基于正交混频的数字下变频技术研究

DDC Technology Based on Digital Orthogonal Mixing

数字下变频(DDC)是软件无线电的关键技术之一,可以将宽带大数据流信号变成窄带低数据流信号,以便后端DSP实时处理;讨论了基于正交混频的数字下变频实现技术,并将它与直接抽取的数字下变频进行对比,显示出其优势,详细给出了数字振荡控制器(NCO)、信号频谱搬移、抽取前的抗混叠滤波器及整数倍抽取的设计方法;通过对一中频信号进行基于正交混频的数字下变频的仿真试验,结果正确解调出了原始信号;表明这种技术简单可行,有较高的实用价值。

DDC （Digital Down Converter） is one of the key techniques of software radio. Wide band high bit-rate digital signal can be transformed to narrow band low bit rate digital signal with DDC technology, so can be processed by DSP in real-time and reduce the high re- quirement of DSP. Discussed the DDC technology based on digital orthogonal mixing, also the design methods of NCO, the transfer of frequency spectrum, the filter and decimation technology are detailed proved. In contrast with directly decimation technology, shows this technology＇s several superiority. The computer simulation in DDC of intermediate frequency signal can be correctly reconciliated out the original signal by. Show that this is a simple, practical and high valuable technology.