64 results about "Cyclic correlation" patented technology

The present invention provides a method and apparatus for multiplexing code division and frequency division transmissions. One embodiment of the method includes accessing at least one first symbol and at least one second symbol, encoding the at least one first symbol according to a frequency division protocol, and encoding the at least one second symbol using a coding sequence having a cyclic correlation property. The method also includes transmitting a radiofrequency signal indicative of the at least one encoded first symbol and the at least one encoded second symbol.

L overlapping forward subarrays with {overscore (q)} (≧q) antenna elements are formed with, where q is the number of desired signals, a cyclic correlation matrix is formed from the cyclic correlations between the received signals of L forward subarrays and a received signal of the first predetermined antenna element, the cyclic correlated matrix is divided into two upper and lower submatrices, an orthogonal projection operator in the noise subspace is calculated by performing a linear operation on these two upper and lower cyclic correlation matrices, then by calculating a spatial spectrum or a polynomial by using the estimated orthogonal projection operator, the directions are estimated from of the position of q highest peaks of the spatial spectrum or the phases of q roots of the polynomial closest to the unit circle in z-plane.

Provided is an apparatus and method for detecting timing errors based on characteristics of cyclic correlation. The apparatus and method can detect the timing errors of many users by using the cyclic characteristics of a midamble code at a time and detects the timing errors based on the characteristics of cyclic correlation to reduce the time required for detecting the users and lower the complexity in terms of Hardware. The apparatus includes a detection section controller, a register, a midamble generator, a midamble shifter, an accumulator, an adder, a shift register and a timing error detector.

The invention discloses a differential cyclic shift spread-spectrum underwater sound communication method, which comprises the following steps: forming a basic spread-spectrum code by 1 to 2 spread-spectrum codes, and adopting a phase or a frequency to modulate a carrier wave to form a corresponding basic spread-spectrum waveform; at a communication sending end, determining the size of cyclic shift according to information to be sent, carrying out differential cyclic shift for the basic spread-spectrum waveform so as to realize multi-modulation, and sending the cyclic shift waveform into an underwater sound channel through a transmitting transducer; adopting a channel matching and filtering method to carry out multi-path combination at a receiving end; and using FFT to carry out quick cyclic correlation for received signals, judging the size of the cyclic shift according to a peak value of a related output waveform, and further carrying out decoding. The method effectively improves the communication rate, has low calculation amount and simple receivers, is convenient to realize in real time, can flexibly adjust the communication rate, can realize the multi-path combination, and has the advantages of good concealment performance, low captured probability and strong confidentiality.

L overlapping forward subarrays with {overscore (q)}(≧q) antenna elements are formed with, where q is the number of desired signals, a cyclic correlation matrix is formed from the cyclic correlations between the received signals of L forward subarrays and a received signal of the first predetermined antenna element, the cyclic correlated matrix is divided into two upper and lower submatrices, an orthogonal projection operator in the noise subspace is calculated by performing a linear operation on these two upper and lower cyclic correlation matrices, then by calculating a spatial spectrum or a polynomial by using the estimated orthogonal projection operator, the directions are estimated from of the position of q highest peaks of the spatial spectrum or the phases of q roots of the polynomial closest to the unit circle in z-plane.

The invention discloses a method for estimating signal source number and an incoming wave direction angle based on a cross-cyclic correlation MUSIC algorithm in an impulse noise environment, which belongs to the field of array signal processing. The method comprises the following steps: firstly, constructing a far-field narrow-band signal source model comprising M array elements and N far-field narrow-band signals, and calculating received data xm(t) at the time t of the m-th array element. Secondly, for the time t, calculating a cross-cyclic covariance matrix R(m,k) of two array elements by using the received data of the any two array elements; and summing and taking a mean value of MxM cross-cyclic correlation covariance matrices R(m,k), and obtaining a cross-cyclic correlation covariance matrix Rmutual. Finally, performing a singular value decomposition on the cross-cycle correlation covariance matrix Rmutual, and calculating its power spectral density P(theta): searching the localspectral peak of the power spectral density P(theta) and obtaining the estimated value of the incoming wave direction of the far-field narrow-band signal. The method for estimating signal source number and incoming wave direction angle based on cross-cyclic correlation MUSIC algorithm in impulse noise environment utilizes the cyclostationary characteristic of the signal, and the cross-correlationfurther removes a random noise and a clutter component on the basis of the auto-correlation, thereby improving the estimation performance of the incoming wave direction angle in the background of a strong impulse noise.

