233 results about "Broadband noise" patented technology

The invention discloses an unmanned aerial vehicle soft landing control method based on track prediction and multi-source cooperative decoy, and the method comprises the steps: introducing a communication protocol recognition mechanism in a blocking process of an instruction link of an unmanned aerial vehicle, and achieving the conversion from extensive broadband suppression to protocol precise interference; the problems that in the prior art, power consumption is high, interference on legal communication is large, and the frequency hopping unmanned aerial vehicle resisting effect is insufficient can be effectively solved. In the scheme, signal integrity is guaranteed through monitoring and preprocessing, an unmanned aerial vehicle link protocol is identified through feature extraction and protocol library matching, and then a targeted interference template is generated, so that the interference effect can accurately fall on key positions such as a leader sequence, a CRC field, a subcarrier or a control frame and the like; therefore, synchronization, verification or data transmission can be destroyed under the condition of low power, and accidental damage of broadband noise to services such as co-frequency Wi-Fi and Bluetooth is avoided.

The invention provides a self-adaptive collaborative acoustic environment active treatment system and method. The system comprises a multi-dimensional environment sensing network module, an intelligent voiceprint recognition and sound field prediction module, an active noise control module, a central intelligent collaborative regulation, diagnosis and self-learning module and a passive acoustic intervention module. The multi-dimensional environment sensing network module collects multi-dimensional sensing data in real time; the intelligent voiceprint recognition and sound field prediction module outputs a voiceprint recognition result and a noise source space coordinate and predicts a sound field evolution trend; the active noise control module outputs a residual noise signal; the central intelligent cooperative regulation, diagnosis and self-learning module outputs an active and passive cooperative control instruction set; the passive acoustic intervention module controls broadband noise to block or change its propagation path. According to the invention, through a dual-channel self-learning mechanism of the deviation diagnosis capability, continuous evolution of system performance can be realized according to a deviation autonomous optimization acoustic model and a control strategy, and accurate, efficient and prospective active treatment is carried out on a complex noise environment.

According to the thin-layer sound absorption superstructure composite acoustic enclosure and the using method, the acoustic enclosure is composed of the cover plate, the conformal frame, the thin-layer sound absorption superstructures and the porous sound absorption materials, the variety of the thin-layer sound absorption superstructures is not limited to one, and the broadband noise reduction effect can be achieved through the parallel superposition design of the thin-layer sound absorption superstructures and the porous sound absorption materials. Wherein the thin-layer sound absorption superstructure can absorb noise in different frequency ranges of medium and low frequency bands, the porous sound absorption material can absorb noise in medium and high frequency bands, and the working bandwidth of the composite acoustic shield after parallel connection and superposition can cover the low, medium and high wide frequency bands. The thin-layer sound absorption superstructure composite acoustic shield further has the advantages of being high in space utilization rate, high in space adaptability, small in thickness, low in surface density and high in material replaceability. Compared with an existing sound insulation cover, on the premise that the thickness is small and the surface density is low, the working frequency band is wider, the sound insulation effect is better, and the sound insulation cover has wide application prospects in noise control of various mechanical and electrical products.

The invention discloses a ventilation-sound insulation integrated ultrathin metasurface grating and a using method thereof. The grating is composed of a perforated cover plate, a bottom plate, a plurality of slender cavities with different lengths formed by separating the perforated cover plate and the bottom plate through wall plates, and a peripheral grid-shaped ventilation area. According to the grille, the excellent broadband sound insulation performance can be achieved on the premise that the high ventilation quantity is guaranteed through a thin layer structure with the thickness as low as about 20 mm. The folded labyrinth resonance sound absorption units with gradient lengths are arranged in the non-ventilation area, broadband continuous sound absorption peaks can be generated, and sound absorption replaces sound insulation, so that broadband sound attenuation performance is obtained. Compared with an existing ventilation and sound insulation grille, the grille structure is thinner, larger in ventilation area and wider in working frequency band, the wide engineering application value of the grille structure is shown, a light-weight and low-frequency broadband noise reduction solution is provided for mechanical equipment such as airplanes, warships, high-speed rails and automobiles, and the mechanical equipment can be widely applied to mechanical equipment such as the airplanes, the warships, the high-speed rails and the automobiles. And the method also has wide application prospects in ventilation and sound insulation systems in green buildings.

