54 results about "Extremely low frequency" patented technology

The invention discloses an intelligent composite cable based on modal isolation and a preparation method thereof. The cable comprises a power transmission layer, a control signal layer, an optical fiber communication layer and an intelligent protection and external shielding layer which are sequentially arranged from inside to outside. The power transmission layer comprises a conductor layer, a conductor insulation layer and a first shielding layer for attenuating a low-frequency strong magnetic field which are sequentially arranged from inside to outside; the control signal layer comprises a total shielding layer and a plurality of control wire cores which are uniformly arranged between the total shielding layer and the power transmission layer along the circumferential direction, and each control wire core is provided with a branch shielding layer; the optical fiber communication layer comprises a plurality of optical fiber groups which are uniformly arranged along the circumferential direction, each optical fiber group is provided with a second shielding layer for electric absorption, and the second shielding layer is a non-metal shielding layer; the intelligent protection and external shielding layer is provided with a third shielding layer used for equipotential shielding. According to the invention, a layered composite structure is adopted, the reliability of mechanical performance is ensured, and an asymmetric shielding framework is adopted, so that full-spectrum interference suppression from extremely low frequency to high frequency is realized.

This invention discloses a smart composite cable based on modal isolation and its fabrication method. The cable comprises, from the inside out, a power transmission layer, a control signal layer, an optical fiber communication layer, and a smart protection / external shielding layer. The power transmission layer comprises, from the inside out, a conductor layer, conductor insulation, and a first shielding layer for attenuating low-frequency strong magnetic fields. The control signal layer comprises a total shielding layer and multiple control cores uniformly arranged circumferentially between the total shielding layer and the power transmission layer, with each control core having a sub-shielding layer. The optical fiber communication layer comprises multiple optical fiber groups uniformly arranged circumferentially, with each optical fiber group having a second shielding layer for electro-absorption; the second shielding layer is a non-metallic shielding layer. The smart protection / external shielding layer has a third shielding layer for equipotential shielding. This invention employs a layered composite structure to ensure mechanical performance reliability and uses an asymmetric shielding architecture to achieve full-spectrum interference suppression from extremely low frequencies to high frequencies.

The application relates to the technical field of semiconductor laser control, and discloses a wavelength stabilization control method of a semiconductor laser, which comprises the following steps: constructing an equivalent heat transfer model of a multi-section semiconductor laser; monitoring the radio frequency data stream duty cycle of a gain section, switching the injection path of a low-frequency pilot signal to extract a global equivalent low-frequency thermal resistance, updating a time-varying low-frequency physical RC node parameter set; combining the transient heat power of the gain section and the equivalent heat transfer model to deduce full-frequency section junction temperature observation data, and decomposing the full-frequency section junction temperature observation data into an extremely low-frequency direct current component, a medium-low-frequency fluctuation component and an extremely transient high-frequency fluctuation component; driving a thermoelectric refrigeration component according to the extremely low-frequency direct current component; generating a medium-low-frequency feedback compensation current according to the medium-low-frequency fluctuation component, combining the extremely transient high-frequency fluctuation component to generate a feedforward compensation current; and injecting the medium-low-frequency feedback compensation current and the feedforward compensation current into a grating section after being combined. The application realizes multi-frequency section decoupling control and improves wavelength stability.

A two-way bass enhancement structure, comprising a bass unit, a thick guide pipe and a thin guide pipe. The input end of the thick guide pipe is connected to the output end of the bass unit, the output end is connected to the sound outlet nozzle of the earphone, and the inner circumferential side of the output end of the thick guide pipe is provided with acoustic damping. The input end of the thin guide pipe is connected to the circumferential side of the thick guide pipe and penetrates through it, and the output end is connected to the sound outlet nozzle of the earphone. The inner diameter of the thin guide pipe is smaller than that of the thick guide pipe. The utility model can not only maintain the information amount of bass, but also directly and efficiently transmit the extremely low frequency part, thereby improving the sound quality.

