98results about How to "Low signal-to-noise ratio" patented technology

The invention discloses a method for estimating the modulation frequency and starting frequency of a linear frequency-modulated signal. The method comprises the following steps of: I, acquiring a data sequence x(n), wherein n=0, 1, 2, ellipsis , N-1; II, initializing parameters; III, calculating the power spectrum Yi(12) of a data sequence xi(m) in an ith short time window; IV, estimating the instant frequency estimated value fi of the data sequence in the short time window by adopting a Rife interpolation algorithm; V, judging whether the data sequences of all short time windows are processed, if not, returning to the step III, otherwise, turning to a step VI; VI, calculating a kth iteration weight; VII, judging whether an iteration weight least square linear fitting stop condition is met, if not, returning to the step VI, otherwise, turning to a step VIII; and VIII, calculating modulation frequency and starting frequency parameters. Due to the adoption of the method, the accuracy ofparameter estimation can be increased on the premise of ensuring rapid estimation without performing complex calculation and parameter search.

The invention discloses a millimeter-grade micro-motion measuring method based on a synthetic broadband pulse Doppler radar. By employing the phase-deduction velocity and range measurement technology, the target movement is precisely measured, and an iteration motion parameter combined estimation method is employed to measure the target millimeter-grade micro-motion and extract target motion parameters precisely; compared with a conventional narrowband micro-motion measuring method, the millimeter-grade micro-motion measuring method is a phase-grade high-precision micro-motion measuring method, the range-measuring precision is the millimeter grade, the velocity-measuring precision is centimeter / second grade, and the requirement of high-precision range and velocity measurement of the radar for micro-motion extraction is satisfied; high resolution ability for the distance is provided, scattering points of a complex target can be separated, and distance and motion information of different scattering points of the target can be simultaneously obtained; the broadband PD processing method can realize echo coherent accumulation and effectively suppress static and low-speed clutters; and with the combination of track filtering information, the broadband enveloping range / velocity measurement precision can be improved, and the requirement of the signal to noise ratio by correct phase unwrapping is reduced.

The invention discloses a method for estimating the cycle slope and the starting frequency of hyperbolic frequency modulated signals. The method comprises the following steps of first, acquiring a data sequence, second, initializing parameters, third, calculating the power spectrum of data in the ith short time window, fourth, estimating the instantaneous frequency fi of the data in the ith short time window by using a maximum gammagraphy method, fifth, estimating the zero crossing point interval gi = 1 / fi of the data in the ith short time window, sixth, judging whether the data of all the short time windows are processed, executing the third step if not processed, otherwise executing the seventh step, seventh, sliding median filtering is conducted on a zero crossing point interval estimating sequence {gi, i = 1, 2, ..., I}, eighth, calculating the kth time interation weight, ninth, judging whether an interation stopping condition is met or not, if not, executing the eighth step again, otherwise executing the tenth step, and tenth, calculating the cycle slope and the starting frequency. According to the method, complex calculating and parametric search are of no need, the stability is strong, and quick and high-precision estimation of the parameters can be achieved.

The invention provides a robust underwater acoustic channel estimation method based on joint norm optimization. A detection signal is sampled to obtain a discrete time sequence; a cost function of underwater acoustic channel response estimation is established on the basis of the thought of joint norm optimization; a support domain of a channel function is defined by using a matched filtering method; and a channel estimation result is modified, and loop iteration is continued to obtain estimation of underwater acoustic channel pulse response. The cost function based on joint norm of a channel response function is constructed through the sparsity of an underwater acoustic channel, so that the requirement of an algorithm on the signal to noise ratio is lowered effectively. Meanwhile, the resolution capability of multipath time delay is enhanced; the problems of heavy computation, large storage amount and high time consumption in channel estimation are solved; and the 'false peak' effect occurring in channel estimation is reduced.

