940 results about "Chirp" patented technology

The invention belongs to the technical field of lasers, and discloses a 9-shaped hybrid mode-locked fiber laser, which comprises a pumping source, a 2 * 2 polarization-maintaining fiber coupler, a nonlinear amplification loop mirror loop connected with the first side of the polarization-maintaining fiber coupler, and a chirp fiber Bragg grating connected with the second side of the polarization-maintaining fiber coupler, the polarization maintaining optical fiber coupler is located at the connecting position of the nonlinear amplification annular mirror loop and a linear arm of the laser resonant cavity and used for coupling laser of the nonlinear amplification annular mirror loop to the linear arm, and after being reflected by the chirp fiber bragg grating, the laser is output to the nonlinear amplification annular mirror loop through the chirp fiber bragg grating. And then the laser on the linear arm is split into two beams of light which are transmitted clockwise and anticlockwise in a loop of the nonlinear amplification annular mirror. Two passive mode locking technologies are combined, rapid and stable mode locking can be achieved, the influence of the environment on the operation state is small, the signal-to-noise ratio of output laser pulses can be increased, and ultra-short pulses with narrower pulse width can be achieved.

A novel wireless technology, referred to as ZChirp, is proposed. ZChirp is based on the chirp modulation that has been used in the past, but with the key distinction of multiplying the chirp with a binary sequence called the Z sequence, which serves dual purposes. First, chirps multiplied with different Z sequences have very low cross-correlations, which significantly reduces demodulation errors due to interference and allows for multiple access. Second, a node can double the communication speed by multiplying different Z sequences depending on the data. Real-world experiments prove that multiplying the chirp with the Z sequence does not increase bandwidth usage or reduce the communication range. The Z sequences have been designed to reduce the interference and the computation complexity.

Embodiments of the present application relate to the technical field of semiconductor lasers, and provide a semiconductor laser and a manufacturing method therefor, which are used to mitigate the problem of chirp in semiconductor lasers. The semiconductor laser comprises: a substrate; a ridge waveguide which is arranged on the substrate and extends in a first direction of the substrate; and a grating which is arranged at a top portion of the ridge waveguide. The grating comprises first regions and second regions periodically arranged in the first direction, each first region comprises a semiconductor material, each second region comprises an insulating dielectric material, and the refractive index of the insulating dielectric material is greater than the refractive index of the semiconductor material.

The invention relates to an all-fiber sub-hundred femtosecond laser based on an SESAM. The all-fiber sub-hundred femtosecond laser comprises the SESAM, a wavelength division multiplexer, a pumping source, a pumping protector, a gain fiber, a chirp fiber bragg grating, an isolator, a reflector, a compression unit and an autocorrelator. According to the invention, the chirp fiber bragg grating with the dispersion amount of 0.115 ps / nm is adopted to compensate positive dispersion in the cavity, so that mode-locked pulse with the spectral width of 23nm is realized. A transmission-type diffraction grating pair is adopted, the pulse width is compressed to 88fs, and the maximum spectral width 27nm is obtained under the dispersion of 0.00087 ps2 in a near-zero cavity. The condition that the optimal spectral bandwidth of the optimal seed source pulse based on the optical fiber chirped pulse amplification laser should be larger than 15 nm is met, and the compression pulse distortion of the amplifier is reduced. By adopting the linear cavity, the SESAM is adhered to the surface of the single-mode optical fiber patch cord for starting mode locking, so that an all-optical-fiber structure of the system is realized, and the single-mode optical fiber patch cord is suitable for industrial integrated application.

