【作者】 刘敏；

【导师】 曹杰；

【作者基本信息】 南京航空航天大学 ， 通信与信息系统， 2004， 硕士

【摘要】 软件无线电在通用的、开放的硬件平台上通过软件定义无线通信功能，而且硬件平台本身也是可扩展可升级的，这就使得通信系统摆脱了硬件的束缚，可以实现各种通信体制的无缝连接，提供灵活多变的服务。 近十多年来，随着相关研究的不断深入以及硬件水平的极大提高，软件无线电的实现逐渐成为现实，在通信系统中的应用越来越广泛。本文主要研究软件无线电在发射机中的应用。为便于在项目中应用软件无线电，首先回顾了一些相关问题，如软件无线电功能模型，硬件平台结构等，这对于深入理解软件无线电，进行工程设计都很有好处。硬件平台结构的模式决定了系统的柔性与扩展性。优秀的结构降低其硬件模块间的耦合，允许系统具有即插即用功能，使通信系统可以方便地扩展升级，还可以降低系统成本，充分发挥软件无线电特有的技术优势。本文还总结分析了发射机数学模型，包括单通道、多通道以及信道化发射机。特别提出了改进的实信号信道化发射机数学模型，通过利用多相滤波与离散傅立叶变换，减少信号处理运算量，这对于强调实时运行的无线通信系统有重要意义。随后讨论了两种典型的数字调制，pi／4-QPSK与GMSK，以及它们传统的实现方法。对非线性的GMSK分析了线性近似方法，这对于在软件无线电中实现GMSK有重要意义。最后详细叙述了软件无线电发射机的硬件实现。它主要由一片DSP与可编程数字上变频器构成，可以通过PC机进行监控，通过加载合适的软件实现各种调制方式如pi／4-QPSK，GMSK等。更多还原

【Abstract】 Software-Defined Radio (SDR) defines radio communication functions using software on a general, open hardware platform that possesses scalability itself, which not only relieves communication systems from the constraints of hardware elements but also enables seamless connection between kinds of wireless communication systems and supports flexible services.Software Defined Radios become to true as a result of fruitful researches in this domain and great progresses achieved by hardware devices in recent more than a decade, and now are found in more and more communication systems. This thesis focuses on application of SDR to a transmitter. To streamline the application, at first some relevant issues are reviewed such as functional model of SDR and hardware platform architecture, which can help us get a good understanding into SDR and facilitate conceiving and developing projects. The flexibility and scalability of a SDR are decided basically by its hardware platform architecture. A good architecture can minimize the coupling between its components and enable plug-and-play, consequently makes a system employing SDR capable of upgrade, scalability and more cost-efficient. And, it also helps us fully exploit exclusive advantages of SDR. This thesis also discusses, from a mathematical perspective, the models of transmitters including unichannel, multichannel and channelized transmitters. A modified real signal model of channelized transmitter is presented that employs multiphase filters and Discrete Fourier Transform to maximize computing efficiency, which can mean much in a radio communication system that requires real-time processing. Then two typical digital modulation schemes, pi/4-QPSK and GMSK, are examined respectively with their conventional implementations. A linear approximation of the non-linear GMSK is proposed to help GMSK to be readily accommodated into a SDR. Finally, this thesis elaborates the construction of the transmitter using SDR that comprises mainly a DSP along with a programmable digital up-converter. The transmitter is capable, when coupled with appropriate software, of digital modulation schemes such as pi-QPSK, GMSK and so forth, and supervised by a personal computer.更多还原