The invention discloses a cable fault on-line detecting and positioning device. The device includes an FPGA module with an NIOS II soft core processor, a high-speed DA module, an isolation coupling module, a high-speed AD module and a conditioning circuit. The FPGA module provides clocks needed by all modules, generates a detection signal formed by modulation of an m sequence and sine waves, performs related operation processing of the detection signal and a reflection signal, and positions cable faults. The high-speed DA module is used for digital analog conversion of the detection signal generated by the FPGA module. The isolation coupling module isolates an output signal of the high-speed DA module and couples the output signal to a cable, and also isolates a reflection signal in the cable and couples the reflection signal to a detection positioning device. The high-speed AD module carries out analog-to-digital conversion of the reflection signal in the cable and then sends the signal to the FPGA module for processing. The conditioning circuit is used for conditioning the output signal of the high-speed DA module and an input signal of the high-speed AD module. The device has an on-line detection function, is high in positioning precision, and exhibits a high anti-interference capability.

Provided is a method for detecting frame sync and frame structure in a satellite broadcasting system, which acquires an estimated value for detecting frame structure and frame sync and overcomes distortion of correlation analysis values by summing differential correlation values for SOF positions in consideration of the variable frame length, and selecting a maximum value in a channel environment with low signal-to-noise ratio and high frequency error. SOF is a sync word indicating the start point of a frame. The method includes the steps of: acquiring SOF differential correlation value sequences; acquiring sums (di,t) of the correlation values normalized for SOF positions based on the number of symbols per frame by using the above-generated SOF differential correlation value sequences; and selecting a maximum value (dz,x) among the sums of correlation values, detecting z as a frame sync position, and detecting x as a frame structure index.

The invention discloses a pipeline weak leakage detecting device and a detecting method based on a fuzzy hyperbolic chaos model and belongs to the technical field of pipeline detection. Two-stage detection is used, the first-stage detection is abnormal signal detection based on a neural network to mark abnormal signals, and the second-stage detection detects the abnormal signals marked by the first-state detection. By the two-stage detection, the first-stage primary detection is fast, the second-stage detection detects the abnormal signals marked by the first-state detection, and leakage detection capability is increased. The two-stage detection can be implemented on a FPGA (field programmable gate array) hardware platform, and overall system response speed is increased. By the double coupling time-varying delay fuzzy hyperbolic chaos model of the second-stage detection, initial value sensitivity and noise immunity of the chaos system is utilized to increase identification capability of weak leakage signals submerged in noise so as to highlight chaos phenomenon, system requirements for signal to noise ratio is lowered, and weak leakage detection is achieved.

The invention provides a single channel communication signal and interference blind separation method based on mutation particle swarm particle filtering (MPSOPF-SCBSS), and belongs to the communication signal processing and communication anti-interference field. In view of the single channel communication signal and interference blind separation problem in the condition of large interference-to-signal ratio, small number of particles and low signal-to-noise ratio, the method adopts Bayesian filtering estimation for communication signal and interference separation. According to the method, a single channel disturbed communication signal state space model is firstly built, the single channel interference and signal blind separation problem is converted into joint estimation of communication symbols and unknown system parameters, and joint estimation is realized through mutation particle swarm optimization particle filtering to achieve the blind separation purpose; through a velocity-displacement update function and a Metropolis-Hastings mutation rule in the particle swarm optimization, the needed particle number in the sequential estimation process is reduced and diversity of the particle set can be ensured. In addition, the provided mutation particle swarm optimization rule reduces demands on the signal-to-noise ratio of communication signals in the single channel disturbed condition.

The invention belongs to the technical field of radar target echo signal parameter estimation, and discloses an echo signal parameter estimation method based on a scaled-down dictionary. The echo signal parameter estimation method based on the scaled-down dictionary comprises the following steps that 1, an initial parameter set {theta <(1)>} is obtained according to all unknown parameters corresponding to scattering centers in an echo signal model, the dictionary A (theta <(1)>) is formed through the initial parameter set {theta <(1)>}, and the number m of iteration times is set to be one; 2, a new parameter set {theta' <(m)>} is obtained by carrying out Bayes learning for the mth time according to the A (theta <(m)>); 3, if m is equal to M, the step 5 is carried out, or, the value of m increases by one and the step 4 is carried out; 4, a new parameter set {theta <(m)>} is obtained according to a refinement method for a parameter set {theta <(m-1)>}, a dictionary A (theta <(m)>) is formed through the parameter set {theta <(m)>}, and then the step 2 is carried out; 5, the number m* of iteration times meets the set condition and is found out; 6, weighting and clustering are carried out on{theta' <(m*)>} according to a K-means clustering method.