The invention discloses a multi-sideband chirp modulation DAS system and a working method thereof, and relates to the technical field of distributed sound wave sensing. The DAS system comprises a narrow linewidth laser, an optical fiber coupler, a phase modulator, an electro-optical modulator, an erbium-doped optical fiber amplifier, an optical fiber circulator, a dense wavelength division multiplexer, a photoelectric balance detector, a data acquisition card, an arbitrary waveform generator, a direct current source and the like. The phase modulator is used for modulating constant-amplitude multi-frequency continuous light, the frequency number of light waves is related to the harmonic number of a microwave modulation signal, the frequency interval is determined by the fundamental frequency of the microwave modulation signal, the continuous light frequency can be flexibly modulated by adjusting the microwave modulation signal, and the modulation bandwidth is large; detected beat frequency signals are compressed into single-frequency signals through pulses, phase information of the single-frequency signals is demodulated, vibration signals along the sensing optical fiber can be detected, the spatial resolution of the system depends on the chirp frequency sweeping range, and the spatial resolution is high.

A centimeter-resolution integrated photonic millimeter-wave (mmWave) radar chip operating in the mmWave V band based on a 4-inch wafer-scale thin-film lithium niobate (TFLN) technology is provided. The fabricated TFLN photonic mmWave integrated circuit has a first electro-optic modulator (EOM) capable of generating a broadband linear frequency modulated mmWave radar waveform through optical frequency multiplication of a low-frequency input signal, and a second EOM for frequency de-chirp of the reflected echo wave, thereby greatly relieving bandwidth requirements for the digital-to-analog converter in the transmitter and analog-to-digital converter in the receiver. In the absence of optical and electrical filters, the radar chip features continuous on-demand tunability of the center frequency and bandwidth, currently only limited by the bandwidths of electrical amplifiers. The radar chip provides a promising way to achieve high resolution sensing and detection for vehicle radar, airborne radar, and smart home in the 6G era.

The invention discloses a frequency offset estimation method and device, electronic equipment and a storage medium, and relates to the technical field of signal processing. In the invention, based on a data signal sent by a signal transmitting end and a local characteristic signal, a subsequent signal used for frequency offset estimation can be obtained, i.e., a fusion signal carrying frequency offset information is obtained; moreover, Chirp-Z transformation is carried out on the fusion signal in a limited residual frequency offset range of a data transmission channel, so that not only is spectrum information of the fusion signal meeting a fine frequency offset estimation requirement obtained, but also the calculation complexity is reduced to a certain extent as the residual frequency offset range is fine, and the accuracy of frequency offset estimation is improved. Namely, high-precision frequency offset estimation is completed under reasonable calculation complexity, so that the problem of insufficient timeliness of signal processing is solved; in addition, in the frequency offset estimation process, the frequency offset estimation precision is further improved by combining the frequency spectrum peak offset.

A system for emulating an over-the-air environment for testing a Frequency-modulated Continuous Wave (FMCW) light detection and ranging (LiDAR) unit under test (UUT). The system includes an optical lens system that receives an FMCW laser signal from the LiDAR UUT, and provides the signals to one or more optical fibers. A slope, chirp timing and intensity of the FMCW laser signal is determined using digital signal processing, and a modulation waveform is determined to emulate an over-the-air (OTA) environment based at least in part on the slope, chirp timing, and intensity. An in-phase quadrature phase (IQ) modulator modulates the FMCW laser signal using the modulation waveform and provides the modulated laser signal back through the optical lens system to the LiDAR UUT.

The invention discloses a compact monolithic dual-wavelength distributed feedback laser device and a manufacturing method thereof, and belongs to the technical field of laser, the laser device is composed of a front part, a middle part and a rear part, and the middle part comprises two equivalent Pi phase shift chirp sampling gratings. The laser is based on a reconstruction equivalent chirp technology and has a tunable wavelength interval. A chirp sampling grating with two equivalent phase shifts is arranged in the laser, and the grating is composed of a front part, a middle part and a rear part. Phase matching is achieved through the microstructure quasi-phase matching technology, it is ensured that a laser resonant cavity reaches the phase matching condition at the phase shift position, and wide-range adjustment expanded from 59.50 GHz to 116.25 GHz can be effectively achieved by changing injection current. The invention has the advantages of accurate wavelength control, simple structure, low power consumption, high integration level and the like.