This application relates to the field of quantum nondestructive testing technology, and discloses a quantum detection device and a xenon atom-based eddy current detection method. The quantum detection device includes an interconnected eddy current probe and a quantum measurement device. The quantum measurement device includes a xenon atom gas chamber for measuring the magnetic field strength of a target eddy current magnetic field. It acquires the target eddy current magnetic field of the target object, measures the magnetic field strength of the target eddy current magnetic field, and obtains the magnetic field strength distribution along the surface of the target object. Based on the magnetic field strength distribution, it detects thickness changes in the target object to obtain the weak point detection result. Its beneficial effect is that by measuring the eddy current magnetic field generated by the target object through a xenon atom gas chamber, it effectively utilizes the characteristics of xenon atoms—long coherence time and extremely low resonance frequency—thereby maintaining high sensitivity to capture weak magnetic fields at extremely low frequencies and obtaining a detection penetration depth far exceeding that of traditional sensors, achieving high-precision nondestructive testing of minute thickness differences inside the target object.

The invention relates to the field of integrated circuit design, in particular to an incremental ADC (Analog to Digital Converter) for weak current detection, which comprises a resettable Sigma-Delta modulator, a resettable accumulator and a control clock, wherein the resettable Sigma-Delta modulator comprises an extremely low frequency low distortion filter, a quantizer and a current feedback DAC (Digital-to-Analog Converter); the extremely-low-frequency low-distortion filter is composed of a first-stage low-pass filter, a second-stage integrator, a first reset switch and a second reset switch. The resettable accumulator has a reset function and is used for accumulating output results of the quantizer; the control clock comprises a reset signal rst and a clock signal CLK; according to the invention, an extremely-low-frequency low-distortion filter structure is used in the resettable Sigma-Delta modulator, so that the problem of performance bottleneck caused by introduction of a pseudo resistor in sub-picoampere-level weak current detection of a traditional second-order incremental ADC is solved, and the dynamic range, the anti-noise capability and the linearity of a system are improved.

Failures in establishing trust during international conflict negotiations frequently result in warfare, as ideological differences often cannot be resolved through rational discourse alone. Empathy between opposing parties is essential for building trust, and oxytocin is recognized for its critical role in facilitating empathy, trust, inter-brain synchrony, and cooperative decision-making. However, prevailing scientific studies typically do not differentiate between the cis and trans isomers of oxytocin, despite evidence that only the trans isomer is pharmacologically active. The present invention provides methods for the separation and quantification of oxytocin isomers, with particular emphasis on the trans isomer's function in social synchrony and decision-making within conflict negotiation contexts. Additionally, the invention explores the role of extremely low frequency electromagnetic radiation permeating the human central nervous system interconnecting neurochemical changes among groups. These advances clarify the unique neuropeptide functions of oxytocin and enhance understanding of its impact on cooperation and conflict resolution.

The device for testing pacemakers in static and extremely low frequency magnetic fields comprises an Agar phantom (6) irradiated by an electromagnetic field source (5) and at least one three-axis static magnetic field sensor (4a) and at least one three-axis alternating magnetic field sensor (4b). These are placed at the same distance from the pacemaker under test (3) to monitor the intensity, direction and spatial distribution of the magnetic field generated by the electromagnetic field source (5) in the area of ​​a single-chamber or dual-chamber tested pacemaker (3) placed in the Agar phantom (6). A test pulse generator (1) is connected to the single-chamber pacemaker (3) by one wire or to the dual-chamber pacemaker (3) by two wires and a response sensor (2) is connected by an electrode to sense the response of the pacemaker (3) in real time. The generator (1), the static magnetic field sensor (4a), the alternating magnetic field sensor (4b) and the response sensor (2) are connected by wires to the communication module (7) and wired or wirelessly connected to a computer (8) for processing, analyzing and visualizing the measured data.

