed.展开更多
The phase-locking process is studied for high-power gyrotron oscillator driven by an external signal. The phase-locking nonlinear differential equations are derived, and the condition of phase-locking is shown and ana...The phase-locking process is studied for high-power gyrotron oscillator driven by an external signal. The phase-locking nonlinear differential equations are derived, and the condition of phase-locking is shown and analyzed. The phase-locking signal can be introduced after gyrotron oscillates into saturation or before it. Two different ways of inputting signal make markable influence on the phase-locking process, this phenomenon is discussed. In this paper, the numerical calculations and analysis are given for gyrotron TE13 mode.展开更多
This paper discusses the chaos and bifurcation for equation x+cosxx+asinx =ebsint. By use of the Melnikov method the conditions to have the chaotic behavior and to have subharmonic oscillations are given.
In this paper,a scheme of commonly-resonated extended interaction circuit system based on high order TMn,mode is proposed to lock the phases of two extended interaction oscillators(EIOs)for generating high power at G-...In this paper,a scheme of commonly-resonated extended interaction circuit system based on high order TMn,mode is proposed to lock the phases of two extended interaction oscillators(EIOs)for generating high power at G-band.Two separate EIOs are coupled through a specific single-gap coupling field supported by a designed gap waveguide with length Lg,which form the phase-locked EIOs based on the commonly-resonated system.As a whole system,the system has been focused on with mode analysis based on different single-gap coupling fields,mode hopping,which present the variation of phase difference between the two-beam-wave interactions when changing Lg.To demonstrate the effectiveness of the proposed circuit system in producing the phase locking,we conducted particle-in-cell(PIC)simulations to show that the interesting mode hopping occurs with the phase difference of O and r between the output signals from two output ports,corresponding to the excitation of the TMn mode with different n.Simulation results show that 1)the oscillator can deliver two times of the output power obtained from one single oscillator at 220 GHz,2)the two EIOs can still deliver output signals with phase difference of O and when the currents of the two beams are different or the fabrication errors of the two EIO cavities are taken into account.The proposed scheme is promising in extending to phase locking between multiple EIOs,and generating higher power at millimeter-wave and higher frequencies.展开更多
Sensorless control of switched reluctance motors(SRMs) often requires a hybrid mode combining low-speed pulse injection methods and high-speed model-based estimation.However,pulse injection causes unwanted audible noi...Sensorless control of switched reluctance motors(SRMs) often requires a hybrid mode combining low-speed pulse injection methods and high-speed model-based estimation.However,pulse injection causes unwanted audible noises and torque ripples.This article proposes an enhanced model-based sensorless approach to extend downwards the speed range in which sensorless control can work without injection.An inertial phase-locked loop (IPLL) based on a stator flux observer is introduced for position estimation.Compared to the conventional phase-locked loop scheme,the IPLL offers a more robust disturbance rejection capability and thus reduces the flux model errors at lower speeds.Experimental results substantiate the feasibility of the extended low-speed operation using the model-based sensorless control approach.展开更多
For Brain-Computer Interface(BCI) systems, improving the Information Transfer Rate(ITR) is a very critical issue. This study focuses on a Steady-State Visually Evoked Potential(SSVEP)-based BCI because of its advantag...For Brain-Computer Interface(BCI) systems, improving the Information Transfer Rate(ITR) is a very critical issue. This study focuses on a Steady-State Visually Evoked Potential(SSVEP)-based BCI because of its advantage of high ITR. Unsupervised Canonical Correlation Analysis(CCA)-based method has been widely employed because of its high efficiency and easy implementation. In a recent study, an ensemble-CCA method based on individual training data was proposed and achieved an excellent performance with ITR of 267 bit/min.A 40-target SSVEP-BCI speller was investigated in this study, using an integration of Minimal-Distance(MD) and Maximal-Phase-locking value(MP) approaches. In the MD approach, a spatial filter is developed to minimize the distance between the training data and the reference sine signal, and in this study, two different types of distance were compared. In the MP approach, a spatial filter is developed to maximize the Phase-Locking Value(PLV)between the training calibration data and the reference sine signal. In addition to the fundamental frequency of stimulation, the harmonics were used to train MD and MP spatial filters, which formed spatial filter banks. The test data epoch was multiplied by the MP and MD spatial filter banks, and the distances and PLVs were extracted as features for recognition. Across 12 subjects with a 0.4 s-data length, the proposed method realized an average classification accuracy and ITR of 93% and 307 bit/min, respectively, which is significantly higher than the current state-of-the-art method. To the best of our knowledge, these results suggest that the proposed method has achieved the highest ITR in SSVEP-BCI studies.展开更多
