【摘要】 论述了GPS(G loba l Pos ition ing System)卫星信号模拟器载波NCO(数控振荡器)和码NCO的系统结构及作用,根据多速率信号处理理论建立DDS(直接数字频率合成器)模型,分析其信号频谱;根据泰勒级数压缩算法分析了载波NCO s ine存储表压缩效率,提出了模拟器码NCO参数更新实现方式.利用verilog在X ilinx’ISE 6.3中完成了载波NCO和码NCO的设计和仿真,并在FPGA中进行了实现.通过程序仿真与系统测试,证明本载波NCO和码NCO模块性能满足GPS卫星信号模拟器系统需求.更多还原

【Abstract】 The system architecture and function of the carrier NCO(numerically controlled oscillator) and code NCO in GPS signal simulator are described.A model for DDS(direct digital synthesizer) is established based on the multi-rate signal processing theory,and the signal spectrum analysis is given.The compression efficiency based on Taylor approximation compression algorithm for mapping from phase to sine amplitude DDS for carrier NCO is discussed,which provides additional improvements in compression.The parameter updating method for code NCO is presented as well.With the Xilinx’ISE6.3 development tool and FPGA using Verilog,the design and simulation of the carrier NCO and the code NCO is implemented.By the procedure simulating and system testing,it is shown that the module specifications of the carrier NCO and code NCO meet the requirement of GPS signal simulator.更多还原