Spread spectrum technique , which can handle variable adverse environments , exhibits unique qualities that have a number of advantages in anti - jamming , anti - noise , reduction of multi - path interference , low power spectral density , privacy , selective addressing and code division multiplexing 扩频通信技术具有优越的抗干扰、抗噪音、抗多径衰落性能，能在低功率谱密度下工作，具保密性、可多址复用和任意选址，能有效克服各种恶劣的信道特性，目前广泛应用于移动通信、雷达、导航、测距、电力线通信等领域。
A cyclic radial shearing interferometer was used to diagnose the wavefront distortion of a laser system and an lcslm ( liquid crysnd spatial ligh modulator ) was used to control it . some results have been summarized as follows : l . according to the theory of scalar quanity diffeaction and the model of the random gaussian phase screen of low frequency wavefront , the effect of the low frequency wavefront with different rms gradient on the focal spot of a laser beam was studied 本论文在激光光束波前畸变检测和控制上进行了新的探索，主要就空间相位调制环路径向剪切干涉仪以及它对波前畸变的检测和液晶空间光调制器及其对中频段波前畸变的控制进行了研究，其研究的内容和取得的成果如下：一、根据标量衍射理论，结合低频波前畸变的高斯随机位相分布模型，研究了不同均方根梯度低频畸变波前对激光光束焦斑聚焦性的影响，并采用描述中频段波前畸变的功率谱密度概念，模拟计算了它对激光焦斑旁瓣的贡献。
We acquired the system ' s dynamic response when the satellite attitude was adjusted and the mode of the antenna . then modal analysis and dynamic analysis have been done to the satellite - antenna system by using the finite element analysis ( fea ) software of ansys . through the analysis we got the system ' s connatural characteristic , the amplitude - frequency characteristic of harmonic response , the power spectrum density of random vibration response , the maximal amplitude and resuming time of impact response 其次借助ansys有限元分析软件，对系统进行了模态分析和动力学响应分析，获得了不同天线结构参数下的卫星?天线系统的固有特性，简谐响应的幅频特性，随机振动响应的功率谱密度，以及冲击响应的最大幅值和恢复时间等。
