373 results about "Clock correction" patented technology

The invention discloses a new method for RAIM (receiver autonomous integrity monitoring) based on a satellite selecting algorithm in a multimode satellite navigation system. The method comprises the steps of first determining space position information of satellites according to a navigation message and eliminating satellites with a small elevation angle according to a shielding angle; determining an observation matrix including only one clock correction item according to clock correction conversion factors in the navigation message; selecting p satellites from N visible satellites so as to be used for positioning calculation of a receiver, acquiring a satellite combination, which enables the GDOP (geometric dilution of precision) to be minimum, through the satellite selecting algorithm to act as calculating satellites, and determining a weight matrix in WLS (weighted least squares) according to parameters such as the carrier-to-noise ratio, the loop bandwidth, pre-check integral time and the like of satellite signals; carrying out RAIM availability detection according to a false alarm rate and a missed alarm rate which are preset by the receiver, and calculating a pseudo-range residual error threshold value after positioning according to the false alarm rate and a degree of freedom in Chi-squared distribution; carrying out global detection at first, then carrying out local monitoring in a circumstance that a fault satellite exists, determining calculation satellites again through satellite selection, and finally carrying out positioning calculation through selecting satellite combinations within the threshold value. The method disclosed by the invention is simple, high in fault recognition rate, not only applicable to multi-mode and multi-fault satellite navigation systems, but also applicable to single-mode and multi-fault satellite navigation systems, thereby providing new ideas for carrying out RAIM by a modern GNSS (global navigation satellite system).

A system and method for enabling a node, such as a mobile user terminal in a wireless communications network, such as an ad-hoc network, to effectively and efficiently determine a clock correction factor for its local clock relative to a local clock of at least one other node. The node calculates a difference between the timing of the local clock of the node and the local clock of the other node based on the timing of signals transmitted between the node and the other node, and information pertaining to the transmission and reception of these signals by the node and the other node as indicated by the respective local clocks of the node and the other node. The system and method further enables a plurality of nodes in an ad-hoc packet-switched communications network to calculate their respective local clock correction factors relative to the local clocks of their neighboring nodes in this manner with minimal message transmissions between the nodes, to reduce the amount of overhead in the network needed for such clock correcting operations.

The invention discloses a Beidou three-frequency non-differential non-combined observation value time transmission system and method. The method includes the steps that phase observation value, pseudo-range observation value, satellite ephemeris, earth rotation, antenna phase center and other parameters of China Beidou satellite navigation systems at two time transmission stations are obtained; data check, gross error reject and cycle slip detection are carried out, error models of ephemeris, tide, relativity, the earth rotation, atmosphere and antenna phase deviation are corrected; an ionospheric virtual observation model with additional ionospheric prior information constraints, spatial domain constraints and time domain constraints is constructed; and a three-frequency non-differentialnon-combinatorial precise single-point positioning model is constructed, a single-point positioning timing solution is carried out on corrected data, and comprehensive clock corrections of receivers of the two transmission time stations are obtained and compared to obtain a time transmission difference; and compared with standard time of one of the two transmission time stations, precise time of the other one of the two transmission time stations is obtained. According to the Beidou three-frequency non-differential non-combined observation value time transmission system and method, the observation noise can be reduced, and the accuracy and reliability of time transmission are improved.

The invention discloses a simulation system of simulating switched Ethernet clock synchronization. The simulation system comprises an Ethernet protocol instruction database, a timer, nodes, a link attribute configuration module, a synchronization topology generation module, a state management module, a state conversion module, a data processing module, a fault detection and processing module, a clock correction module and a result output module. The Ethernet protocol instruction database and the timer satisfy an IEEE802.3ISO/IEC8802-3 standard specification and instruction and state association information indicated in SAEAS6802. The nodes and the link attribute configuration module are used to carry out simulation role configuration so as to obtain a synchronization topology structure. Then, state role management is performed on each node in the synchronization topology structure and different state roles are used to carry out data processing, clock correction and fault detection. And then a state and clock correction result is output. Compared to the current simulation system, by using the simulation system of the invention, strong scalability is showed on an aspect of network model establishment, which is convenient to carry out an effective analysis on a clock synchronization process.