The invention discloses a broadband noise generation method based on predistortion calibration, and relates to the technical field of communication, and the method comprises the steps: S1, setting a flatness threshold value, and screening out an original noise signal needing to be calibrated; s2, generating an inverse filter coefficient and a filter suppression coefficient for the original noise signal; s3, performing frequency response compensation by using an inverse filter coefficient, performing band-pass filtering by using a filter suppression coefficient, performing down-conversion to a baseband, and reducing a sampling rate; and S4, comparing the processed signal with a flatness threshold value, and if the processed signal does not exceed the flatness threshold value, indicating that signal calibration is completed, otherwise, entering calibration again. By introducing a pre-distortion calibration mechanism, the inverse filter coefficient is calculated in real time to compensate the system frequency response, the spectrum distortion caused by a fixed filter is effectively eliminated, and the method has the advantages of realizing dynamic and adaptive filter adjustment, effectively reducing the manual participation frequency and improving the continuous operation capability and the test efficiency of the system.

The invention relates to the field of aviation noise control, and provides an aircraft landing gear noise reduction device and method based on micro metal wire spiral winding. The device part comprises a metal wire and a metal wire fixing buckle, the metal wire is fixed through the metal wire fixing buckle, and meanwhile the size and material parameters of the metal wire are designed in a targeted mode. In the method part, the designed metal wire is wound on a cylindrical bluff body part, possibly generating vortex shedding and vortex-fixing interference, on the nose gear in a spiral winding manner, and the two ends and the axial interval position of the metal wire are fixed through the metal wire fixing buckles, so that the metal wire is ensured to be fastened. Therefore, through the wound metal wires, single-frequency noise in the over-top direction caused by falling of a towing rod vortex can be effectively eliminated, broadband noise is reduced, and the noise control capability of an airplane is improved. The method is suitable for various civil aircraft types, and has the advantages of being simple in structure, remarkable in noise reduction effect, high in practicability, high in adaptability and the like.

The invention relates to the technical field of submarine cable fault detection, in particular to a submarine cable fault detection system. The method comprises the steps that an adjustable low-frequency pulse injection unit injects a low-frequency pulse excitation signal and collects a response signal generated by a submarine cable fault; the multi-source signal fusion acquisition unit acquires a reflected voltage signal, an acoustic signal and a leakage magnetic field signal, and constructs a multi-modal fusion response characteristic matrix; the intelligent broadband noise suppression unit is used for performing noise suppression processing on each modal sub-matrix to obtain a de-noised multi-modal fusion response characteristic matrix; and the intelligent fault positioning interpretation unit is used for constructing a three-dimensional signal fingerprint spectrogram, performing classification analysis on fault events based on a fuzzy clustering algorithm and a depth feature matching model to obtain a fault type, and performing calculation through a path residual fitting method to obtain a fault position. The invention realizes a detection system which does not depend on a special cable structure, can actively excite and fuse multi-source signals, and can position submarine cable faults at high precision.

The invention discloses a design method of a noise reduction fairing, which comprises the following steps: determining a performance demand parameter of the noise reduction fairing, and constructing an initial noise reduction model based on a noise spectrum of a target application scene and an air duct structure defect; structural parameters are designed according to the performance requirement parameters; establishing a fluid-solid-sound coupled parameterized model of the layered composite structure and the flow guide assembly, and performing iterative optimization to generate an optimized configuration of the noise reduction fairing; a fairing prototype is manufactured based on the optimized configuration, actual measurement data are collected, simulation errors are corrected through an empirical regression model, and boundary conditions of a parameterized model are updated; the corrected noise reduction fairing is disassembled into modular assemblies, and an assembly process based on modularization is designed; in the assembling process of the modular assembly, a digital positioning system is adopted to be matched with an assembly interface; through the collaborative design of the layered composite structure and the diversion assembly and the module assembly design of the manufacturing link, the balance of broadband noise suppression and heat dissipation efficiency is realized, and the overall performance is improved.