The utility model relates to the field of radio transceiving, and discloses an ultra-wideband extremely-small-step frequency hopping frequency synthesizer module. According to the invention, the high-speed dot frequency array divides an ultra-wideband frequency 9-18GHz signal into 8 segments, and the 8 segments are respectively shifted and converted to 1000-2200MHz for frequency and phase discrimination, so that the phase discrimination frequency is greatly reduced, excellent phase noise can be obtained, and ultra-wideband frequency coverage is realized at the same time. The adopted high-speed dot frequency phase-locked array is low in phase noise and large in frequency span coverage, the switching time is short through a high-speed switch, large-range fast frequency hopping can be achieved, and powerful support is provided for prolonging the large-range frequency hopping time of a whole circuit system. A DDS direct digital frequency synthesis circuit is adopted, near-end stray is low, high-frequency resolution is provided, and extremely low frequency stepping can be achieved. And the frequency hopping speed is high and reaches below 1uS, so that the rapid frequency hopping of the frequency synthesizer system can be realized.

The invention relates to a buried hill reservoir microfracture evaluation method based on array acoustic logging, and belongs to the technical field of oil-gas exploration and development. The method comprises the following steps: acquiring unipolar longitudinal wave velocity, high-frequency transverse wave velocity and dipolar low-frequency transverse wave velocity from array acoustic logging data; analyzing the sensitivity of the logging frequency band wave velocity with respect to the microfracture density and the aspect ratio by using a BISQ wave velocity dispersion model; carrying out anisotropy correction on the dipole shear wave velocity, and evaluating the micro-fracture development density according to the relative difference between the dipole shear wave velocity and the single-pole high-frequency shear wave velocity; and calculating cut-off frequencies of the unipolar and dipolar transverse wave measurement modes, and evaluating the aspect ratio of the microfracture according to the ratio of the relative difference of the wave velocities of the high and low frequency transverse waves to the difference value of the cut-off frequencies, namely the relative change rate of the transverse wave velocities. According to the method, the micro-fracture development density and the aspect ratio of the buried hill reservoir are represented through the transverse wave velocity difference and the change rate respectively, the uncertainty of a calibration link in a traditional method is effectively avoided, and the method has better applicability to the buried hill reservoir with high heterogeneity and complex lithology.

The invention provides a blind source separation method and system for a single-channel extremely-low-frequency signal, and the method comprises the steps: firstly carrying out the preprocessing of a collected signal through a Hanpur filter, and eliminating the pulse noise, aiming at a large amount of pulse noise generated by a natural environment in an extremely-low-frequency signal channel; secondly, decomposing the single-channel signal sequence into a plurality of independent components through singular spectrum analysis and a kmeans clustering algorithm to construct virtual multiple channels; and finally, separating a source signal with a high interference-to-signal ratio by using a feature matrix-based joint approximate diagonalization algorithm. According to the method, the accuracy of source signal estimation is improved, any probability distribution does not need to be assumed, parameters do not need to be manually selected, and good robustness and universality are achieved.

The present application relates to underwater navigation positioning technology field, provide a kind of near-field radio emission large depth underwater navigation positioning method, system and device. Including the following steps: deploying near-field extremely low frequency electromagnetic signal transmitting device on water surface;Setting underwater receiving unit parameter and placing underwater body;Navigation positioning is carried out to underwater body, and positioning coordinate is obtained.The present application deploys multiple extremely low frequency electromagnetic signal transmitting devices on water surface, each near-field extremely low frequency electromagnetic signal transmitting device emits specific double-frequency radio electromagnetic signal by loop antenna, underwater receiving unit receives the near-field electromagnetic signal of multiple near-field extremely low frequency electromagnetic signal transmitting devices on water surface, combines the position information of near-field extremely low frequency electromagnetic signal transmitting device and the water pressure sensor information of underwater receiving unit, obtains the position information of underwater body by positioning solution, realizes the navigation positioning of large depth underwater body of thousands of meters underwater.

The invention relates to the technical field of magnetic antennas, in particular to a magnetic antenna for polar / very low frequency electromagnetic detection and communication and application thereof.The magnetic antenna comprises an annular frame, permanent magnets and a coil, the permanent magnets are evenly distributed in the annular frame to form a permanent magnet array, the permanent magnet array is an annular Halbach array, and the coil is arranged in the annular frame; a gap is reserved between every two adjacent permanent magnets in the permanent magnet array, and the permanent magnets are arranged at a preset interval angle in the magnetization direction of every two adjacent permanent magnets in the annular direction of the annular frame; the coils are wound on each permanent magnet, all the coils are connected with an external power supply after being connected into the shunt in parallel, and the shunt is used for adjusting the magnitude and phase of current fed into the coils so as to adjust the radiation range of the magnetic antenna. By introducing the Halbach array into the polar / very low frequency magnetic antenna, the radiation efficiency of the antenna is improved to the maximum extent under the condition that the volume is limited, so that the practical application feasibility of the polar / very low frequency magnetic antenna is improved.

