109 results about "Pulse-per-second signal" patented technology

The invention discloses a digital phase discriminator used for a GPS tame crystal oscillator. The digital phase discriminator used for the GPS tame crystal oscillator comprises a 2N frequency divider, a high level pulse width counter, a low level pulse width counter, a pulse per second clock, a phase difference counter clock, a frequency count value latch and a phase error value latch. The 2N frequency divider is used for performing frequency division on 1 Hz PPS signals output by a GPS module. The high level pulse width counter and the low level pulse width counter are used for counting high level pulse widths and low level pulse widths. The pulse per second clock is in input connection with frequency locking enabled signals provided by the outside, is connected with the GPS and performs frequency diversion on inner pulse per second signals output by an OCXO clock. The phase difference counter clock inputs the inner pulse per second signals and PPS signals output by the GPS module, calculates the time difference of rising edges of the inner pulse per second signals and rising edges of the PPS signals, and outputs count values of the phase difference. The frequency count value latch and the phase error value latch are used for achieving the frequency at which an OCXO tracks GPS signals and the PPS signals and meanwhile output frequency values and phase error values. According to the digital phase discriminator used for the GPS tame crystal oscillator, time sequence design is facilitated, and the problem of lead-lag fuzziness of initial phase errors is avoided; the scheme of serial counters is adopted in the frequency counter and the phase measurement counter, so the frequency of the counter clock will not be affected by counting digits.

The invention discloses a method for realizing TD-SCDMA base station synchronization, which is used for synchronizing a base station in the absence of GPS signal and includes that: step1, a GPS receiver receives a GPS satellite signal and transmits pulse per second signal to a synchronization module; the synchronization module adopts the pulse per second signal to measure the deviation value of work frequency and standard frequency of a crystal oscillator, and compute the frequency deviation compensation of the crystal oscillator; step 2, when the GPS receiver receives no GPS satellite signal, the GPS receiver informs the synchronization module; when the synchronization module is informed that the GPS receiver receives no GPS satellite signal, the synchronization module adopts frequency deviation compensation to compensate a frame timing signal generated by a clock signal of the crystal oscillator, and the frame timing signal is used for synchronizing the base station. The invention can eliminate phase deviation caused by the frequency deviation of the crystal oscillator and continuously accumulated with time, and enable the frame timing signal of the base station to be synchronous with frame timing signals of other base stations in longer time.

A control plane, available to all of the line cards in a system, is used to exchange time stamps to align the Time of Day counters in the master line cards. The master line cards are locked to a system clock distributed over the backplane by a timing card. The timing card is locked to timing of a slave line card that is synchronized with the grand master. Each master line card synchronizes updating its Time of Day counter based on a time stamp exchange and a local clock locked to the system clock and without the use of a 1 pulse per second signal.

The invention relates to a clock source device based on a GPS (global positioning system) and a constant-temperature crystal oscillator and a synchronous control method. The clock source device comprises a constant-temperature crystal oscillator module, a master control module, a GPS module, a narrowing circuit module and an auxiliary control module and the like, wherein the constant-temperature crystal oscillator module is connected with the auxiliary control module, the GPS module receives satellite pulse-per-second signals, the auxiliary control module resets a fractional-frequency submodule therein at the regular time according to the satellite pulse-per-second signals and eliminates accumulated errors of the constant-temperature crystal oscillator. The synchronous control method includes calibrating crystal oscillator phase voltage; receiving satellite signals by the GPS module; inputting selected frequency signals to the main control module through a key module; sending the GPS pulse-per-second signals which are subjected to narrowing treatment into the auxiliary control module; sending clock frequency signals of the constant-temperature crystal oscillator module into the auxiliary control module; resetting the fractional-frequency submodule by the auxiliary control module at the regular time according to GPS signals; and selecting signal output frequency signals according to frequency. The frequency signals and UTC (universal time coordinated) are synchronous by the aid of the GPS combined with the constant-temperature crystal oscillator, and the phase error is smaller than 100ns.