The invention provides a pressure wave signal generator and a real-time tracking and positioning method for a detector in a pipe. The pressure wave signal generator is arranged on a flange of the detector in the pipe, and the pressure wave signal generator generates signals when the pressure wave signal generator advances in the pipe along with the detector in the pipe; and the pressure wave signal generator comprises a power take-off gear, a supporting arm, a swinging arm, a first gear, a releaser, a spring, a movement pair, a screw rod, a reducer and a second gear. The method comprises the following steps that real-time pressure signals of the head end of the pipe and the tail end of the pipe are collected, and phase-space reconstruction is conducted; a pressure wave chaos state prediction model is constructed and trained, and a pressure wave chaos state real-time model and a pressure wave chaos state synchronous model are synchronously constructed; the arrival time of the pressure wave signals generated by the pressure wave signal generator to the head end of the pipe and the arrival time of the pressure wave signals generated by the pressure wave signal generator to the tail end of the pipe are detected; and the distance between the detector in the pipe and the tail end of the pipe is calculated. According to the pressure wave signal generator and the real-time tracking and positioning method for the detector in the pipe, real-time tracking and blockage positioning of the detector in the pipe are achieved, the tracking range is large, and the pressure wave signal generator and the real-time tracking and positioning method for the detector in the pipe are not limited by the buried depth of the pipe and the thickness of the pipe wall.

The invention discloses a super-resolution one-dimensional distance imaging method of a step frequency radar and is used for mainly solving the problems of redundancy target, synthetic bandwidth limit on resolution, low signal to noise ratio of one-dimensional distance and instability on noise in the prior art. The realization process comprises the following steps: performing singular value decomposition on echo data with frequency mixing operation of the step frequency radar; serving a signal sub-space as an observation value according to the singular value decomposition result; performing grid division on the radar irradiation distance region to obtain distance units; structuring an observation matrix according to the distance units obtained in the grid division operation and the signal obtained in the frequency mixing operation of the step frequency radar; and recreating a one-dimensional distance image through a CVX convex optimization tool according to the observation value and the observation matrix. The method disclosed by the invention obtains super-resolution one-dimensional distance complex image with high signal to noise ratio without removing redundancy on a condition of low signal to noise ratio of radar echo, so that the method can be applied in super-resolution distance imaging processing of the step frequency radar.

The invention discloses a direction of arrival estimation method based on a multi-baseline distributed array. The direction of arrival estimation method mainly solves the problem that angles are blurry in the estimation process of a target direction of arrival through an existing distributed array. The implantation process of the direction of arrival estimation method comprises the following steps: subarrays are arranged according to a multi-baseline structure, and received data of the array are extracted; a covariance matrix of the received data is estimated and subjected to eigen decomposition to obtain signal subspaces; a space domain rotational invariance equation in each subarray, a space domain rotational invariance equation between the shortest baseline subarrays, and a space domain rotational invariance equation between the longest baseline subarrays are constructed respectively according to the signal subspaces; the equations are solved respectively to obtain a rough estimation without a blur, a precise estimation with a blur of short baselines and a precise estimation with a blur of long baselines; obtained estimation parameters are subjected to matching and deblurring to obtain the target direction of arrival. By means of the direction of arrival estimation method based on the multi-baseline distributed array, the direction of arrival estimation performance of the distributed array under a low signal to noise ratio condition is improved, the physical aperture of the array is further enlarged, and the direction of arrival estimation method can be applied to target identification.

