173 results about "Pulse repetition frequency" patented technology

The invention discloses a laser coaxial beam combining system for improving the repetition frequency of laser pulses, which comprises p polarization pulse lasers, a pulse time sequence controller and n stages of beam combining devices, each stage of beam combining device comprises an s polarization pulse laser, a polarization beam combiner and an electro-optical Q switch, and n is a non-negative integer and is greater than or equal to 1. The invention has the following advantages: a plurality of beams of laser in different polarization states can be combined, the pulse repetition frequency and the output average power of the laser are improved, the optimal pulse energy and peak power are maintained, and coaxial output of pulses in the same polarization state is realized.

A method of simulating radar ground or sea clutter for testing and designing of radar by providing a terrain model including discrete flat ground patches each having a reflectivity, area, surface normal vector, and position within a global coordinate frame, calculating triplet values of reflected energy, range and Doppler shift for each discrete patch of the terrain model for a given position and pose of an antenna with known gain and phase characteristics within the global coordinate frame; and for a given radar receiver sample rate and Pulse repetition frequency (PRF), resampling and integrating over all patches through carrying out a 2D transformation using a non-uniform Fast Fourier Transform. The method can correct the lack of spatial correlation and increase the speed at which realistic ground clutter modelling can be generated.

The invention provides an inter-satellite direct wave interference suppression method and system for synthetic aperture radar satellites. The method comprises the following steps: inputting SAR original echo data and system parameters thereof; calculating a pulse repetition frequency, a signal bandwidth and a frequency modulation rate; performing matched filtering and filtering on the original echo data to obtain an echo signal; and carrying out direct wave interference trapped wave processing and inverse matching filtering processing on the echo signal, and outputting original echo data after suppression processing. According to the method, signal self-correlation processing is adopted for detecting and suppressing the inter-satellite direct wave interference for the first time, the problem that an existing inter-satellite direct wave interference suppression processing method greatly depends on model applicability is solved, and important technical support is provided for subsequent large-scale SAR constellation earth imaging observation; direct wave interference is suppressed through a parameterization method, and the application effect of the SAR satellite in the fields of resource investigation, topographic mapping, disaster monitoring and the like is remarkably improved.

Embodiments of the invention include a plasma system. The plasma system includes a plasma chamber; an RF driver configured to drive bursts into the plasma chamber with an RF frequency; a nanosecond pulser configured to drive pulses into the plasma chamber with a pulse repetition frequency, the pulse repetition frequency being less than the RF frequency; a high pass filter disposed between the RF driver and the plasma chamber; and a low pass filter disposed between the nanosecond pulser and the plasma chamber.

The invention discloses a programmable waveform modulation high-power optical fiber laser system, particularly relates to the field of high-power optical fiber lasers, and is used for solving the problem of power monitoring and control instability caused by alias distortion under high pulse repetition frequency. Micro-amplitude random time jitter is implanted, sampling and pulse rhythm coupling are scattered through synchronous mapping of a time mark and a power sequence, and turn-back pseudo fluctuation is blocked from the source; the abstract evaluation mechanism fuses energy domain and time domain features, and uses a single determination identifier to drive sampling frequency adaptive migration, so that a monitoring link is continuously in a co-prime fraction ratio operation interval, and alias distortion root causes are eliminated; the sampling label and the judgment identification jointly trigger a feed-forward gain matrix to form a monitoring evaluation adjustment compensation closed loop, power aftershock is reduced in real time, stimulated scattering and thermal lens linkage amplification are inhibited, and light beam quality stability and energy smooth distribution are maintained.