A comprehensive simulation was performed to better understand the impacts and effects of the additional technical noises on weak-light phase-locking for LISA. The result showed that the phase of the slave laser tracke...A comprehensive simulation was performed to better understand the impacts and effects of the additional technical noises on weak-light phase-locking for LISA. The result showed that the phase of the slave laser tracked well with the received transmitting light under different noise level, and the locking precision was limited by the phase readout noise when the laser frequency noise and clock jitter noise were removed. This result was then confirmed by a benchtop experimental test. The required LISA noise floor was recovered from the simulation which proved the validity of the simulation program. In order to convert the noise function into real time data with random characteristics, an algorism based on Fourier transform was also invented.展开更多
Visual near-infrared imaging equipment has broad applications in various fields such as venipuncture,facial injections,and safety verification due to its noncontact,compact,and portable design.Currently,most studies u...Visual near-infrared imaging equipment has broad applications in various fields such as venipuncture,facial injections,and safety verification due to its noncontact,compact,and portable design.Currently,most studies utilize near-infrared single-wavelength for image acquisition of veins.However,many substances in the skin,including water,protein,and melanin can create significant background noise,which hinders accurate detection.In this paper,we developed a dual-wavelength imaging system with phase-locked denoising technology to acquire vein image.The signals in the effective region are compared by using the absorption valley and peak of hemoglobin at 700nm and 940nm,respectively.The phase-locked denoising algorithm is applied to decrease the noise and interference of complex surroundings from the images.The imaging results of the vein are successfully extracted in complex noise environment.It is demonstrated that the denoising effect on hand veins imaging can be improved with 57.3%by using our dual-wavelength phase-locked denoising technology.Consequently,this work proposes a novel approach for venous imaging with dual-wavelengths and phase-locked denoising algorithm to extract venous imaging results in complex noisy environment better.展开更多
Raman lasers are essential in atomic physics,and the development of portable devices has posed requirements for time-division multiplexing of Raman lasers.We demonstrate an innovative gigahertz frequency hopping appro...Raman lasers are essential in atomic physics,and the development of portable devices has posed requirements for time-division multiplexing of Raman lasers.We demonstrate an innovative gigahertz frequency hopping approach of a slave Raman laser within an optical phase-locked loop(OPLL),which finds practical application in an atomic gravimeter,where the OPLL frequently switches between near-resonance lasers and significantly detuned Raman lasers.The method merges the advantages of rapid and extensive frequency hopping with the OPLL’s inherent low phase noise,and exhibits a versatile range of applications in compact laser systems,promising advancements in portable instruments.展开更多
The dorsal and ventral visual streams have been considered to play distinct roles in visual processing for action:the dorsal stream is assumed to support real-time actions,while the ventral stream facilitates memory-g...The dorsal and ventral visual streams have been considered to play distinct roles in visual processing for action:the dorsal stream is assumed to support real-time actions,while the ventral stream facilitates memory-guided actions.However,recent evidence suggests a more integrated function of these streams.We investigated the neural dynamics and functional connectivity between them during memory-guided actions using intracranial EEG.We tracked neural activity in the inferior parietal lobule in the dorsal stream,and the ventral temporal cortex in the ventral stream as well as the hippocampus during a delayed action task involving object identity and location memory.We found increased alpha power in both streams during the delay,indicating their role in maintaining spatial visual information.In addition,we recorded increased alpha power in the hippocampus during the delay,but only when both object identity and location needed to be remembered.We also recorded an increase in theta band phase synchronization between the inferior parietal lobule and ventral temporal cortex and between the inferior parietal lobule and hippocampus during the encoding and delay.Granger causality analysis indicated dynamic and frequency-specific directional interactions among the inferior parietal lobule,ventral temporal cortex,and hippocampus that varied across task phases.Our study provides unique electrophysiological evidence for close interactions between dorsal and ventral streams,supporting an integrated processing model in which both streams contribute to memory-guided actions.展开更多