The invention discloses a tower grounding grid multi-frequency composite wave electric field imaging and soil environment medium diagnosis method, which comprises the following steps of: generating a composite excitation signal through superposition of a low-frequency sine wave and a high-frequency CHIRP square wave, and collecting multi-dimensional data such as voltage / current response, soil temperature and humidity, electric field intensity and the like in combination with a distributed sensor array; separating signal features by using wavelet transform and extracting impedance information of a target frequency point; a multi-grid homotopy algorithm is adopted to realize grounding grid three-dimensional resistivity distribution reconstruction, corrosion spots and abnormal areas are marked, and high-precision positioning of underground conductors is completed through UWB radar or a capacitance detector; meanwhile, based on the information entropy maximization optimization frequency band combination, the grounding grid state is comprehensively evaluated in combination with a multi-parameter fusion model. The method has the non-contact patrol capability, the unmanned aerial vehicle carries equipment to scan the grounding grid, the detection efficiency and convenience are remarkably improved, and an efficient and accurate solution is provided for guaranteeing safe operation of the power grid.

The embodiment of the invention provides a target detection method, an integrated circuit, an electromagnetic wave sensor, equipment and a computer readable storage medium, which can improve the accuracy of target detection. The method comprises the following steps: performing intra-chirp distance dimension FFT (Fast Fourier Transform) and inter-frame speed dimension FFT on an echo signal to obtain distance and speed dimension data; performing first constant false alarm processing on the distance velocity dimension data to obtain candidate target detection points; and performing second constant false alarm processing on the candidate target detection point, and performing target detection based on a second constant false alarm processing result.

The invention provides a distributed feedback laser with a double-layer grating structure, and relates to the technical field of lasers, the laser forms an InGaAlAs multi-quantum well active region, an upper sampling grating layer and a lower phase shift grating layer on an n-type InP substrate in sequence, the upper grating layer is designed based on a reconstruction equivalent chirp technology, and the lower phase shift grating layer is designed based on a reconstruction equivalent chirp technology. Two sections of asymmetric modulation areas with sampling periods linearly gradually changing in opposite directions are arranged in the axial direction of the resonant cavity, and the lower grating layer is a quarter-wave phase shift grating matched with the period of the upper seed grating. Through the synergistic effect of equivalent phase modulation and phase shift generated by the double-layer grating, the photon density distribution in the cavity can be improved, the longitudinal space hole burning effect can be weakened, the sensitivity to end face phase fluctuation can be reduced, high single-mode power and large modulation bandwidth can be realized in a wide temperature range, and the double-layer grating is suitable for a high-speed optical communication and coarse wavelength division multiplexing transmission system.

The invention discloses a micro meteorological change real-time monitoring method based on a millimeter wave radar, and relates to the technical field of meteorological monitoring. The method comprises the following steps: carrying out dynamic acquisition on millimeter wave radar signals and carrying out coordinate system conversion; converting the converted information into a programmable chirp signal through a DDS (Direct Digital Synthesizer) chip; performing space-time adaptive filtering processing on the received signal to eliminate interference; abnormal phase points are detected, and a dynamic noise base model is established; inputting the preprocessed phase data into a pre-trained DPGN network, and outputting a weather result map; a lightweight engine is deployed at a radar end to process the weather result map; when it is detected that the weather gradient exceeds a threshold value, weather early warning is triggered. The adaptive chirp waveform modulation is adopted, the frequency slope and the pulse width of the radar transmitting signal are dynamically adjusted according to the real-time environmental noise level, the meteorological monitoring sensitivity and the small change detection efficiency are improved, and the environmental noise interference is optimized.

