375 results about "Clock correction" patented technology

A method for generating satellite clock corrections for a WADGPS network computers satellite clock corrections after removing other substantial error components. Errors caused by the ionosphere refraction effects are removed from GPS measurements taken at reference stations using dual-frequency GPS measurements. The multipath noise are removed by smoothing of GPS pseudorange code measurements with carrier-phase measurements. The tropospheric refraction effect can be largely removed by modeling, and if desired, can be improved by the use of small stochastic adjustments included in the computation of the clock correction. After removing the above error factors, satellite clock corrections are computed for individual reference stations, and an average clock correction is formed for each of a plurality of satellites by taking an average or weighted average of the satellite clock corrections over reference stations to which the satellite is visible.

A satellite clock error is determined for each navigation satellite based on the pseudo-range code measurements, the carrier phase measurements, and broadcast satellite clock errors provided by a receiver network. Differences are determined between the computed satellite clock errors and the broadcast clock errors for each satellite. For each constellation, a clock reference satellite is selected from among the navigation satellites, where the clock reference satellite has the median value of clock error difference for that satellite constellation. A correction is determined for the broadcast clock error by applying a function of the reference satellite's clock error to the broadcast clock error for each satellite in the one or more constellations.

A clock correction circuit includes a delay locked loop (DLL) configured to delay an external clock signal and to generate an internal clock signal, a first duty cycle correction (DCC) unit configured to correct a duty cycle of the external clock signal in response to a first duty cycle code, a second DCC unit configured to correct a duty cycle of the internal clock signal in response to a second duty cycle code, and a duty cycle code generation unit configured to select an output of from outputs of the first and second DCC Units and to generate the first and second duty cycle codes by detecting a duty cycle ratio of the selected output.

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.

A clock correction circuit includes a delay locked loop (DLL) configured to delay an external clock signal and to generate an internal clock signal, a first duty cycle correction (DCC) unit configured to correct a duty cycle of the external clock signal in response to a first duty cycle code, a second DCC unit configured to correct a duty cycle of the internal clock signal in response to a second duty cycle code, and a duty cycle code generation unit configured to select an output of from outputs of the first and second DCC Units and to generate the first and second duty cycle codes by detecting a duty cycle ratio of the selected output.

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.

A clock correction circuit includes a delay locked loop (DLL) configured to delay an external clock signal and to generate an internal clock signal, a first duty cycle correction (DCC) unit configured to correct a duty cycle of the external clock signal in response to a first duty cycle code, a second DCC unit configured to correct a duty cycle of the internal clock signal in response to a second duty cycle code, and a duty cycle code generation unit configured to select an output of from outputs of the first and second DCC Units and to generate the first and second duty cycle codes by detecting a duty cycle ratio of the selected output.

The present invention provides an improved clock correction scheme for multi-carrier transmission systems, based on synchronizing a local receiver with a remote transmitter using estimated phase and frequency drifts between the remote transmitter and local receiver clocks. Also, described are communication devices and methods.

The invention provides a device and a method for correcting error estimation of an analog-digital converter. The method comprises the steps as follows: generating a control signal to finely adjust a numerical control simulation time delay unit according to a correction parameter initial value which is set in advance to adjust time delay amount and correct clock phase error among channels; correcting gain error among channels according to the correction parameter initial value and generating a totality correction signal, buffering the totality correction signal and triggering a counting unit to count, simultaneously calling the totality correction signal in a cache and generating an initial estimation result by using a circular correlation method; setting enabling ends of a low pass filter accumulation unit and a correction parameter updating unit while counting to a preset value, generating the error estimation with the initial estimation result and latching, updating a clock correction parameter and a gain correction parameter according to a gradient descent method, and latching the clock correction parameter and the gain correction parameter, and resetting to correct circulation estimation. The device and the method of the invention improve the estimated accuracy and quickens convergence rate of the estimation correction under the condition of using few effective sample points.

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 provides a clock synchronization method and an apparatus in a transmission system. The method comprises the addition of carry values generated by the decimal portion of a system station clock period in t clock periods is calculated, wherein t is the total delay of a clock correction; a correction delay compensation value is calculated through t, the addition of the carry values and the integer portion of the system station clock period and the correction delay compensation value is used to carry out a synchronization correction towards a system subordinated clock. According to the invention, the problem in the prior art that the precision of system clock synchronization is low is solved and the clock synchronization precision of the system is increased.

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.

The invention relates to a clock?correction technology in the field of microelectronics and discloses a sampling clock?mismatch?background?correction method based on a time-to-digital?converter, which is used for carrying out background?correction on mismatch of a sampling clock?of a time-interleaved analog-to-digital converter and improving performances of the time-interleaved analog-to-digital converter. AND operation is carried out on each adjacent two-phase sampling clock of the time-interleaved analog-to-digital converter, the overlapping part waveform Ai of the adjacent sampling clocks is obtained, a?time domain?waveform width?amplifier is adopted to amplify the width of Ai to obtain Ci, the time-to-digital?converter is used for quantifying Ci to obtain Di, the average value of Di D represents a digital code corresponding to the ideal overlapping width of adjacent two-phase sampling clocks, sampling clock offset in the i channel is obtained through calculation Ei=Di-D, and multiphase?sampling?clock?mismatch?correction can then be realized through Ei statistics and feeding the statistical result to a clock delay?adjustment unit. The sampling clock?mismatch?background?correction method based on time-to-digital?converter is particularly suitable for mismatch correction on the sampling clock of the time-interleaved analog-to-digital converter.

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.

A duty cycle correction circuit includes a first inverter suitable for driving a second clock in response to a first clock; a second inverter suitable for driving the first clock in response to the second clock; and a duty cycle detector suitable for detecting a duty cycle of the first clock or the second clock, wherein driving forces of one or more inverters among the first inverter and the second inverter are controlled based on a duty detection result of the duty cycle detector.

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.

The invention provides a multi-mode GNSS single-frequency cycle slip detecting and repairing method supporting RTPPP and RTK. The method comprises: an inter-epoch difference is constructed; a time-dependent ionized layer error, a tropospheric error and clock correction delay errors between different systems are eliminated; overall least squares estimation is carried out; if a position correction number covariance DX^X^ is larger than or equal to threshold 1, five satellites are selected circularly and a cycle-slip-free combination with the highest reliability is found out to obtain position and clock difference drift correction number; a new residual vector is obtained by back calculation, wherein the residual vector is an inter-epoch cycle slip floating point solution; and the cycle slipfloating point solution is processed by rounding off in an acceptable range to determine whether the cycle slip can be restored or be a gross error. According to the invention, three different empirical thresholds are set based on different detection quantity meanings, so that the probability of missed determination and false determination during the cycle slip restoring process can be reduced.