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985 results about "Frequency noise" patented technology
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Frequency Noise. The term frequency noise refers to random fluctuations of the instantaneous frequency of an oscillating signal. The instantaneous frequency is defined as i.e. essentially as the temporal derivative of the oscillation phase φ . Any random deviation from a purely linear phase evolution is seen as frequency noise. The power...
Hand movement tracking system and tracking method
ActiveCN106679649AAttitude Calculation ImprovementsAccurate solutionNavigation by terrestrial meansNavigation by speed/acceleration measurementsHand movementsLow-pass filter
The invention discloses a hand movement tracking system and a hand movement tracking method. The invention comprises an attitude and heading reference system based on an accelerometer, a gyroscope and a magnetic sensor, and a hand movement tracking method based on the attitude and heading reference system. The hand movement tracking method comprises the following steps: firstly, obtaining a triaxial acceleration measured by the accelerometer, a triaxial angular velocity measured by the gyroscope and a triaxial magnetic-field component measured by the magnetic sensor, performing error compensation on the magnetic sensor by adopting a least square method to establish an error model after an upper computer receives sensor data, eliminating high-frequency noise of the triaxial acceleration by virtue of a window low-pass filter, and establishing an error model for the gyroscope so as to perform error compensation on random drift of the gyroscope; secondly, effectively integrating the gyroscope, the accelerometer and the magnetic sensor by virtue of an improved adaptive complementary filtering algorithm to obtain an attitude angle and a path angle; and finally, performing gravity compensation and discrete digital integration on acceleration signals to obtain a velocity and a track of a hand movement. The tracking system and the tracking method disclosed by the invention can be applied to a man-machine interactive system, is convenient to operate, and is strong in experience feeling.
Owner:ZHEJIANG UNIV
Noise Reduction Apparatus, Systems, and Methods
InactiveUS20090136104A1Improve signal-to-noise ratioReduce noiseCharacter and pattern recognitionMeasurements using NMR imaging systemsFrequency spectrumNoise reduction
This document describes a general system for noise reduction, as well as a specific system for Magnetic Resonance Imaging (MRI) and Nuclear Quadrupole Resonance (NQR). The general system, which is called Calculated Readout by Spectral Parallelism (CRISP), involves reconstruction and recombination of frequency-limited broadband data using separate narrowband data channels to create images or signal profiles. A multi-channel CRISP system can perform this separation using (1) frequency tuned hardware, (2) a frequency filter-bank (or equivalent), or (3) a combination of implementations (1) and (2). This system significantly reduces what we call cross-frequency noise, thereby increasing signal-to-noise-ratio (SNR). A multi-channel CRISP system applicable to MRI and NQR are described.
Owner:ARJAE SPECTRAL ENTERPRISES
Narrow linewidth semiconductor laser device
ActiveUS20060159135A1Improve reliabilityGuaranteed automatic operationLaser detailsSemiconductor lasersLow noiseDiscriminator
There is provided a narrow linewidth semiconductor laser device comprising a semiconductor laser and a low noise current source operatively connected to the laser for supplying current thereto, the current source being particularly adapted to prevent a significant degradation of the frequency noise spectrum of the laser. The laser device also has an optical frequency discriminator providing an error signal representative of the optical frequency of the laser. The laser device also has control means having a feedback network for providing a frequency feedback signal. The feedback network is particularly adapted to the frequency noise spectrum of the frequency discriminator, the frequency noise spectrum of the laser and the tuning response of the laser. The control means is also provided with sequencing means for allowing to automatically enable frequency locking of the laser on the frequency reference of the optical frequency discriminator. The laser device is provided with an enclosure for enclosing the frequency discriminator to isolate the frequency discriminator from external perturbations. Such an arrangement is particularly advantageous since it allows to provide an improved sub-kHz linewidth and a high coherence while being compact, lightweight and highly reliable. Moreover, the narrow linewidth semiconductor laser device of the present invention can advantageously be automatically operated.
