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Amplitude phase control for electro-hydraulic servo system based on normalized least-mean-square adaptive filtering algorithm 被引量:4
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作者 姚建均 富威 +1 位作者 胡胜海 韩俊伟 《Journal of Central South University》 SCIE EI CAS 2011年第3期755-759,共5页
The electro-hydraulic servo system was studied to cancel the amplitude attenuation and phase delay of its sinusoidal response,by developing a network using normalized least-mean-square (LMS) adaptive filtering algorit... The electro-hydraulic servo system was studied to cancel the amplitude attenuation and phase delay of its sinusoidal response,by developing a network using normalized least-mean-square (LMS) adaptive filtering algorithm.The command input was corrected by weights to generate the desired input for the algorithm,and the feedback was brought into the feedback correction,whose output was the weighted feedback.The weights of the normalized LMS adaptive filtering algorithm were updated on-line according to the estimation error between the desired input and the weighted feedback.Thus,the updated weights were copied to the input correction.The estimation error was forced to zero by the normalized LMS adaptive filtering algorithm such that the weighted feedback was equal to the desired input,making the feedback track the command.The above concept was used as a basis for the development of amplitude phase control.The method has good real-time performance without estimating the system model.The simulation and experiment results show that the proposed amplitude phase control can efficiently cancel the amplitude attenuation and phase delay with high precision. 展开更多
关键词 amplitude attenuation phase delay normalized least-mean-square adaptive filtering algorithm tracking performance electro- hydraulic servo system
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Interdecadal Variations of Phase Delays Between Two Nino Indices at Different Time Scales
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作者 卞建春 杨培才 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2005年第1期122-125,共4页
Phase delays between two Nino indices-sea surface temperatures in Nino regions 1+2 and 3.4 (1950-2001)-at different time scales are detected by wavelet analysis. Analysis results show that there are two types of perio... Phase delays between two Nino indices-sea surface temperatures in Nino regions 1+2 and 3.4 (1950-2001)-at different time scales are detected by wavelet analysis. Analysis results show that there are two types of period bifurcations in the Nino indices and that period bifurcation points exist only in the region where the wavelet power is small. Interdecadal variation features of phase delays between the two indices vary with different time scales. In the periods of 40-72 months, the phase delay changes its sign in 1977: Nino 1+2 indices are 2-4 months earlier than Nino 3.4 indices before 1977, but 3-6 months later afterwards. In the periods of 20-40 months, however, the phase delay changes its sign in another way: Nino 1+2 indices are 1-4 months earlier before 1980 and during 1986-90, but 1-4 months later during 1980-83 and 1993-2001. 展开更多
关键词 period bifurcations different time scales phase delay interdecadal variation
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A new method for resolving phase ambiguity in radio interferometry using Earth rotation synthesis
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作者 Huan Zhou De-Zhen Xu +2 位作者 Jian-Guo Yan Shao-Wu Chen Hai-Tao Li 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2021年第7期115-122,共8页
As a key technique in deep space navigation, radio interferometry can be used to determine the accurate location of a spacecraft in the plane-of-sky by measuring its signal propagation time delay between two remote st... As a key technique in deep space navigation, radio interferometry can be used to determine the accurate location of a spacecraft in the plane-of-sky by measuring its signal propagation time delay between two remote stations. To improve the measurement accuracy, differential phase delay without phase ambiguity is usually desired. Aiming at the difficulties of resolving phase ambiguity with few stations and narrowband downlink signals, a new method is proposed in this work by taking advantage of the Earth rotation. The high accurate differential phase delay between the spacecraft and a calibrator can be achieved not only in the in-beam observation mode but also in the out-of-beam observation mode. In this paper we firstly built the model of phase ambiguity resolution. Then, main measurement errors of the model are analyzed, which is followed by tests and validations of the model and method using the tracking data of the Cassini mission and Chang'E-3 mission. The results show that the phase ambiguities can be correctly resolved to generate a 10-picosecond level accuracy differential phase delay. Angular measurement accuracy of the Cassini reaches the milli-arc-second level, and the relative position accuracy between the Chang'E-3 rover and lander reaches the meter level. 展开更多