An A / D converter converts the signal received by an array antenna and frequency-converted to a digital signal by a frequency converter. A correlation detector uses the chip rate as a cycle frequency and calculates a cyclic correlation matrix of spread spectrum signals stored in data storage. A cycle frequency detector detects the cycle frequency of an interference signal output from A / D converter. A correlation detector uses the detection result of the cycle frequency detector as a cycle frequency and calculates a cyclic correlation matrix of the signal, which becomes an interference signal, using the signal output from A / D converter. A direction of arrival is estimated, using the cyclic correlation matrices calculated by correlation detector and the correlation detector calculates the respective eigenvalues and eigenvectors and estimates the directions of arrival of a spread spectrum signal and a signal, which becomes an interference signal.

The invention relates to a propeller shaft frequency searching method based on improved noise envelope signal recognition. The method includes: enveloping an original hydrophone signal, and performingHilbert-Yellow transform on each wavelet packet signal to obtain a wavelet envelope signal; performing wavelet reconstruction to obtain an improved noise envelope signal; calculating a time correlation spectrum, take a line spectrum protruding at the peak of the low frequency band as the suspected shaft frequency; setting a step size smaller than the frequency resolution according to the demand;forming a suspected shaft frequency set with the suspected shaft frequency as the center; performing cyclic correlation calculation on a time correlation spectral signal on each suspected shaft frequency to obtain the frequency statistical amount of a cyclic modulation spectrum; and finally searching the shaft frequency of a target according to the frequency statistical amount. The method of the invention corrects axial frequency offset errors generated by the conventional cyclic modulation spectrum methods in the spectrum calculation process, improves the accuracy of the shaft frequency detection, greatly reduces the calculation amount of the loop iteration, and is convenient to implement in engineering application.

The invention discloses a multi-conflict detection method for a random access channel of an LTE power wireless private network. An access detection unit performs the operations, such as receiving signal and base sequence cyclic correlation operation, binarization processing, noise elimination, waveform size adjustment, etc., on the acquired random access channel information; based on a convolutional neural network of deep learning, the coarse training and the fine training of a convolutional neural network detection model are realized, and a final convolutional neural network detection model is obtained, so that the convolutional neural network detection model detects the preamble of a random access channel and recognize the serious degree of the conflict. The method has the beneficial effects that the RACH conflict is detected by adopting the convolutional neural network based on deep learning, the existing protocol stack does not need to be modified, the conflict detection can be completed at the base station, the more accurate conflict detection performance can be obtained, the throughput of the LTE power wireless private network is improved, and the communication delay is reduced.

In order to suppress pulse noises and the interference of the same-frequency band signal, the invention defines a novel cyclic correlation function and proposes a novel MUSIC algorithm based on Sigmoid cyclic correlation, and applies the algorithm to DOA estimation under stable distributed noises. The simulation result demonstrates that the SCC-MUSIC-algorithm-based novel DOA estimation method enables a good estimation result to be obtained and has the outstanding advantages in a high-impulsive noise environment by being compared with the classical MUSIC algorithm, the class-related-entropy-based CRCO-MUSIC algorithm, and a fractional-lower-order-moment-based FLOM-MUSIC algorithm.

A method for detecting a cyclostationary signal in a signal to be analyzed, received from a transmitter by a receiver or read from a recording medium by a reader device. According to this method, the value of a discrimination function J is estimated, expressed as a quadratic form of the cyclic correlation coefficients of the signal to be analyzed for a set (I*M) of non-zero time shifts and a set (IK) of cyclic frequencies, and the value1-γ(v,Uσ4J)is compared with a wrong detection rate η in order to determine whether said cyclostationary signal is present in the signal to be analyzed, wherein γ(ν,x) is the normalized lower incomplete gamma function, ν is the product of the cardinal (M) of said set of non-zero time shifts and of the cardinal (K) of said set of cyclic frequencies, U is the width of the autocorrelation window on which the cyclic correlation coefficients are calculated, and σ4 is the square of the noise variance.

The invention belongs to the technical field of cyclic stationary signal processing and compressive sensing, and provides an amplitude modulation signal carrier frequency estimation method through cyclic correlation entropy spectrum projection after compressive sensing reconstruction. According to the method, the cyclic correlation entropy spectrum of a signal to be estimated is calculated firstly; then sampling and compression are performed on the cyclic correlation entropy spectrum through a compressive sensing method; then reconstruction of the cyclic correlation entropy spectrum is performed on the compressed data; and finally the corresponding carrier frequency of the signal is estimated through the peak of the reconstructed cyclic correlation entropy spectrum projection according to the modulation mode and the relation between the carrier frequency and the cyclic frequency. The experiment proves that the algorithm has great performance and can perform carrier frequency estimation of the signal under the condition of coexistence of non-Gaussian noise and the interference of the same frequency band and has the advantages of being low in data volume and convenient for storage and transmission.