The present invention belongs to the field of the whole network time synchronization, and especially relates to a multi-mode high-precision timing system and method. The system provided by the invention comprises a Beidou timing unit, a GPS timing unit, an IRIG-B timing unit, a taming timekeeping unit and a timing algorithm unit. The Beidou timing unit, the GPS timing unit and the IRIG-B timing unit are in both-way communication connection with the timing algorithm unit, and the timing algorithm unit is in both-way communication connection with the taming timekeeping unit; and the taming timekeeping unit includes a taming timing circuit, in the condition of Beidou pulse signals, GPS pulse per second signals and IRIG-B pulse per second signals are all lost, the taming timing circuit enters a timekeeping state, and the timing algorithm unit outputs timing time and timing pulse per second. Through adoption of Beidou satellite time, GPS satellite time and IRIG-B code time as external clock source of a timing system, the multi-mode high-precision timing system and method is able to avoid the problem caused by unstable time performance of a PGS satellite, and is high in precision, good in reliability and stable in performance.

The invention discloses a moonlet satellite-and-ground time synchronization method for a ground whole-satellite test. The purpose of satellite-and-ground time synchronization in a simulated flight test is effectively achieved. The satellite service center computer time, the AOCC time and the ground dynamics simulation time are synchronized with the GPS dynamic simulator orbit simulation time by adjusting orbital parameters of a satellite control subsystem, having control over the orbit simulation starting moment of a GPS dynamic simulator and the satellite-and-rocket separation switch state of a moonlet, and using the satellite time correction function, satellite-and-ground time synchronization is achieved, the real in-orbit situation of the moonlet can be simulated, the basis is provided for satellite power distribution, time sequence analysis calculation and instruction arrangement, and reality and effectiveness of the ground whole-satellite test are ensured. Time users use GPS pulse-per-second signals output by a GPS receiver and corresponding integral second time correction data as the time keeping reference and the time correction reference, the difference between the satellite time and the ground time does not change along with the length of the testing time, and accuracy of a ground test system is improved.

The invention provides a time scale signal generator based on standard time pulse signals. The time scale signal generator comprises a crystal oscillator module, a first serial port, a GPS module, a communication and storage control module, a frequency demultiplication function blockset and a phase detection and control function blockset. The crystal oscillator module is used for generating the clock signals of the time scale signal generator, the first serial port is used for receiving time scale frequency allocation commands input by the outside, the GPS module is used for receiving the carrier signals of a connected outer GPS antenna, generating GPS pulse per second signals and outputting GPS locating and time data, the communication and storage control module is connected to the first serial port, and used for generating time scale signal frequency values according to the time scale frequency allocation commands and controlling the time scale signal frequency values to be stored and sent, the frequency demultiplication function blockset is used for carrying out frequency demultiplication on the clock signals according to the time scale frequency allocation commands to generate time scale signals, and the phase detection and control function blockset is used for detecting the phase difference of the GPS pulse per second signals and the fed-back time scale signals, generating controlling signals according to the phase difference to control the frequency demultiplication function blockset and aligning the GPS pulse per second signals and the time scale signals.

The invention relates to a satellite navigation signal simulator calibration and timing type receiver delay device and method. Satellite navigation signals are used in the device and method for simulating and generating standard satellite navigation signals, a detected receiver receives and calculates the signals, a path of pulse-per-second signals is restored, the pulse-per-second signals and pulse-per-second signals output by a simulator are simultaneously transmitted to a high-precision time interval counter to be compared, the delay difference value of the two paths of pulse-per-second signals is obtained in a measurement mode, then the influence of the delay of the simulator, the delay of a cable and the like is removed, and the delay of the detected receiver is obtained. The method and device can overcome the defects of the error and uncertainty accumulation of a comparison method, can overcome the manual observation errors introduced when the delay of the simulator is measured with an oscilloscope method, improve the accuracy of simulator delay measurement and reduce the uncertainty of a measurement result.

