We demonstrate a novel and stable frequency transfer scheme over ground-to-satellite link based on real-time carrier-phase detection and compensation.We performed a zero-baseline measurement with the designed system,a...We demonstrate a novel and stable frequency transfer scheme over ground-to-satellite link based on real-time carrier-phase detection and compensation.We performed a zero-baseline measurement with the designed system,an uninterrupted frequency standard signal is recovered in the reception station without additional post-correction of delay error caused in the route,which is because the phase error of the entire route is tracked and compensated continuously in real-time.To achieve this goal,we employed two carriers in the system and the differential signal is transferred in order to eliminate the instability results from the local oscillator at the satellite transponder as well as the common-mode noise induced in the transfer route and microwave components.The stability of 3×10^(-16) with an integration time of 1 day was achieved and the time fluctuation during one day was measured to be about±20 ps.Error sources and possible solutions are discussed.Our zero-baseline method shows a promising result for real-time satellite-based time and frequency transfer and deserves further research to find whether it works between long-baseline stations.展开更多
In this paper,an effective target locating approach based on the fingerprint fusion posi-tioning(FFP)method is proposed which integrates the time-difference of arrival(TDOA)and the received signal strength according t...In this paper,an effective target locating approach based on the fingerprint fusion posi-tioning(FFP)method is proposed which integrates the time-difference of arrival(TDOA)and the received signal strength according to the statistical variance of target position in the stationary 3D scenarios.The FFP method fuses the pedestrian dead reckoning(PDR)estimation to solve the moving target localization problem.We also introduce auxiliary parameters to estimate the target motion state.Subsequently,we can locate the static pedestrians and track the the moving target.For the case study,eight access stationary points are placed on a bookshelf and hypermarket;one target node is moving inside hypermarkets in 2D and 3D scenarios or stationary on the bookshelf.We compare the performance of our proposed method with existing localization algorithms such as k-nearest neighbor,weighted k-nearest neighbor,pure TDOA and fingerprinting combining Bayesian frameworks including the extended Kalman filter,unscented Kalman filter and particle fil-ter(PF).The proposed approach outperforms obviously the counterpart methodologies in terms of the root mean square error and the cumulative distribution function of localization errors,espe-cially in the 3D scenarios.Simulation results corroborate the effectiveness of our proposed approach.展开更多
The development of precise time synchronization technology is key to the effective application of time-frequency standards.It will significantly promote the application of precise time-frequency standards in the areas...The development of precise time synchronization technology is key to the effective application of time-frequency standards.It will significantly promote the application of precise time-frequency standards in the areas such as Positioning,Navigation,and Timing,lunar navigation,and cutting-edge fundamental physics research.This study presents an improved carrier-phase-based method for time synchronization,which was demonstrated through both laboratory and satellite-ground experiments via the China Space Station(CSS)-ground synchronization system.Initial laboratory experiments confirmed the system’s stability,achieving picosecond-level accuracy,highlighting the robustness of the method in controlled environments.Then,preliminary satellite-to-ground synchronization experiments were conducted using the CSS and ground stations,validating the effectiveness of the carrier-phase-based method.The time synchronization accuracy reached the picosecond-level,significantly surpassing traditional pseudocode techniques,which typically achieve sub-nanosecond level accuracy.Additionally,the Allan Deviation results indicated an improvement in stability by about an order of magnitude compared to traditional pseudocode-based methods.This demonstrates that the carrier-phase-based method can effectively mitigate common sources of system errors and enhance time synchronization capabilities.Therefore,this method can provide an effective technical reference for future applications requiring higher precision in time synchronization.展开更多
Many applications of wireless sensor networks can benefit from fine-grained localization. In this paper, we proposed an accurate, distributed localization method based on the time difference between radio signal and s...Many applications of wireless sensor networks can benefit from fine-grained localization. In this paper, we proposed an accurate, distributed localization method based on the time difference between radio signal and sound wave. In a trilateration, each node adaptively chooses a neighborhood of sensors and updates its position estimate with trilateration, and then passes this update to neighboring sensors. Application examples demonstrate that the proposed method is more robust and accurate in localizing node than the previous proposals and it can achieve comparable results using much fewer anchor nodes than the previous methods.展开更多
基金Project supported by the National Key Research and Development Program of China (Grant No. 2016YFA0302101)the Initiative Program of State Key Laboratory of Precision Measurement Technology and Instruments
文摘We demonstrate a novel and stable frequency transfer scheme over ground-to-satellite link based on real-time carrier-phase detection and compensation.We performed a zero-baseline measurement with the designed system,an uninterrupted frequency standard signal is recovered in the reception station without additional post-correction of delay error caused in the route,which is because the phase error of the entire route is tracked and compensated continuously in real-time.To achieve this goal,we employed two carriers in the system and the differential signal is transferred in order to eliminate the instability results from the local oscillator at the satellite transponder as well as the common-mode noise induced in the transfer route and microwave components.The stability of 3×10^(-16) with an integration time of 1 day was achieved and the time fluctuation during one day was measured to be about±20 ps.Error sources and possible solutions are discussed.Our zero-baseline method shows a promising result for real-time satellite-based time and frequency transfer and deserves further research to find whether it works between long-baseline stations.
