32 results about "Bluestein's FFT algorithm" patented technology

The invention relates to a method for acquiring parameters of electric power harmonic waves by using Hanning window function continuous frequency spectrum interpolation, applicable to harmonic analysis and monitoring on voltage and current of a power network. Firstly, chirp Z transform (CZT) is utilized to accurately extract fundamental wave signal parameters (amplitude, frequency and phase) froman electric signal containing harmonic waves. Then the fundamental wave signal is subtracted from the analyzed electric signal and a Hanning window function is added to cut off the electric signal, and FFT (fast Fourier transformation) is utilized to calculate frequency spectrum of the residual signal. And then frequency values of all the harmonic waves are accurately calculated according to the frequency of a fundamental wave. And finally interpolation is carried out on the Hanning window function in the frequency domain according to each harmonic wave frequency, and the parameter of each electric power harmonic wave is accurately calculated. The method provided by the invention has estimated value accuracy basically equivalent to that of an addition Hanning window FFT bispectrum line interpolation fitting analysis method of electric power harmonic waves, and calculated amount of the method provided by the invention is about 1 / 2 of that of the addition Hanning window FFT bispectrum line interpolation fitting analysis method of electric power harmonic waves.

The invention discloses an automobile forward direction anticollision system signal processing method. In each frequency sweep cycle, the following processes which are performed on upper sweep frequency IQ data and lower sweep frequency IQ data of each channel comprise steps of performing fast Fourier transform FFT on N points of IQ data, performing adaptive threshold detection on transformed plural module value data after transmission, outputting an over-threshold point position, taking an interval between two points as a transformation interval, wherein one point is positioned before the threshold point position and the other one is positioned after the threshold point position, performing chirp-z transformation on M points, performing peak value searching on the data after chirp-z transformation, outputting a peak value point position, calculating a difference frequency and a phase according to the peak value point, outputting an object distance, relative radial speed and an azimuth according to the difference frequency and the phase output distance. The invention enables the system to respond fast through processing and optimizing the signal, is good in practicability and faster.

The invention provides a high-precision real-time microwave velocity and distance measuring device based on a symmetrical triangle LFMCW radar. In the signal emission stage, the device generates up and down frequency sweeping LFMCW signals whose scanning periods are short; in the signal reception stage, the device collects a path of I analog echo signals and a path of Q analog echo signals orthogonal with each other in real time in a de-sloping manner, accumulates echo data coherently, divides the data into an up frequency sweeping group and a down frequency sweeping group, calculates the peak frequency values of the power spectra of the two groups, offsets deviations of the peak frequency values caused by Doppler frequency generated by a target velocity, and combines CZT (Chirp Z Transform) to obtain a high-precision target distance; and at the same time, beating echo data obtained in multiple scanning periods is sampled to form a new data sequence, spectrum analysis is implemented, peak frequency point values are estimated, and the target movement velocity is calculated. According to the device, the symmetrical triangle LFMCW radar can be used to simultaneously measure the velocity and distance of a moving object in a highly precise manner.

At sending end, training symbols are inserted into every other section of digital modulated communication signals and then the signals are sent. The training symbols are composed of special impulse function sequence in frequency domain. At receiving end, FFT transforms received training symbols to frequency domain. In frequency domain, after training symbols are multiplied by conjugate symbols of the training symbols, result is divided into multiple sections with identical length, then corresponding weight factors are assigned to each section, and multiple sections are superimposed as one section. Chirp-Z transform and interpolation operation are carried out for the data in the one section so as to obtain position of maximum amplitude. Frequency shift is evaluated from formula fe=fs(omega-K / 2) based on position of maximum amplitude. fe controls oscillation frequency of oscillator to reach frequency synchronism.

The invention belongs to the radio measurement technical field and relates to an FPGA (field-programmable gate array)-based moving target radar cross section measurement method. According to the FPGA(field-programmable gate array)-based moving target radar cross section high-precision measurement realization method, a conventional frequency domain pulse compression hardware structure is improvedin a distance domain, so that a buffer-based frequency domain pulse compression hardware structure can be realized; the theoretical method described in the background art can be realized with only onemultiplying unit adopted; and a new moving target detection and chirp-z transformation combined hardware structure is proposed in the Doppler domain. The method of the invention has the advantages ofclear module structure, high IP multiplexing degree, simple hardware structure, high measurement accuracy, high processing speed, high real-time performance and low power consumption.

The invention belongs to the technical field of ocean remote sensing and relates to a rapid sea wave simulation method based on Chirp Z transform. The method comprises the following steps: calculating a one-dimensional sea wave frequency spectrum by virtue of wind speed; converting the one-dimensional sea wave frequency spectrum into a sea wave frequency direction spectrum; converting the sea wave frequency direction spectrum into a two-dimensional sea wave number spectrum; and simulating fluctuation of sea wave by carrying out Chirp Z conversion on the two-dimensional sea wave number spectrum for twice. Compared with the prior art, the method provided by the invention has the advantages that the computation amount can be effectively reduced, and the simulation time is saved.

A method is provided for performing real-time spectral analysis of a non-stationary signal. The method includes sampling the non-stationary signal, using an observation window having a length short enough to approximate a stationary signal, to provide an initial set of sampled data, buffering the initial set of sampled data to obtain multiple buffered sets of sampled data, filtering the initial set of sampled data and the buffered sets of sampled data, using corresponding filter responses, to obtain multiple filtered sets of sampled data, and performing a chirp-z-transform (CZT) of the filtered sets of sampled data to provide a set of discrete Fourier transforms (DFT) coefficients. A total signal spectrum of the non-stationary signal is reconstructed using the set of DFT coefficients.