The invention relates to the technical field of synthetic aperture radars, and discloses a dechirp strip SAR waveform design method based on time domain azimuth ambiguity, and the method comprises the steps: obtaining the azimuth output maximum width and synthetic aperture length of an SAR image through calculation; respectively calculating the minimum value and the maximum value of the pulse repetition frequency through the scene size and the synthetic aperture length so as to determine the initial selection range of the pulse repetition frequency; constructing a time domain azimuth ambiguity function, presetting a time domain azimuth ambiguity value, and traversing all pulse repetition frequency values in the pulse repetition frequency initial selection range through the time domain azimuth ambiguity function to obtain a candidate pulse repetition frequency set; in the candidate pulse repetition frequency set, the minimum value of the pulse repetition frequency is used as the final pulse repetition frequency, and the technical problems that the existing time domain azimuth ambiguity is not fully constrained, so that the SAR image has fuzzy artifacts, the imaging quality is influenced and the like are solved.

The present invention discloses a radar HRRP continuous learning method based on a generative adversarial network, comprising the following steps: S1, using measured data including three types of aircraft, namely, a medium-sized propeller aircraft An‑26, a small jet aircraft Cessna, and a large jet aircraft Yark‑42, the radar operates in the C band, has a signal bandwidth of 400 MHz, and a pulse repetition frequency of 400 Hz; S2, processing intensity sensitivity and translation sensitivity in a preprocessing process; S3, using three different HRRP incremental learning task settings under the background of radar HRRP automatic target recognition; S4, training the HRRP data processed by S2 under the three settings according to a continuous learning related method, and redesigning the decoder for the pseudo-replay DGR method to a conditional autoencoder adversarial network CVAEGAN, wherein the CVAEGAN includes an encoder, a decoder, a discriminator, and a classifier; S5, training the HRRP data processed by S2 using a DGR method of the CVAEGAN network.

The application provides a high-resolution wide-surveying-band imaging method, device and storage medium, and belongs to the technical field of data processing. The method is applied to a synthetic aperture radar, and comprises the following steps: the synthetic aperture radar randomly selects a current pulse repetition frequency in a predetermined pulse repetition frequency value range every preset interval, and adjacent two current pulse repetition frequencies are different and discontinuous; according to the current pulse repetition frequency, the synthetic aperture radar transmits a pulse signal and receives a target-reflected echo signal; and the fast iterative soft threshold algorithm is used to process the target-reflected echo signal, so that a sparse reconstructed target imaging result is obtained. The application aims to solve the problem of high-resolution wide-surveying-band of a single-channel SAR system.

The invention discloses a high-precision photon digital-to-analog conversion system based on noise shaping, which is characterized in that a mode-locked laser generates an optical pulse sequence, optical pulses enter a dispersive medium, and periodic pulses are processed by using a fractional order Talbot effect, so that the pulse repetition frequency is improved; the Delta-Sigma (Delta Sigma) modulation module processes a preset target signal and shifts noise to a high frequency band based on an oversampling technology and noise shaping to realize conversion from an analog signal to a digital signal; the pulse signal with the repetition frequency increased is input into the electro-optical modulation module to serve as a sampling source, and a digital signal generated by the delta-sigma modulation module is input into the electro-optical modulation module for intensity modulation, so that the optical pulse carries the characteristics of frequency change and noise shaping of the signal, and fusion from electric signal modulation to optical signal modulation is completed; inputting the pulse signal after electro-optical modulation into a photoelectric detector, and converting an optical signal into an electric pulse signal; the electric pulse signal enters a filtering module, noise in the electric signal is filtered out, and an analog signal is obtained.

The invention relates to the technical field of intelligent sensors, in particular to an unmanned aerial vehicle track intelligent tracking method based on a millimeter-wave radar, which comprises the following steps: receiving echo signals collected by the front end of the millimeter-wave radar, carrying out constant false alarm rate detection and Doppler frequency shift extraction on the echo signals, generating an unmanned aerial vehicle target space coordinate set, and carrying out target tracking on the unmanned aerial vehicle. And mapping the target space coordinate set of the unmanned aerial vehicle to a three-dimensional Euclidean space. According to the method, a non-convex optimization objective function containing beam switching time cost and precision constraint is constructed, and mathematical optimal solution of radar beam resources is realized. The generated adaptive scheduling instruction is used for adjusting the pulse repetition frequency and the beam residence time, it is ensured that radar front-end parameters dynamically evolve along with the target state, overall centroid tracking is emphasized for rigid body formation so as to save resources, independent high-frequency refreshing is emphasized for discrete targets so as to ensure the precision, and the accuracy is improved. And the continuity and robustness of trajectory tracking of the unmanned aerial vehicle in a complex electromagnetic environment are improved.

