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110 results about "Very low frequency" patented technology

Very low frequency or VLF is the ITU designation for radio frequencies (RF) in the range of 3 to 30 kilohertz (kHz), corresponding to wavelengths from 100 to 10 kilometers, respectively. The band is also known as the myriameter band or myriameter wave as the wavelengths range from one to ten myriameters (an obsolete metric unit equal to 10 kilometers). Due to its limited bandwidth, audio (voice) transmission is highly impractical in this band, and therefore only low data rate coded signals are used. The VLF band is used for a few radio navigation services, government time radio stations (broadcasting time signals to set radio clocks) and for secure military communication. Since VLF waves can penetrate at least 40 meters (120 ft) into saltwater, they are used for military communication with submarines.

Low ionosphere intelligent inversion method based on VLF radio wave detection

The invention discloses a low ionosphere intelligent inversion method based on VLF radio wave detection, and the method comprises the steps: collecting ground-based very-low-frequency wave amplitude data, defining a gated cycle unit network objective function as an optimized performance index, and employing a mean square error as the objective function; and carrying out dynamic position updating by adopting a whale optimization algorithm, setting a double-stop criterion, and stopping iterative training to obtain an optimal model when the maximum number of iterations or a verification error convergence threshold value is reached. The calculation result of the LWPC model is used as a training set, the GRU network is used as an objective function estimator from foundation very low frequency data to low ionosphere parameters, the inversion method can accurately approach a real model, and the algorithm performance is effective and feasible and is remarkably improved compared with an existing model.
Owner:NAT SPACE SCI CENT CAS

Wide-area very-low-frequency radio navigation and underwater sound combined underwater navigation positioning method

The invention relates to the technical field of underwater navigation and positioning, and particularly discloses a wide-area very-low-frequency radio navigation and underwater sound combined underwater navigation and positioning method, which comprises the following steps that: a very-low-frequency navigation transmitting station transmits a very-low-frequency radio navigation time service signal; the semi-submersible acoustic beacon receives a very-low-frequency radio navigation time service signal; performing position calibration and time synchronization; the semi-submersible acoustic beacon emits an underwater acoustic navigation signal, and the underwater carrier calculates the three-dimensional coordinates of the underwater carrier according to the received underwater acoustic navigation signal. According to the invention, a shore-based very-low-frequency radio navigation and underwater sound combined navigation mode is adopted, and a very-low-frequency radio navigation time service signal has a certain underwater entry depth, so that the problem of time synchronization between semi-submersible acoustic beacons is solved, and auxiliary calibration of the positions of the semi-submersible acoustic beacons is provided; the semi-submersible acoustic beacon emits an underwater navigation signal to realize navigation and positioning of a deepwater underwater carrier, and reliable navigation service with wide area coverage, high precision and low power consumption is provided for the underwater carrier.
Owner:CHINA STATE SHIPBUILDING CORP NO 707 RES INST

GAN-based lightning very-low-frequency electromagnetic wave signal up-sampling method, terminal and medium

The invention relates to the technical field of thunder and lightning signal sampling, and discloses a GAN-based thunder and lightning very-low-frequency electromagnetic wave signal up-sampling method, a terminal and a medium. The method comprises the following steps: preprocessing a lightning very-low-frequency low-sampling signal and a real high-sampling signal; constructing a generative adversarial network; the generator is used for extracting initial features from the low-sampling signals and performing residual enhancement, then mapping low-sampling features after residual enhancement to a high-sampling dimension through a feature-guided dynamic interpolation mechanism, and performing correction and signal mapping on intermediate features after interpolation to obtain reconstructed signals matched with a target high-sampling rate; the discriminator is used for reconstructing the authenticity probability of the signal; after a generator and a discriminator are jointly trained by adopting an alternative updating mode of discriminator loss and generator loss, a newly input low sampling signal is preprocessed, and a corresponding reconstruction signal is output through the generator. According to the invention, accurate reconstruction from a lightning very-low-frequency low-sampling signal to a high-sampling signal is realized.
Owner:HEFEI UNIV OF TECH +1