The invention discloses an unmanned aerial vehicle instruction link blocking interference method and device based on communication protocol identification, which can effectively solve the problems of high power consumption, large interference on legal communication and insufficient anti-frequency hopping unmanned aerial vehicle effect in the prior art by introducing a communication protocol identification mechanism in the unmanned aerial vehicle instruction link blocking process. Firstly, signal integrity is guaranteed through monitoring and preprocessing, then an unmanned aerial vehicle link protocol is identified through feature extraction and protocol library matching, and then a targeted interference template is generated, so that the interference effect can accurately fall on key positions such as a leader sequence, a CRC field, a subcarrier or a control frame and the like; and synchronization, verification or data transmission can be destroyed under a low-power condition, so that accidental damage of broadband noise to same-frequency Wi-Fi and Bluetooth services is avoided. Meanwhile, through a frequency hopping prediction model and a scheduling mechanism, the interference signal can follow the frequency hopping switching of the unmanned aerial vehicle in real time.

The invention discloses an anti-interference system for a slip ring communication technology, and belongs to the technical field of communication. Aiming at the problems of electromagnetic interference, mechanical vibration and unstable contact of monocrystalline silicon furnace equipment, a collaborative solution is provided. The system comprises a conductive slip ring assembly, a dynamic shielding module, an asymmetric differential transmission module, an intelligent filtering module, an environment sensing module and a contact impedance compensation module, and real-time cooperative control is realized through a bus controller. The dynamic shielding module adopts a liquid metal micro-channel layer and a piezoelectric driving layer, the shielding density is dynamically reconstructed according to the electromagnetic interference frequency band and the vibration intensity, and broadband noise is suppressed; the asymmetric differential transmission eliminates common-mode interference through dynamic phase compensation; the intelligent filtering module adaptively adjusts parameters of a band elimination filter based on a deep learning model, and accurately suppresses time-varying interference; the carbon nanotube composite electric brush stabilizes contact impedance through a pressure feedback mechanism. The system is obviously superior to a traditional static shielding and fixed filtering scheme, and reliable communication requirements are guaranteed.

A method includes defining a design domain for a meta-element configured to be attached to an edge of thin wall structure with an arbitrary boundary condition, and executing a topological optimization process on the design domain and providing a topology optimized shape for the meta-element. The topological optimization process includes an objective function that minimizes a reflection coefficient of flexural waves in the audible frequency range propagating towards and impinging the meta-element.

The invention relates to a seismic phase pickup method based on time-frequency analysis and deep learning, and belongs to the field of seismology, a deep neural network comprising an empirical mode decomposition module, a residual shrinkage module, an LSTM layer, a transformer layer, an up-sampling layer and a convolutional layer is established, a linear rectification function is adopted as an activation function, an Adam adaptive optimization function is adopted for back propagation, and a seismic phase is obtained. And taking a binary cross entropy loss function as a loss function, and taking a mean absolute error function, an error standard deviation, an accuracy rate, a recall rate and an F1 score as evaluation indexes to obtain a deep neural network model. When the frequencies of the noise, the P wave and the S wave are different, empirical mode decomposition can effectively separate the noise, the P wave and the S wave, so that the network is helped to better identify the P wave and the S wave. Even for broadband noise, the noise can be decomposed into different intrinsic mode functions, so that the noise content in the intrinsic mode functions where P waves and S waves are located is reduced. The time-frequency analysis method can effectively improve the anti-noise capability of the network.

The invention discloses a flexible damping noise reduction composite material and application thereof, and relates to the field of damping materials. Efficient absorption of broadband noise is achieved through the design of a double-layer gradient structure of the flexible damping noise reduction composite material. According to the outer layer, carbon fibers and polyester fibers are woven in a three-dimensional mode to form a compact network, and micron-sized modified paraffin phase change microcapsules are embedded into the compact network; in the inner layer, a loose framework is constructed by basalt fibers and polyester fibers, coarse supporting fibers are combined with flexible fibers, and nano silicon dioxide aerogel is loaded. Due to the double-layer synergistic effect, the sound absorption coefficient of the composite material in the full frequency band is improved, the tensile strength is improved, and the composite material has the characteristics of high strength, broadband noise reduction and temperature self-adaption. According to the invention, the noise of the emergency diesel generator or the electric emergency generator car can be reduced to the maximum in all directions, and the emergency diesel generator or the electric emergency generator car can be protected in severe environments such as wind, rain, snow and the like. The damping material prepared by the invention has the effects of high strength and noise reduction.

