Wideband Digital Array Adaptive Beamforming Technology Research

For the need of surpressing interference, phased array radars require adaptive low side-lobe and Jammer nulling; Besides, phased array radars require working in wideband to get high-resolution measurements in range. Large phased array antennas are commonly consisted of hundreds or even thousands of antenna units. To realize a full adaptive digital beamforming, the received signal of each antenna unit must be processed singly, and it means each unit requires a T/R module, which results in a large hardware equipment and large hardware expense. Thus, partially adaptive beamforming based on subarray is suitable for the large phased array system.Firstly, the basic theory about adaptive signal processing for phased array radars has been investigated. It includes the model of the received signal from array and basic algorithm about adaptive beamforming. the results of some approaches are analyzed.In succession, the methods of subarray division by regular and irregular means have been investigated. The solution of the problem of grating lobes and nulls caused by regular subarray division is summarized. Toward narrowband signals,two approaches based subarray,MVDR and equal noise power method,are analyzed. The equal noise power method can reduce the impact of unequal subarray noise power to DBF,whose performance of surpressing interference be close to full adaptive DBF.Then, the algorithms of wideband adaptive beamforming have been put emphasis upon. The phase offset of wideband signal not only depend on the direction of arrival,but also the frequency,which changes in the band.So, we make use of method based on the frequency field,which do DFT to signals.Then ISM and CSM are used to do DBF. Validity of the two methods is proved.Lastly, because large phased array radars usually are planar array, DBF algorithms for 2D planar array are discussed in detail in this paper.The wideband signal processing approaches and subarray adaptive signal processing approaches are used to planar array.then,we put forward the wideband subarray DBF algorithm for planar array.the simulated experiments prove the validity.