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80 results about "Noise rate" patented technology

Signal combined denoising method based on empirical mode decomposition (EMD) and wavelet analysis

The invention belongs to the field of signal processing technologies, and particularly relates to a denoising method of additive white gaussian noise signals at a low signal to noise rate. The method includes the steps that according to autocorrelation of signals, autocorrelation of the signals is solved, the autocorrelation functions of the signals obtain the maximum values at zero points, the amplitude change along with change of time difference and will not attenuate to a small value quickly; EMD is performed on the signals mixed with the gaussian white noise, due to the nature of EMD, the gaussian white noise is not the real white noise any more, however, the statistical property of the white noise approximately exists, in other words, the autocorrelation functions of all the signals mixed with the gaussian white noise obtain the maximum values at zero points, the amplitudes change along with change of the time difference and will attenuate to the small value quickly. Through the difference, IMF components of which the noise plays a main role are selected, and the influences of the noise on the signals can be effectively reduced. Under the condition of the low signal to noise rate, the denoising performance of the method is superior to that of a traditional method, and signal denoising can be completed under the condition of the low signal to noise rate.
Owner:UNIV OF ELECTRONIC SCI & TECH OF CHINA

Full-wave magnetic resonance signal random noise abatement method combining EMD and TFPF algorithms

The invention relates to a full-wave magnetic resonance signal random noise abatement method combining EMD and TFPF algorithms. The method is a 'blind' filtering method in which filtering range designis not needed. The method comprises the steps of firstly utilizing decomposition characteristics of the EMD algorithm to decompose full-wave magnetic resonance signals into different intrinsic mode functions, then using the TFPF algorithm to code signal dominant mode functions into instantaneous frequencies of unit amplitude analytic signals, and utilizing the characteristic that time-frequency distribution of the analytic signals is concentrated along instantaneous frequency to inhibit random noise. The full-wave magnetic resonance signal random noise abatement method combining the EMD and TFPF algorithms has the advantages that few filtering constraint conditions are needed, the operation is simple, there is no need to design a filtering range in a time-frequency domain, and the methodhas high adaptability to full-wave magnetic resonance signals with a low signal-noise rate; the detection efficiency is remarkably improved, a good denoising effect can be obtained only through once measuring, random noise is effectively reduced, signal components are not lost at the same time, the signal-to-noise ratio can be remarkably increased, and the accuracy of later inversion is improved.
Owner:JILIN UNIV

Method for evaluating influence of speckle coherence on ranging accuracy of single-photon laser radar

The invention provides a method for evaluating the influence of speckle coherence on the ranging accuracy of a single-photon laser radar. The method comprises the steps of setting the parameters of the single-photon laser radar system, calculating the autocorrelation function of a receiving aperture of the single-photon laser radar system and the normalized covariance function on the intensity ofthe receiving aperture to calculate the speckle degree of freedom M; calculating the average signal photon number Ns according to the laser radar equation, and calculating the total noise rate Nn of the laser radar system; differentiating time through the detection probability based on the root mean square pulse width [Sigma]s of the laser pulse to obtain the detection probability density functionfs(t) of the echo signal with respect to time t, and obtaining the mean value shown in the description and the variance Var of the time when the detector detects the target point; and obtaining the influence of the speckle coherence on the ranging accuracy of the single-photon laser radar according to the drift error Ra and the random error Rp. The invention has good compatibility, can provide guidance for the system parameter design of the laser radar, improve the detection probability and reduce the ranging error as much as possible under the restraint of satisfying the false alarm probability.
Owner:WUHAN UNIV

Nonlinear amplification-retransmission optimal power allocation method

The invention discloses a nonlinear amplification-retransmission optimal power allocation method. The method comprises the following steps: an ideal amplitude-limiting amplifier model is constructed into a linear model with a Gaussian distortion noise option by using a linearized theory; according to the linear model, the chain equivalent single-to-noise rate of each nonlinear relay, devoted to a target receiver, is calculated; in order to obtain the optimal signal-to-noise rate performance, a maximum-combination-ratio receiver which is capable of realizing the nonlinear distortion is also designed; then, an optimal relay power allocation mathematical model is built, although the optimal power allocation problem is not a convex problem is found by analyzing a curve structure of signal to noise rate and power, the optimal relay power allocation problem can be converted into a convex optimization problem by limiting the maximum emission power; and finally, an optimal power allocation scheme is provided by utilizing a lagrangian multiplier method. A theoretical analysis and simulation result indicates that the method disclosed by the invention is superior to an optimal power allocation algorithm has no sense to nonlinear distortion, and has the capability of effectively improving the system capacity.
Owner:XI AN JIAOTONG UNIV

Ultrashort wave specific signal identification method based on convolutional neural network