Self-adaptive multi-unit very-low-frequency phased-array antenna system and control method thereof

The invention discloses a self-adaptive multi-unit very-low-frequency phased-array antenna system and a control method thereof, and the system comprises an antenna unit which comprises a vertical radiator and a top loading capacitor network erected on the vertical radiator; the central signal processing and distributing unit comprises parallel signal channels with the same number as the antenna units, and the signal channels are integrated with signal adjusting devices; the input end of the feed network is connected to the central signal processing and distributing unit, and the output end is connected to the vertical radiator to transmit a radio frequency excitation signal; the plurality of feedback sensors are arranged in the feed network and are used for monitoring electrical state parameters of signals flowing to the antenna units; the central control unit is connected with the feedback sensor and the central signal processing and distributing unit, monitors electrical state parameters based on the feedback sensor, and controls the signal adjusting device to adjust the amplitude and phase of the excitation signal. According to the invention, the beam forming and directional communication capabilities of the very-low-frequency antenna are realized, and the flexibility of an antenna system is expanded.
Owner:WUHAN SHIP COMM RES INST (NO 722 RES INST OF CHINA STATE SHIPBUILDING CORP)

VLF propagation signal prediction method based on three-dimensional finite element and neural network

The invention discloses a VLF propagation signal prediction method based on a three-dimensional finite element and a neural network, and belongs to the technical field of electronic communication. The method comprises the following steps: firstly, constructing a geosphere-ionosphere waveguide model based on a three-dimensional frequency domain finite element method, and solving by using a multi-grid method to improve the operation efficiency; secondly, constructing a VLF signal propagation data set of a plurality of known paths at one time based on a three-dimensional frequency domain finite element method; then, constructing a neural network model reflecting a mapping relation between an ionized layer electron density parameter and a VLF wave characteristic based on the data set; then, obtaining electron density distribution on a plurality of known paths based on neural network inversion; and finally, carrying out inversion by adopting an inverse square weight formula to obtain electron density distribution on the to-be-solved path. According to the method, the VLF signal transmission characteristics on multiple paths can be simulated at a time, the workload of modeling simulation is effectively reduced, and the method is suitable for the fields of inversion of a multi-path electron density parameter model, prediction of very low frequency wave propagation and the like.
Owner:UNIV OF ELECTRONICS SCI & TECH OF CHINA

Noise reduction method and noise reduction system for very-low-frequency thunder and lightning signals and storage medium

The invention belongs to the technical field of thunder and lightning signal noise reduction, and particularly relates to a noise reduction method and noise reduction system for very low frequency thunder and lightning signals and a storage medium. The noise reduction method comprises the steps of obtaining a plurality of position points of a current mixed lightning signal in a dung beetle algorithm after the mixed lightning signal is obtained; after a position point corresponding to the minimum envelope entropy in the current mixed lightning signal is calculated based on a VMD algorithm, the abscissa and the ordinate of the position point corresponding to the minimum envelope entropy are respectively recorded as an optimal decomposition mode number and an optimal penalty factor; decomposing the current mixed lightning signal into a linear superposition form of a plurality of decomposed signals by using a VMD algorithm based on the optimal decomposition mode number and the optimal penalty factor; after the decomposition signals representing the noise are removed, linear superposition of the remaining decomposition signals is reconstructed, and the very-low-frequency thunder and lightning signals are obtained. According to the method, the noise signal deeply coupled with the very low frequency lightning signal can be efficiently and accurately removed, and the real very low frequency lightning signal is restored.
Owner:HEFEI UNIV OF TECH

Ultra-long-range lightning location method and system based on very low frequency electromagnetic pulse signals

