98 results about "Discrete frequency domain" patented technology

The invention relates to a method for feeding information back on the basis of space time frequency domain, a system, a user device and a base station thereof, which are used in the technical field of wireless transmission, the user device in the invention measures and estimates the quality of a wireless transmission chain circuit of a downlink MIMO system, information such as order, pre-coding matrix key number, communication channel quality indication and the like of the downlink wireless transmission chain circuit is obtained, the selecting characteristics of the communication channel in three dimensional space of spatial domain, frequency domain and time domain are utilized to process the information of the downlink wireless transmission chain circuit in the spatial domain, the frequency domain and the time domain respectively, a feedback method which is used effectively and simply is used to transmit the information of the downlink chain circuit to the base station, the base station optimizes a transmitter according to the information which is fed back by the user device, and thereby the purpose of improving the whole data throughput of a wireless district and the data throughput of the district edge under the precondition that the service quality of the wireless district is considered is achieved.

The invention discloses a bearing life prediction method based on a hidden Markov model and transfer learning. The method comprises the steps of (1) collecting a full-life original signal of a rollingbearing; extracting a feature set containing time domain, time frequency domain and trigonometric function features; (2) inputting the feature set into a hidden Markov model to predict a hidden state, and obtaining a fault occurrence moment; (3) forming a training set by feature sets from all source domains and part of target domains, inputting the training set into the constructed multi-layer perceptron model, obtaining domain invariant features and optimal model parameters through optimization target training, and substituting the optimal model parameters into the perceptron model to obtaina neural network life prediction model; and (4) inputting the remaining target domain feature set into a neural network life prediction model, and predicting the remaining life of the bearing according to the output value. The hidden Markov model is used for automatically detecting the fault occurrence moment, and then the transfer learning based on the multilayer perceptron is used for solving the distribution difference of a source domain and a target domain caused by different working conditions.

An impact load monitoring system for a wind turbine for wind power generation is provided with: an acceleration sensor 28 attached to a step-up gear 18 connected to a main shaft 20; a frequency filter 30 for extracting a monitoring-object component contained in a target frequency domain from vibration data representing a temporal change of amplitude of the acceleration obtained by the acceleration sensor 28; and a determination unit 32 for determining whether or not amplitude of acceleration of the monitoring-object component exceeds a reference value which is set in advance, by comparing the amplitude of the acceleration with the reference value.

The invention discloses a high-precision method for acquiring an FMCW radar distance measurement value and aims to discloses a distance measurement value method with high ranging precision and capableof reducing frequency spectrum errors. The method is implemented by adopting the following technical scheme; sending target beat signals subjected to analog-digital conversion into four parallel timedomain extraction module; sending digital beat signals and sampling rate data acquired respectively into a data zero fill module for time domain zero filling; acquiring discrete frequency domain signals having a length of Ns through discrete Fourier transform (DFT) on time domain signals having a length of Ns acquired by the four time domain extraction module through corresponding DFT modules; sending the discrete frequency domain signals are sent into a data interception and splicing module by the four DFT modules in common-end manner for frequency domain data splicing operation, and an FMCWradar distance measurement value is acquired through a distance measurement value acquiring module based on a mathematic interpolation operation result.

The invention discloses a squint SAR ground moving target extracting method. The squint SAR ground moving target extracting method comprises the following steps that 1, echo signals of a stationary target and a moving target are computed; 2, range direction Fourier transformation is carried out; 3, consistent range walk correction is carried out on a range frequency domain and an orientation time domain; 4, range direction residual phase compensation is carried out; 5, variable parameter extension azimuth nonlinear CS is carried out; 6 the echo signals subjected to the extension azimuth nonlinear CS are multiplied by corresponding azimuth minus factors respectively and are transformed to the azimuth frequency domain; 7, the amplitudes of the two echoes are subtracted, the echo of the stationary target is removed, and stationary target clutter suppression is achieved; 8, amplitude detection and moving target extraction are carried out. The method solves the problems that the range and azimuth are coupled seriously in a ground moving target under the single-channel squint mode and moving target movement parameters are unknown, estimation of movement parameters is not needed, efficiency is higher, and the method can be widely used in the fields of clutter suppression, moving target extraction and the like.

