文献综述
摘要
数字下变频器(DDC：Digital-Down-Converter)是将数字中频信号搬移到基带附近且使数据率降至适宜 DSP 处理的器件，它工作在 ADC 之后，是软件无线电系统的核心部分。数字下变频分为两个基本的模块，数控振荡器NCO(Nu-merical Control Oscillator)混频模块和抽取滤波模块。
FPGA（Field－Programmable Gate Array），即现场可编程门阵列是一种由用户自行配置专用数字集成芯片，具有小型化、低功耗、可编程、数字化和快速方便实用的特点。FPGA 的灵活性与高速处理的能力，使其由一种灵活的逻辑设计平台发展为重要的信号处理元件，在各种软件无线电产品中得到了广泛的应用。
本文研究基于FPGA的数字下变频器的实现方案，在FPGA上设计和实现数字下变频器中的信号分离、数字下混频和滤波抽取等功能模块，并完成系统的仿真和调试。
关键词： DDC 软件无线电 FPGA
Abstract
DDC (Digital-Down-Converter) is a device that moves digital IF signals near the baseband and reduces the data rate to suitable for DSP processing. It works after ADC and is the core part of software radio system. Digital down converter is divided into two basic modules, NCO (Nu-merical Control Oscillator) mixing module and decimation filter module.
Field-Programmable Gate Array is a kind of special digital integrated chip which is self-configurable by users. It has the characteristics of miniaturization,
low power consumption, programmability, digitalization, fast, convenient and practical. The flexibility and high-speed processing ability of the FPGA make it develop from a flexible logic design platform to an important signal processing element, which has been widely used in various software radio products.