The present invention belongs to the field of lightning detection, and specifically relates to an ultra-long-range lightning location method and system based on very low frequency electromagnetic pulse signals, aiming to solve the problem that existing three-dimensional lightning location methods cannot meet the needs of long-range lightning monitoring. The present invention includes: real-time acquisition of lightning electromagnetic pulse data from each detection station and time window screening; secondary matching through signal cross-correlation method; calculation of the initial position of lightning based on the data of secondary matching; iterative optimization through nonlinear least squares algorithm with the initial position of lightning as the center to obtain the lightning position after error optimization; if the distance between the two positions is less than the set error, the optimized lightning position is used as the located lightning position. The present invention can achieve real-time and high-precision detection of lightning activities within a range of thousands of kilometers, with a positioning accuracy of 2-10km within the detection network and positioning accuracy outside the detection network that can be better than 1% of the signal propagation distance. The detection efficiency of lightning within the detection network is higher than 60%, and the maximum detection distance can reach more than 8,000km.
Owner:INST OF ELECTRICAL ENG CHINESE ACAD OF SCI

A gradient voltage-excited miniature extremely wideband directional antenna

The present invention discloses a gradient voltage-excited miniature ultra-wideband directional antenna comprising eight arrays and a logarithmic periodic silicon-based support structure. The arrays are directly bonded to the logarithmic periodic silicon-based support structure, forming periodically arranged array pairs. Each array is directly fed by a voltage source, and each array pair generates strong resonance, enhancing the frequency of the corresponding array and increasing the antenna gain. Eight arrays are bonded above the logarithmic periodic silicon-based support structure, with the eight arrays spaced evenly and distributed in a logarithmic pattern. Eight arrays are bonded below the logarithmic periodic silicon-based support structure, with the eight arrays spaced evenly and distributed in a logarithmic pattern, and the eight arrays are aligned above and below. The present invention utilizes gradient voltage excitation, breaking through the inherent relationship between antenna wavelength and antenna size. This achieves miniaturization while providing extremely wideband coverage from very low frequencies to millimeter waves and enhancing antenna gain.
Owner:ANHUI UNIV

Very-low-frequency three-component coil calibration method based on frequency sweep excitation

The invention belongs to the field of geophysical exploration, and particularly relates to a very-low-frequency three-component coil calibration method based on frequency sweep excitation, which comprises the following steps: acquiring an alternating-current excitation current and a time domain signal of a three-component coil, and performing frequency domain transformation on the time domain signal to obtain a plurality of frequency domain response vectors covering a frequency sweep range; constructing a linear equation set for describing a coil system error based on a plurality of frequency domain response vectors measured under each attitude and the calculated excitation magnetic field reference vector, and solving the linear equation set by using a least square method to obtain a calibration matrix for correcting measurement data; and the calibration matrix is adopted to correct the measurement data of the three-component coil in the use state, so that systematic errors of the very-low-frequency three-component coil can be accurately calibrated and calibrated, and the measurement precision and data reliability of a very-low-frequency electromagnetic method are effectively improved.
Owner:JILIN UNIVERSITY

A method and system for automatically calibrating the analog front-end gain of a very low frequency detection system

The present invention provides a method and system for automatically calibrating the analog front-end gain of a very low frequency detection system. The method comprises: generating a calibration signal sequence based on the total calibration time limit of the analog front-end circuit and the frequency sweep signal period; performing data acquisition on the calibration signal sequence to obtain sampled data; performing signal analysis on the sampled data to obtain the circuit gain of each frequency sweep point, and determining a curve of the gain of each frequency sweep signal varying with frequency; and performing linear interpolation based on the circuit gain of each frequency sweep point to obtain a gain variation curve corresponding to the analog front-end circuit. Through the present invention, the actual circuit gain of the detection system at each frequency point is accurately obtained, thereby significantly improving the accuracy of restoring the true strength of the received signal and solving the problem of insufficient accuracy in the prior art.
Owner:WUHAN UNIV

A method and system for extracting information of a very low frequency station signal based on a phase-locked loop