The annual maximum rainfall event(AMRE)refers to the maximum consecutive five-day rainfall in a year.In North China,these events account for 15%–80%of the total summer(June–August)rainfall amount and pose a great ch...The annual maximum rainfall event(AMRE)refers to the maximum consecutive five-day rainfall in a year.In North China,these events account for 15%–80%of the total summer(June–August)rainfall amount and pose a great challenge for subseasonal-to-seasonal forecasting.Based on data analyses during 1979–2023,this study shows the interannual variability of AMRE is significantly influenced by the phase and amplitude mode of the annual cycle of the East Asian summer monsoon(EASM),characterized by two orthogonal patterns of southeasterly winds at 850 h Pa over the northwestern Pacific.The EASM phase-locked AMRE shows heavy rainfall events occurring extremely early and late in Beijing and surrounding areas,corresponding to the peak southeasterly wind anomalies in June and August.The EASM amplitude-locked AMRE exhibits extreme heavy or light rainfall over southwest areas with normal phase.Therefore,AMRE has a potential predictability on the seasonal time scale due to its phase-and amplitude-locking with the slow variation of the annual cycle of the EASM.展开更多
A wide-range and phase-locked Michelson interferometer technique is described. This technique combined with femtosecond laser is used to measure the spectrum of the rare-earth ion Nd：YVO4, which presents very high si...A wide-range and phase-locked Michelson interferometer technique is described. This technique combined with femtosecond laser is used to measure the spectrum of the rare-earth ion Nd：YVO4, which presents very high signal to noise ratio of interferometric intensity output and higher spectral resolution than traditional grating spectrophotometer.展开更多
In response to the complex working conditions of the power grid caused by the high proportion of new energy access,which leads to insufficient output accuracy of the second-order generalized integrator(SOGI)phaselocke...In response to the complex working conditions of the power grid caused by the high proportion of new energy access,which leads to insufficient output accuracy of the second-order generalized integrator(SOGI)phaselocked loop,this article proposes an improved frequency adaptive phase-locked loop structure for SOGI.Firstly,an amplitude compensation branch is introduced to compensate for the SOGI tracking fundamental frequency signal,ensuring the accuracy of the SOGI output orthogonal signal under frequency fluctuation conditions.Secondly,by cascading two adaptive SOGI modules,the suppression capability of low-order harmonics and Direct Current(DC)components has been improved.Finally,the positive and negative sequence separation method of orthogonal signals is introduced to eliminate the influence of unbalanced components on the phase-locked loop.The comparative experiment with the classic SOGI-PLL method shows that the proposed phase-locked loop structure effectively improves the accuracy of power grid synchronization detection under complex working conditions such as harmonic components,unbalanced components,and frequency fluctuations.It can complete frequency detection within 1.5 power frequency cycles,and the detected fundamental frequency positive sequence voltage has a higher sinuosity and harmonic distortion rate within 0.5%.展开更多
The phase-locked loop(PLL)plays an essential role for synchronizing renewable power generation to the grid.However,as per the grid-code compliance for reactive current support,the PLL output frequency fluctuates signi...The phase-locked loop(PLL)plays an essential role for synchronizing renewable power generation to the grid.However,as per the grid-code compliance for reactive current support,the PLL output frequency fluctuates significantly and exceeds the limitation,which seriously threaten the safe supply of electricity.In this paper,the underlying theoretical mechanism and dominant force behind the maximum PLL frequency deviation are revealed.Accordingly,two feasible approaches are proposed to enhance the PLL frequency stability with validations in experimental results.展开更多
A design of a ll. 6-GHz phase-locked loop （PLL） fabricated in 49-GHz 0. 18-μm CMOS （complementary metal-oxide-semiconductor transistor） technology is described. An analog multiplier phase detector （PD）, a one-p...A design of a ll. 6-GHz phase-locked loop （PLL） fabricated in 49-GHz 0. 18-μm CMOS （complementary metal-oxide-semiconductor transistor） technology is described. An analog multiplier phase detector （PD）, a one-pole passive low pass filter and a three-stage ring oscillator with variable negativeresistance loads build up the monolithic phase-locked loop. The measured rms jitter of output signal via onwafer testing is 2. 2 ps under the stimulation of 2^31 - 1 bit-long pseudo random bit sequence （PRBS） at the bit rate of 11.6 GHz. And the tracking range is 250 MHz. The phase noise in the locked condition is measured to be - 107 dBc/Hz at 10 MHz offset, and that of the ring VCO at the central frequency is -99 dBc/Hz at 10 MHz offset. The circuit area of the proposed PLL is only 0. 47mm×0.72mm and the direct current （DC） power dissipation is 164 mW under a 1.8-V supply.展开更多
CMOS analog and mixed-signal phase-locked loops(PLL)are widely used in varies of the system-on-chips(SoC)as the clock generator or frequency synthesizer.This paper presents an overview of the AMS-PLL,including:1)a bri...CMOS analog and mixed-signal phase-locked loops(PLL)are widely used in varies of the system-on-chips(SoC)as the clock generator or frequency synthesizer.This paper presents an overview of the AMS-PLL,including:1)a brief introduction of the basics of the charge-pump based PLL,which is the most widely used AMS-PLL architecture due to its simplicity and robustness;2)a summary of the design issues of the basic CPPLL architecture;3)a systematic introduction of the techniques for the performance enhancement of the CPPLL;4)a brief overview of ultra-low-jitter AMS-PLL architectures which can achieve lower jitter(<100 fs)with lower power consumption compared with the CPPLL,including the injection-locked PLL(ILPLL),subsampling(SSPLL)and sampling PLL(SPLL);5)a discussion about the consideration of the AMS-PLL architecture selection,which could help designers meet their performance requirements.展开更多
