The Study Of The Multiple-transmitter-multiple-receiver Synthetic Aperture Ladar System For High-resolution And Wide-swath Imaging

Synthetic aperture laser radar(SAL) is a synthetic aperture technology in the application of light band, which has a very good complementary characteristic with synthetic aperture radar(SAR). SAR technology can be used to carry out the general survey in a wide range of earth observation. While SAL technology can be applied to observe the higher resolution for the interested or suspected targets. Moreover, SAL technology can improve at least an order of magnitude of the high-resolution observation than the SAR in the remote measurement in a far range. As a necessary complement to the current high-resolution earth observation technologies, SAL imaging technology has become a new research subject in the field of radar imaging, which has received widespread concerned at home and abroad.At present, the research of SAL technology has been mostly based on the single-transmitter- single-receiver(STST) SAL system. Due to the contradiction between the high azimuth resolution and wide range swath, the STST SAL system cannot meet the requirement of range swath bandwidth in the SAL application. Therefore, the study of the wide swath SAL technology is an urgent problem in the current research. However, the swath bandwidth of SAL cannot be improved from parameter design and signal processing in the STST SAL system. Thus, the research on the wide swath bandwidth of SAL should start from the SAL work scheme so as to break the limitation of STST SAL system to high resolution and range wide swath. In this thesis, a multiple-transmitter-multiple-receiver(MTMR) SAL system in azimuth is designed and the imaging signal processing algorithm of MTMMR SAL is proposed based on the new scheme.The azimuth MTMR SAL system operating in a low pulse repetition frequency(PRF) mode preferentially guarantees the range wide swath and azimuth multiple-channel method solves the problem of azimuth Doppler ambiguity by the way of combination virtue aperture and the real aperture, which realizes imaging with high resolution and wide swath. Direct frequency spectrum combination and adaptive digital beam-forming technology synthetize the multiple Doppler data into wide-bandwidth unambiguous data.This thesis covers the following contents. Firstly, the SAL imaging principle is introduced, which includes the basic operational principle, data recording, signal model, data processing and imaging algorithm. Then, the reason that causes the contradiction between the high azimuth resolution and wide range swath is analyzed in the STSR SAL system. A detailed explanation of the MTMR SAL system is given and the return signal model is investigated at the same. Besides, the direct frequency spectrum combination MTMR algorithm and adaptive digital beam-forming technology to solve the Doppler ambiguity of SAL imaging are proposed due to the problem of Doppler ambiguity at low PRF. Finally, the simulation of three-transmitter-three-receiver SAL system verifies the practicability of the MTMR SAL scheme.The main contribution of this thesis and innovations are:(1) The contradiction between the range swath and azimuth resolution in STSR SAL are analyzed and the azimuth MTMR SAL system are designed.(2) A direct frequency spectrum combination MTMR SAL imaging algorithm of Doppler unambiguity is proposed based on MTMR SAL system.(3) An adaptive beam-forming SAL imaging algorithm of Doppler unambiguity is put forward based on MTMR SAL system.