The Design And Implementation Of The Baseband Signal Generation Unit Of Complex Electromagnetic Environment Simulation

With the progress of science and technology, more and more electronic equipment used in human life and modern battlefield, the electromagnetic environment of space is becoming increasingly complex, played an important effect on human life and the outcome of war. In order to take advantage of the electromagnetic environment,we must fully understand it. So study the baseband signal generating unit of complex electromagnetic environment simulation is very important to the development of human life, technology and military.This thesis describes the design and implementation of the baseband signal generation unit of complex electromagnetic environment simulation.It applyed the baseband signal generation techniques of arbitrary waveform pattern and complex modulation techniques and took structure of "DSP + FPGA + DDR2 + DA board" as the hardware platform.Realized a single device can simultaneously produce up to 24 baseband signals.The frequency, amplitude, modulation, code rate of the baseband signals can be adjusted.The design solution of baseband signal generating unit of complex electromagnetic environment simulation was presented based on the theory of software radio. This solution mainly includes the process of multi-rate baseband signal and the produce of multi-carrier modulated signal two parts. The process of multi-rate baseband signal includes the following three modules: First, establish a data path between the DSP and FPGA to achieve the communication between the DSP and the FPGA. Second, design a memory and control unit of massive high-speed baseband signal data, use DDR2 SDRAM memory to implement fast read and write operation of the baseband signal and realize the playback function of complex electromagnetic environment background signal. Third, the design of variable sampling rate processing module of multirate baseband signal, using the CIC interpolation filter increases the sampling rate of the baseband signal and suppresses mirrored component and harmonic components of the baseband signal effectively. Multi-carrier modulation signal generation module is another focus of this article, uses complex modulation technique to access multi-carrier modulated signal. The multi-carrier modulation signal can be used to simulate background signal of complex electromagnetic environment after being processed by upconversion module and signal conditioning circuit.All functional modules of baseband signal generation unit of complex electromagnetic environment simulation were realized in Xilinx’s FPGA using ISE software, saved system development time effectively.Used Chip Scope software and spectrum analyzer to verify the results of the functional modules, the results show the design of baseband signal generation unit of complex electromagnetic environment simulation meets predetermined requirements.