The Imaging Technology Of Forward-looking Radar

Airborne and spaceborne SAR has been widely applied. The scene imaging can becomparable to optics image for the same purpose. Generally, traditional SAR works inside looking mode. As to the forward looking, it is really difficult for SAR imaging.However, there are many radar applications, such as airborne reconnaissance, missileprecision guidance and airplane landing in bad weather, require the ability of forwardlooking imaging, Therefore, more and more countries attach importance to forwardlooking radar imaging. This paper is dead against to two main systems, forward lookingradar with two antennas and linear array respectively.For the forward looking SAR with single antenna, blind area exists because of thechange of Doppler frequency is small. What’s more, since the target in each sideproduces the same Doppler frequency, there is problem of left/right ambiguity. Tworeceiving antennas is used to achieve forward looking imaging in this paper. Moreaccurate range cell migration correction and azimuth dechirp is performed by dividingup the scene with different depression angles. And then the range-Doppler data iscorresponded to the scene coordinate. Due to the difference of Doppler frequency fromtwo antennas, forward looking image without left/right ambiguity is obtained bychoosing the smaller one of two channels data.The quality of forward looking radar imaging with two antennas is quite limited.Linear array can be put on the radar flat in the azimuth direction, and forward lookingimaging by real aperture can be obtained. The imaging theory is likely to the ScanSAR.This paper educes an efficient method of range processing through range cell migrationanalysis. At the same time, several algorithms of azimuth data matching is introduced,they are validated and analyzed by simulations.However, the length of the linear array is confined by the radar flat size, whichresults that azimuth resolution is hard to meet the practical requirement. This paperindicated that the azimuth signal data after range compress can be approximated as thesignal model of sum of exponents, where the number of exponents is the number ofscatterers in the range cell. Thus, super-resolution imaging methods are applied toforward looking radar imaging with linear array.This paper analyses the systems of forward looking imaging radar with twoantennas and linear array. Corresponding imaging algorithms are used, and the imagingresolution, resistibility of noise and computation efficiency is improved at differentdegree, which has some worthiness of theory and reference.