QAM调制解调技术研究及其FPGA实现

【作者】 朱泳霖；

【导师】 罗桂娥；

【作者基本信息】 中南大学 ， 电子科学与技术， 2010， 硕士

【摘要】 正交振幅调制(QAM)技术有着非常广泛的应用范围,不仅在移动通信领域应用,而且在有线电视传输、数字视频广播卫星通信(DVB-S)等领域也都得到广泛应用。QAM调制技术之所以得到如此广泛的应用,在于它具有很高的频带利用率,这在带宽资源不是很丰富的移动通信和卫星通信中更显现出该调制技术的优越性。本文在对QAM调制解调的基本原理、调制端的基带成形理论和解调端的载波同步理论进行深入研究的基础上,通过Matlab软件的Simulink仿真平台实现了16QAM调制解调系统的建立及实验验证。之后利用Xilinx公司的ISE 9.li软件加载ModelSim6.1b作为软件开发环境,设计并实现了16QAM调制解调系统的伪随机序列发生器、星座映射、基带成形滤波器、载波信号发生器、载波恢复环路和星座逆映射等关键模块。其中基带成形滤波器选择平方根升余弦滤波器,采用分布式(DA)算法实现,可以有效的节约FPGA硬件资源；关于载波信号发生器的设计,本文采取数字坐标旋转(CORDIC)算法实时计算正余弦值的方法,替代传统DDS采用的正弦查表来实现DDS中相位幅度的转换,可以很好的克服DDS中使用ROM表时产生的相位截断误差,极大的提高了DDS的频率和相位分辨率,并显著地节省了FPGA的内部资源；载波恢复则采用通用科斯塔斯环法,这种环路结果简单且容易实现。本文采用Verilog硬件描述语言对16QAM调制解调系统中的关键模块进行RTL级描述,完成了功能上的仿真验证,通过对比验证了设计的正确性,为下一步的硬件实现打下了很好的基础。更多还原

【Abstract】 The modulation technology(QAM) is widely used, and it is used not only in the mobile communication field, but also in other fields, such as wire television transmission field, Digital Video Broadcasting-Satellite communication(DVB-S)field, etc...The reason why QAM modulation technology gets so extensive applicable lies in its high frequency band utilization ratio. This is the modulation technology superiority in the mobile communication and satellite communication fields, in which the bandwidth resources are not so abundant.First of all, this paper introduce the basic principles of QAM modulation and demodulation, especially the base-band shaping theory of modulation and the carrier recovery theory of demodulation, then simulate the whole 16QAM modulation and demodulation system in the Matlab software’s simulink toolbox. Beside research in theory, this thesis designs and built the key parts of 16QAM modulation and demodulation system based on FPGA with the simulation environment, which is constituted by the software of ISE9.1i and ModelSim6.1b. The key parts include the following modules:pseudo-random sequence generator, constellation mapping, base-band shaping filter, carrier signal generator, carrier recovery loop, constellation demapping. The srrc filter is used as base-band shaping filter,which is implemented by DA arithmetic,which achieveds the goal of total used resources redulation of the FPGA; we have adopted the use of CORDIC algorithm to replace the real-time computing sine look-up table in the DDS phase to achieve the conversion rate to overcome the use of DDS when ROM table phase truncation error; corrier recovery is implemented by costas loop,which is easy achieved.This paper achieve the simulation of the key modules of 16QAM modulation and demodulation system by the language of Verilog HDL in the simulation environment. The result of simulation and synthesis proves the correctness of the design. It laid the foundation of the next hardware design.更多还原