30 results about "Cyclic autocorrelation function" patented technology

The invention provides a fault feature extraction method and a fault feature recognition method of a vibration signal of a rolling mill chatter mark, and belongs to the field of rolling mill fault monitoring. The fault feature extraction method analyzes the vibration signal of the chatter mark via autocorrelation demodulation based on a second-order cycle, so unstable vibration signal of chatter mark is processed through frequency demodulation, a demodulated second-order cycle autocorrelation function is sliced according to time domain, and modulation information of the chatter mark vibration signal is kept completely. Therefore, accuracy of fault feature extraction of the vibration signal of the chatter mark is improved. The fault feature recognition method recognizes whether the rolling mill faults exist or not by the form of power spectrum information entropy, influence of rolling mill speed fluctuation needs not to be considered, and the recognition method is simple and accurate.

The invention discloses an online fault diagnosis method and system for a centrifugal pump. According to the method, a vibration sensor is utilized for measuring a radial vibration signal in the operating process of a pump; the radial vibration signal is transmitted to a signal processing module; analysis treatment is conducted based on the cyclostationary theory so that a cyclic autocorrelation function can be obtained and subjected to slice analysis; feature parameters for distinguishing whether the pump breaks down or not and recognizing the breakdown type after it is determined that the pump breaks down are obtained; and a relevant breakdown diagnosis result is obtained by performing comparison and analysis on the feature parameters and corresponding parameters generated when the pump runs normally under the design working condition. According to the online fault diagnosis method and system for the centrifugal pump, diagnosis on mechanical seal damage and cavitation failures can be achieved by measuring the radial vibration signal of the pump, the running feature information of the pump can be reflected in the vibration signal in real time, the information integration degree is high, the number of signal transfer paths is small, the anti-jamming capability is high, and measurement reliability is high; and by analyzing stable components in the cyclic autocorrelation function of the signal, the situation that running is unstable due to the bias condition and consequently signal analysis is disturbed can be avoided, and specific reasons which cause unstable flowing of the centrifugal pump are identified.

The invention discloses a transmitting device and receiving device of a spectral domain channel multiplexing transmission system and method thereof. The emitting device is characterized in that a cyclic delay modulation module is overlaid on a CDD-OFDM (Cyclic Delay Diversity-Orthogonal Frequency Division Multiplexing) transmitting module; the cyclic delay modulation module is used for independently mapping an information bit stream into a cyclic delay modulation vector; and the cyclic delay diversity-orthogonal frequency division multiplexing transmitting module is used for carrying out corresponding cyclic shift operation on an orthogonal frequency division multiplexing symbol according to a modulated cyclic delay vector and modulating the cyclic self-correlation function of a CDD-OFDM signal, therefore a spectral domain channel is established. The invention realizes the multiplexing of an OFDM modulation channel and a cyclic delay modulation channel by embedding the cyclic delay modulation module into the traditional CDD-OFDM standard system, thereby solving the problem that the spectral domain channel is multiplexed on a multi-carrier frequency domain channel; and in addition,the invention obtains the cyclic delay diversity without consuming extra transmitting power and bandwidths and also enhances the transmission rate of the system.

The invention discloses a method and a system for demodulating communication signals in a spectral domain. The method comprises the following steps that: step 1) an estimated value processing unit of a cyclic autocorrelation function calculates a corresponding estimated value of the cyclic autocorrelation function according to one section of received continuous CDM-OFDM (code division multiplexing-orthogonal frequency division multiplexing) cyclic delay modulation signals in the length of L OFDM (Orthogonal Frequency Division Multiplexing cycles; step 2) a cyclic delay detection processing unit respectively calculates corresponding likelihood functions aiming at different cyclic delay values and obtains a corresponding cyclic delay vector according to a maximum likelihood criterion; and step 3) a cyclic modulation vector mapping processing unit maps the cyclic delay vector and obtains a cyclic modulation signal which is sent. The method and system disclosed by the invention can be applied to channel multiplexing and transmission of the spectral domain, and the capacity of the system can be simultaneously increased on the premise of not affecting the transmission of ordinary OFDM signals; and a block computing way is adopted, so that the computational complexity can be greatly reduced and processing time and resources can be saved.