The embodiment of the invention provides a compressor sound insulation structure and a control method thereof. The compressor sound insulation structure comprises a sound insulation cover and a deformation device. The compressor is covered with the sound insulation cover. The sound insulation cover comprises an inner sound insulation layer and an outer sound insulation layer which are sequentially arranged from inside to outside, and a resonant cavity is formed between the inner sound insulation layer and the outer sound insulation layer; the inner sound insulation layer is provided with a plurality of through holes and is made of a shape memory material; the deformation device is arranged in the soundproof cover and used for receiving the operation frequency of the compressor and driving the inner soundproof layer to deform according to the operation frequency so that the hole diameter of the through hole can be changed. Through the arrangement of the resonant cavity, the intensity of low-frequency noise is gradually weakened under the resonance effect, and therefore effective absorption of the low-frequency noise is achieved; by arranging the deformation device and the inner sound insulation layer made of the shape memory material, intelligent adjustment of the hole diameter of the through hole is achieved, so that the sound absorption frequency of the inner sound insulation layer and the resonant cavity is dynamically adjusted, the noise reduction requirement for broadband noise is met, and the operation noise of the outdoor unit is reduced.

This invention discloses a broadband composite sound insulation structure, including a first sound insulation mechanism and a second sound insulation mechanism. The first and second sound insulation mechanisms are disposed opposite to each other, with a closed air layer formed between them. Through the arrangement of the first, second, and air layers, the broadband composite sound insulation structure of this invention can effectively reduce and suppress broadband noise, including high-frequency, mid-frequency, and low-frequency noise. By incorporating the first and second sound insulation panels, noise reduction can be achieved while minimizing external environmental pollution to both the first and second sound insulation layers.

The invention provides an interval adaptive signal detection method and system based on a digital channelized receiver, and belongs to the field of signal detection in passive radars. The problems that in the passive radar signal receiving process of an existing digital channelized receiver, aliasing of signals and broadband noise exists, and power gains of different frequency bands are unequal, so that channelized signals cannot be normally detected are solved. The amplitude and phase information of M paths of signals are obtained by designing a filter bank, performing multiple serial-parallel conversion processing on input data and performing IFFT operation and CORDIC operation on data output by filtering K paths, then m-point self-correlation accumulation is performed on the amplitude of the M paths of signals, and the amplitude and phase information of the M paths of signals is obtained. Meanwhile, a more flexible threshold calculation method is provided, the working and signal detection bandwidth of the channelized receiver is refined, and a new scheme is provided for improving the signal detection adaptivity of the digital channelized receiver. The method is suitable for signal detection in a scene with non-uniform interference and gain distribution in the working bandwidth of the receiver.

The invention discloses a research method and a research system of a broadband efficient composite micro-perforated plate sound absorption structure based on genetic algorithm optimization, a mathematical model of the sound absorption structure is established according to theories such as an acoustoelectric analogy method, a composite micro-perforated plate calculation finite element model is established by using COMSOL software, and sound absorption characteristic research of the composite micro-perforated plate sound absorption structure is carried out. And finally, based on the research and an object-oriented programming language C + +, a sound absorption structure design and optimization platform of the composite micro-perforated panel is developed, the platform performs optimization analysis on basic structure parameters of the composite micro-perforated panel by using a genetic algorithm, and various parameter values with the widest frequency band and the best sound absorption effect are found in a given range. The optimal sound absorption structure under the given thickness is obtained; according to the invention, a new idea is provided for sound absorption performance optimization of an acoustic structure, and a reference is provided for broadband noise control of equipment in the ship field by using a novel micro-perforated plate structure.

