61 results about "Short term stability" patented technology

Positional information of a movable body in a Y-axis direction is measured using an interferometer and an encoder whose short-term stability of measurement values excels when compared with the interferometer, and based on the measurement results, a predetermined calibration operation for obtaining correction information for correcting measurement values of the encoder is performed. Accordingly, by using measurement values of the interferometer, correction information for correcting the measurement values of the encoder whose short-term stability of the measurement values excels the interferometer is obtained. Then, based on the measurement values of the encoder and the correction information, the movable body is driven in the Y-axis direction with good precision.

Positional information of a movable body in a Y-axis direction is measured using an interferometer and an encoder whose short-term stability of measurement values excels when compared with the interferometer, and based on the measurement results, a predetermined calibration operation for obtaining correction information for correcting measurement values of the encoder is performed. Accordingly, by using measurement values of the interferometer, correction information for correcting the measurement values of the encoder whose short-term stability of the measurement values excels the interferometer is obtained. Then, based on the measurement values of the encoder and the correction information, the movable body is driven in the Y-axis direction with good precision.

The invention relates to a high-precision time-delay precompensation optical fiber timing method which comprises the following steps of: firstly, extracting a PPS (Pulse Per Second) signal from a received line code stream and outputting by a terminal station; circularly returning the received line code stream to a center station; recovering the PPS signal from the circularly returned line code stream by the center station; measuring a time interval between a sending PPS and a recovered PPS; subtracting a bidirectional time delay of terminal equipment to acquire an optical fiber link bidirectional transmission time delay; calculating a one-way time delay from the center station to the terminal station; and adding a one-way time delay value of the terminal equipment to acquire a precompensation time delay. The precompensation value is used as a precompensation time delay of the next PPS and coded before the next PPS is sent to the terminal station. The invention has the advantages of uniform reference and high stability and is easy to simultaneously ensure the long-term stability and the short-term stability of time transmission.

The invention provides a high-stability and constant-temperature controller and belongs to the technological field of electronic circuit. The invention comprises a voltage reference circuit (1), a temperature setting circuit (2), a temperature measurement circuit (3), a PI control circuit (4), a limiting protection circuit (5), display circuit (6) and a TEC drive Circuit (7); wherein, the TEC drive Circuit (7) comprises a bridge circuit and a voltage negative feedback circuit. The invention has the strong anti-interference capability, the stable performance, and the reliable work; the invention is suitable for the temperature control of high-power laser diodes to make the diodes work for a long time; the temperature control range is 0 DEG C to 80 DEG C; the short-term stability is 0.02 DEG C; the long-term stability is 0.05 DEG C. Besides the use in the constant temperature control of the high-power laser diodes, the invention can be widely used in other fields of modern technology by adjusting the proper control parameters.

A rubidium atom oscillator is not influenced by a circumference noise or the like, and is excellent in the short-term stability and the phase noise characteristic. A crystal oscillator oscillates a fixed frequency as an atomic resonance frequency. A direct digital synthesizer inputs an output of the crystal oscillator as a system clock and also inputs tuned data corresponding to an error signal generated according to a resonance frequency so as to carry out a variable control of an output frequency. A frequency synthesizer synthesizes and multiplies an output of the direct digital synthesizer and applies a phase modulation with a low-frequency signal. An atomic resonator inputs an output of the frequency synthesizer and detects an error signal with respect to a resonance frequency of rubidium atoms. A tuned-data generating circuit inputs the error signal from the atomic resonator so as to generate the tuned data corresponding to the error signal. The output frequency of the direct digital synthesizer is output from the rubidium atom oscillator.

The invention provides a sophisticated and constant temperature control experiment box and belongs to the technological field of electronic equipment. The invention consists of an incubator (10) and a constant temperature controller. The incubator (10) comprises an insulation component and a thermal transfer component; the constant temperature controller consists of a temperature setting circuit (1), a temperature measurement circuit (2), a subtraction circuit (3), a PI control circuit (4), a limiting protection circuit (5), a TEC drives circuit (VCCS) (6) and a display circuit (7). The invention has the stable performance and the reliable work; the temperature control accuracy is 0.1 DEG C; the short-term stability is plus or minus 2.6*10<-3> DEG C; the long-term stability is plus or minus 0.024 DEG C; the temperature range at the normal temperature is 10 DEG C to 40 DEG C. The invention can not only be used for providing a constant-temperature environment for active lock-mold fiber laser experiment, but also can be used for measurement and testing on small occasions and for detection of gradually changed weak signals.