The invention discloses a clock signal holding method and a clock signal holding device. The method comprises the following steps of: by taking a pulse-per-second signal of a global positioning system (GPS) as reference, adjusting a crystal oscillator according to a formula of DAC=DAC'+k1*delta freq until the clock frequency of the crystal oscillator reaches a nominal value; then adjusting the crystal oscillator according to a formula of DAC=DAC'+k2*delta phase; recording n groups of data on time point t, temperature T and adjustment value DAC of the crystal oscillator; and adjusting the crystal oscillator according to a formula of DAC=aT+bt+DAC HV so as to hold the clock frequency when the pulse-per-second signal of the GPS fails. The technical scheme of the invention can greatly prolongthe holding time of the clock under the same conditions.

The invention discloses a satellite timing service-based wireless communication method and a satellite timing service-based wireless communication device, for realizing multi-point ordered communication without a master control node or a base station signal. The method disclosed by the embodiment of the invention comprises the following steps of: initializing system parameters; carrying out satellite timing service synchronization and generating a pulse-per-second signal and a satellite frame pulse signal; carrying out frame synchronization sequence detection to generate a detection frame pulse signal; correcting the frame pulse signal according to the satellite frame pulse signal and the detection frame pulse signal; carrying out time slot configuration; carrying out coding, modulation and insertion for a frame synchronization sequence in a transmission time slot, carrying out modulation and decoding in a reception time slot, and switching into a transmitting state or a receiving state according to whether service data needs to be sent.

A general simulation system of a measurement and control subsystem of a minisatellite spread spectrum system comprises a measurement and control signal processing simulation module, a measurement and control interface simulation module, a GPS simulation module and a simulation control platform. The general simulation system can achieve radio frequency processing, intermediate frequency processing and baseband processing of measurement and control signals, achieve simulation with physical interfaces of other lower computers, and achieve output or forwarding of GPS pulse per second signals and broadcasting of time and orbital data when being in a semi-physical working mode, wherein the physical interfaces comprises the CAN bus interface, the remote measurement and control interface, the direct instruction interface, the clock output interface and the star arrow separation signal output interface. The general simulation system can receive remote measurement and control data in an LAN bus for interface simulation and GPS simulation when being in a full-digital working mode. Configurable function board cards are selected, the PXI bus technology is adopted, the integration degree is high, configuration is flexible, cost is low, function extension of the system can be conveniently conducted, the requirement for verification of multiple new technologies of the minisatellite measurement and control subsystem can be met, and the electric performance test environment of the measurement and control subsystem can be provided for development of a novel minisatellite platform.

Techniques are disclosed relating to channel sounding. In some embodiments a transmitter transmits a periodic CAZAC sequence beginning at a point in time that corresponds to a timing signal (e.g., a pulse-per-second signal). In some embodiments, a receiver waits to begin processing received sequences for a time interval corresponding to the length of the CAZAC sequence, where the time interval begins at the same time as the timing signal. This may avoid a need for timing synchronization prior to processing, reduce processing and latency in receiver implementations, and may allow determination of a TOA as well as a channel impulse response estimate by correlating a received cyclically-shifted CAZAC sequence with a local version of the transmitted CAZAC sequence.

The invention discloses a system and a method for time delay calibration of a Beidou navigation signal hardware simulator. The system comprises a satellite navigation signal simulator, a signal acquisition module, an isolation amplifier and a signal processing module, wherein the isolation amplifier outputs a first clock signal and a second clock signal; the satellite navigation signal simulator takes the first clock signal as a work clock and outputs a radio frequency analog signal and a pulse per second signal; the signal acquisition module takes the second clock signal as a sampling clock and is used for acquiring the radio frequency GEO (geosynchronous) satellite analog signal and the pulse per second signal; and the signal processing module calculates delay inequality between an initial code phase of the radio frequency GEO satellite analog signal and a pulse per second rising edge of the pulse per second signal based on the acquired radio frequency analog signal and the pulse per second signal to obtain the time delay of the simulator. With the adoption of the technical scheme, a special zero-pseudorange or fixed-pseudorange testing scene is not required to be set in the simulator, and the time delay of the simulator can be calibrated when the simulator simulates output normally.