A method of measuring a delay time of a propagation of a signal in a line in a circuit structure, the method comprises irradiating the line by pulses of a charged particle beam, wherein a pulse repetition frequency of the pulses of the charged particle beam is varied. The method further comprises measuring, for each of the pulse repetition frequencies, a secondary charged particle emission responsive to the irradiating the line by the pulses of the charged particle beam at the respective pulse repetition frequency, and deriving the delay time of the line based on the secondary charged particle emission responsive to the varying of the pulse repetition frequency.

For shear wave imaging with ultrasound, the apparent pulse repetition frequency is increased by combining displacements from different lateral locations. Different combinations based on different shear wave velocities and corresponding time shifts and / or attenuations and corresponding scalings are tested to find a smooth displacement profile for the combination. Once the smooth displacement profile is found, the corresponding shear wave velocity is estimated or determined.

The embodiment of the application provides a parameter inversion method, device and electronic equipment, wherein the parameter inversion method comprises: performing interference suppression on a received incomplete SAR signal to obtain a non-interference signal matrix; wherein the non-interference signal matrix comprises a plurality of non-interference pulse signals with time sequence continuity, and the incomplete SAR signal represents that the SAR signal is incomplete; sequentially performing data processing on each non-interference pulse signal to obtain pulse parameters of each non-interference pulse signal; the pulse parameters at least comprise a stationary phase center position, a termination point, a pulse bandwidth, a pulse signal frequency modulation rate and a peak position; based on the pulse parameters of each non-interference pulse signal, signal parameters of the incomplete SAR signal are inverted to obtain transmission parameters of the incomplete SAR signal; the signal parameters at least comprise a pulse width, a bandwidth, a frequency modulation rate, a pulse repetition interval and a pulse repetition frequency.

FIELD: protective coatings.SUBSTANCE: method for forming a protective oxide-ceramic coating on the surface of products made of valve metals and alloys by the plasma electrolytic oxidation method involves immersing the product as an electrode together with a counter electrode in a bath filled with an aqueous alkaline electrolyte, and supplying rectangular pulses of anodic and cathodic voltage to the electrodes using a pulsed power source. Anode and cathode voltage pulses are supplied with a current-free pause between them, the value of which is 4.8 times the duration of the anode pulse. The amplitude values of the cathode voltage pulses range from 85 to 149 V with a pulse repetition frequency from 1000 Hz to 4000 Hz, while the current pulse repetition frequency is additionally regulated.EFFECT: obtaining oxide-ceramic coatings with specified properties under reduced energy conditions, with lower values of cathode voltage.1 cl, 2 ex

A laser system for multiphoton microscopy comprises a seeder oscillator, fast modulator, amplifier, second modulator, and optical parametric amplifier configured to produce pulses with variable pulse spacing temporally synchronized to a scanner having sinusoidal motion. The variable pulse spacing ensures each pixel receives substantially the same number of laser pulses, eliminating uneven energy distribution of fixed repetition rate systems. The scanner operates at 4-12 kHz frequencies while the seeder oscillator produces femtosecond pulses at 10-100 MHz with 10-100 ns pulse spacing. The optical parametric amplifier outputs wavelengths from 600-1900 nm, with 1300-1700 nm optimized for three-photon microscopy. Methods include synchronizing pulse timing to scanner motion and varying interpulse intervals across scan lines. For 8 kHz scanners with 512 pixels per line, the system achieves 32% energy reduction compared to constant pulse spacing while maintaining 100-150 mW average power on biological samples, preventing thermal damage and enabling video rate imaging.

