目前，扩频技术不仅在军事通信中被大量采用，而且还广泛运用于民用系统，这是由于扩频技术具有许多优越性，包括多址能力、隐蔽性好、抗多径干扰等优点，使其特别适合于无线移动通信环境。它最突出的优点是当扩频增益足够大时，扩频系统具有良好的抗干扰的能力。然而，扩频系统自身的干扰抑制能力总是有限的。在实际的扩频通信中存在着大量的干扰因素，若扩频增益不够大或扩频技术主要用于实现多址时，若不采用其他途径对窄带干扰和宽带干扰进行抑制，将会大大影响系统的性能，导致系统容量大幅度减少。 可见在扩频通信系统中，干扰抑制是一个很重要的问题，影响着整个系统的性能。所以必须采用专门的干扰抑制技术。本文介绍了直扩系统的发射端和接收端的系统框图，从数学原理方面描述了直扩系统的实现过程，同时，对于CDMA系统中采用的抗干扰自适应算法进行了详细的剖析，讨论了CDMA抗干扰常用的随机梯度下降算法、最小均方算法、归一化最小均方算法、直接判决算法、最小输出能量算法和Griffiths’算法。论述了这些算法的代价函数最小化问题，并对它们的收敛性作出了简单的分析。介绍了智能天线技术的发展现状，基本工作原理、接收准则。然后重点研究了DOA估计算法中的多重信号分类算法，旋转不变子空间算法和二维DOA估计算法等等。以上算法均详细论述了算法的原理，阵列模型，深入比较分析了各算法之间的性能差别。最后根据MVDR算法，提出了一个基于智能天线方面的改进算法。在干扰信号的导向矢量矩阵的零空间内，经过正交基矢量的线性组合，用最小二乘法求得最接近期望信号的导向矢量、并同时对各个干扰零陷的权值。本文研究手段是采用科学和工程计算语言MATLAB进行仿真实验。

Currently，Spread-Spectrum(SS) technique has been widely applied both in Military and in eivilian communications for its many advantages，which make it Suitable for the environments of wireless communication.The best advantage is its out standing ability to anti-jam if the processing gain is large enough.However，its ability of inter ference suppression is always limited.The system performance is dramatically degraded and its capaeity is largely reduced if the Processing gain is not sufficiently large and no other methods can be adopted to suppress strong interference. Therefore，interference suppression is crucial issue in SS systems. It is necessary to apply the special suppression techniques in new detection structures. In this paper the figures of sending end and receiving end of the direct sequence spread spectrum system are in troduced.Also it deseribes the realization process of DS-SS system from the maththeory.At the same time various adaptation algorithms used in CDMA system are discussed，such as SGD，LMS，NLMS，decision-direct algorithm，MOE and Griffthms，algorlthm.This paper over views some commnonly used cost function of the adaptation algorithms that minimize them and analyse convergence simply.this paper simply in troduces the emergence,development,basic working theory,characteristics and the merits of smart antenna.Then,the advanced algorithms of DOA estimation on this paper are the multiple signal classification method,esprition of signal paramenters via rotational invariance techniques algorithm and estimation of spatial two-dimension DOA. All of the methods above introduce the algorithms basic theory and array models,and by computer simulation, analyzing the validity and performance of this algorithm deeply.Finally according to the MVDR algorithm, propose one based on the smart antenna aspect improvement algorithm，which can greatly depress the interference, is proposed. within the null space of the steering vectors vectors matrix of interference signals, the weight vector which is closest to the steering vector of the expected signal and deeply depresses the interference signals simultaneously comed be obtained with least square method through the linear combination of orthogonal basis. Computer simulation is carried out to validate the above feasibilities by the research tool of the software MATLAB.