Owner:TERAXION
Nuclear magnetic resonance underground water detection signal noise eliminating method based on independent component analysis (ICA)
ActiveCN104614778AEasy to operateImprove efficiencyDetection using electron/nuclear magnetic resonanceAcoustic wave reradiationData centerIndependent component analysis
The invention discloses a nuclear magnetic resonance underground water detection signal noise eliminating method. The method comprises the steps of: recoding response data entry three groups, each of these three sets of data Fourier transform nuclear magnetic resonance to determine the frequency of the data center in each neighborhood contains frequency harmonics, and frequency harmonic structure and the same frequency, and magnetic resonance corresponding data with sine function of the length of the cosine function, and composition and magnetic resonance response data observed signal using independent component analysis for each group observed signals to separate the mixed signal obtained solution for data reconstruction to eliminate frequency harmonic interference, the three groups of removing harmonic frequency data as observational signals, and then use algorithm processing, weaken the remaining random noise. The invention is to eliminate harmonic frequency noise at the same time, the signal will not destroy any details, without laying a reference coil, simple operation, suppress random noise does not require a lot of data, reducing the processing time.
Owner:JILIN UNIV
High noise immunity sensing methods and apparatus for a capacitive tough device
ActiveUS20130257767A1Reduce probabilityCathode-ray tube indicatorsInput/output processes for data processingTime domainEngineering
High noise immunity sensing methods and apparatus are provided for a capacitive touch device, which sense the capacitive touch device for self capacitance or mutual capacitance or both with different scan frequencies in a frame, to thereby suppress certain frequency noise interference. By combining time domain and space domain noise-eliminating approaches, probabilities of noise interference are reduced, without compromising other parameters.
Owner:ELAN MICROELECTRONICS CORPORATION
Non-contact heart rate measurement method and device based on Euler image magnification
ActiveCN107529646ARealize automatic measurementImage analysisCharacter and pattern recognitionTime domainHeart rate measurement
The embodiment of the invention discloses a non-contact heart rate measurement method and a device based on Euler image magnification, used for solving the technical problems existing in the existingnon-contact heart rate measurement method that the heart rate is great in same-frequency noise interference and is greatly influenced by an environment temperature, isolation signal authenticity lacksjudgment and the like. The non-contact heart rate measurement method and device based on Euler image magnification in the embodiment of the invention comprises the following steps: S1, magnifying tiny change of radial artery jump in a video through an Euler image magnification technology; S2, performing luminance variance statistics on a video frame pixel point luminance channel after magnifyingthe tiny change of radial artery jump in a time domain, performing skin segmentation on the video frame subjected to magnification of the tiny change of radial artery jump, and extracting a radial artery jump area; and S3, performing time-frequency analysis on the radial artery jump area so as to calculate the heart rate.
Owner:GUANGDONG UNIV OF TECH
Broad-band noise-reducing acoustic liner and its manufacture method
InactiveCN101149296AEffective noise reductionPump componentsThermometers using physical/chemical changesBroadbandEngineering
The invention discloses a line to decrease noise for Broad Band and manufacture method. The sound line has the noise elimination hole which is distributed randomly and the size is changed continuously. So it can decrease the noise of broad frequency noise. Because of whole forming, it can not generate the noise dispersion phenomena caused by the sound line joint to influence the noise decreasing effect. In process of Broad Band noise decreasing line, it can get the noise frequency and corresponding noise intension by value simulation of test and get the size range, changing interface and density of noise elimination hole; also it distributes the hole on the sound line basal board to have the good noise decreasing effect.
Owner:BEIHANG UNIV
Noise reduction apparatus, systems, and methods
InactiveUS8232799B2Reduce scan timeReduce data noiseCharacter and pattern recognitionMeasurements using NMR imaging systemsFrequency spectrumNoise reduction
This document describes a general system for noise reduction, as well as a specific system for Magnetic Resonance Imaging (MRI) and Nuclear Quadrupole Resonance (NQR). The general system, which is called Calculated Readout by Spectral Parallelism (CRISP), involves reconstruction and recombination of frequency-limited broadband data using separate narrowband data channels to create images or signal profiles. A multi-channel CRISP system can perform this separation using (1) frequency tuned hardware, (2) a frequency filter-bank (or equivalent), or (3) a combination of implementations (1) and (2). This system significantly reduces what we call cross-frequency noise, thereby increasing signal-to-noise-ratio (SNR). A multi-channel CRISP system applicable to MRI and NQR are described.
