Digital Beamforming And Sidelobe Cancellation Based On Regular Subarray

It requires shipborne phase array radar work under various conditions and stay in the best match state with the environment in the complex naval battle in future. In recent years, application of digital beamforming and the development of real-time adaptive processing technology make the adaptive capability of shipborne phased array radar up to a new level. Digital beamforming adopts digital technique to achieve instantaneous multi-beam, and is able to adapt to the sight interference from zero. Therefore it has the strong ability of adaptive processing and performance of super-resolution and ultra-low side lobe. In radar system, how to make the sidelobes of array pattern improve effectively has become a basic and very critical issue. For the regular digital subarray, we can suppress the sidelobes of the sum and difference beam simultaneously by using two different forms of the weighting in the elements of the array, namely Taylor weighting which can reduce beam sidelobes and Bayliss weighting which are used to reduce the difference beam sidelobes. For conformal plane array, it also need to consider the overall amplitude weighting method, but because conformal array is no longer uniform array, we need to optimize the amplitude weighting to achieve low sidelobes. In addition, we reduce the complexity by using the weight vector which is independent of the azimuth and elevation of target and reduce the loss of SNR(Signal to Noise Ratio).With the development of radar technology and the high demand for modern maritime battlefield, adaptive sidelobes cancellation for radar systems has become more and more important. Adaptive sidelobes cancellation is the combination of signal processing technology and antenna technology, which has become an effective method to suppress the array antenna sidelobe jammer. When the active jammer exists, the LMS(Least Mean Square) criteria is usually used to minimize the cancellation residual output, which can modify the weights of auxiliary antenna adaptively in order to minimize the input power of jamming signal. In other words, there forms space zero at the direction of the jamming signal, thereby the sidelobe jamming is suppressed. In adaptive array system, there are several important factors which can influence the performance of sidelobes cancellation, such as quantization noise, channel noise, the channel inconsistency, target echo signals, the jamming bandwidth, the distance betweenantennas and different method of digital beamforming, etc. As for the selection of the auxiliary channels, which consists of the selection for the number and the position of auxiliary antennas, is also the key factor that affect the sidelobes cancellation performance.Based on the theoretical studies on digital beamforming, we adopt a new method to optimize the weights to form the sum and difference beams in low sidelobes. Furthermore, we analyze the effect of the array element with direction on the pattern of the sum and difference beams with the consideration of the impact of unit pattern. In addition, on basis of the theoretical basis for adaptive sidelobes cancellation, we analyze several important factors which including the jamming signal bandwidth, the distance between the antennas, the number of different auxiliary antennas, as well as mechanical scanning are considered with an emphasis on the impact of the performance of sidelobes cancellation. As demanded in the project, we put forward different schematic designs and the corresponding performance analysis for the selecting of auxiliary channels of the sidelobes cancellation system, and then create the simulation model to optimize the auxiliary channel selecting based on the performance analysis. Finally, according to the design of the program, we give the brief introductions of every functional modules of sidelobes cancellation system and the implementation processing by DSP.