【作者】 张平；

【导师】 张海林； 唐佳廉；

【作者基本信息】 西安电子科技大学 ， 工程硕士（专业学位）， 2015， 硕士

【摘要】 随着无线通信系统的用户量和业务需求的不断增加,有限的频谱资源日益紧缺。宽带通信技术由于频谱利用率高,已成为无线通信发展趋势之一。其中OFDM技术凭着抗干扰能力强、频谱利用率高、支持宽带大容量通信等优点,在宽带无线通信系统中应用越来越广泛。但是OFDM技术同时存在明显的缺点,其中之一就是高峰均比问题。高峰均比信号对功放的非线性特别敏感,易产生非线性失真。而且宽带无线通信系统中,传输的是宽带信号,所以宽带功放的记忆性失真不可忽略。目前,在保持宽带功放的线性放大范围的基础上,补偿非线性失真和记忆性失真为研究内容的预失真技术,已成为宽带功放线性化的研究热点之一。为了解决宽带功放的非线性失真和记忆性失真,使OFDM技术更好得用于宽带无线通信系统,同时提高功放的效率,响应国家“节能减排”基本国策。本文拟在研究OFDM技术原理、宽带功放失真特性和宽带功放模型的基础上,提出两种针对OFDM调制的自适应预失真算法。第一种算法是从时域出发,是基于分离算法的自适应预失真,该方案通过发送合理的测试序列,结合分离算法,分别提取出宽带功放的记忆特性和非线性特性,并且用两张查询表分别对记忆性失真和非线性失真进行矫正和自适应更新。该方案已用于课题组的实际项目中,效果明显:ACLR小于40dB,功放的功率效率可提升10%~15%。第二种算法,是基于OFDM信号的特性,提出来的一种新的频域预失真技术,作者已申请了国家专利。该技术,通过一张查询表模拟出宽带功放的记忆性和非线性特性,可以一次性对宽带功放的记忆性失真和非线性失真进行矫正,经仿真效果显著。该OFDM频域预失真方案,结构简单且实用,大大减少了系统的复杂性,节约了成本。故将两种预失真算法,用于宽带无线系统具有较大的研究意义。更多还原

【Abstract】 With users and business needs of the wireless communication system, limited spectrum will become increasingly crowded. Because the broadband communication technology has high spectrum efficiency, it has become one of the development trends of wireless communication. The OFDM technology has a variety of advantages, including anti-interference ability, high spectrum efficiency, high-capacity broadband communication support, etc. Since, it widely applied in wireless communication system. But OFDM has some huge disadvantages, one of which is high Peak-to-Average-Power Ratio problem. The PRAR of OFDM signal is high, making it particularly sensitive to non-linear amplifier and easy to produce nonlinear distortion. Because the broadband signal is the one transmitted in the broadband wireless communication system, the memory of broadband amplifier distortion can not be ignored. Currently, the research on nonlinear distortion and memory distortion of broadband power while maintaining its linear amplification range, has become one of the hotspots of broadband linear amplifier.In order to solve the non-linear broadband amplifier and memory distortion, better application of OFDM technology to the broadband wireless communication system, while improving the efficiency of the power amplifier in response to the country’s national policy. This paper studies the basic OFDM technology, broadband power amplifier distortion characteristics and broadband amplifier model, and proposes two adaptive pre-distortion algorithms for OFDM modulation. The first technical solution is to be separated from the time domain adaptive pre-distortion algorithm. The program extracts the memory and non-linear characteristics of broadband amplifier by sending a reasonable test sequence and separating algorithm. It uses two lookup tables for memory and non-linear distortion correction and adaptive update respectively. The program has been used in the actual project. Its effect is obvious. ACLR is less than 40 d B, and power amplifier efficiency has been increased by 10% to 15%. The second technical solution is a new frequency-domain pre-distortion technology, which is based on the characteristics of signal of OFDM. Currently the program has applied for a national patent. By using a lookup table simulates nonlinear and memory characteristics of broadband power amplifier, which can redress the distortion from nonlinear and memory of broadband amplifier. The simulation results are obvious. The frequency domain OFDM pre-distortion scheme, the structure of which is simple and practical, can facilitate the improvement of the whole star power amplifier efficiency. Furthermore, it can reduce the complexity of the system and save cost. So, it is significant to research on the application of the two schemes to the broadband wireless communication system.更多还原