The invention relates to a constant current driver of a digital semiconductor laser, belonging to the technical field of electronic equipment. The structure of the constant current driver comprises a front panel (1), a central processing unit (CPU) STC89C51 (2), a button input circuit (3), an LED indicating lamp output circuit (4), a serial communication circuit (5), an A / D converting circuit (6), a D / A converting circuit (7), a power feedback circuit (8), a current feedback circuit (9), a time delay soft start circuit (10), a current output circuit (11) and a display module (12). The constant current driver has the output current of 0-2A, adopts negative feedback structure, effectively improves the output stability, and has the short-term stability being lower than 38ppm; two driving ways which are constant current and constant power are provided by the constant current driver, so that the constant current driver is convenient for use on different occasions; the constant current driver has the protecting functions such as current limitation, soft start, time delay and the like, so as to effectively guarantee the safety of the laser; and program can be controlled and upgraded in system.

The invention discloses a high-precision distributed optical fiber frequency transfer method. Local transferred frequency signals are subjected to frequency halving and then serve as detection signals, the signals are transmitted back and forth between the local end and a remote end through bidirectional wavelength division multiplexing, and detection signals comprising optical fiber link phase noise are obtained at the local end; the returned detection signals and the local transferred frequency signals are subjected to frequency mixing and filtering to obtain phase conjugation signals, and the phase conjugation signals are transmitted to the optical fiber link through another wavelength channel; all users detect forward conjugation signals and backward detection signals, and stable frequency signals are obtained through frequency mixing; and the remote end carries out frequency mixing on the received forward phase conjugation signals and the forward detection signals to obtain stable frequency signals. Influences on frequency transfer short-term stability by backscattering noise can be avoided; the users share the same wavelength, and the fiber frequency long-term stability influences and the cost due to increasing of users can be reduced; and by adopting passive compensation, the method has the advantages of relatively simple and unlimited dynamic range and quick compensation.

The invention relates to accuracy correction of second-level frequency scale on the ground or on a satellite, in particular to a precise domestication conserving method of second-level frequency scale for maintaining original lock in lock-losing situation. In the locking process, controlling and correcting voltage of local frequency scale is obtained; the controlling and correcting voltage is analyzed along with changes of time and temperature; when the second-level frequency scale enters domestication conserving state, temperature data and aging data constructed in the locking process are integrated, thereby calculating compensation voltages of the second-level frequency at various moments and temperatures. The method of the invention uses time frequency signal transmitted by a satellite positioning and timing system to lock the second-level frequency scale, thereby outputting high-precision frequency signal; short-term stability of the method keeps a level the same as that of a local oscillator; and the method effectively reproduces long-term stability and accuracy while receiving standard time frequency signal on a local controlled frequency scale.

The invention relates to a device and method for detecting short-term stability parameters of a frequency source in a digitalization mode. The device comprises an input preprocessing module, an input signal detection and DDS module, a local oscillator clock module, a high frequency clock module, a clock synchronization module, a sampling and digital down frequency conversion module and a stability and phase demodulating module. Low noise band-pass sampling and phase demodulating processing is directly conducted after anti-aliasing filtering is conducted on input signals, frequency stability and phase noise are accurately measured, accuracy and reliability of a measuring system are improved by the utilization of a frequency synthesis technology, a low noise undersampling technology and a cross-correlation statistical average processing algorithm, and the method is simple and quick without complex operations of correction, calibration and the like.

The invention discloses a digital frequency stability measuring method based on total response time. In a digital environment, quantization error in the digital measurement technology is inhibited by use of a clock vernier effect and a digital edge effect, the phase difference between two signals is measured through a digital phase discrimination algorithm, the frequency stability is obtained according to the phase difference, and thus, frequency stability measurement based on total response time is realized. The method can be used to accurately measure the transient stability, short-term stability and long-term stability of different frequency sources and essentially reveal the change rule of the frequency stability of different frequency sources with response time.