The invention relates to the technical field of wireless communication, and discloses a millimeter wave backscatter communication positioning and identification system for multiple tags, which comprises a Chirp signal sending module used for generating and transmitting continuous Chirp signals and receiving signals reflected by customized backscatter tags; and the received signal processing module is used for carrying out demodulation and frequency analysis on the received radar echo signal, determining the distance of the target backscattering tag by measuring the frequency offset of the intermediate frequency signal, and determining the azimuth of the tag through the antenna array of the receiving module. The identity label of the backscattering label is extracted by analyzing the signal intensity; the customized backscattering label is used for adjusting the intensity of the signal reflected back to the radar by changing the reflection state of the backscattering label so as to transmit the identity label of the backscattering label; and the DSSS coding module is used for coding the identity label of the backscattering label so as to increase the signal bandwidth and reduce the signal interference between the labels. According to the method, the customized backscattering tag is matched with the FMCW radar, so that positioning and identification of multiple tags are realized, and the method has a wide application prospect.

The invention belongs to the technical field of metal crack detection, and discloses a metal microcrack ultrasonic detection method, which comprises the following modules: an ultrahigh frequency composite array probe with a center frequency dynamic adjustable range of 5-50 MHz; the dual-mode excitation and receiving module is used for independently generating a pulse reflection mode excitation signal and a diffraction mode chirp frequency modulation signal; the phase-controlled synthetic aperture dynamic focusing module is used for realizing + / -60-degree deflection and sub-wavelength level focusing of acoustic beams; the nonlinear harmonic enhancement module is used for exciting a crack nonlinear effect by superposing 1-2MHz fundamental waves; and a time-space-frequency three-domain data fusion module. According to the method, signal-to-noise ratio collapse caused by the diffraction effect in a traditional method is overcome, more importantly, the system has low-frequency penetrability and high-frequency resolution at the same time due to 80%-120% of broadband coverage of chirp frequency modulation signals, the diffraction signal gain is increased by 20 dB or above, a near-surface blind area is compressed to be within 0.2 mm, and the system can be applied to the field of radar imaging. And the core pain point of missing detection of the near-surface microcracks of the thin-wall component is solved.

The invention provides an ultra-wideband low-absorption low-stress high-reflection thin film based on a gradual change chirp structure, and belongs to the technical field of optical thin films. Different from a mode of mutually combining and superposing high and low refractive index materials of a traditional structured film system to control the reflection bandwidth, the invention provides a logarithmic function gradient chirp structure, the reflectivity index is adjusted by adjusting the total number of film layers, and the reflection bandwidth is adjusted by adjusting head and tail optical thickness coefficients. The problem that the reflectivity is suddenly reduced in a multi-reflection-band superposition reflection gap area when the broadband high-reflection dielectric film is designed is effectively avoided, and the problem of surface distortion caused by thin film stress is reduced by adjusting the film thickness ratio of the stress regulation and control layer to the gradual change main reflection layer. From the perspective of membrane system design, the thickness of the membrane layer is reduced, the preparation period and difficulty are reduced, problems and risks caused by stress are reduced, membrane layer absorption is effectively reduced, and the absorption and stress can be controlled within a proper range in combination with a post-treatment means to effectively support safe and stable operation of the system.

The invention relates to the technical field of radar communication, and discloses a detection identification method and system based on frequency modulation and pseudo-random coding, and the method comprises the steps: a detection device sets waveform parameters, and generates and transmits a Chirp signal to a target device through a radar transmitter; the target device performs frequency and phase modulation on the incident Chirp signal through the electromagnetic metasurface, and then reflects the modulated Chirp signal; and the detection equipment adopts a Chirp signal obtained in the same modulation mode as the target equipment as a matched filter, performs matched filtering on the received echo signal, calculates the code and the distance of the target equipment, and realizes radar detection and target identification. According to the invention, the target passively performs frequency and phase modulation on the incident radar signal through the electromagnetic metasurface, and the detection method can solve the target modulation coding information by knowing the target echo modulation mode so as to identify the target.

