11 results about "Keystone transform" patented technology

The invention discloses an SAR (synthetic aperture radar) fast multi-moving target deception jamming method and a related device, and relates to the technical field of synthetic aperture radar countermeasure. Comprising the following steps: acquiring a first frequency response function which is related to the position of a jammer and is generated by the jammer; obtaining a target frequency response function; performing phase multiplication on the first frequency response function and the target frequency response function at corresponding moments to obtain a jammer frequency response function; and performing convolution modulation on the jammer frequency response function and the SAR signal intercepted by the jammer to obtain a deception jamming signal. Wherein the first frequency response function is a frequency response function generated in real time during the main beam irradiation period of the SAR antenna; the target frequency response function is a frequency response function pre-generated based on SAR parameter information, an SAR target image, Fourier transform, a deramp function and keystone transform.

The invention discloses a field programmable gate array (FPGA)-based KeyStone transformation range migration correction method, which comprises the following steps of: transposing data in a double data rate 3 (DDR3) to a range direction, performing inverse Fourier transformation in the range direction, transposing the data to an azimuth direction and storing the data back to the DDR3; zero padding is carried out on the head and the tail of data in the DDR3 by controlling the dual-port RAM; the data size and the signal parameters are transmitted into a chirp generation module to generate phase compensation so as to calculate a stepping factor; multiplying the zero-filled data by a stepping factor, and performing inverse Fourier transform along the azimuth to obtain a first transform result; carrying out conjugate processing on the stepping factor and carrying out inverse Fourier transform along the azimuth direction to obtain a second transformation result; multiplying the first transformation result and the second transformation result, and performing Fourier transformation along the azimuth to obtain a third transformation result; multiplying the third transformation result by a stepping factor, and performing inverse Fourier transform along the azimuth to obtain a fourth transformation result; and sampling the fourth transformation result in the azimuth direction and carrying out Fourier transformation along the distance direction to obtain a correction result. The method is high in correction efficiency.

The present invention discloses a method for detecting and estimating maneuvering targets for broadband radar. The main steps include: S1: dividing the target velocity search parameter space at equal intervals and shifting the velocity component in the pulse pressure signal to the center of the parameter space; S2: dividing the spectrum of the pulse pressure signal into several narrow frequency bands and extracting them in sequence; S3: applying the MGWO algorithm to the extracted sub-aperture pulse pressure signals to obtain a rough estimate of the target maneuvering parameters of the corresponding sub-aperture; S4: applying least squares estimation to the full aperture to obtain a precise estimate of the target parameters; S5: constructing a corresponding high-order phase compensation function based on the precise estimate to complete Doppler frequency compensation, and performing a first-order Keystone transform on the compensated signal to complete range-azimuth decoupling and complete coherent accumulation of target energy. The present invention effectively solves the problems of range and Doppler movement and can achieve long-term coherent accumulation of maneuvering targets. The invention has good real-time performance, strong noise robustness, and certain engineering practical value.

This application relates to the field of space imaging technology and provides a method for decoupling translational and rotational motion in space-based microwave imaging of space targets based on parameter estimation. The method first uses adjacent cross-correlation and self-focusing methods to perform preliminary compensation for the translational motion components of the microwave imaging echo data. Then, using the first-order translational motion parameters fitted by the former as initial values ​​and minimizing the image entropy of the echo data as the cost function, it combines Keystone transform to optimize and compensate for the translational linear phase components. Next, it uses Keystone transform to compensate for the spatially varied range cell migration caused by the rotational motion components. Finally, it performs a second compensation for the residual translational motion components, obtaining echo data after almost complete compensation of the translational and rotational MTRC. By performing spatially varied phase error compensation and azimuth compression on this data, the imaging result of the space target can be obtained. This method achieves a balance between the efficiency and accuracy of parameter estimation, effectively improving imaging quality.

The application discloses a LFMCW radar Keystone transformation distance walking correction and semi-blind speed effect elimination method and device. In view of the energy defocusing and Doppler tearing problems of the semi-blind speed area caused by Sinc interpolation truncation when the conventional Keystone transformation processes high-speed maneuvering targets, a double-path parallel architecture is adopted. A conventional branch extracts a safe area spectrum; a blind speed branch constructs a time domain compensation factor containing a radar frequency modulation slope and a fast time variable, substitutes high calculation power interpolation by pure physical phase rotation, and realizes extreme focusing of target energy; then, based on a target absolute Doppler index, a point-to-point coordinate mapping mechanism is adopted to seamlessly recombine the focused main lobe into a basic spectrum. The application recovers the coherent accumulation loss caused by interpolation truncation, eliminates the ghost false peaks and speed measurement blind bias at the Doppler cross-border, greatly reduces the consumption of underlying hardware resources, and meets the real-time detection demand.