The invention relates to the technical field of satellite timing, and discloses a GPS and Big Dipper double-mode timing method and system. The method comprises the steps that firstly, satellite signals of a GPS and a Big Dipper are received; secondly, the received satellite signals are processed, and pulse per second signals are output; thirdly, the difference between the output pulse per second signals and pulse per second signals obtained through local clock frequency dividing is measured; fourthly, the difference of the output pulse per second signals and the pulse per second signals obtained through local clock frequency dividing is processed to obtain a frequency difference digital signal; fifthly, the frequency difference digital signal is converted into analog voltage to be output, and a local clock is controlled to be corrected according to the output voltage. According to the GPS and Big Dipper double-mode timing method and system, logic processing, software algorithm processing and frequency division processing are integrated in a control processing device (FPGA) to be achieved, the difficulty of the overall design of the system is lowered, the developing period is shortened, and the material cost is saved.

The invention discloses a time-keeping method of a time synchronization device. The method comprises the following steps: A, receiving a first pulse per second signal; B, acquiring output signal frequency doubled by a constant-temperature crystal oscillator so as to obtain internal working frequency; C, taking the first pulse per second signal as a base, and adopting a PID (Proportion Integration Differentiation) algorithm to adjust the internal working frequency; and D, generating a second pulse per second signal synchronous to the first pulse per second signal according to the adjusted internal working frequency. According to the time-keeping method of the time synchronization device, the PID algorithm is introduced, a PID strategy is applied to adjust the internal working frequency, the second pulse per second signal is generated according to the adjusted internal working frequency and has the advantages of good stability and high synchronism, the implementation procedure of the second pulse per second signal is simple, and high-accurate time keeping can be implemented with lower cost. The invention relates to the time-keeping method of the time synchronization device, which can be widely applied to the technical field of communication.

The invention is applicable to the field of satellite navigation, and provides a time synchronization system and method of a satellite signal simulator, and the satellite signal simulator. The methodcomprises the following steps: receiving a real satellite signal through a satellite signal receiver, generating pulse per second signals, and transmitting the pulse per second signals to an FPGA module of the satellite signal simulator; performing, by the FPGA module, rough counting on the pulse per second signals by using a clock signal to obtain a rough time interval difference between a clockgenerated by a local crystal oscillator and a satellite clock; constructing, by the FPGA module, a carry chain according to the rough time interval difference to perform carry chain refine counting, and calculating an accurate difference value between a clock rising edge and a pulse per second rising edge to obtain an accurate time interval between the local clock and the satellite clock; and correcting, by the FPGA module, the frequency of the local crystal oscillator in a crystal oscillator taming manner according to the accurate time interval, so that the local crystal oscillator generatesan optimized clock signal. By adopting the time synchronization system and method provided by the invention, synchronization with the real pulse per second signals is realized, and the correlation between the satellite signal simulator and a real satellite is enhanced.

The invention provides an automatic forward / reverse direction IRIG-B code decoding method. According to the method, a high precision oscillator clock module provides clocks for all modules, and clock precision is improved with the time filtering compensation algorithm; the direction of an IRIG-B code is identified through an IRIG-B code direction identifying module, the IRIG-B code is then converted into a required IRIG-B code, so that a forward direction IRIG-B code is provided for an IRIG-B code punctual edge identifying module; the IRIG-B code punctual edge identifying module extracts the punctual edge of the IRIG-B code, and a timestamp is provided for an IRIG-B information code identifying module, a pulse-per-second module and a serial port message module; time information is provided for the serial port message module by the IRIG-B information code identifying module; the pulse-per-second module outputs pulse-per-second signals and can provide the pulse-per-second clock synchronization service for clock synchronization equipment; the serial port message module outputs serial port messages and can provide the serial port clock synchronization service for the clock synchronization equipment. According to the automatic forward / reverse direction IRIG-B code decoding method, output time information is high in accuracy, light in fluctuation and good in long-term stability.