The invention discloses a low-coherence interferometric demodulation method based on spectrum nonlinear effect dispersion compensation. The method comprises the following steps: step 1, achieving discrete Fourier transform of interference fringe signals to obtain the magnitude spectrum and the phase spectrum under the discrete frequency domain; step 2, setting a threshold H, taking a region of which the amplitude is larger than H, except for the low-frequency part, as the selected discrete frequency band, calculating wave numbers corresponding to all points in the frequency band, and transforming the phase spectrum from the discrete frequency domain to the wave number domain; step 3, selecting the wave number corresponding to the maximum amplitude in the magnitude spectrum, within the wave number band in which the optical spectrum of a light source is distributed, as the specific wave number, carrying out phase unwrapping in the wave number band, calculating the interference level of the specific wave number, reconstructing the absolute phase of the specific wave number, which directly reflects the range information, according to the relative phase value and the interference level of the specific wave number. The low-coherence interferometric demodulation method realizes high-precision distance demodulation and is suitable for light sources with any wideband.

The invention belongs to the technical field of radar imaging, and discloses a curvilinear track SAR squint imaging method based on an improved slant distance model. The curvilinear track SAR squint imaging method based on the improved slant distance model comprises the specific steps that an equivalent slant distance model is established; a two-dimensional spectrum is derived; the distance walking momentum is calculated and is transformed to the distance frequency domain to complete the distance walking correction in the distance direction; an echo signal in the distance frequency domain is subjected to the fourier transformation in the azimuth direction, and a two-dimensional spectrum of the echo signal is obtained; distance compression, secondary distance compression and distance bending correction are carried out, and the echo signal is subjected to inverse fourier transformation in the distance direction; and an azimuth frequency domain signal is subjected to azimuth compression and inverse fourier transformation in the azimuth direction, and imaging results are obtained. According to the curvilinear track SAR squint imaging method based on the improved slant distance model, on the basis of motion characteristics of a curvilinear track platform, the equation of motion of the curvilinear track platform is subjected to high-order approximation, a four-order equivalent slantdistance model expression is established, based on the slant distance model, the analytical solution of the two-dimensional spectrum of the curvilinear track platform is derived, the conciseness and the high precision of a frequency spectrum is ensured, and full-aperture high-resolution imaging can be achieved.

The invention discloses a PDN capacitor optimizing method based on lossless resonant cavity power supply horizon plane modeling. The method comprises the steps of 1) designing related parameters input in a power supply distribution network; 2) calculating an initial power supply distribution network impedance value according to the result of the step 1); 3) calculating number of decoupling capacitors according to the parameter designed in the step 1); 4) calculating an actual power supply distribution network impedance value Z according to the results of the steps 2) and 3); 5) determining a relation between a discrete frequency point f<n> and the maximum target frequency f<max>, if the f<n> is less than the f<max>, executing a step 6); and if the f<n>is equal to the f<max>, outputting the result of the step 3); and 6) comparing the Z with the target impendence Z<t> designed in the step 1), if Z is greater than Z<t>, returning to the step 3), and or otherwise, adding 1 to the subscript n of the discrete frequency point, and returning to step 4). By adoption of the PDN capacitor optimizing method, the target frequency band is expanded, and the number of the capacitors is reduced while the power supply distribution network design requirement is satisfied, so that the PDN capacitor optimizing method can be used for design and analysis of a high-speed system.

A method may include generating for transmission a repeating sequence of N constant-frequency pulses of width t seconds at interpulse intervals of T seconds, with each pulse in the sequence having a particular constant phase according to a quadratic phase sequence, which phase is applied to each pulse in a first sense of modulation. The method may further include modulating the phase of echo energy received from one or more objects reflecting the transmitted repeating sequence of N constant-frequency pulses with a second sense of modulation opposite to the first sense of modulation. The method may further include producing from the modulated received echo energy N unique and discrete frequency translations of the received echo energy as a function of range r of the reflecting objects, of magnitude equal to multiples of 1 / NT Hz, which may preserve the spectrum of the received echo energy, forming in combination a composite signal frequency spectrum.