The present application belongs to the technical field of very low frequency fluctuation detection, and discloses a very low frequency station signal information extraction method and system based on a phase-locked loop. The present application amplifies and samples a wide frequency signal containing a very low frequency station transmitting signal, sets local MSK demodulation parameters, uses phase-locked loop technology to respectively perform carrier synchronization on the upper and lower frequencies of the MSK modulated signal transmitted by the target monitoring very low frequency station, extracts a baseband synchronization signal and a carrier synchronization signal from the phase-locked loops of the upper and lower frequencies, respectively, calculates the amplitude information of the upper and lower frequencies using the baseband synchronization signal, and further obtains the amplitude information of the target monitoring very low frequency station. The carrier synchronization signals of the upper and lower frequencies are used to extract the frequency of the carrier synchronization signal of the MSK modulated signal transmitted by the target monitoring very low frequency station, and further extract the phase offset information of the target monitoring very low frequency station. The present application can improve the accuracy of very low frequency station signal information extraction.
Owner:WUHAN UNIV

Mechanical very-low-frequency sound source transmitting device and transducer

The invention relates to the technical field of ocean exploration and underwater acoustic communication, in particular to a mechanical very-low-frequency sound source transmitting device and transducer, which comprises a multidirectional transmission structure (1), a radiant panel (2), a main shell (4), a motor (5) and a speed reducer (6), the main shell (4) is of a hollow symmetrical structure and is provided with a top end face, a bottom end face and a plurality of side end faces. The plurality of side end surfaces are encircled to form a regular polygon; the side end surface is provided with a radiation plate (2) as a radiation surface; the inner end face of the radiant panel (2) is in contact with the internal environment of the main shell (4), and the outer end face is in contact with the external environment of the main shell (4); the multidirectional transmission structure (1) is arranged in the main shell (4) and is in contact with the radiant panel (2); rotation of the motor (5) is decelerated through the speed reducer (6) and then drives the multidirectional transmission structure (1), and the multidirectional transmission structure (1) converts rotation motion of the motor (5) into horizontal vibration of the radiant panel (2) so as to achieve underwater very-low-frequency sound source emission.
Owner:INST OF ACOUSTICS CHINESE ACAD OF SCI

Method for Measuring Shallow Shear Wave Velocity of Seafloor Sedimentary Layer Based on Single Vector Hydrophone

The present invention discloses a method for measuring the shear wave velocity of the shallow seafloor sediment layer based on a single vector hydrophone. The measurement method includes: collecting underwater acoustic signals and seafloor interface wave signals excited by a very low frequency sound source near the seafloor using a single vector hydrophone; obtaining the horizontal component of the particle velocity by rotating the quasi-source direction using the horizontal transverse component and the horizontal longitudinal component of the particle velocity; calculating the amplitude ratios between the sound pressure, the vertical component of the particle velocity, and the horizontal component of the particle velocity pairwise, and calculating the interface wave velocity using any one of the amplitude ratios; and finally calculating the shear wave velocity according to the linear relationship between the interface wave and the shear wave. The method of the present invention can accurately estimate the shear wave velocity of the shallow seafloor sediment layer, and the detection device only requires a single vector hydrophone, providing a feasible technical approach for solving long-term problems such as difficult seafloor shear wave measurement, high cost, and low efficiency.
Owner:ZHEJIANG UNIV

Dynamic non-cooperative very low frequency signal carrier frequency and phase measurement method and system

The application discloses a dynamic non-cooperative very low frequency signal carrier frequency and phase measurement system, comprising a high-precision analog-to-digital converter, a high-precision digital-to-analog converter connected with an FPGA module, and a labview host computer connected with the FPGA module, and discloses a dynamic non-cooperative very low frequency signal carrier frequency and phase measurement method. The FPGA module is used for performing carrier frequency estimation and carrier phase rotation correction on MSK signals collected by the high-precision digital-to-analog converter, and the carrier frequency and phase with high precision are transmitted to the labview host computer to be displayed. The application can realize fast and high-precision carrier frequency estimation, has strong noise resistance and a wide estimation range.
Owner:XIDIAN UNIV +1

