OFDM中频信号处理系统设计

【作者】 龚轲；

【导师】 张东彦；

【作者基本信息】 北方工业大学 ， 信号与信息处理， 2012， 硕士

【摘要】 OFDM(正交频分复用)是一种多载波调制技术,其核心思想是将串行高速的数据流转换成并行低速的数据流进行传输。它具有频谱利用率高、抗多径环境、抗频率选择性衰落或窄带干扰等优点,适用于无线信道中的高速数据传输,具有广泛的应用前景,被普遍认为是下一代移动通信系统中的关键技术。本设计详细的研究了OFDM基带通信系统的基本工作原理,对OFDM的调制解调以及其中涉及的关键技术做了相关的分析,并对OFDM通信系统进行了仿真。根据设计的需求,自行设计了一款开放式的软件无线电硬件平台,并在平台上实现OFDM基本的基带设计和中频设计。该硬件平台采用Xilinx公司生产的Spartan3A-DSP FPGA作为数字信号处理芯片,平台上同时包括高速DAC,高速ADC及UART, USB等诸多外围接口设备。本设计使用System Generator来实现OFDM调制与解调算法的设计。System Generator是Xilinx公司开发的系统级建模工具,允许工程师在进行FPGA设计时使用Matlab下的Simulink平台。本设计中OFDM调制端的内容包括QPSK映射、训练序列的插入、IFFT、循环前缀插入等模块的设计。解调端的内容包括信号同步、循环前缀删除、FFT、QPSK解映射等。在此基础上,本设计通过数字信号发生器、数字混频器和插值滤波器的设计,将基带信号进行了数字变频。最后,本设计通过对比发送和接收的数据,证明本设计的可行性。更多还原

【Abstract】 OFDM (Orthogonal frequency division multiplexing) is a multi-carrier modulation technology. The main opinion is to convert the high speed serial data stream to the parallel low-speed data stream. It has lots of advantage, such as high spectrum utilization, strong multipath effects resistance. It can also work well in frequency selective fading or narrowband interference etc. OFDM is suitable for the high speed data transmission in wireless channel. OFDM have widespread application prospect, which is generally considered to be the key technology of the next generation of mobile communication system.This paper studies the basic working principle of the OFDM communication system. At the same time, this paper also analyzes the modulation and demodulation of OFDM, including the key technologies. This paper also contains a comprehensive simulation of the OFDM system.According to the design requirements, an open-planed software defined radio hardware platform is designed in this project. The Xilinx FPGA Spartan3A-DSP is selected as the main digital signal processing chip. High speed ADC, high speed DAC and many peripheral interface equipment are all designed and tested in this hardware platform..This project makes the implementation of a whole OFDM modulation and demodulation based on System Generator. The modulation module contains QPSK mapping, training sequence insertion, IFFT, cyclic prefix insertion. The demodulation contains the OFDM synchronization, delete of the cyclic prefix, FFT, QPSK de-mapping. Based on this achievement, down conversation and up conversation is designed also by System Generator. Finally, by comparing the related data, it is proved that the design is working correctly.更多还原