The invention relates to the technical field of laser micromachining, in particular to a TGV drilling machining system and method based on a space-time modulation Bessel beam, an initial laser beam is output through a laser device, the initial laser beam is modulated into a dynamic pulse sequence through a pulse chirp regulation and control module, axial energy attenuation is compensated, a machining subsystem generates the Bessel beam, and the TGV drilling machining system and method based on the space-time modulation Bessel beam are obtained. The angle is finely adjusted in real time through piezoelectric driving, and a dynamic spatial light modulator loads an exponential decay type phase mask, so that light beam airspace shaping, non-diffraction light beam generation, pulse time sequence and phase parameter synchronous control and high-peak power pulse array are realized, and finally, integrated micro-perforation and channel modification of the glass substrate are realized; and the machining efficiency and precision are obviously improved.

A system may include a digital front end (DFE). The DFE may be configured to generate a command signal. The system may also include a sweeper. The sweeper may be configured to generate an intermediate in-phase signal, an intermediate quadrature signal, and a LO signal based on the command signal. In addition, the system may include a mixer. The mixer may be configured to generate a mixed in-phase signal based on the intermediate in-phase signal and the LO signal. The mixer may also be configured to generate a mixed quadrature signal based on the intermediate quadrature signal and the LO signal. Further, the system may include an amplifier. The amplifier may be configured to generate an in-phase signal based on the mixed in-phase signal and an amplification setting. The amplifier may also be configured to generate a quadrature signal based on the mixed quadrature signal and the amplification setting.

The invention relates to the technical field of power systems, and discloses a cable defect positioning method, system and device, a medium and a product, and the method comprises the steps: taking a Gaussian envelope linear chirp signal as an initial incident signal for frequency domain reflection, optimizing the signal characteristic parameter of the initial incident signal, obtaining an incident signal, and carrying out the positioning of a cable defect. The method comprises the following steps: exciting a target cable through an incident signal, obtaining a reflection signal on a preset measuring point of the target cable, respectively carrying out time-frequency conversion on the incident signal and the reflection signal to obtain an incident time-frequency domain signal and a reflection time-frequency domain signal, and obtaining a time-frequency domain signal and a reflection time-frequency domain signal on the basis of a cross-correlation function. The peak position of a cross-correlation function is determined through the incident time-frequency domain signal and the reflected time-frequency domain signal, the signal propagation defect time delay of the target cable is determined according to the peak position of the cross-correlation function, and the defect position of the target cable is determined according to the signal propagation defect time delay and the propagation speed of the incident signal. Therefore, surrounding signal interference can be filtered out, and the accuracy of cable defect positioning is improved.

The invention relates to the technical field of laser control, and discloses a 920nm femtosecond pulse fiber laser system based on a neodymium-doped fiber. The system comprises a seed laser source system, a pre-chirp system, an amplification system and a compression system, the output end of the seed laser source system is connected with the input end of the pre-chirp system, the output end of the pre-chirp system is connected with the input end of the amplification system, and the output end of the amplification system is connected with the input end of the compression system. Through a pre-chirp management method, the seed pulse can simultaneously realize the improvement of the pulse energy and the violent broadening of the spectrum in the amplification process. And a wider spectrum can obtain a narrower pulse width after being subjected to time domain compression. The narrower the width of the pulse means that the energy is more concentrated, so that the peak power of the laser pulse output after compression is higher, and the problem that narrow pulse width and high energy output cannot be simultaneously realized in the 920nm wave band in the existing fiber laser technology is solved.

The invention discloses a cable copper shielding layer damage and damage opening size detection method, system and device based on the combination of a frequency doubling measurement method and a step-by-step evaluation method and a storage medium, and is applied to the technical field of power equipment state detection. Comprising the following steps: respectively acquiring measurement results of a cable to be measured under Chirp signal injection of Gaussian envelopes with single and double center frequencies, and determining the starting time of an injection signal and the arrival time of a reflection signal according to an extreme value in a time-frequency cross correlation curve; extracting an injection signal and a reflection signal by taking the starting time and the arrival time as extraction starting points and the length of the injection signal as an extraction width, and calculating the damage degree according to the spectrum ratio of the reflection signal to the injection signal; and calculating characteristic impedance based on the damage degree, and sequentially determining the size and length of the central angle of the cable copper shielding layer damage port by using a step-by-step evaluation method. According to the invention, effective detection and positioning of copper shield damage and effective estimation of the damage size are realized.