A first radar transmitter capable of transmitting a pulse-modulated radar signal to a target, a second radar transmitter capable of transmitting a radar signal to the target, a radar receiver capable of simultaneously receiving a radar signal transmitted by the first radar transmitter and reflected by the target and a radar signal transmitted by the second radar transmitter and reflected by the target, and a signal control unit to control one or more of a carrier frequency, a pulse recurrence frequency, and a duty ratio of a pulse-modulated radar signal, and a carrier frequency of a non-pulse-modulated radar signal with respect to the first radar transmitter or the first radar transmitter and the second radar transmitter are provided.

For shear wave imaging with ultrasound, the apparent pulse repetition frequency is increased by combining displacements from different lateral locations. Different combinations based on different shear wave velocities and corresponding time shifts and / or attenuations and corresponding scalings are tested to find a smooth displacement profile for the combination. Once the smooth displacement profile is found, the corresponding shear wave velocity is estimated or determined.

A method may include identifying a time window of a procedure. The method may also include obtaining operational information of the time window. The operational information may include a limit of pulse repetition frequency (PRF) acceleration and a plurality of preliminary radio frequency (RF) PRFs. The method may also include determining a plurality of updated RF PRFs by updating the plurality of preliminary RF PRFs. A rate of variation between any two adjacent updated RF PRFs may be less than or equal to the limit of PRF acceleration. The method may also include causing an RF source to generate electromagnetic waves at the plurality of updated RF PRFs in the time window.

The application provides a pulse repetition frequency type recognition method and device based on graph domain mapping and feature enhancement, and relates to the technical field of radar signal processing. The method comprises the following steps: determining a pulse repetition frequency sequence corresponding to a screened pulse repetition frequency; taking the reciprocal of the pulse repetition frequency sequence to obtain a pulse repetition interval sequence; dividing the pulse repetition interval sequence into multiple subsequences according to a preset length; transforming the multiple subsequences into a Gram difference angle field image according to a graph domain mapping algorithm, and dividing the image into training samples and test samples; constructing a pulse repetition frequency type recognition network, inputting the training samples into the pulse repetition frequency type recognition network, training the pulse repetition frequency type recognition network, and obtaining a trained pulse repetition frequency type recognition network; and inputting the test samples into the trained pulse repetition frequency type recognition network to recognize multiple pulse repetition frequency types. In this way, the recognition accuracy and robustness of the pulse repetition frequency type are improved in a complex non-ideal scene with a high proportion of missed pulses and false pulses.

The application discloses an engine rotor multi-parameter measurement system and method, and the system comprises a first optical comb, a second optical comb, a polarization maintaining optical fiber amplifier, a polarization maintaining optical fiber beam splitter, an integrated polarization maintaining optical fiber ring, an integrated polarization maintaining optical fiber beam combiner, a plurality of high-temperature-resistant optical fiber probes, a high-speed photoelectric detector and a data acquisition and processing system; the pulse repetition frequency of the first optical comb is greater than that of the second optical comb, and the two have a high repetition frequency difference; the plurality of high-temperature-resistant optical fiber probes respectively generate reference light pulses and measurement light pulses; the scanning light pulses emitted by the second optical comb respectively interfere with the plurality of reference light pulses and the plurality of measurement light pulses to generate double-comb interference reference signals and double-comb interference measurement signals; through processing of the reference signals and the measurement signals of each channel, the engine rotor speed, the blade tip clearance, the blade tip timing and the blade vibration parameters are obtained. The application has the advantages of high measurement speed, high measurement accuracy and multi-parameter synchronous measurement.