Low-frequency and very-low-frequency signal monitoring method and device

The embodiment of the invention provides a very low frequency signal monitoring method and device, and the device consists of a signal receiving unit (1), a signal measurement unit (2), a parameter regulation and control unit (3), and a main control unit (4). And the parameter regulation and control unit (3) can respectively set parameters of each working component in the signal receiving unit (1) and the signal measuring unit (2) according to the center frequency and bandwidth list of the main control unit (4), and can control a turntable (5) of an antenna coil (13) to align to the strongest direction of a synchronous measurement signal, so that measurement and data storage of a specific very low frequency signal in the bandwidth are realized. The method is characterized in that collection of monitoring signals and measurement of signal parameters are realized based on synchronization characteristics of known signals, interference signals can be well distinguished, and the accuracy of monitoring data is guaranteed.
Owner:BEIJING SHENGFEIFAN ELECTRONIC SYST TECH DEV CO LTD

Ionosphere parameter inversion method and device

The invention provides an ionosphere parameter inversion method and device, and belongs to the technical field of short-wave communication, and the method comprises the steps: enabling the actually-measured amplitude and phase difference to be mapped into a low-order wave mode excitation amplitude and a complex feature value through the synchronous receiving of the same very-low-frequency transmitting station signal at different transmitting and receiving distances on the ground; and then fast convergence solution is carried out by using a Newton-Raphson method, and ionosphere electron concentration parameters are circularly corrected by using a gradient descent method, so that the residual error of a theoretical calculation result and a measured value is stabilized within a preset threshold, thereby getting rid of excessive dependence on a traditional ionosphere mode, remarkably improving the inversion precision of low ionosphere parameters, and improving the reliability of the low ionosphere. The method has the advantages of simple operation, low cost and long-term operation.
Owner:WUHAN SHIP COMM RES INST (NO 722 RES INST OF CHINA STATE SHIPBUILDING CORP)

A piezoelectrically driven self-biased very low frequency mechanical transmit antenna and method of making the same

The application provides a piezoelectric driving self-biased very low frequency mechanical transmitting antenna and a preparation method thereof. The preparation method comprises the following steps: step one, preparing piezoelectric ceramic material; step two, cutting and slotting; step three, pouring resin; step four, cutting layer sheet; step five, packaging; step six, polarization treatment; step seven, preparing adhesive layer; and step eight, hot-pressing compounding. Compared with the existing magnetoelectric antenna, the self-biased very low frequency mechanical transmitting antenna has the characteristics of self-bias, high piezoelectricity, miniaturization, no additional noise source and electromagnetic interference, and the like, has the advantages of high stress transmission efficiency and small ohmic loss, can realize the miniaturization requirement of the magnetoelectric mechanical antenna, is easy to form a large-scale array, improves the magnetic transmitting performance under zero bias, and achieves the low frequency communication effect.
Owner:WUHAN UNIV OF TECH

Very-low-frequency narrow-band antenna pre-distortion broadband transmitting method

The invention discloses a very-low-frequency narrow-band antenna pre-distortion broadband transmitting method. The core of the very-low-frequency narrow-band antenna pre-distortion broadband transmitting method is composed of double-tuning network parameter calculation and pre-distortion waveform design. The method comprises the following steps: with a constraint condition that transmitter port equivalent impedance is equal to transmitter characteristic impedance under an antenna center frequency, adjusting a load current gain peak frequency to a working frequency by calculating an undetermined parameter so as to realize working frequency point tuning; changing parameters of the double-tuned network to design a low-Q-value target group, acquiring primary and secondary side currents under constant-amplitude excitation, importing the primary and secondary side currents into an actual network of an experimental group, and deducing corresponding excitation voltage; according to the method, tuning and resistance changing are achieved through the double-tuning network, transient current fluctuation suppression is achieved through the pre-distortion design, and the active power utilization rate and the very-low-frequency communication rate of the power amplifier are effectively improved.
Owner:HUNAN UNIV +1

