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

The invention discloses a stable underwater communication node awakening signal detection method. The stable underwater communication node awakening signal detection method comprises the following steps of: S1, emitting a dual-frequency or multi-frequency awakening signal; S2, according to a set initial frequency, transform point number and frequency resolution ratio, executing CZT (chirp z transform) on a unit circle on the awakening signal; S3, searching an extreme value of a zoom spectrum of CZT, judging a signal as the awakening signal if an estimated relative frequency interval and relative amplitude relationship between frequency components are kept unchanged, or judging the signal is not the awakening signal; and S4, after the signal is determined as the awakening signal, powering on an integral communication node to enable the node to be transferred into a working state, and when the node completes working, cutting off a power supply to enable the node to be transferred into a sleeping state. According to the stable underwater communication node awakening signal detection method disclosed by the invention, due to the high frequency resolution ratio, multiple groups of frequencies can be adopted for combination to awaken a plurality of nodes of an underwater sensor network without worrying about mutual interference, so that detection false-alarm is greatly reduced and a service life of the underwater wireless sensor network is prolonged.

The invention discloses a circular synthetic aperture radar imaging method, belonging to the technical field of electronic signal processing. The invention relates to a spatial remote sensing and air-to-ground observation information processing technology, in particular to an onboard circular synthetic aperture radar imaging technology. According to the imaging method, an original oblique plane echo is mapped to the ground plane by solving the inverse of a system kernel function, and the distribution of signals in a wave number domain is obtained by multiplying an azimuth frequency domain with a reference function, so that plane wave approximation is avoided, the problem that the size of an imaging area of the traditional polar format algorithm is limited can be solved, and the imaging of a large imaging scene can be realized; pseudo-polar coordinates are used for replacing rectangular coordinates as an intermediate interpolation transition matrix, and the distribution density characteristic of the signals in the wave number domain is considered, so that the interpolation precision is higher, the obtained image resolution is higher, and the high resolution imaging can be realized; the imaging process only involves one-dimensional interpolation, and fast algorithms such as chirp z transform (CZT) and inverse fast Fourier transform (IFFT) are adopted, so that the method has very high computational efficiency and can realize rapid imaging.

The invention discloses an electric energy quality mixing detection method. The method comprises the following steps of using an inter-harmonic detection method based on a complex modulation refinement spectrum analysis method to detect interharmonics in a power grid; using a voltage fluctuation demodulation method to measure voltage fluctuations in the power grid; and using a flicker measurement method based on chirp Z transform to measure flickering in the power grid. An electric energy quality detection operand is reduced, real-time performance of inter-harmonic detection is increased and a flicker measurement error is eliminated maximumly. The chirp Z transform is used to calculate a frequency and an amplitude of a fluctuation component. An disadvantage that the flicker detection has a large error in a low frequency band is overcome. An effective support is provided for electric energy quality detection result correctness.

The present disclosure provides an imaging method for a Synthetic-Aperture Radar (SAR) in a high squint mode. The method includes: perform perturbation function multiplication for an echo signal in the azimuth Doppler domain-range time domain to eliminate the dependence of an echo signal quadratic azimuth-range coupling factor on the change of a target slant range; perform reference function multiplication in the two-dimensional frequency domain, wherein the reference function is a conjugate function of a point target echo spectrum at a reference slant range; complete compensation of all phases, which do not vary with the range, of a two-dimensional spectrum through the multiplication of the two-dimensional spectrum and the reference function; rectify the differential range migration factor of the echo signal in the two-dimensional frequency domain by utilizing Chirp-Z transform, complete range migration rectification by performing convolution once and phase multiplication twice; compensate an azimuth residual phase through the azimuth phase multiplication, and perform azimuth compression to obtain a focused SAR image. The method of the present disclosure can perform highly efficient and precise imaging for high squint SAR data.

The invention provides a linear chirp z transform based frequency offset estimation algorithm in an M-QAM (M-ary Quadrature Amplitude Modulation) coherent optical communication system, which comprises the following steps that: a smaller amount of M-QAM signal receiving sample values are selected for four-power; the FFT (Fast Fourier Transform) is conducted to obtain a frequency corresponding to the maximum spectral value to be recorded as a roughly estimated value; the linear CET (Chirp z Transform) of four-power signals is conducted near the roughly estimated value to obtain a frequency corresponding to the maximum spectral value; and the frequency is divided by four to obtain a frequency offset estimated value of M-QAM signals. The linear chirp z transform based frequency offset estimation algorithm does not adopt a gradient descent method, a Newton method and other methods depending on a step size and the number of symbols, but adopts a method that the frequency is finely estimated by CZT with a fixed computation load. Since the CZT can be realized by the FFT with fast algorithm, the complexity of the algorithm can be obviously reduced in the algorithm, and meanwhile, the algorithm is applied to all-order QAM signals.

A system and method for symbol rate estimation using vector velocity that does not require any prior knowledge of the signal's structure and is accurate in the presence of frequency offset and noise. An input signal is converted to a symbol constellation path signal, and a velocity signal representing a velocity of the symbol constellation path signal is generated. A first frequency spectrum of the velocity signal is generated by performing a Fast Fourier transform on the velocity signal, and a maximum peak value of the first frequency spectrum, a first bin below the maximum peak value, and a second bin above the maximum peak value are identified. A Chirp-Z transform is performed on the velocity signal using the first bin and the second bin as coefficients, wherein performing the Chirp-Z transform generates a second frequency spectrum including only frequencies within the range of the first bin and the second bin, and wherein the second frequency spectrum presents a higher resolution than the first frequency spectrum. A maximum peak value of the second frequency spectrum is identified, wherein the maximum peak value of the second frequency spectrum corresponds to the symbol rate of the input signal.