The invention provides an ionosphere non-coherent scatter radar differential phase detection method, comprising steps of 1 computer simulation and modeling research, 2 non-coherent scatter software radar verification test, 3 non-coherent scatter radar verification test, and 4 optimization and improvement of the radar echo numerical module, the parameter extraction algorithm and the test method according to the computer simulation and practical detection result. The invention can simultaneously and fast obtain the parameters of the high accuracy electronic density of the whole ionosphere height, the electronic temperature, the ion temperature, the plasma drift speed in the direction perpendicular to the magnetic line, etc.

A system architecture for a receiver to process multiple signals on a common carrier frequency from a satellite. The receiver is arranged such that the receiver receives input data transmitted from the satellite. A pilot signal is tracked from the input data using a correlation channel, and a data signal is tracked from the input data using a data code generator operatively connected to the correlation channel. In one embodiment of the invention, the data signal generator creates replica code for the data signal. In another embodiment of the invention, the system can switch between the data signal generator and pilot signal generator based upon the signal-to-noise ratio of the incoming signal.

The invention discloses a symmetrical triangular linear frequency modulation continuous wave type laser radar target detecting method. The method comprises the steps of modulating a laser signal through a chirped signal to obtain a modulating signal; processing the modulating signal to obtain an emission signal, a first intrinsic signal and a second intrinsic signal; performing coherence for the first intrinsic signal and the second intrinsic signal through an echo signal to calculate a fixed part of a frequency difference value due to the frequency variation caused by the distance in the difference frequency between the echo signal and the first intrinsic signal and the second intrinsic signal and Doppler shift fd caused by speed; calculating the target speed v through fd; calculating t through fx; calculating Tfly-in, r=cTfly-in and S=r / 2 through t so as to solve the distance. According to the method, the echo signal is subjected to coherence with the first intrinsic signal and the second intrinsic signal, and the mutually combined result enables the dynamic range of the laser flying range of the detected target to reach the distance corresponding to the whole symmetric triangular linear frequency modulating cycle; the dynamic range of the radar detecting range is doubled that in the prior art.

A method for synchronizing a RFID receiver, comprising receiving an input signal from a RFID tag, said input signal comprising a preamble section, creating a first reference waveform, comprising at least a fraction of said preamble section, calculating a first correlation value by correlating said input signal and said first reference waveform, creating a second reference signal so that there is virtually zero correlation between said first reference waveform and said second reference waveform, and using said first correlation value and said second correlation value for adjusting synchronization timebase, wherein the sign and the size of said second correlation value indicates the size and the sign of phase inaccuracy of the synchronization timebase.

A Wireless Regional Area Network (WRAN) receiver comprises a transceiver for communicating with a wireless network over one of a number of channels, and an Advanced Television Systems Committee (ATSC) signal detector for use in forming a supported channel list comprising those ones of the number of channels upon which an ATSC signal was not detected. The ATSC signal detector computes at least one cyclostationary feature of a received signal for determining if the received signal is an incumbent ATSC broadcast signal.

The invention provides a Brillouin spectrum signal quality improving method. According to the method, reference Brillouin spectrum data are generated according to test parameters, the cross-correlation algorithm is used for accurately recognizing Brillouin signals from test Brillouin spectrum data with a lower signal-to-noise ratio through the reference Brillouin spectrum data, thus, the Brillouin spectrum signal recognizing capacity and the strain computational accuracy can be improved, and application of BOTDR products in long-distance optical fibers and severe construction environments can be greatly improved. By the adoption of the scheme, the signal-to-noise ratio requirement for the Brillouin signals is greatly reduced; the testing distance is increased; the stability of strain test results is improved; hardware modification is not needed, and therefore the improvement cost is low.