The invention discloses a low-frequency broadband sound absorption metamaterial adaptive wing and a design method thereof, and belongs to the technical field of aircraft design. The problem that in the prior art, a traditional aircraft wing and a design method thereof are difficult to achieve the low-frequency and broadband noise reduction effect is solved. The wing comprises a leading edge inner side slat, a leading edge outer side slat, a main wing, a trailing edge inner side flap and a trailing edge outer side flap, the leading edge inner side slat and the leading edge outer side slat are connected with the front side of the main wing, and the trailing edge inner side flap and the trailing edge outer side flap are connected with the rear side of the main wing; the metamaterial sound absorption strips are embedded into concave cavities of the leading edge inner side slat and the leading edge outer side slat respectively, the metamaterial sound absorption strips are embedded into the leading edge of the main wing, each metamaterial sound absorption strip is composed of a Helmholtz resonator array composed of single-layer Helmholtz resonator units, and each metamaterial sound absorption strip is provided with a micro-perforated surface with continuous curvature. The noise reduction level of the wing is effectively improved, the sound absorption frequency band is wider, and the method can be applied to sound absorption wing design.

The invention provides a broadband noise adaptive active noise reduction control method, which belongs to the technical field of noise reduction control, and comprises the following steps of: 1, acquiring and enhancing an original reference signal for target broadband noise; step 2, multi-channel coherence calibration is carried out based on the enhanced reference signal; step 3, generating a control signal based on the calibrated reference signal; 4, collecting an error signal based on an error microphone arranged in a vehicle compartment; and step 5, performing adaptive parameter updating based on the calibrated reference signal and error signal. The problems of slow algorithm convergence and poor noise reduction performance caused by inaccurate reference signal spectrum capture, easy pollution and poor multi-channel coherence in the existing method are solved, and efficient and stable control of broadband noise is realized.

The invention provides an alternating-current weak current high-precision detection system and method, and the system comprises a copper-nickel alloy shielding cover which is used for inhibiting space power frequency radiation interference and power system broadband noise, and a magnetic sensitive element which is used for converting the detected magnetic field change into a corresponding initial current signal, the trans-impedance amplifier is used for converting the initial current signal into a voltage signal; the adaptive noise suppression module collects a power frequency fundamental wave reference signal and a harmonic wave reference signal, generates a harmonic wave anti-phase counteracting signal, and performs anti-phase counteracting on real noise of the initial current signal; the analog-to-digital converter is used for converting the voltage signal into a discretized digital signal, and the discretized digital signal comprises a target signal and a random noise signal; and the FPGA coherent demodulation module is used for carrying out cross-correlation operation and narrow-band filtering on the target signal and the random noise signal to separate out a micro-current signal. The technical problems that in the prior art, composite noise covering is limited, the frequency fluctuation adaptability is poor, and microvolt-level signals are difficult to capture are solved.

The present disclosure provides a method for optimizing a broadband noise of an inductive magnetic field sensor as well as a magnetic field sensor, including: determining a functional relationship between an induced voltage of a coil and an effective permeability of a magnetic core of the inductive magnetic field sensor; determining an equivalent voltage noise expression of a temperature variation-induced permeability noise of the magnetic core according to the functional relationship; determining a key influencing factor of the magnetic core according to the equivalent voltage noise expression of the temperature variation-induced permeability noise of the magnetic core; modifying the magnetic core according to the key influencing factor of the magnetic core to optimize the temperature variation-induced permeability noise of the magnetic core; and constructing a dual-channel composite multi-stage modulation signal-noise separation circuit to optimize a low-frequency band noise and a high-frequency band noise of the inductive magnetic field sensor.