The invention discloses a satellite bidirectional time frequency transmission method. The method comprises the following steps of S1. building a satellite bidirectional time frequency transmission link; S2. synchronizing a device timestamp; S3. acquiring four phase difference observation quantities; and S4. calculating a clock difference Tau(t)-Tau(t) of two stations. The satellite bidirectional time frequency transmission method with high precision and high stability can be performed even a user does not change the existing mature commercial device, has a simple measurement process, isparticularly suitable for metering remote time frequency transmission of high-performance atomic clocks like a hydrogen atomic clock and a caesium atomic clock in a laboratory, and can improve remotetime comparison precision and frequency short-term stability remarkably.

Provided is a high-precision active optical fiber microwave frequency transmission system, comprising a local end, an optical fiber link, and a far end. The local end and the far end are connected through the optical fiber link. The local end sends a forward signal. The far end receives the forward signal and returns the signal to the local end. The local end processes a to-be-transmitted frequency signal and a backward signal, and drives the sent forward signal to be conjugate with phase jitter introduced by a single-direction optical fiber link. The forward signal received by the far end is a stable microwave frequency signal. Through a method of frequency conversion, influence of back scattering noise is prevented, signal to noise ratio is improved, being beneficial for improving short stability of frequency transmission. Forward and backward transmission share the same fiber and wave, wavelength asymmetry caused by using wavelength division multiplexing is eliminated, and influence of wavelength interval on frequency transmission long-term stability is prevented.

The invention provides an optical fiber high-precision timing device and method based on single photon detection. The method comprises the steps that: an atomic clock source sends a clock signal and asecond pulse signal to a timing center station; the timing center station generates an encoded optical pulse signal by using the clock source signal and injects the encoded optical pulse signal intoa fiber link; a terminal station partially reflects the encoded optical pulse signal and returns the encoded optical pulse signal to the same fiber link; the center station returns the encoded opticalpulse signal by using a single photon detector, measures loopback delay and calculates and compensates single-direction propagation delay by using loopback transmission delay; the terminal station performs photoelectric conversion on the encoded optical pulse signal which is subjected to delay pre-compensation by the center station to complete time synchronization. The device and the method havethe advantages of uniform benchmark, high stability and the guarantee of the long-term stability and short-term stability of time transmission at the same time.

The invention relates to a high-precision optical fiber microwave frequency transmission system, which comprises a local end, an optical fiber link and a far end, wherein the local end and the far endare connected through the optical fiber link; the local end sends a forward signal, the far end receives the forward signal and returns the signal to the local end, the local end processes a to-be-transmitted frequency signal and a backward signal, generates a signal which is conjugated with phase jitter introduced by the one-way optical fiber link and sends the forward conjugated signal to the far end. The forward conjugated signal received by the far end is a stable microwave frequency signal. The high-precision optical fiber microwave frequency transmission system avoids influences of backscattering noise through a method of frequency conversion, thereby improving the signal-to-noise ratio, and being conducive to improving the short-term stability of frequency transmission; and meanwhile, forward and backward transmission share the same fiber and wave, so that wavelength asymmetry introduced by using wavelength division multiplexing is eliminated, and influences imposed on the long-term stability of frequency transmission by the wavelength interval are avoided.

A cold atom all-optical state selection device comprises vacuum flange, an optical state-selecting region, a magneto-optical trap, and a cavity base connected in sequence from top to bottom; when thecold atomic fountain clock starts to work, based on the magneto-optical trap cooling, trapping to get cold atomic groups and simultaneously preparing the clock state during the throwing of the cold atomic groups. The invention not only greatly increases the number density of the clock state atoms, but also shortens the height of the whole clock, thereby greatly shortening the dead time of the intermittent clock, thereby achieving the purpose of shortening the cycle and improving the short-term stability of the cold atomic clock. The device has a simple structure and is easy to implement, and can be used as a core device of a laser cold atomic clock.