Owner:ARJAE SPECTRAL ENTERPRISES
Measuring device of noise characteristics of laser
ActiveCN102353523AHighly integratedReduce complexityTesting optical propertiesPhase noiseMeasurement device
The invention relates to a measuring device of the noise characteristics of laser, consisting of a conversion system of noise fluctuation of the laser and a detecting and processing system. The measuring device mainly comprises a circulator, a 3*3 coupler, a first photoswitch, a second photoswitch, optical fiber, a first Faraday rotation reflector, a second Faraday rotation reflector, a frequencyshifter, a first photoelectric detector, a second photoelectric detector, a third photoelectric detector, a fourth photoelectric detector, a data acquisition card and a computer. The measuring devicedisclosed by the invention has the capability of simultaneously measuring the noise characteristics comprising the intense noise power spectral density, the phase noise power spectral density, the frequency noise power spectral density, the line width and the Allen variance with frequency instability, of the laser, has the characteristics of high integration level and simpler and more concise structure, has no any limitation to the laser to be measured without an extra active control measure, thereby increasing the measuring reliability of the noise characteristics of the laser.
Owner:SHANGHAI INST OF OPTICS & FINE MECHANICS CHINESE ACAD OF SCI
Micro-mechanical resonant electrometer with ultra-high sensitivity
ActiveCN106645999AHigh sensitivityReduce the amplitudeElectrical measurementsBand-pass filterClosed loop
The invention, which belongs to the MEMS field, discloses a micro-mechanical resonant electrometer with ultra-high sensitivity. The method comprises a mechanical structure design method of an electrometer header and a testing circuit design method. Compared with the prior art using a movable resonator charge input polar plate, the mechanical structure design enables the conversion efficiency between the electrostatic force and the axial stress to be improved; and with a micro-mechanical lever, the electrostatic force increases to improve mechanical sensitivity. When an external charge is inputted, rigidity disturbance on a resonator I increases and thus the localization phenomenon of the mode becomes dramatic. Meanwhile, the two provided resonators with different structures employ differential detection structures; the differential amplification circuit is used for detecting the amplitudes of the resonators and eliminating feed-through signals, so that the signal to noise ratio of the detection signal can be improved. In terms of the testing circuit design, a closed-loop testing plane is employed. To be specific, a signal at a detection electrode passes through a trans-impedance amplifier, a subtracter, a band-pass filter and a comparator and then is loaded at an alternating-current drive electrode to form a closed loop; rectification and filtering are carried out on two paths of outputs of the subtracter and dividing is carried out to obtain a direct-current voltage signal reflecting an amplitude ratio of two resonators. With a closed-loop drive detection circuit, the amplitude and frequency noise of the resonator can be reduced.
Owner:NORTHWESTERN POLYTECHNICAL UNIV
Method of obtaining underwater acoustic channel reciprocity by using compressed sensing
ActiveCN103701749AImprove estimation accuracyReciprocityMulti-frequency code systemsTransmitter/receiver shaping networksTime domainChannel parameter
The invention discloses a method of obtaining underwater acoustic channel reciprocity by using compressed sensing and relates to underwater acoustic communication. The method is used for obtaining accurate channel parameters from OFDM (Orthogonal Frequency Division Multiplexing) received signals and ensuring the reciprocity of underwater acoustic channels. According to a compressed sensing theory, an OMP algorithm is used for reconstructing time domain impulse noise interference and wide single frequency noise interference, and eliminating the noise interference by observed quantity. For the time domain impulse noise interference, the time domain impulse noise interference is estimated by virtual subcarrier at a receiving end, is reconstructed by the OMP algorithm and is eliminated; the wide single frequency noise extracted at the receiving end has sparsity at a frequency domain, domain conversion is not needed, a measurement matrix is utilized, and the wide single frequency noise interference is reconstructed according to the OMP algorithm and is eliminated. The upper row and the lower row of underwater acoustic channels after the time domain impulse noise interference and the wide single frequency noise interference are eliminated are identical in channel states, namely, the underwater acoustic channels are provided with the reciprocity.
Owner:XIAMEN UNIV
Method and system based on differential phase contrast imaging reduction quantitative phase image
InactiveCN106768396AHigh resolutionImprove refactoring effectOptical measurementsMicroscopesImaging conditionComputer image
The invention discloses a method and system based on a differential phase contrast imaging reduction quantitative phase image, and relates to the field of the computer imaging. The stable method from a target image to a reduction quantitative phase image is established. The method is capable of firstly establishing a differential phase contrast imaging two-dimensional optical phase transfer function H(u), and establishing the relation between the H(u), a frequency domain function of a differential phase contrast image (the figure is as shown in the specification) and the quantitative phase information, finally executing the deconvolution operation to recover the quantitative phase information through the phase transfer function of the differential phase contrast imaging. The method is capable of further researching a method of quantitatively recovering the phase information under the asymmetrical illumination pattern formed by multi-axis division so as to enhance the reconstitution capacity of the phase information in the different directions, and using the mathematical optimization to reduce the frequency noise increase caused by the direct deconvolution. The method is capable of overcoming the defects that the traditional quantitative image acquisition operation is complicated and the imaging condition is rigorous, and the obtained image resolution is higher.