关键词 radio interferometry Earth rotation synthesis phase ambiguity differential phase delay Cassini mission Chang'E-3 mission
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Method for differential phase delay resolution of phase referencing VLBI technique and its experimental verification
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作者 Huan Zhou Jian-Guo Yan +2 位作者 De-Zhen Xu Yong Huang Hai-Tao Li 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2021年第11期267-272,共6页
The phase referencing Very Long Baseline Interferometry(VLBI)technique is a newly developed tool to measure the angular position of a deep space exploration probe in the plane-of-the-sky.Through alternating observatio... The phase referencing Very Long Baseline Interferometry(VLBI)technique is a newly developed tool to measure the angular position of a deep space exploration probe in the plane-of-the-sky.Through alternating observations between the probe and a nearby reference radio source,their accurate relative angular separation can be obtained from the radio images generated by this technique.To meet the requirements of the current orbit determination software,differential delay should be firstly derived from those radio images.A method to resolve the differential phase delay from the phase referencing VLBI technique is proposed in this paper,and as well the mathematical model for differential phase ambiguity resolution is established.This method is verified with practical measurement data from the Chang’E-3 mission.The differential phase delay between the Chang’E-3 lander and rover was derived from the phase referencing VLBI measurements,and was then imported into the Shanghai astronomical observatory Orbit Determination Program(SODP)to calculate the position of the rover relative to the lander on the lunar surface.The results are consistent with those acquired directly from radio images,indicating that the differential phase ambiguity has been correctly resolved.The proposed method can be used to promote applications of the phase referencing VLBI technique in future lunar or deep space explorations,and more accurate orbit determination becomes promising. 展开更多
关键词 phase referencing VLBI technique differential phase delay radio interferometry Chang’E-3 mission
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Using receiver operating characteristic curves to evaluate the diagnostic value of the combination of multislice spiral CT and alpha-fetoprotein levels for small hepatocellular carcinoma in cirrhotic patients 被引量:30
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作者 Guang-Sheng Jia Guang-Long Feng +5 位作者 Jin-Ping Li Hai-Long Xu Hui Wang Yi-Peng Cheng Lin-Lin Yan Hui-Jie Jiang 《Hepatobiliary & Pancreatic Diseases International》 SCIE CAS CSCD 2017年第3期303-309,共7页
BACKGROUND: The various combination of multiphase enhancement multislice spiral CT (MSCT) makes the diagno- sis of a small hepatocellular carcinoma (sHCC) on the back- ground of liver cirrhosis possible. This stu... BACKGROUND: The various combination of multiphase enhancement multislice spiral CT (MSCT) makes the diagno- sis of a small hepatocellular carcinoma (sHCC) on the back- ground of liver cirrhosis possible. This study was to explore whether the combination of MSCT enhancement scan and alpha-fetoprotein (AFP) level ficiency for sHCC. could increase the diagnostic ef- METHODS: This study included 35 sHCC patients and 52 cir- rhotic patients without image evidence of HCC as a control group. The diagnoses were made by three radiologists em- ploying a 5-point rating scale, with postoperative pathologic results as the gold standard. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diag- nostic value of the three MSCT combination modes (arterial phase+portal-venous phase, arterial phase+delayed phase, arterial phase+portal-venous phase+delayed phase) and AFP levels for sHCC on the background of liver cirrhosis. RESULTS: The area under ROC curve (AUC), sensitivity, and specificity of the combination of arterial phase+portal- venous phase+delayed phase were 0.93, 93%, and 82%, respectively. The average AUC of the arterial phase+portal- venous phase+delayed phase combination was significantly greater than that of the arterial phase+portal-venous phase (AUC=0.84, P=0.01) and arterial phase+delayed phase (AUC=0.85, P=0.03). Arterial phase+portal-venous phase had a smaller AUC (0.84) than arterial phase+delayed phase (0.85), but the difference was insignificant (P=0.15). After combining MSCT enhancement scan with AFP, the AUC, sensitivity, and specificity were 0.95, 94%, and 83%, respectively, indicating a greatly increased diagnostic efficiency for sHCC. CONCLUSIONS: The combination of AFP and 3 phases MSCT enhancement scan could increase the diagnostic efficiency for sHCC on the background of liver cirrhosis. The application of ROC curve analysis has provided a new method and reference in HCC diagnosis. 展开更多