The invention discloses a high-reliability frequency source device, and aims to provide a frequency source device with high reliability, and good long-term and short-term stability. The equipment is implemented through the following technical scheme: two three-in-one antennas and signal amplifiers are adopted by a receiving switching unit and are connected in series to form a 2*3 signal switching matrix; the 2*3 signal switching matrix switches received satellite signals via multichannel receiver chips and a one-out-three switch; the one-out-three switch receives three paths of satellite second signals which can be of a same source or different sources; one path of the satellite second signals selected is fed into a one-to-three power divider; three paths of same-source satellite second signals obtained by power dividing are respectively transmitted to a locking unit so that the input same-source satellite second signals are locked and are respectively output to a signal processing unit A and a signal processing unit B; and the other path of satellite second signals passing through the one-to-three power divider is used for carrying out frequency correction disciplining on a rubidium clock; standard frequency signals are transmitted to a signal processing unit C via a rubidium clock phase locking unit; and thus, three standard frequency signals of the same source are formed and output.

The invention discloses a method and a device for optimizing short-term stability parameters of an atomic frequency standard, which belong to the field of the atomic frequency standards. The method comprises the steps that a plurality of working parameter points are set; each working parameter point includes a plurality of experiment points which correspond to different parameters to be optimized, each parameter to be optimized corresponds to the plurality of experiment points, and the quantities of the corresponding experiment points are the same, the experiment points corresponding to the same parameter to be optimized are evenly distributed in a value area including two end points of the parameter to be optimized, at most one same experiment point exists in every two working parameter points, and the frequency of each experiment point in all the working parameter points is the same; each parameter to be optimized includes modulation depth, modulation frequency and microwave power; according to each working parameter point, the modulation depth, the modulation frequency and the microwave power are respectively regulated; and frequency discrimination gradient of the atomic frequency standard corresponding to each working parameter point is calculated, and the optimal working parameter point is selected. The method and the device improve the short-term stability of the atomic frequency standard.

The invention belongs to the field of pharmaceutical preparations, and provides an andrographolide nano suspension and a preparation method thereof. The andrographolide has low solubility in water, can be easily excreted by P-gp, has high metabolism rate, and thus, has lower dissolution rate and lower in-vivo bioavailability. In order to enhance the dissolution rate and bioavailability of the drug, a P-gp inhibitor TPGS and an ionic stabilizer SDS are selected to prepare the andrographolide nano suspension by using a medium grinding technique; by using the particle size and distribution as evaluating indicators, a Box-Behnken center combined degisn test optimized preparation technique is utilized to prepare the andrographolide nano suspension; and freeze-drying is used for solidifying. After carrying out the characterization, the research in short-term stability, Caco-2 permeability and in-vitro dissolution, and the in-vivo pharmacokinetic and pharmacodynamic research, the results indicate that the andrographolide nano suspension can increase the dissolution rate of andrographolide and enhance the oral-administration bioavailability and anti-inflammatory action.

The invention relates to a device for dynamically adjusting the crystal oscillator stability of a WiMAX base station and a realization method thereof. The device includes a frequency counter, a phase detector, a crystal oscillator, a digital-to-analog converter and a GPS receiver. It uses the 1pps signal output by the GPS receiver to calibrate the stability of the crystal oscillator output signal frequency, which can quickly adjust the error accuracy of the crystal oscillator to within 0.5Hz, and finally stabilize the error accuracy of the crystal oscillator within 0.01Hz. The feature of this method is to pre-calculate the adjustment coefficient between the phase detector and the crystal oscillator. During dynamic calibration, the error value of the crystal oscillator can be directly calculated only by calculating the error value of the phase detector. Using the adjustment coefficient to adjust the crystal oscillator error is a novel method in the field of crystal oscillator adjustment. This method has a fast calibration speed and a simple algorithm. It can quickly adjust the oscillation frequency of an ordinary crystal oscillator to high accuracy, and has long-term stability and short-term stability. all good.

Positional information of a movable body in a Y-axis direction is measured using an interferometer and an encoder whose short-term stability of measurement values excels when compared with the interferometer, and based on the measurement results, a predetermined calibration operation for obtaining correction information for correcting measurement values of the encoder is performed. Accordingly, by using measurement values of the interferometer, correction information for correcting the measurement values of the encoder whose short-term stability of the measurement values excels the interferometer is obtained. Then, based on the measurement values of the encoder and the correction information, the movable body is driven in the Y-axis direction with good precision.