We present an ameliorated arctangent algorithm based on phase-locked loop for digital Doppler signal processing,utilized within the heterodyne detection system. We define the error gain factor given by the approximati...We present an ameliorated arctangent algorithm based on phase-locked loop for digital Doppler signal processing,utilized within the heterodyne detection system. We define the error gain factor given by the approximation of Taylor expansion by means of a comparison of the measured values and true values. Exact expressions are derived for the amplitude error of two in-phase & quadrature signals and the frequency error of the acousto-optic modulator. Numerical simulation results and experimental results make it clear that the dynamic instability of the intermediate frequency signals leads to cumulative errors, which will spiral upward. An improved arctangent algorithm for the heterodyne detection is proposed to eliminate the cumulative errors and harmonic components. Depending on the narrow-band filter, our experiments were performed to realize the detectable displacement of 20 nm at a detection distance of 20 m. The aim of this paper is the demonstration of the optimized arctangent algorithm as a powerful approach to the demodulation algorithm, which will advance the signal-to-noise ratio and measurement accuracy of the heterodyne detection system.展开更多
A radiation hard phase-locked loop （PLL） is designed at 2.5 GHz using silicon on sapphire complementary metal-oxide-semiconductor process. Radiation hardness is achieved through improving circuit design without sacr...A radiation hard phase-locked loop （PLL） is designed at 2.5 GHz using silicon on sapphire complementary metal-oxide-semiconductor process. Radiation hardness is achieved through improving circuit design without sacrificing real estate. Stability is guaranteed by a fully self-bias architecture. The lock time of PLL is minimized by maximizing the loop bandwidth. Frequency tuning range of voltage controlled oscillator is significantly enhanced by a novel load configuration. In addition, multiple bias stages, asynchronous frequency divider, and silicon on sapphire process jointly make the proposed PLL more radiation hard. Layout of this PLL is simulated by Cadence Spectre RF under both single event effect and total induced dose effect. Simulation results demonstrate excellent stability, lock time 〈 600 ns, frequency tuning range [1.57 GHz, 3.46 GHz], and jitter 〈 12 ps. Through comparison with PLLs in literatures, the PLL is especially superior in terms of lock time and frequency tuning range performances.展开更多
A multimode interference(MMI)structure is designed to simplify the fabrication of quantum cascade laser(QCL)phase-locked arrays.The MMI geometry is optimized with a sufficient output channel distance to accommodate co...A multimode interference(MMI)structure is designed to simplify the fabrication of quantum cascade laser(QCL)phase-locked arrays.The MMI geometry is optimized with a sufficient output channel distance to accommodate conventional photolithography and wet etching process by which power amplifier array is fabricated without using the complicated two-step etching-regrowth or dry etching technique.The far-field pattern with periodically modulated peaks reveals that the beams from the arrays are phase-locked.Furthermore,the frequency tuning performance of the MMI-based phase-locked arrays is studied using the Littrow-configuration external cavity structure.A wavelength tuning range of more than 60 cm^(−1) is demonstrated,which will eventually realize the high power,frequency tunable,large-scale phase-locked arrays,and their application in spectroscopy.展开更多
文摘We present an experimental study on tilt-tip（TT） and phase-locking（PL） control in a coherent beam combination（CBC） system of adaptive fiber laser array.The TT control is performed using the adaptive fiber-optics collimator（AFOC）,and the PL control is realized by the phase modulator（PM）.Cascaded and simultaneous controls of TT and PL using stochastic parallel gradient descent（SPGD） algorithm are investigated in this paper.Two-fiber-laser-,four-fiber-laser-,and six-fiber-laser-arrays are employed to study the TT and PL control.In the cascaded control system,only one high-speed CMOS camera is used to collect beam data and a computer is used as the controller.In a simultaneous control system one high-speed CMOS camera and one photonic detector（PD） are employed,and a computer and a control circuit based on field programmable gate array（FPGA） are used as the controllers.Experimental results reveal that both cascaded and simultaneous controls of TT using AFOC and PL using PM in fiber laser array are feasible and effective.Cascaded control is more effective in static control situation and simultaneous control can be applied to the dynamic control system directly.The control signals of simultaneous PL and TT disturb each other obviously and TT and PL control may compete with each other,so the control effect is limited.
