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.

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.

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.

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 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 (R_e^kα(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.

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.