The invention discloses a clock correcting method and a clock correcting system based on an IP network for a wireless base station, wherein the clock correcting method comprises a correction data collection process, in which the wireless base station acquires at least two groups of correction data, each of which includes first, second, third and fourth time stamps, wherein the first time stamp is the time when the wireless base station sends a clock synchronization request to a clock synchronization server, the second time stamp is the time when the clock synchronization server receives the clock synchronization request, the third time stamp is the time when the clock synchronization server sends a clock synchronization response to the wireless base station, and the fourth time stamp is the time when the wireless base station receives the clock synchronization response; and a clock correction process, in which the wireless base station calculates a correction frequency error using the correction data and corrects the local clock according to the correction frequency error, wherein the correction frequency error is calculated according to a formula. The invention is capable of correcting the frequency offset of a wireless base station to provide a more accurate clock.

A system and method for closed loop clock correction includes adjusting two or more input signals comprising at least one in-phase clock and one quadrature clock, and applying adjusted quadrature clock signals to a device capable of generating a 4-quadrant interpolated output clock phase. An interpolated output clock phase is delayed to form a clock for a measurement device. Two or more adjusted input signals are measured on a measurement device over a range of interpolated output clock phases. Errors are determined on the in-phase clock and the quadrature clock using sampled information from the measurement device. The in-phase clock and the quadrature clock are adapted using determined error information.

The invention provides a Beidou short message technology based multi-mode and multi-frequency maritime precisely positioning method which comprises the following steps: first, using an automatically downloaded and updated IGU ultra-fast track to solve the track correction information, the clock correction information and the atmospheric correction information; second, conducting real-time RTCM data stream decoding; and accessed by data stream, using the IF model and the MW model respectively to calculate the correction information of the observation value and the wide-lane ambiguity information; carrying out reasonable transformation to the solved correction information; extracting the effective fractional part of the information for decoding and using the Beidou short message technology to broadcast it to a user. And while a mobile station receives real time data streams, it receives the Beidou short message data and decodes the data for the recovery of effective correction information. According to the invention, the IF model and MW model are used to seek the real-time dynamic position of a mobile station through the PPP technology; and the method attempts to achieve fixed ambiguity so as to provide the user with high-precision positioning. Compared with the prior art, the method of invention is highly precise and stable. The method can also be applied widely and practically.

The invention provides a high-precision inter-satellite laser ranging assistant precise point positioning method. According to the method, a navigation satellite carries a high-precision inter-satellite laser ranging load; a ground operation control system determines a system deviation parameter between a signal receiving and transmitting starting point of satellite laser ranging equipment and a phase center of an L-waveband satellite load antenna and uploads the system deviation parameter to the satellite; the satellite arranges inter-satellite ranging information and system deviation information into a transmitting sign; a ground point positioning user receives the inter-satellite laser ranging information and the system deviation information while receiving an L-waveband navigation signal; and an inter-satellite laser ranging observed quantity, an L-waveband pseudo-range, a carrier phase observed quantity, a navigation message, a precise orbit product and other data are utilized ina combined mode to complete precise point positioning, so that the precise position of the user is determined. Through the method, positioning initialization time can be shortened, the requirement onprecise clock correction and orbit product update frequency is lowered, and kinematic precise point positioning efficiency is improved.

The invention discloses a high precision positioning method based on a PPP algorithm as well as a system and relates to the field of GNSS high precision positioning application. Centimeter-level highprecision positioning can be realized by being independent of a ground positioning base station, only depending on a mobile terminal, utilizing a double frequency GNSS carrier phase and an observed pseudorange value and combining a GNSS precise orbit and clock correction. The system comprises a GNSS double frequency signal receiving module, a wireless wide area network module, a low orbit navigation enhanced satellite signal receiving module and a microprocessor. The positioning method obtains the original pseudorange and carrier phase observation data by adopting GNSS double frequency observation data and GNSS precise correction, then fixes integer ambiguity by utilizing an LAMBDA algorithm and finally performs recursion and convergence on an ionized layer combined observation linear equation by adopting an expansion Kalman filtering equation, thus location information is obtained. The method and system which are disclosed by the invention have the advantages of convenience in use, high reliability and low cost.