文摘The mean climatology and the basic characteristics of the ENSO cycle simulated by a coupled model FGCM-1.0 are investigated in this study. Although with some common model biases as in other directly coupled models, FGCM-1.0 is capable of producing the interannual variability of the tropical Pacific, such as the ENSO phenomenon. The mechanism of the ENSO events in the coupled model can be explained by “delayed oscillator” and “recharge-discharge” hypotheses. Compared to the observations, the simulated ENSO events show larger amplitude with two distinctive types of phase-locking： one with its peak phase-locked to boreal winter and the other to boreal summer. These two types of events have a similar frequency of occurrence, but since the second type of event is seldom observed, it may be related to the biases of the coupled model. Analysis show that the heat content anomalies originate from the central south Pacific in the type of events peaking in boreal summer, which can be attributed to a different background climatology from the normal events. The mechanisms of their evolutions are also discussed.
文摘The phase-locking process is studied for high-power gyrotron oscillator driven by an external signal. The phase-locking nonlinear differential equations are derived, and the condition of phase-locking is shown and analyzed. The phase-locking signal can be introduced after gyrotron oscillates into saturation or before it. Two different ways of inputting signal make markable influence on the phase-locking process, this phenomenon is discussed. In this paper, the numerical calculations and analysis are given for gyrotron TE13 mode.
基金Project Supported by the National Natural Science Foundation of China
文摘This paper discusses the chaos and bifurcation for equation x+cosxx+asinx =ebsint. By use of the Melnikov method the conditions to have the chaotic behavior and to have subharmonic oscillations are given.
基金Supported in part by the National Natural Science Foundation of China(62401125)the Natural Science Foundation of Sichuan Province(2023NSFSC1376)the Fundamental Research Funds for the Central Universities(ZYGX2024J008)。
文摘In this paper,a scheme of commonly-resonated extended interaction circuit system based on high order TMn,mode is proposed to lock the phases of two extended interaction oscillators(EIOs)for generating high power at G-band.Two separate EIOs are coupled through a specific single-gap coupling field supported by a designed gap waveguide with length Lg,which form the phase-locked EIOs based on the commonly-resonated system.As a whole system,the system has been focused on with mode analysis based on different single-gap coupling fields,mode hopping,which present the variation of phase difference between the two-beam-wave interactions when changing Lg.To demonstrate the effectiveness of the proposed circuit system in producing the phase locking,we conducted particle-in-cell(PIC)simulations to show that the interesting mode hopping occurs with the phase difference of O and r between the output signals from two output ports,corresponding to the excitation of the TMn mode with different n.Simulation results show that 1)the oscillator can deliver two times of the output power obtained from one single oscillator at 220 GHz,2)the two EIOs can still deliver output signals with phase difference of O and when the currents of the two beams are different or the fabrication errors of the two EIO cavities are taken into account.The proposed scheme is promising in extending to phase locking between multiple EIOs,and generating higher power at millimeter-wave and higher frequencies.
基金supported in part by the National Natural Science Foundation of China 52307069in part by 2024 Tertiary Education Scientific Research Project of Guangzhou Municipal Education Bureau under Grant2024312176in part by the Project of Hetao Shenzhen-Hong Kong Science and Technology Innovation Cooperation Zone under Grant HZQB-KCZYB-2020083。
文摘Sensorless control of switched reluctance motors(SRMs) often requires a hybrid mode combining low-speed pulse injection methods and high-speed model-based estimation.However,pulse injection causes unwanted audible noises and torque ripples.This article proposes an enhanced model-based sensorless approach to extend downwards the speed range in which sensorless control can work without injection.An inertial phase-locked loop (IPLL) based on a stator flux observer is introduced for position estimation.Compared to the conventional phase-locked loop scheme,the IPLL offers a more robust disturbance rejection capability and thus reduces the flux model errors at lower speeds.Experimental results substantiate the feasibility of the extended low-speed operation using the model-based sensorless control approach.
基金supported by the National Natural Science Foundation of China (Nos. 61431007 and 91320202)
文摘For Brain-Computer Interface(BCI) systems, improving the Information Transfer Rate(ITR) is a very critical issue. This study focuses on a Steady-State Visually Evoked Potential(SSVEP)-based BCI because of its advantage of high ITR. Unsupervised Canonical Correlation Analysis(CCA)-based method has been widely employed because of its high efficiency and easy implementation. In a recent study, an ensemble-CCA method based on individual training data was proposed and achieved an excellent performance with ITR of 267 bit/min.A 40-target SSVEP-BCI speller was investigated in this study, using an integration of Minimal-Distance(MD) and Maximal-Phase-locking value(MP) approaches. In the MD approach, a spatial filter is developed to minimize the distance between the training data and the reference sine signal, and in this study, two different types of distance were compared. In the MP approach, a spatial filter is developed to maximize the Phase-Locking Value(PLV)between the training calibration data and the reference sine signal. In addition to the fundamental frequency of stimulation, the harmonics were used to train MD and MP spatial filters, which formed spatial filter banks. The test data epoch was multiplied by the MP and MD spatial filter banks, and the distances and PLVs were extracted as features for recognition. Across 12 subjects with a 0.4 s-data length, the proposed method realized an average classification accuracy and ITR of 93% and 307 bit/min, respectively, which is significantly higher than the current state-of-the-art method. To the best of our knowledge, these results suggest that the proposed method has achieved the highest ITR in SSVEP-BCI studies.
