中文摘要：

在OFDM-CR系统中，感知用户过大的旁瓣会造成对主用户的干扰，必须抑制．主动干扰抑制方法（AIC ）抑制深度不够，且对OFDM符号的循环前缀（CP ）长度敏感．针对这一问题，本文提出了一种非正交的主动干扰抑制方法（NAIC ）：其干扰抵消子载波（CC ）主要插入在非正交的频率位置上，具有更好的旁瓣抑制效果．并将NAIC与加窗法结合（NAIC-win），进一步抑制感知用户的旁瓣和减小非正交CC带来的载波间干扰（ICI）．NAIC-win比AIC方法的抑制深度增加50dB ，而引入的ICI几乎可忽略．和EAIC-CP方法比，NAIC-win方法在使用更短的CP、更少CC子载波、更小的ICI条件下，得到更大的旁瓣抑制深度，提高了频带利用率，减小了计算量．理论分析与实验结果表明：NAIC-win方法在OFDM-CR系统旁瓣抑制中优于AIC ，EAIC-CP等方法．

英文摘要：

In OFDM based cognitive radio（CR） systems ,the large sidelobe of frequency spectrum of secondary users （SU） may cause severe interference to the primary user and the sidelobe spectrum must be suppressed .Active interference cancellation （AIC ） can′t null the spectrum deep enough and it is sensitive to the cyclic prefix （CP ） .In this paper ,a non-orthogonal AIC （NA-IC） technique is proposed for the sidelobe suppression of OFDM CRs .In NAIC ,cancellation carriers （CCs） are inserted at the loca-tions which are non-orthogonal to the subcarriers of the SU such that the sidelobe can be more significantly suppressed .Moreover , the windowing technique is used to reduce interference effects from non-orthogonal CCs （NAIC-win ） to SU and more deeply sup-press the sidelobe spectrum of SU .NAIC-win can obtain sidelobe suppression depth 50dB more than AIC with very little inter-carri-er interference （ICI ） .Compared to EAIC-CP ,NAIC-win can suppress the spectrum sidelobe deeper ,increase the spectrum efficien-cy ,and lower the computation burden with shorter CP ,less CC and ICI .Theoretical analysis and numerical simulations validate that NAIC-win method significantly outperforms the conventional AIC and EAIC-CP methods in sidelobe suppression for OFDM CR systems .