The invention relates to a method for correcting a clock of automatic ship identifying terminal equipment. The method comprises the following steps that: a clock correcting module acquires a UTC (universal time coordinated) time through a GPS (global position system) module and calculates errors of a local time through the UTC time; the error of a local clock is calculated after the errors are accumulated for a period; three levels of clock adjusting parameters are calculated through the errors; a clock compensating module compensates the local time according to the three levels of clock adjusting parameters so as to control the error of the local clock within a relatively small range, then the purpose of clock correction is achieved. By utilizing the method, AIS (automatic identification system) ship automatic identification terminal equipment can correct the error caused by the inaccuracy of the local clock, ensure that the synchronous error between the local time and the UTC time is not larger than 0.1 time slot (2.6ms) within half an hour under the condition that the UTC time reference is lost, and ensure that the AIS time synchronization in broadcast messages is still met. Therefore, the problem that the message transmission of other equipment is influenced when the AIS ship automatic identifying terminal equipment transmits a message due to the fact that the equipment time is not synchronous with the UTC time is solved.

The invention discloses a time synchronization method based on intersatellite bidirectional distance measurement. The time synchronization method comprises the steps of performing modeling on clock correction of a clock through a quadratic polynomial; considering effect of frequency variations, making a satellite-borne atomic clock model adopt three state components, and establishing a state equation of filtering; performing pseudorange measurement on two satellites establishing an intersatellite link in a constellation through an intersatellite bidirectional distance method, and establishing an observation equation; performing Kalman filtering according to the state equation and the measurement equation of the system; performing synchronous filtering on time through centralized Kalman filtering or decentralized Kalman filtering; analyzing effect of the quantity of the intersatellite links on time synchronization accuracy, and selecting the scheme with the highest cost performance according to comparison of simulation results under different quantities of the intersatellite links. By means of comparison of centralized filtering and decentralized filtering and comparison of filtering accuracy under different quantities of the intersatellite links, referential experimental schemes are put forward, and measurement synchronization accuracy is improved.

The invention discloses a clock-correcting method and clock-correcting equipment. The clock-correcting method comprises the following steps of: acquiring the clock information of a current system when a timing cycle comes; comparing the clock information of the current system and the determined reference information of the system clock to obtain the deviation information of a system clock in the current timing cycle; determining the numerical information for every clock correction according to the preset clock correction frequency and the deviation information; and correcting the clock information of the system by using the numerical information when every clock interrupt cycle comes. By the method, the determined numerical information for correcting the clock information of the system every time is small; and the correction of the system clock is realized through a micro-adjustment mode, so that the problem that because the system clock hops suddenly due to large correction numerical information when the system clock is corrected in the prior art, equipment in the system works abnormally can be avoided, and the reliability and stability of the system are improved.

The invention discloses an independent integrity detection method of a receiver capable of simultaneously detecting and identifying multiple faults. The method comprises the steps of firstly determining a satellite position according to a navigation message, eliminating a satellite with a relatively low elevation angle, and determining an observation matrix which only contains a clock correction term; carrying out parity decomposition on the observation matrix to obtain a parity vector p and a multi-epoch cumulative parity vector P, calculating test statistics separately and carrying out weighting to obtain new test statistics sigma, and comparing the new test statistics sigma with a threshold T to obtain a fault detection result; and carrying out fault mode assumption according to the quantity of faults, and detecting the faults in various fault modes to identify multiple faults. The method is simple, the detection and recognition rate is high, abrupt faults and multiple faults can be detected and recognized, and the method also has a very high detection and recognition rate on small soft faults.

The invention relates to a time synchronization and scheduling method for a vehicular Ethernet. The time synchronization and scheduling method for the vehicular Ethernet comprises the steps of: S1, time synchronization starting optimization: performing local clock deviation correction by calling locally stored link delay, simultaneously, shortening a node synchronization message period, and accelerating a synchronization process; S2, static master clock selection: determining synchronous messages of all nodes, and determining a clock having the highest priority as a master clock; S3, synchronous redundant path selection: performing redundant path selection by adopting a clock correction message section in the synchronous messages, and filtering the delay time; and S4, real-time double-window scheduling: distributing messages sent by sending nodes into three priority queues, and dividing time windows into two periods, so that messages of all the sending nodes are sent synchronously. Compared with the prior art, the time synchronization and scheduling method for the vehicular Ethernet disclosed by the invention has the advantages of improving the practical synchronization stability,ensuring real-time scheduling and the like.