This invention discloses a compressor operation control method, device, air conditioning equipment, and storage medium. The method includes: obtaining the target operating frequency of the compressor; if the target operating frequency is lower than a set frequency, obtaining the compressor's operating current; determining a first frequency limiting zone adapted to the compressor's operating current based on M preset frequency limiting zones, wherein the frequency limiting zone is used to limit the compressor's minimum operating frequency, and the minimum operating frequency of each frequency limiting zone is lower than the set frequency, and M is an integer greater than 1; controlling the compressor's operating frequency based on the first frequency limiting zone to ensure that the compressor's operating frequency is not lower than the minimum operating frequency of the first frequency limiting zone. This invention solves the technical problem of low stability of compressors operating at extremely low frequencies.

The utility model relates to an extremely-low-frequency power-free weak signal generator. The extremely-low-frequency power-free weak signal generator comprises a body. A driving assembly, a voltage generating assembly and a collecting ring are arranged in the body; the voltage generation assembly is in clearance fit with the body, the driving assembly faces the voltage generation assembly and drives the voltage generation assembly to rotate in a mode of blowing out airflow, and the voltage generation assembly cuts a geomagnetic field when rotating to generate an electric signal; the voltage generation assembly is connected with the collector ring and outputs an electric signal through the collector ring. The structure provided by the utility model has no input of external electric signals, can reduce the noise influence caused by a circuit at a signal end, and improves the authenticity of signals. Besides, through the principle that the voltage generation assembly cuts the geomagnetic field to generate induced electromotive force, stable microvolt-level signals can be generated, and the test requirements of the geomagnetic ocean current meter front-end amplifier can be well met.

This invention discloses a method and system for calculating the ultra-fine spectrum of a sampled signal, belonging to the field of weak signal detection technology. Calculating the spectrum of signals with extremely long sampling times presents problems such as large data volume and high computer memory requirements. This method divides the sampled data sequence of an ultra-low bandwidth modulated signal into segments of equal duration. Each segment is then subjected to quadrature demodulation, filtering, and decimation concatenation. The processed segments are then sequentially concatenated, and finally, a time-frequency transformation is performed to obtain the signal spectrum with ultra-fine frequency resolution. This calculation method significantly reduces the amount of data required for time-frequency transformation, allowing the processing of massive amounts of sampled data to be completed on a conventionally configured computer, yielding signal spectra with frequency resolution at the millihertz or even microhertz level. This allows for the observation and understanding of the extremely low-frequency spectral structure or near-end phase noise of the signal. This calculation method has strong versatility.

The invention relates to the technical field of underwater navigation and positioning, and provides a near-field radio emission large-depth underwater navigation and positioning method, system and device. Comprising the following steps: deploying a near-field extremely-low-frequency electromagnetic signal transmitting device on the water surface; setting parameters of an underwater receiving unit and laying an underwater carrier; and navigating and positioning the underwater carrier to obtain a positioning coordinate. A plurality of extremely-low-frequency electromagnetic signal transmitting devices are deployed on the water surface, each near-field extremely-low-frequency electromagnetic signal transmitting device transmits a specific double-frequency wireless electromagnetic signal through a loop antenna, and an underwater receiving unit receives near-field electromagnetic signals of the near-field extremely-low-frequency electromagnetic signal transmitting devices on the water surface. Position information of the underwater carrier is obtained through positioning calculation by combining position information of the near-field extremely-low-frequency electromagnetic signal transmitting device and water pressure sensor information of the underwater receiving unit, and navigation positioning of the large-depth underwater carrier of thousands of meters underwater is achieved.

