滤波多音频中的滤波器组设计技术研究

【作者】 高有军；

【导师】 高振明；

【作者基本信息】 山东大学 ， 通信与信息系统， 2005， 硕士

【摘要】 近几十年以来,随着半导体技术和计算机技术的不断发展,无线通信已经逐渐成为人类日常生活中不可缺少的组成部分,而大量的用户需求反过来又促进了无线通信的发展。 随着声音、图像和数据通信业务在互联网和无线通信中的快速增长,对下一代通信系统的定义成为新的研究热点。在这种现代宽带无线通信系统中对数据速率的要求将超过几兆bps,这意味着数据传输时需要占用相当大的信道带宽且信道的时延扩展将大于一个传输符号的符号周期,因此如何在有限的带宽内高速可靠地传输信息是极为重要的。 加性噪声以及由多径传播导致的符号间干扰(ISI)限制了高速率无线通信技术的发展。在高达几兆bps的传输速率下,传输符号的符号周期小于信道的时延扩展,从而产生ISI。因此在利用传统的单载波调制方式进行高速率无线通信时需使用多抽头均衡器,从而使系统的复杂度大大增加。研究表明,如果多径信道的时延扩展(信道记忆长度)远小于一个传输符号的符号周期,则由多径传播造成的ISI可以忽略不计,所以,我们可以利用多载波传输技术在不降低信息传输速率的条件下使信道中的传输符号的符号周期远大于多径信道的时延扩展,从而可以有效地对抗由多径传播造成的ISI。 正交频分复用(OFDM)技术是当今通信技术研究中的一个热点。作为一种多载波技术,它具有抗多径干扰能力强、频谱利用率高等优点。然而OFDM技术也存在着一些缺点,如容易受频率偏移影响、符号同步困难等,这些问题都制约着OFDM在无线信道中的应用[1]。 滤波多音频(FMT)技术相对于OFDM是一种新兴的多载波技术。该技术的主要特点是各子载波具有很高的频谱约束性,对系统频率偏差不敏感。FMT技术克服了OFDM技术易受频率偏差影响的问题,但是其滤波器组在系统中引入了ISI,因此,FMT中需要引入子信道均衡技术来消除滤波器组的影响。 本文介绍了滤波器组多载波(FB-MC)传输技术的基本原理,给出了更多还原

【Abstract】 Wireless communication has played a more and more important role in peoples’ daily life with the development of semiconductor and computer technologies in recent decades, which in turn promote the rapid expansion of the wireless communication.The definition of the next generation of mobile communication is the new emphasis of research with the rapid increase in sound, image and data communications over the internet and wireless. The demand on data rate in this broadband wireless communication system will exceed several Mbps, which means the delay time of the delayed waves will become greater than one symbol time and a larger bandwidth is needed. So it is important to transmit data over band limited channel in a high data rate reliably.High data rate in wireless communication is limited by additive noise and the Inter-symbol Interference (ISI) owing to multipath propagation. When the data rate is more than several Mbps, there is ISI because the signal duration is shorter than the channel delay spread. In conventional single-carrier modulation, the system complexity will increase greatly due to the multi-taps equalizer used in high data rate wireless communication. The effects of the ISI are negligible so long as the delay spread of the multipath channel is significantly shorter than the duration of one transmitted symbol. So multi-carrier transmission technology can be used to overcome this limitation.Nowadays, Orthogonal Frequency Division Multiplexing (OFDM) is a key technology in the mobile communication field. As one of the multi-carrier transmission technologies, OFDM can reduce the multipath fading effect with high frequency efficiency. However there are some disadvantages in OFDM system such as sensitivity to frequency offset, symbol synchronization and so on. All of these limit the application of OFDM in wireless environment.Filtered Multitone (FMT) Modulation is a new multicarrier technology incontrast to OFDM. In FMT system, the spectrum of each subchannel has a high level of spectral containment. So the Inter-channel Interference (ICI) of FMT is negligible compared to other noise, while it often appears in OFDM system because of its sensitivity to frequency offset. However, subchannel equalization is needed in order to reduce the remaining ISI introduced by the filter banks.In this thesis we introduce the filter bank based multicarrier (FB-MC) transmission technology and give the practical efficient implementation structure. In the following, we introduce the principle of OFDM and FMT technology in filter bank view point.In the chapter 3, we analyze the basic theory of filter bank modulation in FMT emphatically, and do research on the design of prototype filter. Several indice and methods for design of filter are derived. At the end, the simulations of the performance of the prototype filters designed by the methods in wireless environment are studied. The simulation results imply that FMT technology still has good performance in wireless environment.The chapter 4 of the paper studys the optimization of filter bank and the prototype filter. We can get better performance of system by optimizing the indice of prototype filter. The simulation result shows the effect of the optimization of prototype filter.Because of the limitation of the time and some objective conditions, we only simulate parts of the design of the prototype filter. And there are many topics which are not studied including other optimization design, for example, to get the largest achievable bit rate, there is trade-off between the subchannel spectral containment between ISI. We will further our study in later days.更多还原