Based On The Part Of The Sub-array Digital Beam Forming Technology

For the need of cruise missile defense, phased array radars require large aperture to get high-resolution measurements in angle and 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 with complex system architecture and large hardware expense. Thus, partially adaptive beamforming based on subarray is suitable for the large phased array system.Firstly, the flow of signal processing for phased array radars and the model of the received signal from array has been investigated. Then some basic approaches about adaptive beamforming are introduced, such as minimum variance distortionless response (MVDR), least squares (LS) and the rank reduction algorithm based on eigendecompose, and the results of these approaches are analyzed.In succession, the methods of subarray division by regular and irregular means have been investigated. The problem of grating lobes and nulls caused by regular subarray division is discussed. The origin of grating lobes and nulls is analyzed, and the rules of subarray division to avoid them are summarized.Then, the algorithms of partially adaptive beamforming based on irregular subarray have been put emphasis upon. The influence of the scrambling of subarray is analyzed. It is caused by the unequal noise powers form different subarrays. A beamforming algorithm named signal subspace method (SSM), which reduces the influence of noise have been studied. The algorithms of source number estimation have also been introduced. Finally, a partially adaptive beamforming algorithm based on irregular subarray is proposed. Through the estimation of source number, the noise subspace could be removed form the signal subspace received by the subarray. Then MVDR method is used to calculate the weighting vector. A set of results of computer simulation are given to show that the influence caused by the scrambling of subarray could be reduced. Because large phased array radar use broadband signal mostly, the subarray level partially adaptive beamforming for broadband signal have been investigated. First of all, some full adaptive broadband beamforming algorithms have been introduced, and the results of them have been analyzed, including LCMV and inconnected signal method (ISM). Then a subarray level partially adaptive beamforming algorithm with less computational complexity and performance reduction has been proposed. The signal processing is in the frequency domain by applying the previous algorithm at each frequency bin and the results of computer simulation are given to show the availability of the algorithm.