The invention discloses a porcelain insulator nondestructive testing device and method based on chirp modulation photoacoustic spectroscopy. The device comprises a signal generator, a signal processing module and a signal processing module, the laser is connected with the signal generator; the power amplifier is connected with the laser; the laser collimator is connected with the power amplifier; and the signal collector collects the sound wave signals, converts the sound wave signals into electric signals, transmits the electric signals to the computer through a cable for data processing, obtains a spectrogram of the sound wave signals, and judges whether defects exist in the porcelain insulator or not according to the spectrogram. According to the porcelain insulator nondestructive testing device adopting chirp modulation and photoacoustic spectroscopy, characteristic frequency scanning is achieved through chirp modulation, a porcelain insulator acoustic signal spectrogram is obtained through the solid photoacoustic effect, non-power-cut nondestructive testing of porcelain insulators can be achieved, and the detection efficiency of porcelain insulator defects is greatly improved.

The invention belongs to the technical field of communication, and particularly relates to a high-robustness multi-channel frequency shift Chirp modulation signal generation method and system for a time-frequency doubly selective channel. The method comprises the following steps of: 1, calculating robust code digits based on statistical characteristics of time delay and Doppler frequency shift of an ionized layer channel; 2, based on the number of robust code bits in the step 1, setting an address code, and realizing RO-MFSCM signal mapping of binary information bits; 3, modulating and transmitting the RO-MFSCM signal based on the information mapping in the step 2, thereby realizing the transmitting process of the RO-MFSCM signal; step 4, based on the emission signal in the step 3 and the robust code digit in the step 1, the receiver carries out robust domain energy aggregation on the RO-MFSCM signal; and step 5, based on the multi-channel robust domain energy aggregation signal in the step 4, adopting a multi-channel parallel demodulation algorithm and de-mapping to realize the receiving process of the RO-MFSCM signal under the time-frequency doubly selective channel. The method aims at the transmission fading problem of the FSCM signal in the ionosphere time-frequency doubly selective channel.

The invention provides a chirp modulation-based downlink wake-up receiver implementation method and system, and the method comprises the steps: S1, transmitting a preset wake-up frame to achieve the synchronization with terminal equipment before a transmitter of a wake-up receiver transmits a data frame, the wake-up frame comprises a pure carrier of a preset frequency, a lead code, and a terminal device address sequence and a data sequence based on Manchester encoding; s2, the transmitter generates a baseband signal conforming to a radio frequency front-end mode of the receiver through the wake-up frame, and the baseband signal is subjected to up-conversion and then transmitted in a 433MHz frequency band; and S3, the terminal equipment monitors a channel at any time, demodulates the wake-up frame through envelope detection and intermediate frequency amplification, demodulates a data frame, and finally synchronously sends a wake-up signal and data obtained through demodulation to a post-stage circuit. According to the invention, by designing the wake-up sequence and manufacturing the wake-up circuit, asynchronous wake-up with ultra-low power consumption is realized for the Internet of Things terminal equipment.

The invention discloses a non-intrusive permanent magnet synchronous servo motor bearing fault on-line diagnosis method and system, and the method comprises the steps: injecting a chirp current signal in a tuning stage, calculating a frequency response function through combining with a rotating speed feedback signal, and determining a resonant frequency according to the frequency response function; calculating a theoretical characteristic order according to the motor bearing size parameter; in a motor operation stage, collecting a motor rotating speed signal and determining a theoretical characteristic frequency according to the theoretical characteristic order; determining an optimal resonance demodulation frequency band according to the resonance frequency and the theoretical characteristic frequency, and performing band-pass filtering on the motor rotating speed signal according to the optimal resonance demodulation frequency band; an envelope signal of the filtered signal is calculated online through an orthogonal demodulation algorithm, the frequency spectrum of the envelope signal is obtained through FFT analysis, threshold comparison is conducted on the frequency spectrum of the envelope signal and the amplitude corresponding to the theoretical characteristic frequency, and fault diagnosis result judgment is completed. According to the invention, on-line diagnosis of the bearing fault of the permanent magnet synchronous servo motor under the condition of low-performance chip resources is realized.