Lightweight monopole launch antenna for aerostat

This invention discloses a lightweight monopole transmitting antenna for an aerostat. From the inside out, it comprises a central reinforcing filler made of multi-strand twisted lightweight reinforcing fibers, a binding layer made of polytetrafluoroethylene film, a non-metallic reinforcing layer woven from non-metallic reinforcing fibers, an inner sheath made of extruded polyethylene, a radiator layer woven from metal wires, and an outer sheath comprising a semi-conductive outer sheath and a metal-woven outer sheath. The semi-conductive and metal-woven outer sheaths have the same outer diameter and alternately cover the outside of the radiator layer. This invention offers advantages such as miniaturization, lightweight, corona resistance, high current resistance, and fatigue resistance, resulting in high reliability and practicality, meeting the requirements for rapid deployment of long-range very low frequency (VLF) communication systems using aerostats.
Owner:8TH RES INST OF CETC +1

A wide low-frequency sound-absorbing damping cover layer structure and design method

The application belongs to the technical field of preparation and determination of aviation equipment absorbing material, and discloses a wide low-frequency sound absorption and vibration reduction covering layer structure and a design method. The design method comprises the following steps: by changing the geometric parameters of a single unit composed of an embedded neck hole diameter d, an embedded neck length l and a cavity wall plate height L, the strong non-local coupling between a plurality of embedded rubber Helmholtz resonators is changed, the impedance of the embedded rubber Helmholtz resonator is changed, and the overall structure of the wide low-frequency sound absorption and vibration reduction covering layer structure of the sound absorption metasurface array is obtained by the weak coupling resonance sound absorption mechanism; the embedded rubber Helmholtz resonator is composed of an embedded neck, a damping rubber coating layer and a sound absorption cavity. The non-local coupling between the plurality of embedded rubber Helmholtz resonators in the multi-element metasurface array is adjusted, effective broadband impedance modulation is realized, and strong dissipation of broadband sound energy is realized at very low frequency.
Owner:HARBIN ENG UNIV

Method for suppressing environmental interference of very low frequency atomic magnetometer based on polarization selective reception

The application provides a very low frequency atomic magnetometer environment interference suppression method based on polarization selection reception, wherein a precession main magnetic field B e and -B e are respectively applied by a main magnetic field coil in z direction and -z direction in front and back two regions of a gas chamber e and -B e regions are detected by using detection laser in x direction; external very low frequency signals are detected by interaction with atoms polarized in z direction to make the atoms produce precession signals in xOy plane, so that the signals are detected by light detection; when the external signals are linear polarization, according to the selection rule of angular momentum conservation, the precession signals of atoms in B e and -B e regions are offset, so that the system does not respond to linear polarization signals; for circular polarization signals, only atoms in B e or -B e region have precession signals, so that the detection of circular polarization signals is realized. The technical scheme of the application is applied to solve the technical problem of environmental magnetic noise interference of a very low frequency atomic magnetometer in an actual application scene in the prior art.
Owner:BEIJING AUTOMATION CONTROL EQUIP INST

Low-frequency through-the-earth communication transmitting antenna for wireless detonator and use method

The invention belongs to the technical field of wireless detonators. The invention discloses a low-frequency through-the-earth communication transmitting antenna for a wireless detonator, and the antenna comprises a transmitter which is used for generating a low-frequency / very-low-frequency radio-frequency power signal with a specific frequency, wherein the power signal carries a detonation instruction; the tuner is connected with the transmitter and is used for enabling the output impedance of the transmitter to be matched with the input impedance of the low-frequency through-the-earth communication antenna, so that the power of the transmitter is most effectively transmitted to the low-frequency through-the-earth communication antenna; the low-frequency through-the-earth communication antenna is connected with the tuner and is used for receiving a signal transmitted to the low-frequency through-the-earth communication antenna by the tuner and generating an alternating electromagnetic field signal; wherein the transmitter, the tuner and the low-frequency through-the-earth communication antenna are respectively provided with a cable plug, and the cable plugs are in quick release connection through connecting cables; the tuner and the low-frequency through-the-earth communication antenna form a group of low-frequency through-the-earth communication mechanisms, the transmitter is connected with the multiple groups of low-frequency through-the-earth communication mechanisms, and an antenna array is formed among the multiple groups of low-frequency through-the-earth communication mechanisms.
Owner:RONGGUI SICHUANG BEIJING TECH