The invention relates to a channel estimation method and a channel estimation system based on cyclic correlation. The method comprises the following steps of: 1, performing frame synchronization on received signals to acquire initial position information, and selecting the corresponding received signals as a training receiving sequence according to the initial position information; 2, performing cyclic correlation operation on the training receiving sequence and a locally known training sequence to acquire a time domain channel impulse response; and 3, analyzing multipath distribution of a channel according to the time domain channel impulse response, if a selected position of the training receiving sequence is required to be adjusted, adjusting the selected position of the training sequence according to an analysis result, selecting the training receiving sequence again and returning to perform the step 2, otherwise, outputting a final channel estimation result. By the method and the system, interference between a training sequence and a data sign in the conventional time domain synchronous (TDS)-orthogonal frequency division multiplexing (OFDM) system can be avoided, the precision of channel estimation is improved and the system complexity is reduced.

The invention relates to a cyclic correlation channel estimation method and device. The method comprises the following steps: S110, providing a cyclic sequence set [CH1 CH2], wherein the content of the sequence CH1 is the same as the content of the sequence CH2; S120, performing channel estimation for the cyclic sequence set [CH1 CH2] through cyclic shift to obtain a time-domain channel h; S130, performing FFT for the time-domain channel to obtain a frequency-domain channel H; S140, adjusting the amplitude of the frequency-domain channel to ensure that the signal effective value RMS(h) of the frequency-domain channel is equal to RMS(H); and S150, performing interpolation calculation for the adjusted frequency-domain channel, and filtering to obtain a channel estimation value. According to the cyclic correlation channel estimation method and device disclosed by the invention, the problem that a single carrier communication system is difficult to quickly estimate the amplitude and phase information of each path in multi-path channels can be solved.

Provided is an apparatus and method for detecting timing errors based on characteristics of cyclic correlation. The apparatus and method can detect the timing errors of many users by using the cyclic characteristics of a midamble code at a time and detects the timing errors based on the characteristics of cyclic correlation to reduce the time required for detecting the users and lower the complexity in terms of Hardware. The apparatus includes a detection section controller, a register, a midamble generator, a midamble shifter, an accumulator, an adder, a shift register and a timing error detector.

The invention discloses an IDMA system communication method based on CCSK modulation. The communication method comprises the following steps: on the basis of a traditional IDMA system, a transmittingend selects a basic sequence with a good correlation, performs CCSK modulation for the basic sequence, and then sends modulated data based on a traditional transmitter structure; and at a receiving end, the received data is firstly subjected to demodulation judgment according to an iterative detection algorithm of the traditional IDMA system, and then the data judged by each user is subjected to CCSK demodulation by using a cyclic correlation detection method. According to the method disclosed by the invention, the cyclic shift of the basic sequence carries data transmission through the introduction of CCSK modulation, and the anti-interference ability of the system can be effectively improved on the basis of maintaining original advantages of the system.

A method for an analog-to-digital converter correcting error estimation includes: according to a correction parameter preset initial value, generating a control signal and finely tuning a digital control delay cell, adjusting a delay amount, and correcting a clock phase error between channels; according to a correction parameter initial value, correcting a gain error between channels, generating and buffering a general correction signal, and triggering a counting cell to start counting, and calling the general correction signal in a buffer and generating a preliminary estimation result by using a cyclic correlation method; when counting to a preset value, setting low-pass filter accumulating cell enable ends and a correction parameter updating cell, generating an error estimation result from the preliminary estimation result and latching it, updating a clock correction parameter and a gain correction parameter according to a gradient descent method, and latching them, and resetting to carry out cyclic estimation correction.

The invention relates to a method for estimating channel of digital TV terrestrial broadcasting and a device thereof, which pertains to the technical filed of digital information transmission and is applicable to national standard digital TV terrestrial broadcasting (GB 20600-2006) systems, digital communication systems, telemetry and telecontrol systems and other relevant systems and technical fields. Under the frame head modes of PN420 and PN945 of digital TV terrestrial broadcasting, the multipath channel impulse response which falls into the prefix length range of the frame head PN sequence can be estimated by the following processing of sampling sequence of symbol rate after synchronization: (a) synchronization and pre-processing; (b) cyclic correlation; (c) channel impulse molding. The method and the device of the invention utilize diversity gain brought by the PN sequence correlation, have good anti-noise performance, can effectively reduce interference resulting from non-ideal autocorrelation of the PN sequence , accurately and fast estimate the multipath channel impulse response which falls into the prefix length range of the frame head PN sequence and have the advantages of high estimation accuracy, small calculation amount and low implementation complexity compared with other methods.