The invention discloses a large-scale ultra-sparse plane array rapid layout method with controllable minimum pitch, the layout method is divided into two steps: initial optimization with unlimited minimum spacing and correction optimization with limited minimum spacing. S01: in the initial optimization, array layout with dense grid is adopted, array element excitation is randomly initialized, anda fast synthesis array optimization algorithm with grid spacing not equal to half wavelength is proposed, i.e., iterative Chirp-Iterative Chirp-z transform (ICZT); on this basis, the improved ICZT isproposed to synthesize low sidelobe level, and the concept of filling factor is introduced to reduce the number of array elements gradually to achieve the purpose of sparse array, and the condition ofiteration termination is improved to obtain the array layout with the lowest sparse rate as far as possible. S02: in the correction optimization, the concept of discarding exponent is proposed, and the array element is discarded to satisfy the constraint of array element spacing. The invention completes the fast layout of a large-scale ultra-sparse planar array with controllable minimum pitch.

The invention discloses a polar coordinate format imaging method for the bistatic forward SAR of the mobile platform, comprising the following steps: transforming the parallelogram wave spectrum support domain of MP-BFSAR into a horizontal quasi-rectangular shape using a wave spectrum support domain affine transformation method; then realizing the re-sampling from a wave spectrum distance vector polar coordinate to a cartesian coordinate by a direction vector chirp-z transformation; performing a distance compression and a scene center motion compensation; realizing the re-sampling from a wavespectrum direction vector polar coordinate to a cartesian coordinate by using a method of accumulating a upsampling map in the direction vector; performing a two-dimensional inverse Fourier transformto obtain a coarse imaging result; and obtaining a final imaging result by defocus correction. The utilization of the wave spectrum collected by the present invention is significantly improved compared to the prior art methods.

A digital watermark detection device includes a first chirp z-transform unit (202a) and a second chirp z-transform unit (202b) for estimating the cochlear delay characteristics simulated by cochlear delay filters that were used in embedding digital watermark data in an acoustic signal. The digital watermark data embedded in the acoustic signal is detected based on the cochlear delay characteristics estimated in accordance with the result of chirp z-transform applied by these first chirp z-transform unit (202a) and second chirp z-transform unit (202b).

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.

The method includes following steps and devices. At sending end, specific PN sequences are inserted into every other section of digital modulated communication signals and then the signals are sent. PN sequence is C=(v X u). At receiving end, matched filtering is carried out for baseband signal containing PN sequence with frequency being converted so as to output P pieces of signals in complex number. Using likelihood function and FFT transforms the said complex signals to frequency domain, from which coarse position omega 0 of max. amplitude is found. Using Chirp-Z transform finds position increment information omega1. quadratic interpolation is carried out for omega1 to obtain position increment omega, which is exact position of max. amplitude. Frequency shift fe is calculated from formula fe=fs.(omega+omega0 - M.P/2)/K.M.P. fe controls oscillation frequency of oscillator to reach frequency synchronism. The invention also includes receiver and transmitter for implementing the method.

The invention discloses an LS (Least Square) based phase information calculating method in a complex environment. The method comprises the following steps of simultaneously calculating by adopting short-time chirp-z transform, obtaining signal frequencies, at different moments, of a reference channel through a selected amplitude maximum method and calculating and extracting multiple signal frequencies, exceeding a detection threshold, at the different moments, of the reference channel by adopting a short-time multi-target frequency detection algorithm; and calibrating actual signal frequencies, at the different moments, of the reference channel by adopting a matching discrimination method, which particularly comprises: calculating phase values, corresponding to frequency values of the reference channel at the different moments, of different receiving channels by adopting an LS method. By using the method provided by the invention, the frequency of a useful signal is extracted from a disorderly signal frequency spectrum; a disorderly frequency spectrum brought by random noise and clutter is abandoned; by utilizing the signal frequencies obtained by discriminatory analysis, a mathematic model between an observed signal and a signal initial phase is constructed; and next, the information of the signal initial phase of the corresponding receiving channel is calculated and obtainedby adopting an LS algorithm, so as to be called by other application of target location and the like.

The invention discloses a wavelength tag information analysis device and an analysis method. The received sampling signals are subjected to chirp-Z transform (CZT) analysis continuously by J times by a logic processing unit, and the frequency-related information of the continuous J times of each wavelength tag frequency in the sampling signals is counted to resolve wavelength tag information, wherein J is an integer larger than zero. Based on the characteristic of CZT that can select an arbitrary start frequency and frequency resolution (or stop frequency), the device and method provided by the invention can realize spectral zooming during frequency analysis by subjecting the sample signal to Z transform, thereby obtaining higher start frequency resolution, and reducing frequency measurement error caused by picket fence effect.

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.

The invention belongs to the field of satellite receiver baseband signal processing and relates to a Beidou B1 signal high sensitivity capturing method based on chirp-Z transform, so as to reduce signal energy loss caused by FFT computing fence effects and improve the receiver sensitivity. By using a Beidou B1 signal capturing result in a parallel correlation + FFT method, a Doppler frequency rough estimation result and a pseudo code phase are obtained; according to the pseudo code phase of the capturing result, the local pseudo code phase is adjusted, chirp-Z transform capturing is carried out on signals near the Doppler frequency, the capturing peak is effectively improved, and the receiver sensitivity is improved. The method is mainly applied to high sensitivity capturing on Beidou No.2 B1 frequency point satellite navigation signals and can also be applied to capturing and processing on other similar signals.