The invention provides an ultrasonic three-dimensional imaging method and system based on an FPGA, and relates to the technical field of ultrasonic imaging, and the method comprises the steps: transmitting a chirp signal, receiving an echo signal reflected by a target object, and carrying out the preprocessing; carrying out adaptive filtering, constant false alarm rate detection, adaptive beam forming and three-dimensional positioning algorithm processing on the preprocessed signal to generate target position data; and performing three-dimensional point cloud image reconstruction on the target position data by using a density-based spatial clustering algorithm and a deep learning model, and outputting a target three-dimensional image. Through the innovation of a signal processing algorithm and the collaborative design of the system, the technical bottlenecks of a traditional ultrasonic sensor in detection distance, anti-interference, real-time performance and positioning precision are solved, and the three-dimensional sensing capability with high reliability and strong environmental adaptability is provided for intelligent driving.

The invention discloses a method and a device for positioning a steel rail telescopic regulator based on dynamic and static data fusion. The method comprises the following steps of: acquiring track geometric data, a railway track curve and machine account information of which the distance from the steel rail telescopic regulator is within a preset distance range; according to a railway track curve and ledger information, carrying out initial correction on the track geometric data; performing modal decomposition on the track geometric data after the initial correction by using an adaptive chirp signal modal decomposition algorithm; performing Wigner time-frequency analysis on the track geometric data after modal decomposition to generate a mileage frequency diagram; converting the mileage frequency diagram into a mileage energy diagram by utilizing a preset moving window edge spectrum analysis algorithm; according to the mileage energy diagram and the ledger information, the position of the steel rail telescopic adjuster is determined, the efficiency and accuracy of positioning the steel rail telescopic adjuster can be improved, the positioning time and labor cost are reduced, and then the stability and safety of high-speed railway driving performance are improved.

Mastering systems and methods of fabricating waveguides and waveguide devices using such mastering systems are described. Mastering systems for fabricating holographic waveguides can include using a master to control the application of energy (e.g. a laser, light, or magnetic beam) onto a liquid crystal substrate to fabricate a holographic waveguide into the liquid crystal substrate. Mastering systems for fabricating holographic waveguides in accordance with embodiments of the invention can include a variety of features. These features include, but are not limited to: chirp for single input beam copy (near i.e. hybrid contact copy), dual chirped gratings (for input and output), zero order grating for transmittance control, alignment reference gratings, 3:1 construction, position adjustment tooling to enable rapid alignment, optimization of lens and window thickness for multiple RKVs simultaneously, and avoidance of other orders and crossover of the diffraction beam.

The invention discloses an underwater acoustic adaptive transmission method based on channel prediction, and belongs to the technical field of communication. The method comprises the following steps of: 1, designing a transmitting link of an underwater acoustic self-adaptive transmission system based on channel prediction; and 2, designing a receiving link of the underwater acoustic adaptive transmission system based on channel prediction. According to the method, chirp parameters are dynamically selected on a sending link based on a predicted channel state, then adaptive transmission is carried out on an imitated radio frequency division multiplexing signal, channel state information is estimated through embedded pilot frequency at a receiving end, channel characteristics are fully learned through a channel prediction model of Transform, and the channel state information is subjected to channel prediction. And the obtained accurate future channel state information is used for balancing and self-adaptive parameter adjustment, and the flexibility and the transmission reliability of underwater acoustic communication are improved by the method provided by the invention. The method is very suitable for a half-duplex-based underwater acoustic adaptive transmission system, and the excellent performance of the method is fully embodied.