全数字接收机中的下变频技术研究

Study on Down-Conversion Technology in All Digital Receiver

数字下变频(Digital Down-Conversion,DDC)是实现全数字接收机的核心技术之一。下变频包括混频和抽取两个关键模块,中频输入信号通过数字混频器变换到基带,并经抽取滤波器降低采样率,从而进一步减少后端实时处理的计算量。采用MATLAB对数字下变频模块进行性能仿真和高效的设计,给出优化的多级抽取滤波器设计结果;并结合基于软件无线电构架的BPSK通信体制,证明数字下变频算法稳定可靠,适用全数字接收机的设计要求。

Digital down-converter plays a key role in the implement of all digital receiver.Mixer and decimator are two main modules of DDC.The received IF signal was converted to base-band by using mixing module.The decimation filter is used to reduce calculation burden in real-time process at a low sampling rate.The function simulation and the efficient design of DDC by MATLAB is described.The optimized design of Polystage-decimation filter is given too.The simulation result shows that the DDC module is effective and satisfies the requirements of systems when it is implemented in digital IF BPSK receiver based on software radio.