The invention provides a frequency domain CPRI frame encapsulation method and a BBU executing the method. The method comprises the steps of configuring a CPRI frame header part based on the long-term stability content, the part including a reference signal power field, a PDCCH power field, a system bandwidth field and an antenna number field; and configuring a CPRI frame effective load part, including compressed I / Q data and sub frame header part based on short-term stability content.

A system for optimizing short-term stability of a clock from a clock source synchronized with a first reference clock source with long-term stability transmits numbers of clocks of a first reference clock from the first reference clock source (21, 22, 23, 24) to the clock source (8) between an initialization time and a plurality of times in each case in a data-packet-oriented network (9). The clock from the clock source (8) is adjusted by correcting a difference between numbers of clocks of the first reference clock which are received in the clock source (8) and numbers of clocks of the first reference clock between the initialization time and the respective times at which the numbers of clocks of the first reference clock are received. In addition, numbers of clocks of a second reference clock for the data packet are transmitted to the clock source (8) at individual times with the number of clocks from at least one second freewheeling reference clock source (111, 112). The maximum difference between the first reference clock and the second reference clock from the clock source (8) is known. The difference between the clock from the clock source (8) and each second reference clock is limited to a first adjustable threshold value.

The invention discloses a constant temperature crystal oscillator high-precision frequency control device and a control method thereof. The device comprises a control computer, an MCU single chip, a high-precision digital-analogue converter and a constant temperature crystal oscillator; the control computer is used for converting an appointed voltage value into a serial instruction to output to the MCU single chip; the MCU single chip is used for converting the serial instruction into a binary instruction in tri-channel 24bit so as to transmit to the high-precision digital-analogue converter as an analogue time sequence; the high-precision digital-analogue converter is used for producing appointed analogue voltage amount to control the frequency of the constant temperature crystal oscillator. Electric control voltage resolution of the constant temperature crystal oscillator is improved to achieve 7.82muV; a constant control voltage is given to the constant temperature crystal oscillator, the stability of the output frequency achieves the nominal extremity which is 7.8*10<-14>(@average time: 8s); only one serial port of the computer is occupied and a data acquiring card channel cannot be occupied, thus the control process to the constant temperature crystal oscillator is simplified; the short-term stability of the constant temperature crystal oscillator after being locked by an atom fountain device achieves 2.8*10<-13>tau<-1 / 2>.

The invention provides a hydrogen and cesium time scale fusion method based on Vondik-Cepek filtering. Firstly, using an exponential filtering method for respectively generating a clock group time scale for a hydrogen clock group and a cesium clock group; and then selecting a Vondik-Cepek combined filtering key parameter according to a least square principle, and further performing performance enhancement on the cesium clock group time scale through differential information of the hydrogen clock group time scale time sequence, thereby obtaining a hydrogen-cesium fusion time scale. According tothe method, the noise is effectively suppressed, meanwhile, the characteristics of hydrogen and cesium atomic clocks can be considered, fusion is carried out on the clock group scale level, and the time scale with good long-term and short-term stability is generated.

The invention discloses a coherent population trapping atomic frequency standard and a method for improving the short-term stability thereof and belongs to the field of atomic frequency standards. The atomic frequency standard comprises a voltage controlled crystal, a polarized excitation unit, a physical unit, a servo loop, a control unit and a system relaxation time detection unit. The polarized excitation unit is used for producing microwave searching signals according to the output frequency of the atomic frequency standards; the physical unit is used for producing optical detecting signals under the effect of the microwave searching signals; the servo loop is used for producing synchronous phase demodulation signals performing synchronous phase demodulation on the optical detecting signals; the control unit is used for producing rectifying voltage affecting the voltage controlled crystal according to the synchronous phase demodulation signals; the system relaxation time detection unit is used for detecting the system relaxation time delta t of the atomic frequency standard; the control unit is further used for performing timing control on an optical switch and the servo loop of the physical unit according to the system relaxation time delta t and controlling the servo loop to perform synchronous phase demodulation on the optical detecting signals produced by the physical signals after controlling the optical switch of the physical unit to switch on for N delta t.