The invention relates to a GNSS tri-frequency precise single-point positioning ambiguity fixing method and belongs to the technical field of satellite navigation and positioning. The GNSS tri-frequency precise single-point positioning ambiguity fixing method comprises the steps of achieving precise single-point positioning resolving method by utilizing a tri-frequency pseudo-range and carrier phase observed value based on precise satellite ephemeris and clock correction provided by an IGS and phase delay correction resolved by a network; utilizing extra-wide-lane phase pseudo-range combination to resolve extra-wide-lane complete-cycle ambiguity, combining a resolved ionized-layer-free combination observed value ambiguity to resolve narrow-lane complete-cycle ambiguity and finally obtaining ambiguity-fixed high-precision single-point positioning result. By means of the GNSS tri-frequency precise single-point positioning ambiguity fixing method, the number of parameters to be estimated is decreased, computing efficiency is improved, and meanwhile precise single-point positioning ambiguity resolving success rate, positioning precision and reliability are improved.

The invention discloses a rough synchronization method for satellite bidirectional time comparison. A satellite bidirectional time comparison system is established, rough clock correction is measured, a phase micro-leap module (11) is used for adjusting a 1PPS phase and realizing rough synchronization, and lastly rough synchronization of 1PPS between two stations is realized. According to the rough synchronization method for satellite bidirectional time comparison, a rough synchronizer (9) is in series connection with a satellite bidirectional time comparison slave station (2) to directly measure the initial clock correction of the 1PPS of a master atomic clock (3) and the 1PPS of a slave atomic clock (6), the phase micro-leap module (11) is used for adjusting the 1PPS of the slave station, and therefore rough alignment of master time and slave time of satellite bidirectional time comparison is realized; a control module (13) is used for measuring and processing the clock correction and controlling the operation time sequence of devices; rough synchronization of the time of the master station and the time of the slave station is realized under the condition that other means are not needed, and therefore the autonomy and independence of the satellite bidirectional time comparison system are improved.

A ring oscillator including a plurality of buffer units, each of which has a cross-coupled structure, for generating clock signals using a bias voltage having a predetermined voltage level applied thereto, wherein the clock signals have a swing width corresponding to the bias voltage.

The invention relates to a method and a system based on a big dipper short message precision track and clock correction broadcasting. The method comprises steps of performing difference processing on the positions of a satellite position of a precise ephemeris and a satellite position of a broadcasting ephemeris to generate coordinate correction in a protocol earth-fixing system XYZ direction, performing difference processing on the satellite clock difference of the precise ephemeris and the satellite clock difference of the broadcasting satellite, correspondingly converting the generated coordinate correction in the earth-fixing system XYZ direction to the radial direction, the tangential direction and the normal direction of the satellite, generating track correction information needed to be broadcasted, performing averaging processing on the generated clock difference correction to obtain an average value of the satellite difference correction, subtracting average value of the satellite clock difference correction from the satellite clock difference correction to obtain clock correction information to be broadcasted, and performing data encoding on the generated track correction information and obtained clock difference correction information to generate first information according to a first preset format. The invention improves the navigation positioning precision and greatly improves the shortcoming of poor precision of the broadcast ephemeris.

Disclosed are a satellite positioning method and a satellite positioning system. The system includes satellites, a base station, and an observation station. A monitoring terminal and a correction parameter information generation device are arranged at the observation station. The monitoring terminal receives observation data transmitted from the satellites. The correction parameter information generation device generates correction parameters based on the observation data, and the correction parameters are sent to the base station. The base station is provided with a switch and a message parameter overlay, coding and broadcasting device. The switch receives basic navigation messages from the satellites. The message parameter overlay, coding and broadcasting device programs the correction parameters through protocol overlay to the basic navigation messages, and sets the broadcasting of an integrated code message that incorporates the correction parameters. The code message is sent fromthe switch to the satellites through an uplink injection link. The satellites broadcast the integrated code message received from the base station. The correction parameters include one or more of thesub-region comprehensive correction number, the satellite orbit correction number, the satellite clock correction number, and the ionosphere correction number.