The invention belongs to the technical field of acoustics, and discloses a low-frequency and broadband noise reduction acoustic structure and a design method of the acoustics structure.The acoustics structure comprises a plurality of acoustics structural parts and embedded parts, at least one embedded part is arranged in the multiple acoustics structural parts in a penetrating mode, and the multiple embedded parts are arranged on the same embedded part. The acoustic structural parts communicated with the openings in the two ends of the embedded part are arranged in pairs and form a first element together with the embedded part, the acoustic structural part not communicated with the embedded part is a second element, and the first element and the second element are arranged in parallel. Compared with the prior art, when sound waves pass through the acoustic structural members which are arranged in pairs, coupling resonance generated in the acoustic structural members can widen the silencing frequency band at a certain resonant frequency in a low-frequency range, the additionally arranged embedded members can enable the acoustic structural members to generate a new silencing frequency band, and the weak coupling effect existing between the parallel elements can continue to widen the silencing frequency band. Finally, the low-frequency and wider-band noise elimination and reduction effect is achieved.

The invention discloses an aircraft low-noise bionic flap based on side edge local turbulent flow and a design method, and belongs to the field of aircraft design. The high lift device is composed of a slat and a main wing, the high lift device comprises an inner flap, an outer flap, a noise reduction system and a driving system, the inner flap and the outer flap are installed on the high lift device, the noise reduction system is arranged at the end, close to the outer flap, of the inner flap, and the noise reduction system is driven by the driving system located in the inner flap; the noise reduction system comprises bionic nodules and asymmetric wingtip end plates, the bionic nodules are arranged on the end face of the inner flap, and the asymmetric wingtip end plates are arranged on the two sides of the inner flap. Aiming at the problems of influence on aerodynamic performance, generation of extra noise and complex structure in a flap side edge noise reduction method, the invention provides an aircraft low-noise bionic flap based on side edge local turbulent flow, and the effect of reducing intermediate-frequency broadband noise of the flap is achieved while the aerodynamic performance of a high lift device is ensured.

The invention discloses a PDCCH (Physical Downlink Control Channel) blind detection method and device, terminal equipment and a storage medium. The method comprises the following steps: acquiring a broadband signal to interference plus noise ratio and broadband noise power; determining a current blind detection aggregation grade sequence according to the broadband signal to interference plus noise ratio; according to a current blind detection aggregation level sequence, performing blind detection on all candidate sets under each aggregation level in sequence, and determining a physical resource position of a current candidate set; calculating a CCE-level signal to interference plus noise ratio and CCE-level noise power of a control channel unit of the current candidate set; according to the CCE-level signal to interference plus noise ratio and the CCE-level noise power of the current candidate set, and the broadband signal to interference plus noise ratio and the broadband noise power, carrying out early stop judgment; and if early stop is needed, current candidate detection is stopped, and next candidate set detection is started. By means of the scheme, the blind detection quality can be guaranteed, meanwhile, the blind detection time is shortened, and the system power consumption is saved.

The disclosure relates to systems and methods for enhancing active noise cancellation (ANC) in a vehicle, particularly for addressing challenges associated with broadband noise control. The present disclosure introduces a novel approach of subband adaptive filtering (SAF) that significantly reduces computational load and improves noise cancellation within a wide spectrum. The noise elimination system comprises a reference sensor, an adaptive weight filter, a loudspeaker, an error microphone, a signal processing unit, a sub-band processing module, a gradient determination module, an adaptive step size determination module, a sub-band adaptive weight updating module and a weight transformation module. By reducing complexity and improving convergence rate and stability of adaptive filter weights, the disclosed methods enable ANC to be implemented in environments with limited processing capabilities without sacrificing performance.

The invention discloses an aero-generator fan blade synchronous vibration acoustic identification method and system, a medium and equipment, and the method comprises the steps: determining a microphone array layout through parameters of a fan model; sound pressure time domain signals of multiple channels of the fan are synchronously collected through a microphone array; arranging the multi-channel sound pressure time-domain signals in sequence to construct a time-domain signal matrix; performing spectral analysis on the sound pressure time-domain signal by adopting a fast Fourier transform algorithm to obtain a spectrogram of the sound pressure time-domain signal of each channel, and monitoring whether a broadband noise component of which the blade passing frequency amplitude of the fan exceeds a first preset value and the frequency band distribution is greater than a preset range appears by monitoring the spectrogram; if not, it is indicated that the fan is in a normal working state, when the fan blades vibrate synchronously, the vibration of the blades is reflected through the frequency and the frequency doubling acoustic mode of the frequency, and the vibration pitch diameter and the frequency of the fan blade disc are output through the frequency passing acoustic mode of the blades on the basis of the frequency coupling relation.