The invention relates to an arrester resistive current monitoring method based on a GPS synchronization pulse per second. The method comprises the following steps that the phase difference phi1 between the leakage current and the position of the rising edge of the GPS pulse per second is solved through sampling and operation; the phase difference phi2 between a PT reference voltage signal and the position of the rising edge of the GPS pulse per second is solved through sampling and operation; the phase difference deltaphi between the PT reference voltage signal and the leakage current is solved according to phi1 and phi2 and deltaphi=|phi2-phi1|; the resistive current is obtained through Ir=Iq*cos(deltaphi) and according to the total current obtained through measurement and an RC parallel equivalent module of a zinc oxide arrester. Correspondingly, the invention further relates to an arrester resistive current monitoring device based on the GPS synchronization pulse per second. After a GPS receiver is connected with a satellite, the arrester resistive current monitoring device can output pulse per second signals synchronously, the error is at the level of 0.1 uS, and the current situations that an existing monitoring method and device are complex and difficult in PT sampling and reference and the like are improved.

The present invention relates to the field of communication transmission, especially to a clock and time frequency integrated transmission method and device. A sending module receives time standard and frequency standard input by an external portion; the time standard obtains B-code code elements through a coding unit; a standard frequency Fs is employed to generate a high-frequency work frequencyFns through a frequency multiplier circuit; the time standard and the frequency standard performs frequency phase modulation to achieve synchronization and generate time-frequency integrated signals;a restoring unit restores a corresponding B-code code element waveform; a decoding unit solves the B-code waveform and outputs time information and pulse per second signals; a frequency restoring unit restores standard frequency signals, and the standard frequency signals are output after shaping. The clock and time frequency integrated transmission method and device employ IRIG-B codes to perform time transmission and complete accurate frequency transmission at the transmission bottom layer to achieve time-frequency integrated transmission through signals with the same transmission frequencyperiod and different duty ratios, namely, one transmission link achieves accurate transmission of the time and the frequency based on the B codes, and therefore, the link reusing is achieved, the cost is low, the structure is simple, and the transmission is reliable.

The invention provides an image shooting moment determining method and system. The method comprises the following steps: low-precision moment information and a pulse per second signal are acquired from a Beidou time service module, wherein the low-precision moment information takes integral second as the minimum precision; the shooting frame rate of a monitoring camera is acquired so as to obtain an exposure trigger sequence corresponding to the shooting frame rate; the pulse per second signal is taken as a first exposure trigger signal of the exposure trigger sequence according to the shooting frame rate, and the monitoring camera is controlled for the first exposure; follow-up exposure is implemented sequentially by an exposure controller of the monitoring camera according to the exposure trigger sequence; and the shooting moment of each image corresponding to the exposure trigger sequence is calculated according to the low-precision moment information and the shooting frame rate. The invention further provides a vehicle speed detection method and system. With adoption of the scheme, the problem that the monitoring camera cannot acquire the image shooting moment accurately can be solved, and the vehicle traveling speed monitoring precision can be improved.

The invention discloses a multi-beam sonar multi-channel seabed echo and movement attitude and position simulator which comprises a data generating module, a control module, a data storage module, a digital-to-analog conversion module and multi-channel seabed echo signals. Multi-beam seabed data can be generated by the data generating module, the control module is connected with the data generating module, the data storage module and the digital-to-analog conversion module are respectively connected with the control module, and the multi-channel seabed echo signals are connected with the digital-to-analog conversion module; a control interface and synchronous signals on the control module are respectively connected with tested multi-beam sonar, and the multi-channel seabed echo signals can be outputted; movement attitude and movement position data can be generated by the data generating module in real time after the synchronous signals are received, and can be outputted to to-be-tested equipment via an output interface, and pulse-per-second signals are simultaneously outputted from a pulse-per-second signal interface on the control module. The multi-beam sonar multi-channel seabed echo and movement attitude and position simulator has the advantages that real measurement procedures can be simulated in laboratories, and accordingly problems of high cost and long cycle of debugging and testing modes due to the fact that multi-beam sonar devices and auxiliary equipment need to be transmitted to specific sea areas to be actually measured can be solved.