Owner:UNIV OF ELECTRONICS SCI & TECH OF CHINA
Stable cold field emission electron source
ActiveUS8736170B1Improved emission stabilityReduce noiseMagnetronsTransit-tube electron/ion gunsConventional transmission electron microscopeDesorption
A cold field emission (CFE) electron source for a focused electron beam system such as a transmission electron microscope (TEM), scanning transmission electron microscope (STEM), or scanning electron microscope (SEM) is disclosed. The source employs an emitter enclosure electrode behind the CFE tip which, in conjunction with the extractor electrode, defines a closed volume that can be thoroughly cleaned by electron impact desorption (EID) and radiative heating from a heated filament located between the emitter enclosure electrode and extractor electrode. The extractor electrode may have a counterbore which restricts backscattered electrons generated at the extractor from reaching portions of the source and gun which have not been cleaned by EID. Pre-cleaning of the emitter enclosure electrode and extractor electrode prior to cold field emission substantially improves both source emission stability and frequency noise characteristics, enabling source operation over time intervals adequate for application to TEMs, STEMs, and SEMs.
Owner:FEI CO
Eeg high-frequency oscillation signal detecting system based on convolution neural network
InactiveCN110236536AIncrease flexibilityHigh sensitivityDiagnostic recording/measuringSensorsEpileptogenic focusData pre-processing
Owner:UNIV OF ELECTRONICS SCI & TECH OF CHINA
Method for characterizing steel fatigue crack propagation behavior for casing drilling
InactiveCN102607948AEliminate the effects of background noiseSimple formulaMaterial strength using tensile/compressive forcesWell drillingNoise
The invention discloses a method for characterizing a steel fatigue crack propagation behavior for casing drilling. The method comprises the steps of: firstly, sampling casing drilling steel, preparing a sample and cleaning; secondly, carrying out low-frequency noise testing on the sample before fatigue; thirdly, carrying out fatigue testing on the sample; fourthly, carrying out low-frequency noise testing on the sample after fatigue; and fifthly, analyzing, extracting and processing low-frequency noise data before and after the fatigue testing according to low-frequency l / f noise information before and after the fatigue, and characterizing a fatigue crack propagation behavior of the sample. Through two times of low-frequency l / f noise testing before and after the fatigue propagation, the influence of background noise of the sample is eliminated, more complex formula derivation and mathematical calculation in common characterizing methods are avoided, no strict requirements are required for the shape of the sample, the fatigue testing quantity is favorably reduced, the testing cost is lowered, and the fatigue crack propagation behaviors of various samples can be conveniently subjected to sampling and fatigue service life estimation; and the method has the characteristics of convenience in use, low cost and convenience in popularization.
Owner:XI'AN PETROLEUM UNIVERSITY
Method, device and system for controlling variable-frequency air conditioner
ActiveCN104132429AContinuous noise controlSmooth noiseSpace heating and ventilation safety systemsLighting and heating apparatusEngineeringControl variable
The invention discloses a method, device and system for controlling a variable-frequency air conditioner. The method includes the steps of obtaining running frequencies of the variable-frequency air conditioner and noise signals corresponding to the running frequencies; generating a frequency and noise distribution curve of the variable-frequency air conditioner on the basis of the running frequencies and the noise signals; determining one or more target frequencies of the variable-frequency air conditioner according to the distribution curve, wherein the values of the noise signals corresponding to the target frequencies are not higher than the preset noise threshold value; controlling the variable-frequency air conditioner to run at the target frequency corresponding to the running request of the variable-frequency air conditioner. By means of the method, device and system for controlling the variable-frequency air conditioner, the problem that in the prior art, noise changes are large in the running process of a variable-frequency air conditioner system is solved, and the effects of ceaselessly controlling noises of the variable-frequency air conditioner and being low in noise are achieved.