关键词 hepatocellular carcinoma receiver operating characteristic multi-slice spiral CT ALPHA-FETOPROTEIN delayed phase imaging
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Improved estimation of rotor position for sensorless control of a PMSM based on a sliding mode observer 被引量:8
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作者 Wahyu Kunto Wibowo Seok-Kwon Jeong 《Journal of Central South University》 SCIE EI CAS CSCD 2016年第7期1643-1656,共14页
This work proposes a new strategy to improve the rotor position estimation of a permanent magnet synchronous motor(PMSM) over wide speed range. Rotor position estimation of a PMSM is performed by using sliding mode ob... This work proposes a new strategy to improve the rotor position estimation of a permanent magnet synchronous motor(PMSM) over wide speed range. Rotor position estimation of a PMSM is performed by using sliding mode observer(SMO). An adaptive observer gain was designed based on Lyapunov function and applied to solve the chattering problem caused by the discontinuous function of the SMO in the wide speed range. The cascade low-pass filter(LPF) with variable cut-off frequency was proposed to reduce the chattering problem and to attenuate the filtering capability of the SMO. In addition, the phase shift caused by the filter was counterbalanced by applying the variable phase delay compensation for the whole speed area. High accuracy estimation result of the rotor position was obtained in the experiment by applying the proposed estimation strategy. 展开更多
关键词 rotor position estimation permanent magnet synchronous motor sliding mode observer adaptive observer gain cascadelow-pass filter variable cut-off frequency variable phase delay compensation
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A Fiber Optic Sensor for 2,4-dichlorophenol Analysis based on Optical Composite Oxygen-sensitive Film 被引量:3
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作者 TONG Yilin ZENG Zhihong +2 位作者 YU Kan BAO Jiaqi YIN Juanjuan 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2020年第4期743-749,共7页
A novel fiber optic sensor based on optical composite oxygen-sensitive film was developed for determination of 2,4-dichlorophenol(DCP).The optical composite oxygen-sensitive film consists of tris(2,2’-bipyridyl)dichl... A novel fiber optic sensor based on optical composite oxygen-sensitive film was developed for determination of 2,4-dichlorophenol(DCP).The optical composite oxygen-sensitive film consists of tris(2,2’-bipyridyl)dichloro ruthenium(II)hexahydrate(Ru(bpy)3Cl2)as the fluorescence indicator and iron(III)tetrasulfophthalocyanine(Fe(III)PcTs)as bionic enzyme.A lock-in amplifier was used for detecting the lifetime of the composite oxygen-sensitive film by measuring the phase delay of the sensor head.The different variables affecting the sensor performance were evaluated and optimized.Under the optimal conditions(i e,pH 6.0,25℃,Fe(III)PcTs concentration of 5.0×10^-5 mol/L),the linear detection range,detection limit and response time of the fiber optic sensor are 3.0×10^-7-9.0×10^-5 mol/L,4.8×10^-8 mol/L(S/N=3),and 220 s,respectively.The sensor displays high selectivity,good repeatability and stability,which have good potentials in analyzing DCP concentration in practical water samples. 展开更多
关键词 2 4-dichlorophenol optical composite oxygen-sensitive film fiber optic sensor phase delay
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Analyses of noncommensurate sampling used in high-precision regenerative pseudo-noise ranging systems 被引量:3
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作者 徐兆斌 金小军 +1 位作者 张朝杰 金仲和 《Journal of Central South University》 SCIE EI CAS 2014年第3期963-969,共7页
A high-precision pseudo-noise ranging system is often required in satellite-formation missions. But in an actual PN ranging system, digital signal processing limits the ranging accuracy, only level up with meter-scale... A high-precision pseudo-noise ranging system is often required in satellite-formation missions. But in an actual PN ranging system, digital signal processing limits the ranging accuracy, only level up with meter-scale. Using non-integer chip to sample time ratio, noncommensurate sampling was seen as an effective solution to cope with the drawback of digital effects. However, researchers only paid attention to selecting specific ratios or giving a simulation model to verify the effectiveness of the noncommensurate ratios. A qualitative analysis model is proposed to characterize the relationship between the range accuracy and the noncommensurate sampling parameters. Moreover, a method is also presented which can be used to choose the noncommensurate ratio and the correlation length to get higher phase delay distinguishability and lower range jitter. The simulation results indicate the correctness of our analyses and the optimal ranging accuracy can be up to centimeter-level with the proposed approach. 展开更多
关键词 regenerative pseudo-noise (PN) ranging system range jitter phase delay distinguishability noncommensurate sampling correlation length