A method and system for eliminating the low-frequency oscillation between generators. By way of measuring the absolute rotor angle of a generator and controlling the rotor rotational speed, the absolute rotor angles obtained through measurement are the same when each GPS pulse per second signal arrives. The absolute rotor angles are angles of the internal potential Eq of the generator leading a GPS reference vector. Through the absolute rotor angle, zero steady state error control of the frequency and the rotor angle is achieved and the position of the generator rotor can remain unchanged in the PPS determined rotating coordinate system, thus suppressing the low-frequency oscillation better even without the need of remote measurement and achieving automatic local balance of active power during variation of loads. Accordingly, the power fluctuation on transmission lines is decreased while safe and stable operation of a large-scale interconnected power grid is achieved.

The embodiment of the invention provides a data acquisition time synchronization system and method, and relates to the technical field of mobile surveying and mapping. The method comprises the following steps: synchronizing GPS time contained in a GPS signal to system time of a data acquisition time synchronization system by taking a GPS pulse per second signal as a time synchronization referencewhen the GPS signal and the GPS pulse per second signal transmitted by a GNSS receiver are received; when the GPS signal and the GPS pulse per second signal transmitted by the GNSS receiver are not received, generating an internal pulse per second signal, and updating the preset initial time by taking the internal pulse per second signal as a reference to obtain the system time of the data acquisition time synchronization system, and further controlling data acquisition time of data acquisition modules to be synchronous, and obtaining the synchronous navigation data. No matter whether the GPSsignal exists or not, the system time can be updated according to the pulse per second signal, the accuracy of the system time is guaranteed, it is guaranteed that accurate time and position information can be obtained, and the stability of the system is enhanced.

The invention relates to a method for enhancing synchronization accuracy of network equipment of industrial Ethernet; at first, the method comprises, aiming at perturbed problem generated by uncertainness of communication protocol stack software in the process of execution, the following steps: 1, implementing phase alignment automatically upon the electrification of equipment; 2, simultaneously receiving synchronization messages and pulse-per-second signal of a time server on the network; 3, comparing local time with time of the time server; 4, judging the direction regulated by a local clock according to the received time message and the local time; 5, averagely assigning time deviation resulted from computation into synchronization intermittence; secondly, velocities of clock crystal oscillators of the equipment are deviated, and the method comprises the steps: A), setting maximal regulating amount of each synchronization intermittence upon the electrification; B), computing the regulating amount in this synchronization intermittence; C), computing regulating times in this synchronization intermittence; and D) averagely assigning the regulating amount to each regulation period.

The invention relates to the technical field of time synchronization and discloses a punctuality compensating circuit and method for a pulse per second. The punctuality compensating circuit comprises a time service receiver, a crystal oscillator, a frequency division processing unit, a first counter, a second counter and a comparator, wherein the time service receiver provides standard second signals; the crystal oscillator provides system crystal oscillator signals; the frequency division processing unit processes the system crystal oscillator signals to provide shaped second signals; the shaped second signals enable the first counter to count the system crystal oscillator signals, and then the first counter is controlled by the standard second signals to stop and latch counting; the shaped second signals enable the second counter to count the system crystal oscillator signals; the comparator outputs pulse per second signals generated after punctuality compensation when the count values of the two counters are equal, and the frequency division processing unit and the second counter are reset through the pulse per second signals respectively. According to the punctuality compensating circuit and method for the pulse per second, a deviation compensation mode for punctuality signals is provided, crystal oscillator errors are effectively corrected, and high-precision punctuality is guaranteed.

A method and system are provided for converting an enhanced Long Range Navigational (eLORAN) signal to a Precision Time Protocol (PTP) signal. Network devices can be located within buildings and not have access to a GPS signal directly from a GPS satellite. Network devices may also be located in a line of sight of a GPS satellite but may lose the GPS signal. An adapter is provided that takes an eLORAN signal, when a GPS signal is lost or not available, and converts the signal into a PTP and other signals to act as timing, synchronization, and syntonization inputs into the network devices. In some cases, the network devices can have a PTP client to receive the PTP signal, one pulse per second signal, and a ten (10) megahertz frequency signal. In other cases, the network devices do not have a PTP client, but can receive a time of day message, one pulse per second signal, and the 10 megahertz frequency signal.