基金supported by the Space Science Research Projects in Advance(Grant No.O930143XM1)the Scientific Equipment Development and Research Project(Grant No.Y231411YB1) of Chinese Academy of Sciences
文摘A comprehensive simulation was performed to better understand the impacts and effects of the additional technical noises on weak-light phase-locking for LISA. The result showed that the phase of the slave laser tracked well with the received transmitting light under different noise level, and the locking precision was limited by the phase readout noise when the laser frequency noise and clock jitter noise were removed. This result was then confirmed by a benchtop experimental test. The required LISA noise floor was recovered from the simulation which proved the validity of the simulation program. In order to convert the noise function into real time data with random characteristics, an algorism based on Fourier transform was also invented.
基金funded by National Key R&D Pro-gram of China(2021YFC2103300)National Key R&D Program of China(2021YFA0715500)+2 种基金National Natural Science Foundation of China(NSFC)(12227901)Strategic Priority Research Program(B)of the Chinese Academy of Sciences(XDB0580000)Chinese Academy of Sciences President's International Fellowship Initiative(2021PT0007).
文摘Visual near-infrared imaging equipment has broad applications in various fields such as venipuncture,facial injections,and safety verification due to its noncontact,compact,and portable design.Currently,most studies utilize near-infrared single-wavelength for image acquisition of veins.However,many substances in the skin,including water,protein,and melanin can create significant background noise,which hinders accurate detection.In this paper,we developed a dual-wavelength imaging system with phase-locked denoising technology to acquire vein image.The signals in the effective region are compared by using the absorption valley and peak of hemoglobin at 700nm and 940nm,respectively.The phase-locked denoising algorithm is applied to decrease the noise and interference of complex surroundings from the images.The imaging results of the vein are successfully extracted in complex noise environment.It is demonstrated that the denoising effect on hand veins imaging can be improved with 57.3%by using our dual-wavelength phase-locked denoising technology.Consequently,this work proposes a novel approach for venous imaging with dual-wavelengths and phase-locked denoising algorithm to extract venous imaging results in complex noisy environment better.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2021YFA0718300 and 2021YFA1400900)the National Natural Science Foundation of China(Grant Nos.11920101004,11934002,and 92365208)+1 种基金Science and Technology Major Project of Shanxi(Grant No.202101030201022)Space Application System of China Manned Space Program.
文摘Raman lasers are essential in atomic physics,and the development of portable devices has posed requirements for time-division multiplexing of Raman lasers.We demonstrate an innovative gigahertz frequency hopping approach of a slave Raman laser within an optical phase-locked loop(OPLL),which finds practical application in an atomic gravimeter,where the OPLL frequently switches between near-resonance lasers and significantly detuned Raman lasers.The method merges the advantages of rapid and extensive frequency hopping with the OPLL’s inherent low phase noise,and exhibits a versatile range of applications in compact laser systems,promising advancements in portable instruments.
基金supported by European Union–Next Generation EU(LX22NPO5107(MEYS))the Czech Science Foundation(20-21339S)+2 种基金the Grant Agency of Charles University(GAUK 248122 and 272221)ERDF-Project Brain Dynamics(CZ.02.01.01/00/22_008/0004643)the Ministry of Health of the Czech Republic Project NU21J-08-00081.
文摘The dorsal and ventral visual streams have been considered to play distinct roles in visual processing for action:the dorsal stream is assumed to support real-time actions,while the ventral stream facilitates memory-guided actions.However,recent evidence suggests a more integrated function of these streams.We investigated the neural dynamics and functional connectivity between them during memory-guided actions using intracranial EEG.We tracked neural activity in the inferior parietal lobule in the dorsal stream,and the ventral temporal cortex in the ventral stream as well as the hippocampus during a delayed action task involving object identity and location memory.We found increased alpha power in both streams during the delay,indicating their role in maintaining spatial visual information.In addition,we recorded increased alpha power in the hippocampus during the delay,but only when both object identity and location needed to be remembered.We also recorded an increase in theta band phase synchronization between the inferior parietal lobule and ventral temporal cortex and between the inferior parietal lobule and hippocampus during the encoding and delay.Granger causality analysis indicated dynamic and frequency-specific directional interactions among the inferior parietal lobule,ventral temporal cortex,and hippocampus that varied across task phases.Our study provides unique electrophysiological evidence for close interactions between dorsal and ventral streams,supporting an integrated processing model in which both streams contribute to memory-guided actions.