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PHOTOACOUSTIC VISCOELASTICITY IMAGING OF BIOLOGICAL TISSUES WITH INTENSITY-MODULATED CONTINUOUS-WAVE LASER 被引量:2
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作者 YUE ZHAO SIHUA YANG 《Journal of Innovative Optical Health Sciences》 SCIE EI CAS 2013年第4期27-32,共6页
In this paper,a novel photoacoustic viscoelasticity imaging(PAVEI)technique that provides viscoelastic infornation of biological tissues is presented.We deduced the proocess of photoacoustic(PA)ffct on the basis of th... In this paper,a novel photoacoustic viscoelasticity imaging(PAVEI)technique that provides viscoelastic infornation of biological tissues is presented.We deduced the proocess of photoacoustic(PA)ffct on the basis of thermal viscoelasticity theory and est ablished the relationship between the PA phase delay and the vicoelasticity for soft solids.By detecting the phase delay of PA signal,the viscoelasticity distribution of absorbers can be mapped.Gelatin phantoms with diferent densities and different absorption cofficients were used to verify the dependence of PA VEI measurements.Moreover,tissue mimicking phantoms mixed with fat and collagen at different concentrations were used to testify the feasibility of this technique with reli able contrast.Finally,the PAVEI was sucossfully applied to discrimination between biological tissue constituents.Our experimental results demonstrate that this novel technique has the potential for visualizing the anatomical and biomechanical properties of biological tissues. 展开更多
关键词 PHOTOACOUSTIC phase delay viscolasticity IMAGING
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FPGA-based High-precision Measurement Algorithm for the Ultrasonic Echo Time of Flight 被引量:3
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作者 王伯雄 张金 《Journal of Measurement Science and Instrumentation》 CAS 2010年第2期103-107,共5页
Based on the evaluation of advantages and disadvantages of high-precision digital time interval measuring algorithms, and combined with the principle of the typical time-difference ultrasonic flow measurement, the req... Based on the evaluation of advantages and disadvantages of high-precision digital time interval measuring algorithms, and combined with the principle of the typical time-difference ultrasonic flow measurement, the requirements for the measurement of echo time of flight put forward by the ultrasonic flow measurement are analyzed. A new high-precision time interval measurement algorithm is presented, which combines the pulse counting method with the phase delay interpolation. The pulse counting method is used to ensure a large dynamic measuring range, and a double-edge triggering counter is designed to improve the accuracy and reduce the counting quantization error. The phase delay interpolation is used to reduce the quantization error of pulse counting for further improving the time measurement resolution. Test data show that the systexn for the measurement of the ultrasonic echo time of flight based on this algorithm and implemented on an Field Programmable Gate Army(FleA) needs a relatively short time for measurement, and has a measurement error of less than 105 ps. 展开更多
关键词 ultrasonic flow measurement time of flight phase delay interpolation
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Land deformation monitoring in mining area with PPP-AR 被引量:5
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作者 Hu Hong Gao Jingxiang Yao Yifei 《International Journal of Mining Science and Technology》 SCIE EI 2014年第2期207-212,共6页
The mining area deformation monitoring theory and method using precise point positioning (PPP) ambi- guity resolution (AR) were studied, and an ambiguity fixing model with satellite and receiver combina- tion phas... The mining area deformation monitoring theory and method using precise point positioning (PPP) ambi- guity resolution (AR) were studied, and an ambiguity fixing model with satellite and receiver combina- tion phase delay (CPD) was proposed for zero-differenced PPP ambiguity fixing and its corresponding formula derivation was given. The data processing results for I h at six IGS stations in China show that 93% of ambiguities can be fixed within 10 min and all ambiguities can be fixed within 15 min. After ambi- guity fixing, the positioning accuracy is improved by more than 85% in the E and N directions, with abso- lute positioning accuracy reaching millimeter level, and it was improved by 70% in the U direction, reaching centimeter level; the proposed zero-differenced ambiguity fixing model can effectively improve the convergence rate and positioning accuracy in PPP. Data monitoring continuously conducted for half a year at four COPS stations of Shanxi China Coal Pingshuo Group validated the feasibility of using PPP in mining area deformation monitoring. 展开更多
关键词 Deformation monitoring precise point positioning Ambiguity Combination phase delay (CPD) Ionosphere-free combination