The present Invention relates to methods and devices for sending and receiving electrical signals through "dissipative" media such as soil, mud, or sea / fresh water to distances extending to several tens of meters. Present methods for sending through such media use very high-power levels ranging to Mega-Watts and employ large equipment. Very Low Frequency (VLF) and Extremely Low Frequency (ELF) communication systems used to communicate with submarines are an example. In contrast, methods and devices disclosed here are powered by general purpose batteries (such as Lithium-Ion batteries) and can be used with consumable items as small as a mobile phone. The invention achieves this functionality by combining near field resonant magnetic coupling with symbol stretching at the transmitting end and matched filtering at the receiving end. While the range of near field magnetic coupling is limited to approximately 1' (30 cm), the combination disclosed in the invention enables to send / receive signals extending to several tens of meters. This new technology (the combination) opens several new applications. At present, there is no systematic methodology to detect victims of natural or man-made disasters such as landslides, earthquakes, and disasters where the victims are buried in media such as soil or mud. The invention can be used to add functionality to consumer devices such as mobile phones or similar so that they can be easily located. Alternatively, a novel device one can easily carry (smaller that the size of a mobile phone) can be introduced, which would be very useful for communities living in countries prone to natural disasters. Scanning for victims can be done fast by mounting the search device on a drone. The methods and devices disclosed can also be used for underwater communication between diver to diver and diver to vessel and the technology is especially suitable for freshwater applications. In addition, this technology can also be used for communication in mines in emergency situations. It is suggested to use in emergency situations due to low data rates.

The utility model relates to a three-frequency coupling resonance water molecule nanocluster optimization filtering device which comprises a pipe body, a sound wave oscillation generator is arranged in the pipe body, a terahertz waveguide layer is arranged on the inner surface of the pipe body, an electromagnetic coil is arranged on the outer surface of the pipe body, and when water flows through the pipe body, the electromagnetic coil is arranged on the inner surface of the pipe body. Water is in frictional contact with the terahertz waveguide layer, the terahertz waveguide layer is stimulated to emit terahertz waves to penetrate through the water, the electromagnetic coil emits extremely-low-frequency electromagnetic waves to penetrate through the water, and the sound wave oscillation generator actively emits sound waves to penetrate through the water. When the device is used as a filter element for filtering water, terahertz waves, extremely-low-frequency electromagnetic waves and sound waves cooperatively resonate to activate water. Compared with the prior art, stable micromolecule nanocluster water is generated, and the activation effect of the water is improved.

The application relates to a deep water depth setting transmitting transducer, which comprises a transducer body, the transducer body comprises an upper ring shell and a lower ring shell, metal support plates are arranged on the upper ring shell and the lower ring shell respectively, the upper ring shell and the lower ring shell are tightly connected through press-fit bolts and the metal support plates are jointly enclosed to form a closed cavity, the two metal support plates are arranged in parallel, a plurality of strong rope tensioning mechanisms are arranged between the two metal support plates, the length of the strong rope tensioning mechanism in a natural state is consistent with the height of the cavity, an inflation valve is further arranged on the upper ring shell, and the inflation valve can be used for pre-charging gas into the cavity. The application takes a conventional extremely low frequency and ultra-low frequency bending disc transducer as a design basis, realizes deep water working capacity through a pre-charged high-pressure gas compensation mode, and achieves the purpose of increasing working water depth under the condition that the maximum external size, weight of the bending disc transducer and the transmitting system are not changed.

The invention provides an underwater spherical object detection method and device based on an underwater carrier. The method comprises the steps that an underwater carrier carries an electric field emission module and an electrode receiving array to maneuver underwater, the electric field emission module releases extremely low frequency alternating current into water, and a specifically distributed electric field is formed in a target area; the electrode receiving array is used for measuring space electric field signals in real time and acquiring electric signal amplitudes of multiple paths of measuring electrodes relative to the reference electrode; processing the amplitude of the electric signal, calculating the variable quantity of the electric signal relative to the initial state, and judging whether a target exists or not and the relative distance and orientation of the target according to the extreme value change and distribution characteristics of the variable quantity; a control signal is generated based on the judgment result, and the movement direction and speed of the underwater carrier are adjusted to be close to a target; and after approaching the target, carrying out video and image discrimination, if the target is not the target, searching again, and if the target is the target, giving an alarm. According to the invention, the detection efficiency and accuracy can be effectively improved.