The invention relates to the technical field of biomedical signal processing and medical electronics, in particular to a blood pressure measuring method for non-invasive exercise blood pressure monitoring. The method aims to solve the technical problem of low blood pressure measurement accuracy caused by broadband noise interference and failure of a fixed parameter model in a motion state in the prior art. According to the technical scheme, the method comprises the steps that a cardiac cycle reference signal and a Korotkoff sound signal are synchronously collected, a sampling window is calculated in a self-adaptive mode by utilizing a cycle triggering feature point gating mechanism and combining a heart rate, and time domain precise interception of the signals is achieved; carrying out root mean square calculation and Savitzky-Golay filtering on the intercepted signal, and keeping waveform characteristics while denoising; constructing a multi-dimensional feature regression model containing a peak value, skewness, kurtosis and dynamic template similarity so as to accurately judge systolic pressure and diastolic pressure; an automatic recharging mechanism is triggered by monitoring signal quality, and strong interference is physically avoided. The method has the advantages of being high in anti-noise capacity, high in feature extraction robustness and accurate and reliable in measurement result.

This invention discloses a frequency conversion circuit, a wireless communication circuit, an apparatus, a system, and a method. The technical solution of this invention, through optimization and improvement of existing passive frequency conversion circuits, can further reduce costs. Furthermore, by directly feeding the broadband noise signal into the resonant unit from the second modulation port without other loss circuits, the path loss of the broadband noise signal can be reduced, thereby obtaining more oscillation signals. This allows more oscillation signals to be fed into the modulation element for mixing, ultimately resulting in more frequency conversion signals. In other words, with the same initial radio frequency signal power, the frequency conversion circuit can produce more frequency conversion signal power, correspondingly reducing the power consumption of the frequency conversion circuit and achieving a longer wireless operating distance.

The invention discloses a shielded cable electricity testing method based on ground loop impedance potential lifting, and relates to the technical field of measurement. The electroscope comprises an electricity testing step, an induction electrode on the cambered surface of the electroscope is used for obtaining induced electricity, a broadband direct sampling framework is formed on the physical level, and broadband direct sampling of millivolt-level power frequency displacement current characteristics is achieved. Based on a variational mode decomposition-Duffing oscillator fusion weak signal extraction algorithm, a variational mode decomposition algorithm is utilized to adaptively strip broadband noise and higher harmonics, a reconstructed signal is subjected to scale normalization and then introduced into a critical chaotic state Duffing oscillator algorithm, phase transition of a phase track from a chaotic attractor to a large-scale limit cycle is monitored, and a weak signal is extracted. A non-linear dynamic weak signal extraction algorithm is formed on the algorithm level, and weak power frequency features masked by strong noise are accurately recognized; a broadband direct acquisition framework and a weak signal extraction algorithm form a dual detection framework, and a quasi-induction electric signal is detected and judged in the live part verification process of the shielded cable.

This utility model discloses a negative pressure compressor silencer made of composite sound-absorbing material, including a negative pressure fan body and a silencer pipe fixedly installed on the air inlet end of the negative pressure fan body. An air inlet channel is fixedly installed on the inner wall of the silencer pipe, and a primary noise reduction mechanism is provided on the inner wall of the air inlet channel near the pipe opening. The primary noise reduction mechanism includes an air inlet cylinder fixedly installed on the inner wall of the air inlet channel, and multiple air inlets are opened on the outer wall of the air inlet cylinder. This utility model, through the inner ring silencer cylinder, outer ring silencer cylinder, and silencer ring cylinder of the primary noise reduction mechanism forming a multi-stage sound absorption structure, utilizes the cooperation between the silencer holes and the annular cavity to allow sound waves to reflect and diffract between different cavities, effectively absorbing mid-to-high frequency noise. The coaxial and annular array distribution design of the air inlets guides the airflow to enter evenly, reducing the generation of eddy noise. The composite structure of the perforated metal cylinder and the sound insulation felt further blocks the transmission of noise, improving the broadband noise reduction effect.