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A Fiber Optic Sensor for Determination of 2,4-dichlorophenol based on Iron(Ⅱ) Phthalocyanine Catalysis 被引量:2
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作者 王永红 TONG Yilin +4 位作者 黄俊 LI Kun LIU Huichao DING Liyun LI Mingtian 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2015年第6期1317-1320,共4页
A new fi ber optic sensor based on the oxidation of 2,4-dichlorophenol(DCP) catalyzed by iron(II) phthalocyanine(Fe(II)Pc) was developed for the determination of DCP. The optical oxygen sensing fi lm containin... A new fi ber optic sensor based on the oxidation of 2,4-dichlorophenol(DCP) catalyzed by iron(II) phthalocyanine(Fe(II)Pc) was developed for the determination of DCP. The optical oxygen sensing fi lm containing fl uorescence indicator Ru(bpy)3Cl2 was used to detect the consumption of oxygen in solution. Moreover, a lock-in amplifier was used to determine the lifetime of the sensor head by detecting its phase delay change. The results reveal that the sensor has a linear detection range of 1.0×10^-6- 9.0×10^-5 mol/L and a response time of 5 min. The sensor also has high selectivity, good repeatability and stability. It can be used effectively to determine DCP concentration in real samples. 展开更多
关键词 2 4-dichlorophenol iron(II) phthalocyanine phase delay change fiber optic sensor stability
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A new high-precision gravity solid tidal model for Precision Gravity Measurement Facility 被引量:1
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作者 Chuang Xu Rongrui Xu +1 位作者 Wenrui Zeng Jianguo Yan 《Geodesy and Geodynamics》 2020年第4期265-272,共8页
It is significant for establishing gravity datum to construct precise gravity solid tidal model,A simple method with relatively low performance is to interpolate tidal parameters from the global gravity solid tide mod... It is significant for establishing gravity datum to construct precise gravity solid tidal model,A simple method with relatively low performance is to interpolate tidal parameters from the global gravity solid tide models.A competitive approach is to determine local gravity solid tidal model by harmonic analysis using long-time serial gravity observations.In this paper a new high-precision gravity solid tidal model for Precision Gravity Measurement Facility is estimated from two co-site gravimeters in the cave laboratory using modern international standard data processing techniques,whose accuracy is evaluated further by comparing with previous publications.The results show that:(1)the determined gravity solid tidal models from two co-site gravimeters are in good agreement with each other,of which the maximum differences for amplitude factors and phase delays don’t exceed 0.01700%and 2.50990°,respectively.(2)the performance of the obtained gravity solid tidal model is 0.00411 for amplitude factors and 0.24120°for phase delays,which is a little better than that of previous publications using superconducting gravity data from Wuhan station.(3)our results and methods are corrective and effective.(4)our model is tiny different from that provided by Wuhan station,which implies that it is necessary to construct a gravity solid tidal model for Precision Gravity Measurement Facility,rather than just adopting existing models at Wuhan station.Our results are helpful in realizing the goal of Precision Gravity Measurement Facility. 展开更多
关键词 Gravity solid tidal model Precision gravity measurement facility Amplitude factor phase delay
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CATIA AIDED RADOME ANALYSIS USING GEOMETRIC OPTICS METHOD 被引量:1
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作者 Li Gaosheng Jia Lei +1 位作者 Ming Yongjin Cao Qunsheng 《Journal of Electronics(China)》 2012年第6期562-566,共5页
In this paper, the Geometric Optics (GO) method using the approximate ray paths coupled with the Computer Aided Tri-dimensional Interface Application (CATIA) meshing modeling are implemented to analyze the performance... In this paper, the Geometric Optics (GO) method using the approximate ray paths coupled with the Computer Aided Tri-dimensional Interface Application (CATIA) meshing modeling are implemented to analyze the performance of electric large three-dimensional dielectric radome-enclosed antenna of arbitrary contour shape. The surfaces of the radome are approximated by planar triangular patches, the influences of various number of patches on power transmission coefficient and Insertion Phase Delay (IPD) via an ogive and a conical radome are discussed by the hybrid method. The simulation results indicate that computational error from planar triangular patches can limit in one percent, meeting the engineering application requirements. 展开更多
关键词 Geometric Optics (GO) Computer Aided Tri-dimensional Interface Application (CATIA) RADOME Power transmission coefficient Insertion phase Delay (IPD)
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An aquifer model with a parameter characterizing the inhomogeneity of media