The invention belongs to the technical field of radio signal identification, and particularly relates to an ultrashort wave specific signal identification method based on a convolutional neural network. The method comprises the following steps: performing short-time Fourier transform for a specific signal in a sample library, and acquiring a signal time-frequency spectrum, wherein the specific signal is a signal containing a frame synchronization code in a signal transmission data frame structure; training a convolutional neural network model with the time-frequency spectrum; and identifying the specific signal in ultrashort wave communication through the trained convolutional neural network model. In the method provided by the invention, firstly, visual characteristics, presented on the time-frequency spectrum, of the specific signal are analyzed, and training is executed through the convolutional neural network model, thus, identification of the ultrashort wave specific signal is realized, and signal identification rate is improved; and finally, through a simulation experiment, influence of aliasing interference on an ultrashort wave channel is reduced effectively, ultrashort wave specific signal identification under low signal-to-noise rate is realized, moreover, anti-interference performance can be improved through optimizing network structures and increasing the number ofnetwork layers, so the method provided by the invention has relatively strong practical application value.
Owner:PLA STRATEGIC SUPPORT FORCE INFORMATION ENG UNIV PLA SSF IEU

Carrier tracking device capable of adaptively adjusting parameters

The invention discloses a carrier tracking device capable of adaptively adjusting parameters, comprising an A / D (Analogue / Digital) converter, an orthogonal down convertor, a digital control oscillator, an estimation module, an integrator, a main carrier frequency demodulation and phase demodulation device and a loop filter, wherein an orthogonal down convertor module utilizes a local reference signal to carry out digital down conversion on a sampling signal output by the A / D converter to generate a baseband signal; the digital control oscillator generates the local reference signal according to a carrier frequency offset control word and a carrier tracking frequency control word; the carrier frequency offset control word is generated by the estimation module according to the baseband signal; the carrier tracking frequency control word is generated by the loop filter according to a frequency demodulation and phase demodulation error signal; the main carrier frequency demodulation and phase demodulation device generates the frequency demodulation and phase demodulation error signal according to an integrated signal; and the integrator and the loop filter determine the integrated time and loop filtering parameter according to selected parameters and the selected parameters are determined according to a signal to noise rate of the baseband signal by the estimation module. The carrier tracking device disclosed by the invention can realize the self-adaptive tracking on an upstream carrier signal according to the estimation of the baseband signal of an input signal.
Owner:XIAN INSTITUE OF SPACE RADIO TECH

Method for measuring related parameters of sensitivity, linearity and dark noise of charge coupled device (CCD) chip

The invention discloses a method for measuring related parameters of sensitivity, linearity and dark noise of a charge coupled device (CCD) chip, and mainly solves the problems of low measurement precision and incomplete measurement parameters in the prior art. The method comprises the following steps of: selecting a wavelength eta corresponding to the moment that the quantum efficiency of the CCD chip is maximal, and setting a tunable wavelength monochromatic uniform light source system to generate monochromatic light with the wavelength eta; selecting a series of integration time, and controlling the CCD chip to shoot image information and upload the image information to a computer by taking the integration time as parameters; selecting needed images by using corresponding computer software, and calculating the mean gray value mu, the time domain variance sigma<2> of the images and a system gain K; and calculating a saturation level mup.sat, a signal-to-noise rate (SNR), an absolute sensitivity threshold value mup.min, a dynamic response range DR and a nonlinearity error LE by using the acquired parameters. The method for measuring the related parameters of the sensitivity, the linearity and the dark noise of the CCD chip has the advantages of high parameter measurement precision, high stability and complete measurement parameters.
Owner:XIDIAN UNIV

Surface classification method based on single-photon laser radar background noise rate

The invention discloses a surface classification method based on a single-photon laser radar background noise rate. On the basis of a mirror reflection theory, an expression of a water surface photonreflection noise rate is proposed is put forward; a background noise rate model is established by combining system parameters, environmental parameters and target characteristic parameters and mathematical expressions of a land background noise rate and a water body background noise rate are given respectively; a surface classification noise rate threshold value is obtained through calculation; and according to significant difference between land and water background noise rates, a statistical noise rate substituted into original point cloud data of the laser radar can be compared with a noiserate threshold to judge the surface type. According to the classification method, the dependence on a digital topographic map or a high-resolution remote sensing image required by the traditional method is eliminated; and used auxiliary data are available. The method having advantages of rapidness and high efficiency can be used for realizing high-precision surface type classification in coastalareas. The method is applied to the MABLE original point cloud data and the classification effect is excellent.
Owner:WUHAN UNIV

Distributed compression forwarding system of multi-relay network under Gaussian source and design method

The invention discloses a distributed compression forwarding system of a multi-relay network under a Gaussian source and a design method. A source sends a simulated Gaussian signal, performs distributed source coding at a relay node, and performs the digital transmission. Since the simulated signal is transmitted, the index for system performance evaluation is the signal-to-noise ratio. A theoretical analysis frame of the system is proposed in consideration that the sending power of each relay node is the same and all noises powers are the same under an additive Gaussian white noise channel, a rate-distortion function of the multi-relay network is established by use of the CEO theory, and the connection between a sensing network and a digital communication network is established in combination with a Shannon channel capacity theory. An optimal design theory method of the system is proposed, and the power distribution is performed between the sensing network and a communication network based on the signal-to-noise rate under a condition that the total power is limited, thereby enabling the signal-to-noise rate to achieve the maximum. The theoretical analysis and the simulation result show that the optimal compression forwarding system provided by the invention can provide better signal-to-noise ratio in comparison with an amplification forwarding system.
Owner:NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
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