Owner:GREE ELECTRIC APPLIANCES INC
Integrated micro-mechanical thermopile infrared detection system and method for producing the same
The invention provides an integrated micromechanical thermopile infrared detection system and a manufacture method thereof. The system comprises a thermopile detector and a signal processing circuit, wherein the signal processing circuit comprises a preposed amplifier, a band-pass filter, a main amplifier and an oscillator. The method is characterized in that integrated design and manufacture of a uniwafer of the thermopile detector and the signal processing circuit are realized; and compatibility of a MEMS sensor and a CMOS circuit can be realized by manufacturing the thermopile detector and the signal processing circuit simultaneously and using a standard CMOS process. The structure of the thermopile detector in the system comprises a (silicon) matrix, a framework, a thermoelectric couple, a support arm, an infrared absorption layer, etching openings; and the intermediate suspended infrared absorption layer can be provided with the etching openings with different shapes, and dry etching working gas enters a substrate etched silicon releasing structure through the etching openings. The structure of the signal processing circuit in the system uses wave chopping technology to reduce the effect of low-frequency noise on a signal.
Owner:SHANGHAI INST OF MICROSYSTEM & INFORMATION TECH CHINESE ACAD OF SCI
Small size dust collector motor cabin with noise reduction function
InactiveCN103169422ASmall footprintReasonable useSuction cleanersSupports/enclosures/casingsNoise reductionWide band
The invention discloses a small size dust collection motor cabin with a noise reduction function. The small size dust collection motor cabin with the noise reduction function comprises a motor cover, a motor assembly, a front-located filter, a motor shell, an exhaust filter element and a lower portion bottom plate, wherein a suction inlet is formed in the top of the motor cover, an exhaust cavity is formed between the motor shell and the lower portion bottom plate and in the outer side of the exhaust filter element, and a wide band silencer which is formed by an L-type noise reduction cavity and a cylindrical noise reduction cavity is arranged on the exhaust cavity portion of the lower portion bottom plate. According to the small size dust collection motor cabin with the noise reduction function, the size of the space occupation of the L-type noise reduction cavity is small, the limited space of the motor shell can be utilized reasonably, the noise reduction effect to single frequency noise is good, and the small size dust collection motor cabin with the noise reduction function has the noise reduction function for the noise with frequency from 4000 Hz to 10,000 Hz. In addition, the partial space formed by the geometrical shape of the motor shell is sufficiently utilized, a partition plate type silencer is additionally arranged on the motor shell wall, and by using the contraction noise reduction cavity formed by partition plates, the value of the sound pressure which can be reduced is 7 dB, and the value of the overall sound pressure is reduced by 3.8 dB.
Owner:NANJING LG PANDA APPLIANCES
Hybrid valve for attenuation of low frequency noise
A hybrid valve assembly for an exhaust system includes an exhaust tube having a bore defining an exhaust flow path. A vane is mounted within the bore and is moveable between an open position and a closed position. A resilient member biases the vane toward the closed position. A valve actuator has an ON position where movement of the vane is actively controlled by the valve actuator and an OFF position where movement of the vane is passively controlled by exhaust gas flow.
Owner:FAURECIA EMISSIONS CONTROL TECH GERMANY
Constant-speed air conditioner beat vibration determining method and device
ActiveCN106123242ATimely rectificationImprove experienceMechanical apparatusSpace heating and ventilation safety systemsFrequency spectrumPeak value
Owner:HISENSE (SHANDONG) AIR CONDITIONING CO LTD
System and method for testing laser frequency noise power spectrum density based on Mach-Zehnder interferometer
InactiveCN102183362AStable observationTest working point stabilityTesting optical propertiesNoise power spectrumDirect test
The invention discloses a system and a method for testing laser frequency noise power spectrum density based on a Mach-Zehnder interferometer. A laser central frequency is locked at an orthogonal point of an interference curve of the Mach Zehnder interferometer through a feedback loop, so the system works in a good linearity range, converts laser frequency noise into light intensity, and fulfillsan aim of performing direct test through an electronic frequency spectrograph; and a frequency observation point avoids 1 / f noise of the test system through the frequency shift by an acousto-optic frequency shifter. The invention provides the stable testing method which is used for testing laser frequency noise power spectrum density, is applied to an electronic frequency spectrograph, provides ameans for analyzing the influence of laser frequency noise on an optical system, and has significant scientific meaning and application value.