基金partially supported by the National Natural Science Foun-dation of China(No.62071389).
文摘In this paper,an effective target locating approach based on the fingerprint fusion posi-tioning(FFP)method is proposed which integrates the time-difference of arrival(TDOA)and the received signal strength according to the statistical variance of target position in the stationary 3D scenarios.The FFP method fuses the pedestrian dead reckoning(PDR)estimation to solve the moving target localization problem.We also introduce auxiliary parameters to estimate the target motion state.Subsequently,we can locate the static pedestrians and track the the moving target.For the case study,eight access stationary points are placed on a bookshelf and hypermarket;one target node is moving inside hypermarkets in 2D and 3D scenarios or stationary on the bookshelf.We compare the performance of our proposed method with existing localization algorithms such as k-nearest neighbor,weighted k-nearest neighbor,pure TDOA and fingerprinting combining Bayesian frameworks including the extended Kalman filter,unscented Kalman filter and particle fil-ter(PF).The proposed approach outperforms obviously the counterpart methodologies in terms of the root mean square error and the cumulative distribution function of localization errors,espe-cially in the 3D scenarios.Simulation results corroborate the effectiveness of our proposed approach.
基金funded by National Key Research and Development Program(NO.2023YFB3906500)Space Application System of China Manned Space Programthe National Nature Science Foundation of China(Grant NO.42030105 and NO.12273045).
文摘The development of precise time synchronization technology is key to the effective application of time-frequency standards.It will significantly promote the application of precise time-frequency standards in the areas such as Positioning,Navigation,and Timing,lunar navigation,and cutting-edge fundamental physics research.This study presents an improved carrier-phase-based method for time synchronization,which was demonstrated through both laboratory and satellite-ground experiments via the China Space Station(CSS)-ground synchronization system.Initial laboratory experiments confirmed the system’s stability,achieving picosecond-level accuracy,highlighting the robustness of the method in controlled environments.Then,preliminary satellite-to-ground synchronization experiments were conducted using the CSS and ground stations,validating the effectiveness of the carrier-phase-based method.The time synchronization accuracy reached the picosecond-level,significantly surpassing traditional pseudocode techniques,which typically achieve sub-nanosecond level accuracy.Additionally,the Allan Deviation results indicated an improvement in stability by about an order of magnitude compared to traditional pseudocode-based methods.This demonstrates that the carrier-phase-based method can effectively mitigate common sources of system errors and enhance time synchronization capabilities.Therefore,this method can provide an effective technical reference for future applications requiring higher precision in time synchronization.
文摘Many applications of wireless sensor networks can benefit from fine-grained localization. In this paper, we proposed an accurate, distributed localization method based on the time difference between radio signal and sound wave. In a trilateration, each node adaptively chooses a neighborhood of sensors and updates its position estimate with trilateration, and then passes this update to neighboring sensors. Application examples demonstrate that the proposed method is more robust and accurate in localizing node than the previous proposals and it can achieve comparable results using much fewer anchor nodes than the previous methods.