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作者 王六桥 李善因 《Acta Seismologica Sinica(English Edition)》 CSCD 1994年第2期309-319,共11页
A fissured aquifer model used in petroleum engineering has been studied by the author. It is found that thefissure-induced inhomogeneity which appeared in reservoir media can be expressed by a delay timeτ whichcharac... A fissured aquifer model used in petroleum engineering has been studied by the author. It is found that thefissure-induced inhomogeneity which appeared in reservoir media can be expressed by a delay timeτ whichcharacterizes the process of transition from unsteady to steady seepage flow. Comparison between the fissured aquifer model mentioned above and corresponding homogeneous media is given in this paper. The expression of the characteristic delay timeτis independently derived by using the fissured porous media modeland by solving the characteristic time of an one-dimensioned diffusion equation in turn. The result shows thatthe τ value is in direct proportion to L2. L is the average size of aquifer rock blocks cut by fissures network.The larger the L value, the longer the fissures is and the less the density of fissure is. For identifying the inhomogeneity manifestation of aquifer, a criterion related with the characteristic time of external force action isproposed. In addition, a suggestion on the in-situ measurement of the new aquifer parameter, the 1 value, isgiven. 展开更多
关键词 INHOMOGENEITY fissured porous media unsteady seepage flow time delay phase delay
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Relative position determination of a lunar rover using the biased differential phase delay of same-beam VLBI 被引量:12
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作者 CHEN Ming LIU QingHui +2 位作者 WU YaJun ZHAO RongBing DAI ZhiQiang 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2011年第12期2284-2295,共12页
When only data transmission signals with a bandwidth of 1 MHz exist in the rover, the position can be obtained using the differential group delay data of the same-beam very long baseline interferometry (VLBI). The rel... When only data transmission signals with a bandwidth of 1 MHz exist in the rover, the position can be obtained using the differential group delay data of the same-beam very long baseline interferometry (VLBI). The relative position between a lunar rover and a lander can be determined with an error of several hundreds of meters. When the guidance information of the rover is used to determine relative position, the rover's wheel skid behavior and integral movement may influence the accuracy of the determined position. This paper proposes a new method for accurately determining relative position. The differential group delay and biased differential phase delay are obtained from the same-beam VLBI observation, while the modified biased differential phase delay is obtained using the statistic mean value of the differential group delay and the biased phase delay as basis. The small bias in the modified biased phase delay is estimated together with other parameters when the relative position of the rover is calculated. The effectiveness of the proposed method is confirmed using the same-beam VLBI observation data of SELENE. The radio sources onboard the rover and the lander are designed for same-beam VLBI observations. The results of the simulations of the differential delay of the same-beam VLBI observation between the rover and the lander show that the differential delay is sensitive to relative position. An approach to solving the relative position and a strategy for tracking are also introduced. When the lunar topography data near the rover are used and the observations are scheduled properly, the determined relative position of the rover may be nearly as accurate as that solved using differential phase delay data. 展开更多
关键词 same-beam VLBI biased differential phase delay relative position determination lunar rover
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Photonic microwave true time delays for phased array antennas using a 49 GHz FSR integrated optical micro-comb source[Invited] 被引量:6
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作者 XINGYUAN Xu JIAYANG Wu +6 位作者 THACH G.NGUYEN TANIA MOEIN SAI T.CHU BRENT E.LITTLE ROBERTO MORANDOTTI ARNAN MITCHELL DAVID J.Moss 《Photonics Research》 SCIE EI 2018年第5期I0055-I0061,共7页
We demonstrate significantly improved performance of a microwave true time delay line based on an integrated optical frequency comb source. The broadband micro-comb(over 100 nm wide) features a record low free spectra... We demonstrate significantly improved performance of a microwave true time delay line based on an integrated optical frequency comb source. The broadband micro-comb(over 100 nm wide) features a record low free spectral range(FSR) of 49 GHz, resulting in an unprecedented record high channel number(81 over the C band)—the highest number of channels for an integrated comb source used for microwave signal processing. We theoretically analyze the performance of a phased array antenna and show that this large channel count results in a high angular resolution and wide beam-steering tunable range. This demonstrates the feasibility of our approach as a competitive solution toward implementing integrated photonic true time delays in radar and communications systems. 展开更多