The invention relates to a communication method combining chaos and MIMO (Multiple Input Multiple Output) and belongs to the technical field of communication. According to the method, for the defects of low transmission rate, high error rate and low confidentiality of a correlation delay shift keying (CDSK) chaotic communication scheme, a frequency modulated signal is dispersed in multiple channels for transmission, a delayed signal is equally divided into M sections by a segmentation cyclic shifter, and the M signal sections are cyclically shifted right for n sections according to information code elements and added into an original chaotic signal to form an output signal. Therefore, the confidentiality is remarkably improved and the information transmission rate is remarkably increased in comparison with an FM-CDSK scheme; under the same error rate, the signal-noise ratio is greatly improved in comparison with the FM-CDSK scheme; an improved chaotic confidential communication system adopting the method has wide application prospects in the fields of images, military confidential information and the like.

The invention discloses a GSM external radiation radar signal processing method based on digital modulation and demodulation. The GSM external radiation radar signal processing method mainly solves reference signal purification problems of an external radiation source system based on digital modulation and demodulation. The GSM external radiation radar signal processing method comprises the steps that a signal of a reference channel is modulated and demodulated so as to obtain a pure emission signal; the local regenerated pure emission signal is used for conducting clutter cancellation, distance-Doppler detection is conducted, and detection and position information extraction of a moving object are finished. The core of the GSM external radiation radar signal processing method is purification conducted on the reference signal in the reference channel, multi-path and noise influences from the reference signal are removed, the correlation of a target echo signal in an echo channel is improved, and detection power of the system is improved.

The invention discloses a method for detecting dual-channel monopulse angle error in frequency domain, belonging to the technical field of radio frequency antenna self-tracking. The invention includesFFT processing of the sum signal and the difference signal receiving channel, correlation and accumulation of sum signal and the difference signal, filtering between FFT frames, normalization and other processing steps, and realizes the detection of high-performance monopulse angle error. The digital demodulation of the angular error based on the frequency domain has the advantages of many kindsof working signals, fast response speed, high integration degree, low working signal-to-noise ratio, convenient delay correction and high phase correction precision, and is an important improvement to the prior art.

The invention relates to a towed passive array sonar low signal-to-noise ratio ship moving target detection method. According to a tracking-before-detection method, the motion characteristics of a target are utilized; the multi-frame information of the target is accumulated; an exhaustive search idea is utilized to decompose the overall motion trail search problem of the target into a hierarchicaloptimization problem; the detection result of the target is given while the motion trail of the target is given; the position description of ship motion target (positive sample) and clutter (negativesample) signals is given, and meanwhile, the positive and negative samples of an azimuth course graph are also automatically established; a time-space domain joint feature extraction method is provided through the spatial-temporal characteristic analysis of the motion target and random clutter signals of the azimuth course graph, and the problem of underwater acoustic target detection feature extraction by using machine learning can be effectively solved.

The invention, which belongs to the technical field of leakage detection, relates to a leak detection and positioning method for vacuum equipment. A vibration signal of a current state of vacuum equipment is collected and framing processing is carried out on the collected vibration signal; each frame of data are decomposed into a plurality of signal components at different frequency ranges; the signal components are processed to extract a suspected leak sound signal component and a suspected leak sound frequency range; the suspected leak sound signal component is processed to detect whether leak exists; if so, a leak point is localized by combining a practical vibration propagation model and energy consumption features of different locations of the vacuum equipment. According to the method provided by the invention, the vibration signal is used as a processed object, so that leak of vacuum equipment can be discovered timely and accurately and the leak point location can be localized rapidly. On-line monitoring of the leak state of the vacuum equipment is realized; and the operation safety factor and economy of the vacuum equipment are improved.

The invention relates to a terahertz synthetic aperture radar (SAR) multi-frequency vibration error compensation method. Platform vibration, especially high-frequency vibration, may introduce additional phases related to the vibration frequency into a radar azimuth signal, which may cause a terahertz SAR image to be out of focus and present a phenomenon of paired echo. The method of the inventionincludes the following steps of: establishing an echo signal model under the terahertz SAR multi-frequency vibration according to a multi-frequency vibration geometric model of a terahertz SAR platform; completing paired echo focusing by adopting a terahertz SAR high-frequency vibration imaging method, introducing BEMD decomposition to perform platform vibration component separation and vibrationfrequency estimation, sequentially selecting BIMF components in high-frequency sinusoidal form to carry out time domain reconstruction, adopting a parameter space method to find a peak value, determining the amplitude and initial phase of the vibration component, and constructing a compensation function to complete the high-frequency vibration error compensation of the platform until no significant high-frequency vibration components are detected. The scheme of the invention realizes accurate compensation of terahertz SAR multi-frequency vibration errors, and effectively improves the imaging quality of the actual terahertz SAR platform.