The invention is applicable to the field of satellite navigation, and provides a time synchronization system and a method of a satellite signal simulator, and the satellite signal simulator. The method comprises the following steps: receiving a real satellite signal through a satellite signal receiver, generating a second pulse signal, and transmitting the second pulse signal to an FPGA module ofa satellite signal simulator; performing coarse counting on the second pulse signal by the FPGA module by using the clock signal to obtain a coarse time interval difference between a clock generated by the local crystal oscillator and a satellite clock; performing carry chain fine counting by the FPGA module by constructing a carry chain according to the rough time interval difference, and calculating an accurate difference value between a clock rising edge and a pulse per second rising edge, thereby obtaining an accurate time interval between a local clock and a satellite clock; and correcting the frequency of the local crystal oscillator in a crystal oscillator taming mode by the FPGA module according to the accurate time interval, so that the local crystal oscillator generates an optimized clock signal. According to the method, synchronization with a real pulse per second signal is achieved, and correlation between the satellite signal simulator and a real satellite is enhanced.

The invention discloses a method and a system for eliminating the low-frequency oscillation between generators. According to the method, the absolute rotor angles of the generators are measured, and the rotation speeds of generator rotors are controlled, so that when each GPS (Global Positioning System) pulse per second signal arrives, the absolute rotor angles obtained through measurement are identical; the absolute rotor angles are angles leading GPS reference vectors of internal electric potential Eq of the generators. The method and the system for eliminating the low-frequency oscillation between the generators have the advantages of being capable of realizing the indifference control on frequencies and rotor angles by controlling the absolute rotor angles of the generators, being capable of ensuring that the locations of the generator rotors are unchanged in a PPS (Pulses Per Second) defined rotating coordinate system, well suppressing the low-frequency oscillation under the condition that the remote measurement is not need, also being capable of realizing active automatic local balance during changing in load, preventing the power fluctuation of call wires and ensuring the safe and stable operation of large-scale interconnected networks.

The invention relates to a high-precision optically pumped magnetometer frequency measurement device and method based on GPS (global positioning system) time receiving. The device comprises a GPS receiver, an FPGA (field programmable gate array) board, a frequency calculation module, a crystal oscillator correction module, a multiplexer and a constant temperature crystal oscillator, wherein the GPS receiver is used for providing GPS pulse-per-second signals, the GPS receiver, the FPGA board, the frequency calculation module and the crystal oscillator correction module are sequentially connected, the multiplexer is connected with the FPGA board, and the constant temperature crystal oscillator is connected with the multiplexer and the crystal oscillator correction module and used for providing clock pulse signals. Measuring site limitation caused by GPS time receiving can be removed, and frequency measurement precision is conveniently improved by a multi-channel cooperative counting method. Besides, the high-precision frequency measurement device constructed by the method is simple to implement, strong in adaptability, high in flexibility, good in electromagnetic compatibility and quite suitable for sensors such as an optically pumped magnetometer with frequency output testing results.

The invention relates to a chaotic synchronous realizing method based on GPS in the technical field of wireless digital communication. The method includes the following steps: a GPS receiving unit provides a globally uniform pulse per second signal and time code for each node of network; the whole network bottom layer uses ZIGBEE wireless communication protocol, the current time information is read after each node of the network is started, and the frequency hopping period and the time offset in the period are computed. The frequency of the next hopping of each node of the network is computed according to the time offset and the appointed frequency hopping computing formula, thereby finishing the de-hopping process. The invention can complete frequency hopping network deployment and frequency hopping communication; GPS time is used as third party time to carry out frequency hopping synchronization, thereby eliminating multiple information alternation by traditional frequency hopping synchronous method to complete frequency hopping synchronization, and simplifying the process of frequency hopping synchronization; and the chaotic frequency hopping sequence is used so that the whole frequency hopping system is more safe and reliable.