基金jointly supported by the National Natural Science Foundation of China(Grant Nos.U2242205 and 42375033)the Second Tibetan Plateau Scientific Expedition and Research(STEP)program(Grant No.2019QZKK0105)+1 种基金the Basic Scientific Research and Operation Foundation of CAMS(2023Z018)the S&T Development Fund of CAMS(Grant No.2023KJ036)。
文摘The annual maximum rainfall event(AMRE)refers to the maximum consecutive five-day rainfall in a year.In North China,these events account for 15%–80%of the total summer(June–August)rainfall amount and pose a great challenge for subseasonal-to-seasonal forecasting.Based on data analyses during 1979–2023,this study shows the interannual variability of AMRE is significantly influenced by the phase and amplitude mode of the annual cycle of the East Asian summer monsoon(EASM),characterized by two orthogonal patterns of southeasterly winds at 850 h Pa over the northwestern Pacific.The EASM phase-locked AMRE shows heavy rainfall events occurring extremely early and late in Beijing and surrounding areas,corresponding to the peak southeasterly wind anomalies in June and August.The EASM amplitude-locked AMRE exhibits extreme heavy or light rainfall over southwest areas with normal phase.Therefore,AMRE has a potential predictability on the seasonal time scale due to its phase-and amplitude-locking with the slow variation of the annual cycle of the EASM.
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.60677051 and No.10774193） and the National Key Basic Research Special Foundation （No.G2010CB923204）.
文摘A wide-range and phase-locked Michelson interferometer technique is described. This technique combined with femtosecond laser is used to measure the spectrum of the rare-earth ion Nd：YVO4, which presents very high signal to noise ratio of interferometric intensity output and higher spectral resolution than traditional grating spectrophotometer.
基金supported by the Science and Technology Project of China Southern Power Grid Co.,Ltd.(Grant No.ZBKJXM20232471)the National Key R&D Program of China(Grant No.2021YFB1600200)the Innovation Capability Support Program of Shaanxi(Grant No.2022KXJ-144)。
文摘In response to the complex working conditions of the power grid caused by the high proportion of new energy access,which leads to insufficient output accuracy of the second-order generalized integrator(SOGI)phaselocked loop,this article proposes an improved frequency adaptive phase-locked loop structure for SOGI.Firstly,an amplitude compensation branch is introduced to compensate for the SOGI tracking fundamental frequency signal,ensuring the accuracy of the SOGI output orthogonal signal under frequency fluctuation conditions.Secondly,by cascading two adaptive SOGI modules,the suppression capability of low-order harmonics and Direct Current(DC)components has been improved.Finally,the positive and negative sequence separation method of orthogonal signals is introduced to eliminate the influence of unbalanced components on the phase-locked loop.The comparative experiment with the classic SOGI-PLL method shows that the proposed phase-locked loop structure effectively improves the accuracy of power grid synchronization detection under complex working conditions such as harmonic components,unbalanced components,and frequency fluctuations.It can complete frequency detection within 1.5 power frequency cycles,and the detected fundamental frequency positive sequence voltage has a higher sinuosity and harmonic distortion rate within 0.5%.
基金supported by the National Natural Science Foundation of China under Grant 52407069the Science and Technology Project of Zhejiang Province under Grant 2024C01254the China Postdoctoral Science Foundation under Grant 2024T170766 and 2024M762824。
文摘The phase-locked loop(PLL)plays an essential role for synchronizing renewable power generation to the grid.However,as per the grid-code compliance for reactive current support,the PLL output frequency fluctuates significantly and exceeds the limitation,which seriously threaten the safe supply of electricity.In this paper,the underlying theoretical mechanism and dominant force behind the maximum PLL frequency deviation are revealed.Accordingly,two feasible approaches are proposed to enhance the PLL frequency stability with validations in experimental results.
基金The National High Technology Research and Devel-opment Program of China (863Program) (No2001AA312010)
文摘A design of a ll. 6-GHz phase-locked loop （PLL） fabricated in 49-GHz 0. 18-μm CMOS （complementary metal-oxide-semiconductor transistor） technology is described. An analog multiplier phase detector （PD）, a one-pole passive low pass filter and a three-stage ring oscillator with variable negativeresistance loads build up the monolithic phase-locked loop. The measured rms jitter of output signal via onwafer testing is 2. 2 ps under the stimulation of 2^31 - 1 bit-long pseudo random bit sequence （PRBS） at the bit rate of 11.6 GHz. And the tracking range is 250 MHz. The phase noise in the locked condition is measured to be - 107 dBc/Hz at 10 MHz offset, and that of the ring VCO at the central frequency is -99 dBc/Hz at 10 MHz offset. The circuit area of the proposed PLL is only 0. 47mm×0.72mm and the direct current （DC） power dissipation is 164 mW under a 1.8-V supply.