The present invention provides a method and apparatus for multiplexing code division and frequency division transmissions. One embodiment of the method includes accessing at least one first symbol and at least one second symbol, encoding the at least one first symbol according to a frequency division protocol, and encoding the at least one second symbol using a coding sequence having a cyclic correlation property. The method also includes transmitting a radiofrequency signal indicative of the at least one encoded first symbol and the at least one encoded second symbol.

The method for estimating a propagation round trip delay, existing between a base station and a terminal, and comprised within a predetermined round trip delay range, comprises the following steps: transmitting from the base station on a downlink a start order signal (30) to the terminal, after reception by the terminal of the end of the start order signal, sending a signature signal from the terminal to the base station on a uplink, receiving at the base station within a signature receiving time slot (28) the signature signal (34, 38, 42), processing at the base station the received signature signal to provide a round trip delay information. The processing step comprises a cyclic correlation step performed within a fixed correlation time window (54) by using a unique reference sequence (48).

The invention provides a rolling bearing fault diagnosis method based on cyclic correlation entropy. The rolling bearing fault diagnosis method includes the steps that bearing data of a rolling bearing under different fault states are collected correspondingly, and the fault characteristic frequency of each fault is calculated; the bearing data are subjected to windowing treatment, and divided into a plurality of data blocks, a gaussian kernel function is selected as a kernel function of the cyclic correlation entropy, and average cyclic correlation entropy of each data block and Fourier transformation results of Fourier transformation mean values of the average cyclic correlation entropy in an f domain are calculated; and according to projections of the Fourier transformation results in an alpha domain, spectrum distribution results of fault signals are obtained, and according to the spectrum distribution results of the fault signals and the fault characteristic frequency of the bearing data under each fault state, fault types of the bearing are judged. According to the rolling bearing fault diagnosis method based on the cyclic correlation entropy, fault bearing signals under thenon-gaussian noise environment, especially under the impact noise interference condition can be better processed, and the requirements of engineering practice can be better met.

The present invention relates to a method for detecting the presence or the absence of a spread spectrum signal in a frequency band of interest of a received signal, wherein:the autocorrelation function of said received signal is calculated for a set (S*) of non-zero time shift values (m);at least one cyclic correlation coefficient on (Rekα(m)) of the autocorrelation function is determined for said time shift values;the energy of the autocorrelation function is estimated from the quadratic sum of the values assumed by said cyclic correlation coefficient for said time shift values;the thereby estimated energy is compared with a predetermined threshold value and the presence or absence of said spread spectrum signal in the received signal is inferred from the result of the comparison.

The invention relates to a novel satellite signal FFT parallel-acquisition algorithm widely applied to different satellite receivers. According to the invention, firstly, it is assumed that there is no bit flip; digital IF signals and local recurrent signals are subjected to cyclic correlation operation to get the related results; in the operation process, the FFT operation is divided into two parts of a sum to reduce the FFT operation points and calculated amount; and secondly, it is assumed that there is a bit flip; the digital IF signals and local recurrent signals are subjected to even-odd partitioning and correlation operation to obtain related result; meanwhile, in the operation process, the FFT operation is subjected to segmentation; and finally, the related results obtained at two times are compared, and the maximum is the maximum peak acquired. The novel parallel-acquisition algorithm designed by the invention can effectively overcome the problem of bit flip and prolong the coherence integration time. Compared with traditional acquisition algorithms, the calculated amount of the proposed novel acquisition algorithm is reduced. The whole process is relatively high in processing efficiency and relatively good in algorithm performance.

Embodiments of the invention exploit cyclostationarity of linearly modulated signals, transmitted through fading channels, to provide robust blind and data-aided mobile speed estimators. Embodiments of the invention utilize at least two methods of cyclic-correlation- and cyclic-spectrum-based methods and extension to space-time speed estimation at the base station in macrocells. In comparison with background art methods, the new estimators of the embodiments of the invention can be used without any need for pilot tones, and are robust to additive stationary noise or interference of any color or distribution. In addition, embodiments of the invention can also be implemented blindly, which can increase the data throughput. Performance results of the estimators of the embodiments of the invention are illustrated via extensive Monte Carlo simulation results.

