Broadband Constant Beamwidth Digital Beam Formation And Realization

Digital array radar (DAR) is a fully digitized phased array radar in which digital beamforming technique is used both in receiving and transmitting. Because both transmit and receive beamformings are realized in digital form, DAR has higher flexibility of digital processing and offers a number of attractive features than conventional phased array radar. Besides, for the advantages of wideband signal in several aspects over the narrow band signal, wideband signal processing has become an important research direction in array signal processing. In this dissertation, the wideband DBF with its implementation are investigated deeply and systematically. The main works are as followers:1.Basic theory of array signal processing is studied. The narrowband and wideband signal expressions are given. The mathematical models of the signal arriving at the array are analyzed. And the principle of conventional DBF is studied. The influences of different ways of beam controlling and weighting are also discussed and compared and correlative simulations are given. Further more, MVDR DBF method is introduced.2.The principle of wideband DBF, especially the wideband constant beamwidth(WCB) DBF based on sub-band decomposition is studied. Two thoughts of designing constant beamwidth DBF: changing the element number of array according to the frequency and changing the weights according to the frequency are introduced. The spatial resample method,Bessel function method and improved Bessel function method are studied. The application of occasions,the complexity of computations and the accuracy of results of these three methods are analyzed. Further more, the implementation of WCB DBF through designing a group of FIR filters by frequency sample method in time domain is also studied.3.A universal digital signal processing system based on ADSP_TS202S+FPGA is presented in detailed. The computational performance of this system can be up to 14.4GFLOPS per second. How to realize the wideband DBF based on the hardware platform is studied.