This invention provides a drive circuit for inverter loads, relating to the field of inverter technology. It includes a control module, a drive module, a power supply module, a signal acquisition and processing module, and a load matching module. The load matching module has impedance matching, tuning matching, and shaping filtering functions, providing universally adaptable drive capabilities for most types of motors and ultrasonic transducers. The power supply module uses high-speed MOSFETs, and the drive module uses a high-speed drive chip to adapt to the high-speed MOSFETs, offering a wide frequency range. A DDS waveform generation module is used to achieve PWM wave output at different frequencies, with extremely low frequency change steps and smooth transitions. Combining a variable step-size algorithm and a LADRC algorithm, it can automatically and accurately lock the operating resonant frequency of the inverter load within a certain frequency range. The employed linear LADRC algorithm adjusts the behavior of the drive circuit through real-time measurement and estimation, adapting to the variations and uncertainties in the complex working environments of motors and ultrasonic transducers.

1. Name of the product in this design: Uniaxial zero-frequency sensor. 2. Application of this design: A sensor for high-precision measurement under static or extremely low frequency (near DC) signals. 3. The key design feature of this product is its shape. 4. The image or photograph that best illustrates the design's key points: 3D view 1.

The present application relates to an extremely low frequency electromagnetic wave bidirectional magnetic sensing device and method, the device includes a controller, an antenna module including an antenna body, an excitation unit and a mutual induction unit, and an analog-to-digital conversion module, the excitation unit and the mutual induction unit are connected to the antenna body so that the antenna module is in an excitation state and a mutual induction state respectively, when the antenna module is in an excitation state, the controller obtains data to be transmitted, and converts the data to be transmitted into an excitation signal according to the encoding rule of the extremely low frequency pulse sequence, and transmits the excitation signal to the excitation unit, so that the excitation unit is driven to generate an excitation electromagnetic wave in the antenna body, when the antenna module is in a mutual induction state, the controller receives an induction signal through the antenna body, and analyzes the received data in the induction signal according to the encoding rule of the extremely low frequency pulse sequence, thereby realizing the excitation and mutual induction process of the device. The device is applied to realizing bidirectional communication between inside and outside in a shielded area, and can improve the quality of data transmission.

The application provides a wind turbine tower inherent frequency real-time identification method and electronic equipment, and belongs to the technical field of wind power generation equipment state monitoring and fault diagnosis. The method comprises the following steps: S1, collecting vibration signals of a wind turbine tower; S2, pre-processing the vibration signals to filter out direct current components and extremely low frequency noises; S3, performing grouping processing on the pre-processed signals, performing frequency spectrum analysis on each group of signals, and extracting effective frequency points; S4, performing clustering analysis on a plurality of the effective frequency points based on a density clustering algorithm, and identifying a characteristic cluster representing the inherent frequency of the tower; and S5, calculating the real-time inherent frequency of the tower according to the characteristic cluster. The application can stably and automatically extract the characteristic cluster representing the real inherent frequency of the tower from strong noise and non-stationary vibration data, finally realizes automatic identification and tracking of the inherent frequency without manual intervention, and provides reliable technical support for intelligent monitoring of the structure health of the wind turbine.

This invention specifically relates to a time-varying finite element modeling method for extremely low frequency (UHF) sound fields under dynamic internal wave processes, belonging to the field of underwater acoustic physics. The method first simulates the internal wave propagation process using the modified Korteweg-de Vries equation based on background field environmental information, and then obtains the vertical modes of the internal waves using the Taylor-Goldstein equation to construct a dynamic sound velocity field. Secondly, in a fluid-structure interaction model containing multiple layers of seabed media, the wave equation is solved using the finite element method to achieve time-varying calculation of the UHF sound field. This invention can precisely characterize the spatiotemporal evolution of the sound velocity field under complex terrain and dynamic internal wave disturbances, accurately simulate the distribution characteristics of the UHF sound field throughout the entire internal wave propagation process, and is suitable for sound field prediction and analysis in sea areas with high internal wave incidence, such as the South China Sea.