The invention belongs to the technical field of communication signal modulation analysis under non-Gaussian noise environments, and discloses a modulation parameter estimation method for OFDM signalsunder Alpha stable distribution noises. The method comprises the following steps: performing nonlinear transformation on received OFDM signals, and calculating generalized cyclic autocorrelation functions of the signals; extracting specific cyclic frequency sections of the generalized cyclic autocorrelation functions, and implementing available symbol length estimation on the OFDM signals by searching spectral peaks of the specific cyclic frequency sections; and extracting specific time delay sections based on available symbol length estimation, and implementing symbol length estimation on theOFDM signals by searching spectral peaks of the specific time delay sections. Under Alpha stable distribution background noises, when the mixed signal-to-noise ratio is greater than -1dB, the root-mean-square error of available symbol length estimation of the OFDM signals is close to 0, and when the mixed signal-to-noise ratio is greater than 3dB, the root-mean-square error of symbol length estimation of the OFDM signals is close to 0.

The invention relates to a spectrum sensing method based on a modulation signal cyclic autocorrelation function symmetric peak value. The method includes: enabling a cognitive user to perform cyclic autocorrelation function calculation on the received signal to form a two-dimensional signal detection domain, finally searching a symmetrical peak point in the signal detection domain to judge whether a main user signal exists or not, judging that the main user signal exists if the symmetrical peak point exists in the two-dimensional signal detection domain, or else judging that the main user signal does not exist. In order to ensure the false alarm probability of spectrum sensing, a symmetric peak point significance level factor is introduced in the symmetric peak point searching process. According to the method, whether a main user signal exists or not is judged according to the symmetry of a peak value of a modulation signal cyclic autocorrelation function; no priori knowledge of any main user signal and channel is needed, the influence of channel noise fluctuation on the spectrum sensing performance is eliminated, and the problem of signal spectrum sensing in a small signal-to-noise ratio and channel noise fluctuation environment is solved.

The invention relates to a method for estimating parameters of a single signal or mixed-frequency signals in a given band. The method includes the following steps: receiving (E0) a single signal or mixture of signals y(t) in a given frequency band, determining (E3) for L, a strictly positive real number taken in a set of q, q being strictly positive, predetermined value {L₁, . . . ; L_q]} of the spectral correlation function (I), where (II) is the cyclic autocorrelation function for raising the sampled version y(n) of the signal y(t) to the power of L, where F_t[.] is the Fourier transform, and where, for each q, α can separately take one or more discrete values and/or cover one or more value ranges, —processing (E4) each transform LSCFy(f, α), L being taken in a set of q, q being strictly positive, predetermined values [L_i; . . . L_q] for extracting therefrom a set of peaks p_i, that is, local maxima detected on the basis of the variables f and α or on the basis of the single variable f for each discrete value of α, each of said peaks being characterized by a triplet [Lap_i, LFFp_i, Lap_i] are respectively the frequency and cyclic frequency at which said triplet is located and LAp_i is the amplitude thereof, and identifying (E5) groups of triplets [Lap_i, LFp_i, Lαp_i] as being the signature left by a set of parameters making up the signals present in the given frequency band.

The invention discloses a spectral correlation subspace direction finding method based on symmetric cycle frequencies. Cyclic autocorrelation functions are established according to cyclostationarity of received signals, and by utilizing weak correlation between the cyclic autocorrelation functions of the symmetric cycle frequencies, a cyclic cross correlation matrix is constructed, so that direction finding accuracy is superior to that of an existing spectral correlation subspace direction finding method, and the spectral correlation subspace direction finding method has a higher direction finding correct probability.

