【作者】 李佳伟；

【导师】 漆兰芬；

【作者基本信息】 华中科技大学 ， 电磁场与微波技术， 2006， 硕士

【摘要】 新一代移动通信对于高速率、高可靠性数据传输设计和应用有很高的期望。为了满足期望数据传输速率的高质量服务,有很多困难有待解决。无线信道的设置受到整个传输系统的限制,随时间的多径衰减是限制无线信道容量的主要原因之一。空时分集是克服多径衰减的常用办法。MIMO(Multiple Input Multiple Output)技术就是在这种情况下被提出。它利用空时分集技术,可以在传输特性恶劣的无线信道中实现高速数据传输,具有广阔的应用前景。本论文针对MIMO系统的信道容量和射频前端收发系统进行研究,提出系统方案并对收发系统方案的主要模块进行分析和仿真。该系统采用时分双工方式,包括收发切换电路、本地振荡源,三路发射通道和三路接收通道。射频通道工作于2.4GHz,发射机采用直接调制方案,接收机采用超外差方案。每路发射通道包括I/Q正交调制、预放、自动功率控制(APC)、功放和收发切换等子电路模块。每路接收通道包括低噪声放大器、变频器、声表面波滤波器和中频调制等子电路模块。发射模块提供与基带处理部分的接口,可以和接收模块一同构成完整的MIMO实验通信系统。本文首先就MIMO系统信道容量进行分析,研究了分布式MIMO系统中天线选择对于系统信道容量的影响,得出在传输矩阵秩小于发射天线数时,在不降低传输矩阵秩的情况下,对基站和基站的发射天线数目进行选择可以提高系统的信道容量。然后根据射频前端的指标要求,讨论了射频收发系统的设计方法,确定了系统的收发方案,对发射机和接收机的主要模块进行仿真,并分析了各子模块主要的性能指标,达到试验目的。最后对论文工作进行了总结,分析了不足之处,并给出建议,为进一步的后续研究提供参考。更多还原

【Abstract】 New generation wireless communication needs high speed and reliable data transmission. In order to deliver the desired data rates with high quality of service several difficulties has to be overcome. The wireless channel sets the limit for all transmissions. Time varying multipath fading is one of the major limitations in wireless channels. Diversity in space and time is a common way to defeat the multipath fading. MIMO(Multiple Input Multiple Ourput) technique is presented in this situation. The Space-Time coding is used by MIMO to achieve high speed data transmission in a limited frequency bandwidth with comparably low cost.This article focuses on the research of channel capacity of MIMO system and transmitting module of RF front-end for MIMO mobile terminal, provides a scheme of transmit and receive system based on software simulations. The transmitting module,which is TDD scheme,works at 2.4GHz and consists of a T/R switch,a local oscillator, three transmitter channels and three receiver channels. The transmitter adopt the scheme of direct modulation which consists of several circuits elements such as an I/Q Quadrature Modulator, a Pre-Amplifier,an AGC circuit, a Power Amplifier , a T/R switch and a PLL Frequency Synthesizers, etc. The receiver adopt the scheme of superheterodyne which consists of several circuits elements such as a Low noise amplifier, a Transducer, a surface acoustic wave filter and a Intermediate frequency Modulator, ect. The transmitter and the receiver can be combined with the Baseband Processing Module to build up an MIMO demonstration communication system.First , the channel capacity of MIMO system is discussed, and the channel capacity with antennas selection is calculated. When the order of the transmit matrix is lower than the number of transmit antennas, without reduce the order of the transmit matrix, the selection of base stations and the number of transmit antennas can enhance the channel capacity.Secondly, according to the demands of the MIMO system, the design theories of the RF transmitter and receiver is discussed. The important modules of the transmitter and the receiver are analyzed and simulated.In the end of this article, the deficiencies of the work are pointed out, and the suggestions are made for future research.更多还原