The invention relates to a multipath time delay estimation method and a device based on compressed sensing in a dense environment, and the method comprises the steps: S1, setting a reference signal, and preprocessing a received signal and the reference signal to a set length; S2, performing cyclic correlation processing on the received signal and the reference signal to obtain a cyclic correlationfunction; S3, expressing the obtained cyclic correlation function as an inverse Fourier transform form as a parameter signal; S4, generating a parameter matrix according to the parameter signals; S5,adopting a measurement matrix, constructing a sparse base dictionary, and performing compressed sampling on the time delay parameters by using a compressed sensing algorithm; and S6, carrying out matching tracking on the observation signal by adopting an orthogonal matching algorithm to obtain a multipath time delay parameter. Compared with the prior art, the method has the advantages of improving the resolution capability of time delay signal estimation in the dense environment and the like.

The invention discloses a weak feature extraction method based on combination of singular value decomposition and a correlation entropy theory. The method comprises a singular value decomposition module, a correlation entropy induction measure calculation module, a signal reconstruction module and a cyclic correlation entropy spectrum estimation module. The method comprises the following steps: firstly, performing two-dimensional conversion on signals to obtain a Hankel matrix, and performing singular value decomposition on the Hankel matrix formed by the signals to obtain singular values and corresponding singular components; then calculating a correlation entropy induction measurement value of the original signal and each singular component, determining a threshold value according to the distribution of the correlation entropy induction measurement values, and selecting the singular component of which the correlation entropy induction measurement value is lower than the threshold value; performing signal reconstruction on the selected singular component to obtain a noise-reduced signal; finally estimating the cyclic correlation entropy spectrum of the reconstructed signal, and observing the signal characteristics. The method can effectively discriminate the singular components, and has a good noise reduction effect, thereby extracting the weak features of the signals.

The invention provides a GPS L1 rapid and accurate capturing method. The method comprises the following steps: carrying out half-chip sampling and expansion on a spreading code; performing intermediate frequency down-conversion and resampling on the satellite data; performing frequency mixing on a carrier signal obtained by accumulating a plurality of local carrier sequences corresponding to a preset Doppler frequency group and the processed satellite data to complete Doppler down-conversion so as to obtain zero Doppler data; segmenting the zero Doppler data of 2T (T < = 10) milliseconds by taking 1 millisecond as the length, and respectively performing coherent accumulation on the data of the first T milliseconds and the last T milliseconds to obtain two segments of satellite data with the length of 1 millisecond; performing FFT operation, complex number multiplication and IFFT operation on the processed spreading code and satellite data to obtain a cyclic correlation result; respectively solving moduli of the two sections of cyclic correlation results, searching a maximum value in the two sections of cyclic correlation results, if the maximum value exceeds a preset threshold, judging that coarse capture is successful, and calculating a corresponding satellite signal code phase at the moment; if the maximum value does not exceed the preset threshold, updating the preset Doppler frequency group to perform the next group of Doppler capture; and determining the section in which the maximum value appears in the two sections of satellites with the length of T milliseconds, and selecting the section of satellite data to carry out Doppler accurate acquisition. According to the method, the Doppler acquisition precision is improved while the search speed is increased.

The embodiment of the invention provides a modulation mode determination method and device. The method comprises the steps: obtaining cyclic correlation entropy spectral density of a modulated signal;based on cyclic correlation entropy spectral density, determining cyclic correlation entropy spectrum characteristics of the modulated signal; based on cyclic correlation entropy spectrum characteristics and a pre-trained modulation mode prediction network model, determining a modulation mode of the modulated signal; based on the above processing, enabling the cyclic correlation entropy spectrumcharacteristic of the modulated signal to represent the high-order moment characteristic of the modulated signal; due to a fact that the high-order moment characteristic of the modulated signal is notchanged due to the influence of noise, the high-order moment characteristic of the modulated signal can represent the real characteristic of the modulated signal, and the accuracy of the determined modulation mode of the modulated signal is high based on the cyclic correlation entropy spectrum characteristic of the modulated signal, so that the problem that a receiving end cannot demodulate to obtain a correct original signal in the prior art can be avoided to a certain extent.

The invention relates to a magnetic resonance response signal parameter extraction method and system based on cyclic correlation, which are used for extracting parameters in magnetic resonance response signals of a nuclear magnetic resonance water detector. Gaussian white noise components and power frequency harmonic noise components in the magnetic resonance response signals are suppressed through a cyclic correlation processing method, so that the extraction precision of the magnetic resonance response signal parameters is improved. Then parameter estimation is carried out on the obtained cyclic correlation function to be solved, so that the exploration precision of underground water is improved, and technical support is provided for application of a nuclear magnetic resonance sounding technology in underground water exploration.