关键词 Photonic microwave true time delays for phased array antennas a 49 GHz FSR integrated optical micro-comb source
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Group delay and phase delay in GNSS systems 被引量:1
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作者 Reuben BERRY Philip G.MATTOS Izzet KALE 《Geo-Spatial Information Science》 SCIE EI 2013年第3期210-219,共10页
GNSS signals have previously been modulated using binary phase shift keying but this modulation scheme is being replaced by binary offset carrier(BOC)modulation.Research has considered how the BOC signals might be aff... GNSS signals have previously been modulated using binary phase shift keying but this modulation scheme is being replaced by binary offset carrier(BOC)modulation.Research has considered how the BOC signals might be affected differently when passed through a surface acoustic wave(SAW)filter.The concern has been that because of the split spectrum nature of the BOC signals,the upper and lower side-lobes will be delayed significantly differently.This was suggested because SAW filters have nonlinear phase characteristics and therefore different frequencies are delayed differently.It was suggested that this difference in delay will result in greater distortion of the correlation triangle.A delay magnification effect was also mentioned when analyzing the delay of a BOC signal.It was not understood why the theoretical delay calculations did not match up with the actual results in both hardware and simulation.This paper clarifies some of the confusion and explains why the“delay magnification”applies to phase delay but not group delay.This paper also takes a look at how the code phase delay can vary with frequency and correlator spacing as a result of the SAW filter properties. 展开更多
关键词 group delay phase delay SAW filter non-linear phase GNSS delay compensation
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Optical True Time Delay for Phased Array Antennas Composed of 2×2 Optical MEMS Switches and Fiber Delay Lines
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作者 Back-Song Lee Jong-Dug Shin Boo-Gyoun Kim 《光学学报》 EI CAS CSCD 北大核心 2003年第S1期487-488,共2页
We proposed an optical true time delay (TTD) for phased array antennas (PAAs) composed of 2×2 optical MEMS switches, single-mode fiber delay lines, and a fixed wavelength laser diode. A 3-bit TTD for 10 GHz PAAs ... We proposed an optical true time delay (TTD) for phased array antennas (PAAs) composed of 2×2 optical MEMS switches, single-mode fiber delay lines, and a fixed wavelength laser diode. A 3-bit TTD for 10 GHz PAAs was implemented with a time delay error less than ± 0.2 ps. 展开更多
关键词 for TTD in MEMS Optical MEMS Switches and Fiber Delay Lines Optical True Time Delay for phased Array Antennas Composed of 2 of
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New high-accuracy spacecraft VLBI tracking using high data-rate signal:A demonstration with Chang'E-3 被引量:2
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作者 ZHOU Huan XU DeZhen +2 位作者 CHEN ShaoWu LI HaiTao DONG GuangLiang 《Science China(Technological Sciences)》 SCIE EI CAS CSCD 2016年第4期558-564,共7页
As the scientific data volume in deep-space exploration rapidly grows,spacecraft heavily relies on high data-rate signals that span several megahertz to transmit data back to Earth.Employing high data-rate signals for... As the scientific data volume in deep-space exploration rapidly grows,spacecraft heavily relies on high data-rate signals that span several megahertz to transmit data back to Earth.Employing high data-rate signals for high-accuracy radiometric interferometry can simultaneously deal with data transmission and spacecraft navigation.We demonstrate very long baseline interferometry(VLBI)tracking of the Chang’E-3 lander and rover to determine their relative lunar-surface position using downlink high data-rate signals.A new method based on the VLBI phase-referencing technique is proposed to obtain the differential phase delay,which is much more accurate than the differential group delay acquired by conventional VLBI approaches.The systemic errors among different signal channels have been well calibrated using the new method.The data from the Chang’E-3mission were then processed,and meter-level accuracy positions of the rover with respect to the lander have been obtained.This demonstration shows the feasibility of high-accuracy radiometric interferometry using high data-rate signals.The method proposed in this paper can also be applied to future deep-space navigation. 展开更多
关键词 spacecraft VLBI tracking high data-rate signal differential phase delay Chang'E-3 deep-space navigation
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