Deng Yunkai

A new method of improving the accuracy of the hyperbolic range equation

The range equation employed in the current low earth orbital Synthetic Aperture Radar (Leo-SAR) systems is the hyperbolic range equation (HRE). The key parameters of it are effective velocity and effective squint angle. Traditionally the calculation method of the two values may lead to large errors, and it is only fit for Leo-SAR with moderate space resolution. To get the azimuth resolution on the order of one meter or even higher, an improved method based on the accurate second-order Doppler parameters is used in this paper to decrease the errors of the two parameters above. Then we can get the improved hyperbolic range equation (IHRE). The theory is validated by the parameters of TerraSAR-X, and the image with the space resolution around 0.35m is focused perfectly.

Determination of Ocean Wave Propagation Direction Based on Azimuth Scanning Mode

The purpose of this letter is to show that the azimuth scanning mode of a synthetic aperture radar can be applied to deriving ocean wave spectra and determining the wave propagation direction for the first time, which reveals its enormous potential and great future in ocean observation. The improved Doppler beam sharpening imaging algorithm is used to produce a sequence of individual subimages of ocean waves in the same scan region from different aspect angles with a high revisit rate. These subimages have an inherent property that they are formed at different discretely delayed times. Therefore, wave propagation direction can be determined from a pair of wave images in different scans. Several different methods are applied to the real airborne radar wave data, including the methods of scan sum (taking the standard Fourier spectrum of the scan-summed image), spectral sum, spectral phase shift, and cross-correlation function of subimages. The processing results demonstrate the effectiveness of the algorithms.

Scanned beam synthesis technique with projection matrix algorithm for phased-array fed offset paraboloid antennas

A novel phased-array fed offset paraboloid antenna synthesis technique based on projection matrix algorithm is presented. Far-field of the array fed offset paraboloid antenna is calculated based on Physical Optics theory. The excitation coefficients of the feed array are determined under phase only control constraint. Antenna patterns are synthesized efficiently using PMA. Namely the beam direction, half-power beam width and side-lobe level are well controlled. Numerical simulation results are given to demonstrate the feasibility of the method.

Spotlight SAR Raw Data Simulation Using Frequency Scaling Algorithm

SAR (synthetic aperture radar) raw signal simulation is an important tool for study and testing of different SAR processing algorithms and new SAR systems. In this paper, the system transfer function of spotlight-mode SAR is evaluated and its accuracy is described. And, frequency scaling algorithm (FSA) is employed to actualize the coupling relation between the range and azimuth in the 2-dimension frequency. An advantage of the frequency scaling algorithm is that it requires only FFT (fast Fourier transform) and complexity multiplication and avoids interpolation.

Study on the Correction of Saturated SAR Data

In this paper, the saturation characteristic of saturated SAR raw data is discussed and a new method based on optimal quantization theory to restore the raw data is proposed. A flow chart shows the procession of the algorithm. Experimental results show that the performances of radar signal processing using the restored data are better than those of traditional means using the raw data.