This invention discloses a method and apparatus for processing echoes and estimating motion parameters of uniformly accelerated moving targets. The method includes: acquiring the frequency-coded target echo signal of a uniformly accelerated moving target; performing baseband echo processing to obtain a pulse-compressed echo; performing range compensation and frequency domain transformation processing to obtain a fast-time Fourier transform echo; performing second-order non-standard Keystone transform processing to obtain a second-order non-standard transform signal; performing acceleration estimation and compensation processing to obtain a compensated echo; performing first-order non-standard Keystone transform processing to obtain a first-order non-standard transform signal; performing echo coherent accumulation processing to obtain a coherently accumulated echo; and performing motion parameter estimation to obtain motion parameter estimation results, including the target's initial range and target velocity. This invention achieves echo processing and motion parameter estimation, improves estimation accuracy, and reduces the computational load. This invention can be widely applied in the field of radar signal processing technology.

A microwave photon radar ultra-wideband signal processing method based on Keystone conversion comprises the following steps: S1, carrying out digital down-conversion on an intermediate frequency sampling signal to respectively obtain baseband signals of an I path and a Q path; s2, performing inter-channel phase calibration on the baseband signals of the I path and the Q path; s3, performing beam forming on the signal after phase calibration to obtain a sum-path beam signal; s4, performing pulse compression processing on the sum path beam signal, wherein the pulse compression processing comprises the steps of performing fast Fourier transform, matched filtering, Keystone transform-based range migration correction and inverse fast Fourier transform on the sum path beam signal in sequence; and S5, performing coherent accumulation on the signal after pulse compression processing, and generating a two-dimensional spectrogram containing target distance and radial speed information. According to the invention, an efficient solution is provided for the problem of range migration under the ultra-wideband signal, and the advantages are obvious.

A method for automatically selecting time points for multi-target ISAR imaging includes the following steps: S1: performing pulse compression on a broadband echo sequence for multi-target imaging; S2: performing range image averaging and calculating the waveform entropy of the average range image; S3: taking the time corresponding to the range image with the maximum waveform entropy as the time reference and performing a Keystone transform; S4: performing azimuth compression on the range image sequence to obtain a multi-target range-Doppler two-dimensional image; S5: after target separation on the range-Doppler plane, performing motion compensation and R-D imaging processing on each target to obtain an ISAR image of each target. By calculating the waveform entropy of the average range image, the present invention can automatically select the time point at which the multi-target overlap is minimized, thereby improving computational efficiency. The automatically selected time point exhibits the best separability of target echoes, thereby improving imaging efficiency.

This invention relates to a low signal-to-clutter ratio ISAR imaging method for ship targets based on multi-aperture rotation alignment. Specifically, it relates to ISAR signal processing and imaging, and more specifically to a ship target ISAR imaging method. The purpose of this invention is to address the problem that existing methods cannot simultaneously solve non-stationary Doppler blurring, sub-aperture rotation errors, and strong clutter interference during the imaging process, leading to low accuracy in ship target ISAR imaging. This invention establishes an echo signal model of the three-dimensional motion of ship targets in a marine environment and introduces sea clutter interference. It utilizes Keystone transform combined with a minimum entropy phase autofocus algorithm to compensate for range migration and phase error in the pulse-compressed signal. The full-aperture observation data is divided into multiple sub-aperture data blocks to generate sub-image sequences. A screening threshold is introduced to select high-quality sub-frames. The rotation error of each preferred sub-image relative to the reference frame is estimated and resampled for correction. Finally, a geometric mean fusion algorithm is used to preserve the strong scattering point features of the target.

This application discloses a high-speed target acceleration estimation method based on biorthogonal Fourier transform. First, the received echo signal is subjected to an FFT transform in the fast clock dimension. Then, a Keystone transform is performed in the slow clock dimension to correct for range travel, stretching and compressing the echo signal. Next, a moving target detection (MTD) method is used to coarsely estimate the target velocity, obtaining an ambiguous target velocity, and Doppler filtering is applied in the frequency domain to improve the signal-to-noise ratio. Then, the Doppler frequency of the signal is compensated based on the estimated value. Next, based on the Keystone transform, a biorthogonal basis opening is performed on the echo signal using a BFT transform to estimate acceleration and compensate for target acceleration. Finally, the MTD method is used to de-ambiguate the range and velocity, obtaining the precise target velocity and range. This method can increase the linear dynamic range of signal processing and improve the improvement factor; it also solves the problem that the Keystone transform alone cannot eliminate the effects of acceleration when analyzing accelerating targets.

This invention proposes a multi-station radar high-speed target detection method based on axis rotation and dual-core Radon cubic phase. The implementation steps are as follows: range travel compensation is performed on the signal after second-order Keystone transform based on an improved axis rotation method; Doppler diffusion compensation is performed on the potential target signal based on the dual-core Radon cubic phase function; the data correlation results between the measured values ​​and the target are calculated, and the multi-station radar high-speed target detection results are obtained. In the range travel compensation of the second-order Keystone transform signal, this invention only rotates the fast time axis of each range block signal, improving the two-dimensional parameter search for range and velocity into a one-dimensional rotation angle search, thus reducing the computational load; the Doppler diffusion compensation of the potential target signal based on the dual-core Radon cubic phase function transforms the high-dimensional parameter search into an instantaneous frequency change rate search, improving detection efficiency and detection probability.