Owner:ZHEJIANG UNIV
Circuits and methods for controlling switching noise in switched-mode circuits
InactiveUS7142819B1Analogue/digital conversionElectric signal transmission systemsControl switchInformation level
A method of controlling noise in a pulse width modulation circuit includes varying a sample frequency and a range of information levels, wherein each sample within a data sample stream at the sample frequency represents a level within the range of information levels, to shift in frequency noise generated at the sample frequency during encoding of the data sample stream into pulse width modulated patterns.
Owner:CIRRUS LOGIC INC
Clothes dryer moisture sensing circuit
ActiveUS7345491B2Suppress noiseImprove accuracyResistance/reactance/impedenceMaterial moisture contentElectrical resistance and conductanceVoltage drop
A moisture sensing circuit for a clothes dryer in which clothes tumble during drying has a pair of spaced apart electrode sensors for sensing the electrical resistance of the clothes when the clothes contact the electrodes. The circuit has an active filter for suppressing noise related to the operating line frequency of the clothes dryer to provide a filtered voltage signal representative of voltage drop across the electrode sensors with the line frequency noise suppressed.
Owner:MABE CANADA
Time sequence signal efficient denoising and high-precision reconstruction modeling method and system
ActiveCN111046824AEffective denoisingEffective refactoringCharacter and pattern recognitionNeural architecturesNoise reductionData pre-processing
The invention provides a time sequence signal efficient denoising and high-precision reconstruction modeling method and system. The method comprises: carrying out data preprocessing on original pulsewave signals; selecting a preset signal duration, and dividing the pulse wave signals after data preprocessing into a prediction set, a training set and a test set; selecting a convolutional neural network as a basic model of the deep convolutional noise reduction auto-encoder, and obtaining a deep convolutional noise reduction auto-encoder model according to a signal denoising requirement; inputting the training set into a deep convolution noise reduction auto-encoder model for training, and optimizing and selecting parameters of the deep convolution noise reduction auto-encoder model by using the regularization parameters and the test set to obtain an optimal deep learning model; and inputting the noisy pulse wave signal prediction set into the optimal deep learning model to obtain deepstructure features, performing signal reconstruction and denoising processing, and evaluating model performance. According to the method, denoising and reconstruction of the pulse wave signals are effectively carried out, and a new thought is provided for filtering same-frequency noise interference in the pulse wave signals.
Owner:SHANGHAI JIAO TONG UNIV
Method and system for identifying marine oil spill object by marine radar
ActiveCN101915910AReduce extractionEasy extractionRadio wave reradiation/reflectionSea wavesDisplay device
The invention discloses a method and system for identifying a marine oil spill object by a marine radar. The method of the invention comprises the following steps: A, converting output image signals from radar projection into Descartes projection; B, correcting images and compensating motion; C, processing the radar images corrected in the step B by a Gamma filtering method, reserving marginal information and simultaneously filtering high-frequency noise of the radar images; D, detecting a strong signal area in the images, according to the distribution of signal strength in the images, determining the saturated state strength as the strength threshold of the signal area, and directly deleting the signal data exceeding the strength threshold; and E, carrying out image segmentation by a gray level co-occurrence matrix method to abstract the marine oil spill object. The system comprises a radar main controller, a marine radar controller, a junction box, an acquisition device, a processing device and a display device. The invention utilizes the noise wave information such as ocean wave and the like to obtain a small object, identifies the oil spill object by a texture algorithm, and can better abstract the marine oil spill object.