基金supported by the Pioneer Hundred Talents Program,Chinese Academy of Sciences.
文摘CMOS analog and mixed-signal phase-locked loops(PLL)are widely used in varies of the system-on-chips(SoC)as the clock generator or frequency synthesizer.This paper presents an overview of the AMS-PLL,including:1)a brief introduction of the basics of the charge-pump based PLL,which is the most widely used AMS-PLL architecture due to its simplicity and robustness;2)a summary of the design issues of the basic CPPLL architecture;3)a systematic introduction of the techniques for the performance enhancement of the CPPLL;4)a brief overview of ultra-low-jitter AMS-PLL architectures which can achieve lower jitter(<100 fs)with lower power consumption compared with the CPPLL,including the injection-locked PLL(ILPLL),subsampling(SSPLL)and sampling PLL(SPLL);5)a discussion about the consideration of the AMS-PLL architecture selection,which could help designers meet their performance requirements.
基金supported by Key Research Program of Frontier Science,Chinese Academy of Sciences(Grant No.QYZDB-SSW-SLH014)the Yong Scientists Fund of the National Natural Science Foundation of China(Grant No.61205143)
文摘We present an ameliorated arctangent algorithm based on phase-locked loop for digital Doppler signal processing,utilized within the heterodyne detection system. We define the error gain factor given by the approximation of Taylor expansion by means of a comparison of the measured values and true values. Exact expressions are derived for the amplitude error of two in-phase & quadrature signals and the frequency error of the acousto-optic modulator. Numerical simulation results and experimental results make it clear that the dynamic instability of the intermediate frequency signals leads to cumulative errors, which will spiral upward. An improved arctangent algorithm for the heterodyne detection is proposed to eliminate the cumulative errors and harmonic components. Depending on the narrow-band filter, our experiments were performed to realize the detectable displacement of 20 nm at a detection distance of 20 m. The aim of this paper is the demonstration of the optimized arctangent algorithm as a powerful approach to the demodulation algorithm, which will advance the signal-to-noise ratio and measurement accuracy of the heterodyne detection system.
文摘A radiation hard phase-locked loop （PLL） is designed at 2.5 GHz using silicon on sapphire complementary metal-oxide-semiconductor process. Radiation hardness is achieved through improving circuit design without sacrificing real estate. Stability is guaranteed by a fully self-bias architecture. The lock time of PLL is minimized by maximizing the loop bandwidth. Frequency tuning range of voltage controlled oscillator is significantly enhanced by a novel load configuration. In addition, multiple bias stages, asynchronous frequency divider, and silicon on sapphire process jointly make the proposed PLL more radiation hard. Layout of this PLL is simulated by Cadence Spectre RF under both single event effect and total induced dose effect. Simulation results demonstrate excellent stability, lock time 〈 600 ns, frequency tuning range [1.57 GHz, 3.46 GHz], and jitter 〈 12 ps. Through comparison with PLLs in literatures, the PLL is especially superior in terms of lock time and frequency tuning range performances.
基金supported by the National Basic Research Program of China(Grant Nos.2018YFA0209103 and 2018YFB2200504)the National Natural Science Foundation of China(Grant Nos.61991430,61774146,61790583,61674144,61774150,and 61805168)+1 种基金the Beijing Municipal Science&Technology Commission,China(Grant No.Z201100004020006)the Key Projects of the Chinese Academy of Sciences(Grant Nos.2018147,YJKYYQ20190002,QYZDJ-SSW-JSC027,and XDB43000000).
文摘A multimode interference(MMI)structure is designed to simplify the fabrication of quantum cascade laser(QCL)phase-locked arrays.The MMI geometry is optimized with a sufficient output channel distance to accommodate conventional photolithography and wet etching process by which power amplifier array is fabricated without using the complicated two-step etching-regrowth or dry etching technique.The far-field pattern with periodically modulated peaks reveals that the beams from the arrays are phase-locked.Furthermore,the frequency tuning performance of the MMI-based phase-locked arrays is studied using the Littrow-configuration external cavity structure.A wavelength tuning range of more than 60 cm^(−1) is demonstrated,which will eventually realize the high power,frequency tunable,large-scale phase-locked arrays,and their application in spectroscopy.