Very-low frequency wave propagation model resolution enhancement method and system based on deep network

The invention provides a deep network-based very low frequency wave propagation model resolution enhancement method and system, and belongs to the field of very low frequency fluctuation detection and application. Firstly, a low-resolution data set and a high-resolution data set of very-low-frequency station signal distribution are constructed, then a CNN structure is designed and is divided into a feature extraction core module and an image reconstruction core module, the feature extraction module is responsible for extracting deep features from an LR image, and the image reconstruction module improves the resolution of an output image through up-sampling and super-resolution reconstruction. Secondly, randomly disorganizing a data set after preprocessing, and dividing the data set into a training set and a verification set according to a proportion; in a model reasoning stage, CNN realizes accurate reconstruction of a high-resolution signal field through depth feature analysis of an LR image, converts a completely trained lightweight network model into a format suitable for engineering deployment, and finally seamlessly integrates the model into an LWPC propagation model, so that the resolution of propagation field intensity distribution is effectively improved.
Owner:WUHAN UNIV

Multi-unit very-low-frequency transmitting antenna system and tuning method thereof

The invention provides a multi-unit very-low-frequency transmitting antenna system and a tuning method thereof, and belongs to the technical field of very-low-frequency transmitting antennae, and the multi-unit very-low-frequency transmitting antenna system comprises a plurality of antenna units, a plurality of tuning pavilions, a plurality of low-voltage feeder lines, a transmitter and a plurality of ground nets, the plurality of tuning pavilions are respectively positioned near the central position of each group of antenna units, each tuning pavilion consists of a plurality of tunable coils with the same structure, and the tuning pavilions are connected with the root parts of the antenna units; the plurality of low-voltage feeders are respectively connected with the transmitter and the plurality of tuning booths, the transmitter is located at the geometric center of the antenna array formed by the plurality of antenna units, and the transmitter is connected with the low-voltage feeders through the shunt device and the high-voltage isolation switch; the plurality of ground nets are respectively laid by taking the plurality of antenna units as the center, each ground net is composed of a plurality of local ground nets which are laid in a radial shape, and the plurality of ground nets are connected through metal ground net wires or are kept independent and not connected. According to the invention, the complexity and difficulty of antenna design and construction are obviously reduced, and the dependence on the terrain of an antenna array is reduced.
Owner:WUHAN SHIP COMM RES INST (NO 722 RES INST OF CHINA STATE SHIPBUILDING CORP)

Adaptable low frequency receive antenna and method

An adaptable low frequency (LF) or very low frequency (VLF) receive antenna is configured to provide an amplified analog signal and / or a digital signal to a receiver. Such an adaptable LF / VLF receive antenna may be used with older generations of analog and digital receivers as well as newer generations of digital receivers that use a digital feed. Thus, an LF / VLF receive antenna in accordance with the present disclosure may be used to replace an existing antenna connected to an analog receiver and will continue to work when the analog receiver is upgraded in the future so as to ease the transition to newer digital receivers. In one or more embodiments, the digital signal may be further processed within the LF / VLF receive antenna so as to reduce its bandwidth and permit transmission of the processed digital signal over a data network.
Owner:ROCKWELL COLLINS INC

Very-low-frequency sinusoidal vibration mechanism and water sound pressure calibration device