The invention belongs to the technical field of pulse power, and particularly discloses a frequency superposition pulse circuit based on an avalanche transistor, a generator and a control method. According to the frequency superposition pulse circuit, the frequency superposition pulse circuit is composed of the multiple pulse units, the finally output repetition frequency pulse is composed of the outputs of the multiple pulse units, superposition on the frequency is achieved, and the pulse repetition frequency can be improved while the pulse amplitude can be effectively guaranteed. The pulse repetition frequency of a single pulse unit can be effectively reduced while the purpose of high repetition frequency output is achieved, the problem that the repetition frequency of output pulses of a single Marx circuit based on an avalanche transistor is insufficient is solved, meanwhile, the problem that the avalanche transistor and a resistor in the single pulse unit generate heat under high repetition frequency pulses can be effectively relieved, and the pulse repetition frequency of the single pulse unit can be effectively reduced. And thermal damage of the device under high repetition frequency pulses is avoided. The n isolation diodes in the same pulse unit are connected in series, so that the output end of the whole pulse unit generates high voltage, an isolation effect is achieved, and false triggering of m pulse units is avoided.

The present application relates to radar target recognition tracking technical field, especially in the field of phased array radar multi-target adaptive identification method and system, including: first, the radar echo and platform attitude data are acquired, the velocity distribution is extracted and the target is divided into two groups of high speed / low speed; for high speed group, the displacement prediction parameter is extracted to adaptively adjust the beam pointing sequence, for low speed group, the pulse repetition frequency is determined based on the residence time window and the frequency shift characteristics, and the resource allocation scheme is generated; then the attitude correction result is integrated into the beam control parameter, the adaptive observation sequence is generated combined with the resource scheme, and the trajectory information is tracked in real time; again, the Doppler shift deviation is estimated according to the trajectory, the gain / bandwidth and other signal processing parameters are compensated online, and the corrected target position and velocity are output. The present application realizes three-dimensional high-precision identification, continuous stable tracking and efficient resource utilization in complex dynamic scene.

The invention relates to the technical field of space imaging, and provides a space target space-based microwave imaging parameter optimization method and device. According to the method, through predicting a target intersection section of a detection satellite and a space target, an average relative speed, a minimum intersection distance and an orbit prediction error component of the detection satellite and the space target are extracted from the target intersection section; determining the optimized detection time length and the optimized detection frequency of the detection satellite at least based on the minimum intersection distance and the orbit forecast error component, and determining the optimized imaging time length of the detection satellite at least based on the average relative speed and the minimum intersection distance, and multi-constraint cooperative solution is carried out on the pulse repetition frequency PRF of the detection satellite at least based on the average relative speed and the minimum intersection distance to obtain the optimized PRF, microwave imaging parameter optimization design of quantitative model and actual scene constraint is realized, the efficiency is high, the application scene is wide, and the method is suitable for large-scale popularization and application. And powerful support is provided for precision improvement and engineering landing of a space-based microwave imaging technology.

The present invention discloses a short cavity structure for achieving dual locking of high-repetition-rate femtosecond lasers. The short cavity structure comprises a metal bottom box, a metal top box, a temperature detection element, a piezoelectric actuator, a semiconductor refrigeration plate, and a gain fiber. The metal bottom box and the metal top box are provided with grooves for fixing the gain fiber. The piezoelectric actuator is fixed in the cutout of the metal bottom box and achieves rapid locking of the laser resonant cavity output pulse repetition rate by stretching the gain fiber. The gain fiber is fixed to the upper surface of the piezoelectric actuator. The temperature sensing area of ​​the temperature sensing element is placed in the side opening of the metal bottom box. The cooling surface of the semiconductor refrigeration plate is bonded to the bottom surface of the metal bottom box to suppress the influence of ambient temperature changes on the laser resonant cavity output pulse repetition rate, thereby achieving slow locking of the laser resonant cavity repetition rate. The present invention overcomes the sensitivity of the short cavity laser output pulse repetition frequency to the environment and achieves long-term and precise locking of the short cavity laser output pulse repetition frequency.

