Since the envelope of modulated signal fluctuates , these methods generate unwanted intermodulation distortion ( imd ) products in a nonlinear radio frequency ( rf ) power amplifier ( pa ) . so it is necessary to use linearization technique to reduce the adjacent channel interference ( aci ) 但包络变化的调制信号经过非线性射频功放后会产生交调分量，因此必须采用线性化技术来减少由此产生的邻道干扰。
As far as linearity and efficiency are concerned , several techniques and theoretical analyses on linearity are extensively demonstrated . hybrid use of linear techniques and adaptation technologies in sdr are fully studied so that it can provides amplify with broadband , high efficiency and linearity . the paper presents a new scheme of an adaptive feedforward correction connected with a predistorter to amplify in sdr 在高效线性放大方面，广泛讨论了射频功放的几种线性化技术和非线性理论分析基础，深入研究了在软件无线电中组合使用线性化技术和自适应技术以保证宽带、高效率的线性放大，创新地提出了基于软件无线电宽带线性射频放大的预失真和自适应前馈线性技术结合的方案。
The rationale of the ofdm and the nonlinear effect of the power amplifier on the ofdm signals are presented in this paper , the principle of the adaptive digital predistortion is also introduced . on the basis of the rascal algorithm , this paper puts forward an improved algorithm that converges fast with low computing load and the related simulation . analysis on the quantity of the predistortion in the ofdm is also given 本文首先介绍了ofdm的基本原理以及功率放大器非线性对ofdm信号的影响；然后阐述了自适应数字预失真技术的基本原理，对其中使用的算法进行了分析和改进，使其在大幅节省资源的同时提高了收敛速度，并给出了相应的仿真结果；最后给出ofdm系统中关于预失真器设计的量化分析，并指出了今后线性化技术的发展趋势。
The nonlinear influence on multiple carriers signal , such as am / am and am / pm conversion , has been analyzed in this paper . some common linearization techniques , such as feedback , feed - forward and pre - distortion , have also been introduced and compared , which shows that feed - forward is the preferred linearization approach for application in this paper 本文分析了微波功率放大器的非线性特性，特别是am / am转换和am / pm转换对多载波信号的影响，也介绍了反馈、前馈、预失真等各种常用线性化技术的基本原理，并对它们的优缺点进行了比较总结。
