Design And Implementation Of The Broadband Signal Generator Based On AD9957

As a modern electronic device,the wideband signal generator plays a more and more important role in radar field,which can generate a variety of waveforms to evaluate the performance of radar equipment.Using the wideband signal generator can save a lot of manpower and material resources,it's an economical and practical assessment method.This thesis is based on the theory of the direct digital frequency synthesis,quadrature digital up conversion and multi-channel coherent technology.The wideband signal generator is designed with a high-performance QUDC chip AD9957,which can produce 40 channels synchronous signals.There are many advantages,such as large output signal bandwidth,good synchronization performance and strong expansion abilities.The specific research content of this thesis is as follows:Firstly,this thesis analyzes the working principle of wideband signal generator,including direct digital frequency synthesis and quadrature digital up conversion.Then,according to the characteristics of wideband signal generator,the multi-channel coherent technology is improved,and a design that can generate multiple-channel coherent signals is proposed.Then,this thesis completed the hardware design of the wideband signal generator.Starting from the design requirements,the FPGA+AD9957 architecture was used to design the hardware schematic and circuit board to complete the design of the wideband signal generator.The hardware part is mainly composed of ten signal generator boards,interface board,960 M frequency multiplexer,multiple power splitters,and other peripheral devices.The signal generator board consists of one FPGA and four AD9957 s,and is responsible for the up-conversion of the baseband data.The interface board is responsible for the scheduling of data and control commands.The 960 M frequency multiplexer is responsible for providing a pure reference clock,and the power splitter is responsible for the synchronous transmission of signals between boards.Next,this thesis completed the software logic design of the wideband signal generator.Through programming the FPGA by Verilog,various logic design methods are used.For example,ping-pong algorithm,edge synchronization method,and state machine method.The flexible control of these modes finally achieved the function of synchronously outputting 40 channels of wideband signals.At the end of the thesis,this thesis tests the single frequency signal,linear frequency modulation signal(LFM)and synchronization signal,and gives the test results and analysis.The results show that the broadband signal generator designed in this thesis has high output signal frequency,large bandwidth,multiple waveform types,and good synchronization performance,which has met the design requirements and has a good application in practical projects.