The invention discloses a modularized multi-level converter extremely-low-frequency circulating current injection power loss control method. The method comprises the following steps of 1, constructing a loss model of a modularized multi-level converter; 2, converting a loss optimization problem of the modular multilevel converter into a minimization problem of a bridge arm current absolute average value; 3, solving alpha 1 and alpha 2; 4, obtaining an optimal initial phase angle; and step 5, obtaining a frequency-doubled circulation amplitude with the minimum loss, and performing injection according to the optimal initial phase angle. The maximum voltage ripple under the extremely low frequency working condition only reaches twice of the rated frequency, and is far lower than the capacitance voltage fluctuation of a traditional modular multilevel converter under the extremely low frequency operation condition; the bridge arm current of each phase of bridge arm is controlled to be kept as the optimal bridge arm current, meanwhile, the severe fluctuation of the capacitor voltage of the modular multi-level converter under the extremely low frequency working condition is inhibited, and finally, the loss optimization of the modular multi-level converter under the extremely low frequency working condition is realized.

The application relates to the technical field of magnetic antennas, in particular to a magnetic antenna for ELF / VLF electromagnetic detection and communication and application thereof, which comprises a ring-shaped frame, permanent magnets and coils, multiple permanent magnets are uniformly arranged in the ring-shaped frame to form a permanent magnet array, the permanent magnet array is a ring-shaped Halbach array, and a spacing is left between every two adjacent permanent magnets in the permanent magnet array, and the magnetization directions of every two adjacent permanent magnets along the ring direction of the ring-shaped frame are arranged at a preset interval angle; the coils are arranged around each permanent magnet, all the coils are connected in parallel and then connected with an external power supply through a shunt, and the shunt is used for adjusting the current size and phase fed into the coils so as to adjust the radiation range of the magnetic antenna. The application introduces the concept of the Halbach array into the ELF / VLF magnetic antenna, maximally improves the antenna radiation efficiency under the condition of limited volume, and improves the practical application feasibility of the ELF magnetic antenna.

This invention discloses an ultra-high stability laser system based on dual-path independent composite frequency stabilization and sum-frequency modulation, belonging to the field of precision laser spectroscopy and frequency control technology. The system includes two seed lasers (1560 nm and 1064 nm), a dual-wavelength common-cavity ultra-stable module, two acousto-optic frequency shift and dual-reference absolute frequency stabilization modules, and a nonlinear sum-frequency modulation (SFG) module. Full-time-scale frequency noise suppression is achieved through a three-stage cascaded closed loop consisting of a MHz fast loop, a kHz slow loop, and a Hz extremely slow loop. An acousto-optic modulator is placed in the sampling optical path fed into the ultra-stable cavity, and physical decoupling of the fast and slow loops is achieved through radio frequency bridging. The extremely low-frequency error signal detected by NICE-OHMS is fed back to the PPMgOLN crystal temperature or AOM driving frequency to compensate for the thermally induced drift of the nonlinear crystal. The system ultimately outputs a 633 nm laser power of not less than 50 mW, with a short-term frequency instability better than 5 × 10⁻⁶ mW. ‑15 @1 s.

The present invention discloses a vital sign and consciousness monitoring system based on active and passive radar. Based on existing millimeter-wave radar for vital sign monitoring, this system uses a low-sidelobe, high-gain, high-sensitivity dual-frequency receiving antenna to receive millimeter-wave echo signals and brain wave signals, namely, Ka-band and brain wave band signals. Simultaneously, an extremely low frequency (0-20 MHz) high-sensitivity receiver is added to the high-sensitivity receiver module to receive and condition the brain wave radiation signals. The signal processing module then samples and analyzes the processed data. The analyzed data is compared with the processed data of normal individuals stored in the data storage module. When the difference exceeds a threshold, it indicates that the patient's vital signs or consciousness are abnormal, and an early warning signal is issued. The present invention is a non-contact monitoring system based on active and passive radar. It accurately collects vital sign and brain wave signals, enabling real-time, continuous, and dynamic monitoring of the patient's vital signs and consciousness, thereby facilitating the rapid recovery of patients under good rest conditions.