A method is provided for sending at least a first data signal and a second data signal, the data being divided into data blocks of fixed size including a header field of predetermined size, the data signals being sent to at least one data processing device adapted to apply a cyclic autocorrelation function with parameter k enabling the first and second data signals to be identified. The value of the parameter k is a function of a ratio between the size of the data blocks and the predetermined size of the header field. The method includes modifying the size of the header field of the data blocks before sending the first data signal, the value of the parameter k and the size of the data blocks remaining unchanged. A method is also provided for processing signals sent in accordance with the sending method.

The invention relates to a method and device for generating a single-carrier frequency domain equalization unique word sequence. The method comprises the following steps: exporting a PN sequence generated by a shift register; and adding a direct current component D to the PN sequence to generate a unique word sequence UW. The unique word sequence UW generated by the method provided by the invention has ideal cyclic autocorrelation function characteristics, that is, the autocorrelation values of other positions except the peak value of the autocorrelation function are 0, and the PN sequence subjected to direct current correction is used as the UW of SC_FDE, so that accurate channel transmission characteristics can be obtained through measurement, channel characteristic correction is performed on received signals, and the receiving performance is improved.

The invention belongs to the technical field of communication, and discloses a signal-to-noise ratio estimating method of time frequency overlapping OFDM signals under a frequency spectrum sharing mode. The method comprises the steps of firstly computing a cyclic autocorrelation function of received time frequency overlapping OFDM signals, capturing a cross section in which delay is less than chip time when oversampling ratios of component signals are equal or unequal, and then estimating overall power of the component OFDM signals by extracting a discrete spectrum line from the cross section; and at last estimating the overall power of the received signals according to values of the cyclic autocorrelation function when both the delay and cycle frequency are zero, thus estimating a signal-to-noise ratio of the time frequency overlapping OFDM signals. According to the method provided by the invention, the signal-to-noise ratio of the time frequency overlapping OFDM signals can be effectively estimated; not only the signal-to-noise ratio of the time frequency overlapping OFDM signals can be estimated, but also prior parameters such as the oversampling ratio and the chip time of the component signals can also be estimated.

The invention discloses a transform domain communication system and a realization method of the transform domain communication system. A transmitting terminal comprises a first random phase frequency spectrum sequence generating module and a first inverse Fourier transform module, and the transform domain communication system is characterized in that a first CCSK (Circular Cyclic Shift Keying) modulation module, a second CCSK modulation module, an imaginary number multiplying unit module and a branch signal superposition module are arranged; a receiving terminal comprises a second random phase frequency spectrum sequence generating module, a signal conjugating module, a Fourier transform module, a first multiplying unit module, a second inverse Fourier transform module, a real number data extracting module, an imaginary number data extracting module, a first peak searching module and a second peak searching module. According to the system and the method disclosed by the invention, the characteristic that the maximum value in a circular cyclic self-correlation function is real number is utilized, and different data flows are loaded on a base modulation waveform by a real number branch and an imaginary number branch, so that the data transmission rate of the transform domain communication system is increased, and further the utilization ratio of the system frequency spectrum is increased.

The invention relates to a spectrum sensing method based on cyclostationarity upon random occurrence of a master user signal. The method comprises the steps of segmenting spectrum sensing time of a cognitive user according to the reciprocal of master user signal cycle frequency; for each segment, building a transversal vector, composed of a plurality of cyclic autocorrelation functions, namely a cyclic autocorrelation function vector; computing estimation of a covariance matrix of the cyclic autocorrelation function vectors of all segments, and computing a corresponding judgment statistics; computing a corresponding judgment threshold according to preset false alarm probability; comparing the judgment statistics with the judgment threshold; when the judgment statistics is larger than the judgment threshold, judging that a current frequency band has the master user signal which appears randomly during a perception process; and otherwise, judging that the current frequency band does not have the master user signal.