Owner:DALIAN MARITIME UNIVERSITY
Narrow linewidth semiconductor laser device
ActiveUS7471710B2Reduce frequencyImproved sub kHzLaser detailsSemiconductor lasersLow noiseDiscriminator
Owner:TERAXION
Optical sampling using intermediate second harmonic frequency generation
InactiveUS20030007205A1Improve dynamic rangeHigh speed machiningLaser detailsUsing optical meansBandpass filteringBeam splitter
An optical sampling method and apparatus use a probe pulse source of a predetermined optical wavelength range, e.g., 1560 nm, to sample incoming optical pulses in approximately the same wavelength range. The probe pulse source is frequency-doubled e.g., using a frequency doubler such as a nonlinear PPLN crystal, to obtain an intermediate second harmonic which may be filtered with a 780 nm bandpass filter to eliminate at least source frequency noise background. The filtered intermediate second harmonic is then mixed with the user input signal using an optional polarizing beam splitter and a dichroic beam splitter. The mixed signal is sent to a sum frequency generating (SFG) nonlinear crystal, e.g., a PPLN crystal, where the resulting frequency is near the third harmonic. The output from the SFG PPLN crystal may be filtered using a bandpass 515 nm filter to remove unwanted wavelengths and processed to measure / sense the near third harmonic content using a photomultiplier tube (PMT). Beyond the PMT, the output may be sent to a microprocessor for analysis and display on a cathode ray oscilloscope as necessary. 80-85% power conversion efficiency in the frequency doubler, a 60 or 65% photon conversion efficiency in the sampler and handling of 600+ GHz bandwidths, as well as background noise reduction are possible by using the invention.
Owner:AGILENT TECH INC
Drive circuit and method of drive light source and controller
InactiveCN102014543AHigh precisionDoes not affect dimming controlElectrical apparatusElectroluminescent light sourcesEngineeringBrightness perception
The invention discloses a drive circuit and method of a drive light source and a controller. The drive circuit comprises a frequency controller and a switching module, wherein the frequency controller receives a first dimming signal; if a light source is controlled according to the first dimming signal, the light source emits the preset brightness; when the frequency of the first dimming signal is within at least one preset range, the frequency controller generates a second dimming signal according to the first dimming signal, wherein when the frequency of the second dimming signal is beyond the at least one preset range, the switching module switches on and off alternately according to the second dimming signal so as to acquire the preset brightness; when the frequency of the first dimming signal is beyond the at least one preset range, the switching module switches on and off alternately according to the first dimming signal so as to acquire the preset brightness. The frequency of the dimming signal in the drive circuit is less than the preset maximum threshold value all along, therefore, the frequency noise cannot influence the dimming control of the light source and the precision of the drive circuit is improved.
Owner:AOTU ELECTRONICS WUHAN
Optical time domain reflectometer based on double acoustic-optical modulators and common-mode rejection method of optical time domain reflectometer
ActiveCN103900623AReduce frequencyReduce the impactConverting sensor output opticallyTime-domain reflectometerTime domain
The invention discloses an optical time domain reflectometer based on double acoustic-optical modulators and a common-mode rejection method of the optical time domain reflectometer. The method includes the following steps that a laser device outputs an optical signal; the optical signal is divided into two routes of optical signal bodies, and the optical signal bodies are modulated; direct frequency beating is conducted on the two routes of optical signal bodies so that frequency noise of the laser device can be eliminated and a reference signal can be generated; the first route of optical signal bodies enter a sensing optical fiber after being amplified, and a measurement signal is obtained after frequency beating is conducted on the back scattered light of the sensing optical fiber and the second route of optical signal bodies; the measurement signal and the reference signal are collected, phase demodulating is conducted, and phase comparison is conducted on the reference signal and the measurement signal to obtain a signal to be measured. The two acoustic-optical modulators are adopted, and by means of the method of conducting common-mode rejection by introducing the reference signal, influences of frequency noise of the laser device in the phase sensitive optical time domain reflectometer and frequency noise of the acoustic-optical modulators on the measurement result are reduced.
Owner:WUHAN WUTOS
High-frequency muffler used on automobile intercooler intake pipe
InactiveCN104234890AImprove noise reductionIncreased anechoic bandwidthIntake silencers for fuelResonant cavityTurbocharger
The invention discloses a high-frequency muffler used on an automobile intercooler intake pipe. The high-frequency muffler comprises a high-frequency muffling structure and a main pipeline connected on the intercooler intake pipe; a closed shell is positioned and connected on the periphery of the main pipeline, at least two partitions are arranged in the closed shell radially to enable at least two resonant cavities and an expansion cavity to be formed in the closed shell, each resonant cavity is communicated with the main pipeline through a group of small round through holes formed in the circumference of the main pipeline, the expansion cavity is directly communicated with the main pipeline, and the resonant cavities and the expansion cavities jointly form the high-frequency muffling structure. In a limited engine room space, the high-frequency muffler is wider in muffling frequency band, excellent in muffling performance and capable of more effectively lowering high-frequency noise such as squeal and surge generated in the working process of a turbocharger.
Owner:CHONGQING CHANGAN AUTOMOBILE CO LTD
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