The present application is directed to radiolabeled cyclic polyazapeptides, pharmaceutical compositions comprising radiolabeled cyclic polyazapeptides, and methods of using the radiolabeled cyclic polyazapeptides. Such polyazapeptides can be used in imaging studies, such as Positron Emitting Tomography (PET) or Single Photon Emission Computed Tomography (SPECT).

The invention discloses a failure diagnosis method for a power transformer winding based on a GSMallat-NIN-CNN network. The failure diagnosis method includes: measuring a vibration condition of the transformer winding by using a multi-channel sensor to obtain multi-source vibration data of the transformer; converting the multi-source vibration data obtained through measurement into gray-scale images through GST gray-scale conversion; decomposing, by using a Mallat algorithm, each gray-scale image layer by layer into a high-frequency component sub-image and a low-frequency component sub-image, and fusing the sub-images; reconstructing fused gray-scale images, and coding vibration gray-scale images according to respective failure states of the transformer winding; establishing a failure diagnosis model for the transformer based on the GSMallat-NIN-CNN network; and randomly initializing network parameters to divide a training set and a test set, and training and tuning the network by using the training set; and testing the trained network by using the test set.

The invention relates to a distance detection system and method. The distance detection system is characterized in that the distance detection system comprises a signal processing module, a transmitting source, an amplifier, a loop device and an antenna; the transmitting source is connected to the input end of the amplifier, the signal processing module and the loop device are connected to the output end of the amplifier, the loop device and the antenna are connected with each other, and the output end of the loop device is further connected to the signal processing module; and the transmitting source is used for transmitting signals of variable frequency. The distance detection system and method have the advantage that the distance detection system and method solve the problems that in anexisting ranging system, a cross-correlation function method in a flight time detection method has poor measurement accuracy, a variable threshold detection method has high signal-to-noise ratio andis prone to being interfered, and a phase difference method can have a narrow measurement range.

The invention provides a long frequency band radar target jogging feature estimation method. The technical scheme is that a target narrow band echo obtained by a low frequency band radar is subjected to N point discrete sampling to obtain discrete signals, then complex logarithm operation is performed on the discrete signals, phase modulation signals are obtained by phase ambiguity resolving and are subjected to frequency spectrum estimation, and a target jogging spectrum is obtained by calculating, so the jogging feature of the target is obtained. The long frequency band radar target jogging feature estimation method is suitable for a low frequency radar small-amplitude jogging target, the estimation precision of jogging parameters is high, applicable systems have wide frequency bands and the signal to noise ratio demand is low.

The invention relates to a contact type vibration photon sensor using Doppler effect and a manufacturing method thereof. The contact type vibration photon sensor using the Doppler effect comprises an outer packaging layer (9), and the outer packaging layer (9) further comprises a silicon-based material (1) and a mirror surface body (2). The silicon-based material (1) comprises a side wall (10) and a cavity (11) which is surrounded by the side wall (10), and the top of the cavity (11) is open; and the mirror surface body (2) is arranged in the cavity (11), a mirror surface layer (21) is arranged on the top of the mirror surface body (2), the side face of the mirror surface body (2) is connected with the side wall (10) through a cantilever beam (22), and the cantilever beam (22) is in a spring shape. According to the contact type vibration photon sensor, the Doppler effect is used for providing accurate precision, the spring-shaped cantilever beam is used, the amplitude of the mirror surface body (2) can be improved, and the sensitivity of the sensor during vibration induction is improved.