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Improved Azimuth Compression with fractional fourier transform (FRFT) has been studied. Compared to using classic matched filtering technique, the image focused by FRFT has better resolutions. It has been founded that under the condition that chirp's bandwidth keeps the same, the longer pulse duration, the higher resolution of the signal after FRFT operation to this chirp. This paper applies FRFT...
One method can by Broyden-Fletcher-Goldfard-Shano (BFGS) algorithm and fractional fourier transform(FRFT) arrive at a reconstruction of a scene illuminated by SAR. Because there is only one argument (rotation angle α) in the BFGS process, it only needs several iterations to reach converge when processing one certain range bin and have much better impulse response than that of using matched filtering,...
Linear frequency modulated (LFM) continuous wave (CW) synthetic aperture radar (SAR) is promising in airborne earth observation with compact, lightweight, cost-effective and high resolution advantages. For CW imaging radars, however, weak targets may be submerged by sidelobes of strong range interferences including transmitter leakage and nadir signal, especially when the slant range is far. This...
Here automatic range cell migration correction (RCMC) is studied. Classic RCMC in Range-Doppler Algorithm (RDA) is realized by sinc interpolation so that exact instantaneous slant range distance between antenna phase center (APC) and scatterers is necessary. However, the later element above could not be satisfied especially in airborne SAR. Inspired by improved global method used for ISAR range alignment,...
An X-band Synthetic Aperture Radar (SAR), the mini-SAR, mounted on an eight-rotor Unmanned Aerial Vehicle (UAV), has been designed, built and tested at Shanghai Jiao Tong University, China. The main purpose of this work is to design a light-weight, cost-effective and easy-handy miniaturize SAR system with the ability to make repeated flights for an extended study. Real-time collected data can effectively...
The fractional Fourier transform (FRFT) is a potent tool to analyze the chirp signal. Here a novel SAR imaging technique based on FRFT is studied. We apply FRFT to range compressed data instead of executing RCMC and Azimuth compression. By FRFT, we estimate 1) Doppler rate, 2) amplitude 3) azimuth beam center crossing time which means azimuth location of a point target in image in accurate way. The...
The core problem of microwave imaging is to acquire high azimuth resolution. The universal solution is synthetic aperture radar (SAR) utilizing the relative movement between radar and target scene. Recently some researchers propose a novel imaging scheme called microwave staring imaging for motionless platform based on wavefront modulation in azimuth. However, it's not suitable for low-speed platform...
Here feature extraction of a generic SAR target is studied. We apply a new data model to target feature extraction and improve SAR image quality. The data model we construct contains (1) envelope, (2) location of the target. The envelope shape can be controlled by four parameters, and location information is indicated by frequency pair in both range and cross-range. These parameters would be estimated...
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