【作者】 杨永齐；

【导师】 冯文江；

【作者基本信息】 重庆大学 ， 电路与系统， 2006， 硕士

【摘要】 软件无线电以通用的可编程逻辑器件或数字信号处理器构建硬件平台,以软件方式实现不同应用功能,是当前移动通信领域的研究热点之一。理想的软件无线电是将数字化处理尽可能靠近天线端,直接在射频进行数字化。由于受模数和数模转换器以及数字化处理芯片处理速度的限制,目前的软件无线电系统大多采用折中的中频数字化实现方案,通过增加专用的数字变频器或者采用可编程逻辑器件设计专门的数字下变频器,将射频信号变换到中频,再进行中频数字化处理。改变射频信号的采样频率,在应用上能带来极大灵活性。采用专用DDC芯片完成数字下变频,虽然具有抽取比大、性能稳定等优点,但价格昂贵,灵活性不强,不能充分体现软件无线电的优势。用可编程逻辑器件取代或部分取代专用ASIC芯片可提高数字下变频的灵活性。本文就是针对软件无线电的数字变频技术展开研究,通过对数字下变频的信号处理相关理论和关键模块的分析和设计,研究采用可编程逻辑器件设计数字下变频的实现技术。本文的主要研究工作包括以下几个方面的内容:(1)在总结软件无线电系统中数字下变频技术的基本组成、技术特点和国内外现状的基础上,阐述了数字下变频设计相关的信号采样理论、多速率信号处理理论和数字信号正交变换理论。(2)在掌握数字下变频基本原理的基础上,深入研究其实现的关键技术,包括数字混频技术、NCO优化设计技术以及用于抽取滤波的高效数字滤波器设计技术等,设计了两套数字下变频实现方案。(3)针对本文所设计的数字下变频实现方案,结合某基于软件无线电技术设计的数字通信系统中数字下变频的实际需要,完成了各个功能模块的仿真研究和硬件仿真测试,并对测试结果进行了分析。基于FPGA实现的数字下变频,能充分体现软件无线电系统高的灵活性和宽的适应性,本文所设计的数字下变频系统有一定的通用性。更多还原

【Abstract】 Software Radio carry out each kind of function undertaken by software on the hardware platform composed of general PLD or digital signal processor. Software radio is one of the hotspots in mobile communication research. The ideal Software Radio is to make the digitization process as far as possible approaches the antenna. That is, analog-to-digital conversion is done in radio frequency. Due to the poor processing speed of A/D/A conversion and DSP processor, Software radio often adopts inter-specific schemes of digital intermediate frequency(IF). By using specific DDC&DUC or PDC (Programmable down Converter), the radio frequency signal is converted to intermediate frequency (IF) signal. Then the processing of digitized signal is undertaken in IF. It will be much flexible in the application that changing the sample frequency of radio frequency analogy signal. The analysis indicates that the specific DDC chip has many virtues, such as having great decimation ratio and steady performance. But it too expensive, less flexible and can’t exhibit the advantage of software radio.In this dissertation, signal processing of DDC is investigated. Based on the theory of DDC signal processing and the analysis and design on the key module, the technology of design DDC using PLD is focused on. The paper mainly includes some follows:This thesis analysis signal sample theory in DDC, multi-speed signal processing theory as well as digital signal orthogonal theory based on the basic structure of DDC, technology characteristic and actuality of domestic and foreign. So the PLD complete or partially replace the specific ASIC chip to develop the flexibility of DDC.In this paper, we deeply study the key techniques including digital mixing, design of optimum NCO and high-efficiency digital filter used for decimation based on the basic principle of DDC. We put forward two scheme of DDC in the thesis.Focus on the scheme of DDC and adapt to the demand of DDC in the actual digital communication system based on the software radio, we accomplish the simulation and hardware testing of each function module and analyse the testing result.The DDC based on the FPGA can show adequately the great flexible and broad adaptability of software radio. The DDC system in the paper has definite generality.更多还原