The present application relates to a dual-comb laser, and in particular to a direction-polarization multiplexing single-cavity dual-comb laser, which solves the technical problems of the prior art that pulse components in different polarization directions are difficult to separate, leading to high difficulty in dual-polarization mode locking, harsh implementation conditions, or difficulty in adjusting the pulse repetition frequency difference, and the numerical value is small, or the mutual coherence of the output pulse sequence is low, and the signal-to-noise ratio is low. The present application adopts a full polarization maintaining optical fiber resonant cavity with a polarization beam splitter as a central node and a double-linked ring cavity structure composed of ring structure A and ring structure B. The laser transmitted in the counterclockwise direction in the ring structure A is cut off, and the laser transmitted in the clockwise direction is separated by the polarization beam splitter and transmitted in the opposite direction in the ring structure B, partially output, and partially returned to the ring structure A, thereby realizing cyclic oscillation.

The invention relates to a method and system for machining small holes in a transparent hard and brittle material and an intelligent terminal, and relates to the technical field of laser machining. Searching a corresponding concentric circumference scanning track from a preset track database based on the punching diameter; acquiring laser parameters and galvanometer parameters; searching a corresponding period distribution diagram from a preset parameter database based on the galvanometer parameters; calculating pulse interval time based on the pulse repetition frequency; determining jump time based on the pulse interval time and the period distribution diagram; adjusting the laser parameter based on the jump time to obtain an actual laser parameter; and performing a vector dotting process on the perforated material. The laser drilling device has the advantages that the jumping time is set, so that each pulse falls within the moving stable period of the galvanometer, and the laser drilling stability is improved.

The present specification describes a system for eliminating X-ray crosstalk between a plurality of X-ray scanning systems and passive radiation detectors. The system includes a frequency generator for generating a common operational frequency, a high-energy X-ray source or scanning system coupled with the frequency generator for receiving the common operational frequency and configured to modify the pulse repetition frequency of the high-energy X-ray source or scanning system in order to synchronize with the common operational frequency and a low-energy X-ray scanning system and / or passive radiation detection system coupled with the frequency generator for receiving the common operational frequency and having a processing module configured to remove data associated with the common operational frequency at an instance of time if the high-energy X-ray source or scanning system has emitted X-rays at the instance of time.

The application discloses an interferometric SAR synchronization method of radar inter-satellite link combined with Ka-band link cross correction, and aims at the problems of interrupting normal SAR imaging or existing initial phase winding in the existing synchronization link method, and proposes a cross correction scheme of X-band radar inter-satellite link combined with Ka-band high-precision synchronization link. The system adopts a common reference source to ensure the phase correlation, and different synchronization time sequences are designed, that is, the X-band link is synchronized at a low frequency to eliminate the initial phase winding, and the Ka-band link is synchronized at a high frequency same as the SAR pulse repetition frequency (PRF) to realize high-precision phase measurement. During ground processing, the initial phase error of the Ka-band compensation function is corrected by using the X-band synchronization data, so that a high-precision phase synchronization compensation function is obtained, and the echo of the secondary satellite is compensated. The application solves the problem of initial phase winding under the premise of not interrupting the normal SAR imaging time sequence, and significantly improves the phase synchronization precision, image quality and absolute height measurement reliability of the dual-satellite interferometric SAR system.

The present application relates to a kind of quantum key distribution codec silicon-based chip and its matching method, belong to quantum key distribution technical field.The chip of the present application includes optical power distribution unit, photoelectric detector, micro resonant cavity and codec, photoelectric detector calculates input optical pulse repetition frequency, selects the codec matched with the optical pulse repetition frequency, controls the resonant wavelength of the micro resonant cavity connected to the selected encoder to be consistent with the wavelength of input optical pulse, input optical pulse to the branch where the codec is located, controls the resonant wavelength of the micro resonant cavity connected to the codec not matched with the optical pulse repetition frequency, so that the wavelength difference between the resonant wavelength and the wavelength of input optical pulse is greater than the set threshold value.The problem that the key cannot be effectively generated due to the different pulse repetition frequency matched between the transmitter encoder and the receiver decoder when different manufacturers or the same manufacturer different generations of QKD equipment are networked is solved.