The invention relates to a very-low-frequency sinusoidal vibration mechanism and a water sound pressure calibration device, and the mechanism comprises a servo motor which is used for providing rotation power; the harmonic reducer is connected with an output shaft of the servo motor and is used for reducing the rotating speed and improving the output torque; the driving shaft is connected with the output end of the harmonic reducer, and a sine curve guide groove is formed in the driving shaft; and the guide crank is provided with a tip part matched with the sine curve guide groove in the driving shaft, and the tip part is matched with the sine curve guide groove to enable the rotary motion of the driving shaft to be converted into the linear motion of the guide crank. According to the sine vibration mechanism, lower vibration frequency and higher stability can be generated, the harmonic reducer and the servo motor are introduced into the sine vibration mechanism for driving for the first time, lower frequency can be generated, and the influence of waveform distortion degree introduced by the sine vibration mechanism is reduced.
Owner:THE 715TH RES INST OF CHINA SHIPBUILDING IND CORP

Very low frequency sensitivity calibration device, system and method of vector hydrophone

The invention relates to the field of vector hydrophone calibration, and discloses a very low frequency sensitivity calibration device, system and method of a vector hydrophone, the device comprises a base and a co-vibration unit which can be horizontally or vertically installed on the base, the co-vibration unit comprises a square frame, and a vibration exciter and a co-vibration slide block which are installed in the square frame, the co-vibration sliding block is connected with the vibration exciter, the vibration excitation direction of the vibration exciter is the horizontal axial direction of the co-vibration unit, and the co-vibration sliding block can move in the square frame under the action of the vibration exciter; the co-vibration slide block is provided with a horizontal fixing groove and a vertical fixing groove which are used for fixing the vector hydrophone. According to the invention, the sensitivity calibration of the vector hydrophone in the horizontal and vertical directions can be realized through one set of device, the use flexibility of the device is greatly enhanced, and the calibration of the vector hydrophone under a very low frequency condition can be realized; the problem that in an existing calibration method, a liquid column tube is poor in planar standing wave uniformity and parallelism under excitation of lower than 20 Hz is effectively solved.
Owner:OCEANOGRAPHIC INSTR RES INST SHANDONG ACAD OF SCI

Self-attended auxiliary system and method based on circuit parameter monitoring

The invention provides a self-attended auxiliary system and method based on circuit parameter monitoring, and relates to the technical field of very low frequency fluctuation detection and application. The system comprises at least three single-chip microcomputer monitoring modules, wherein each single-chip microcomputer monitoring module comprises a parameter acquisition interface, a control output interface, a display interface and a communication interface; the parameter acquisition interface is connected to monitored target equipment and is used for acquiring key operation parameters of the target equipment; the control output interface is used for outputting a control signal to connected target equipment so as to perform control operation; the display interface is connected with the local information display unit; the single-chip microcomputer monitoring modules are in communication connection through the communication interfaces. According to the invention, a modular design with a single-chip microcomputer as a core is adopted, the system has the functions of parameter real-time monitoring, state judgment, redundancy fault tolerance, equipment control, information display and the like, communication linkage is carried out, and automatic management and fault self-recovery under an unattended condition can be realized.
Owner:WUHAN UNIV

Receiving and releasing device for very low frequency transmitting antenna

The invention discloses a receiving and releasing device for a very-low-frequency transmitting antenna, and belongs to the technical field of very-low-frequency transmitting antennas. The winding and unwinding device comprises a rack, a winding displacement assembly and a winding drum assembly. The rack is of a U-shaped structure; the wire arranging assembly comprises a driving unit and a connecting block, and the driving unit is located on the rack; the winding drum assembly comprises a first motor, a winding drum, a swing arm and a fixed pulley, the first motor is located on one side plate of the rack and is in transmission connection with the winding drum, the swing arm is rotatably arranged on the connecting block, a rotating shaft of the swing arm is arranged in the first direction, and the fixed pulley is rotatably inserted into the swing arm; and the outer peripheral wall of the fixed pulley is provided with a wire slot for accommodating a very-low-frequency transmitting antenna. The winding and unwinding device for the very-low-frequency transmitting antenna is simple in structure, the occupied space is small after the very-low-frequency transmitting antenna is wound, and the problem that the very-low-frequency transmitting antenna is broken due to friction damage can be avoided.
Owner:WUHAN SHIP COMM RES INST (NO 722 RES INST OF CHINA STATE SHIPBUILDING CORP)