On the basis of high speed hybrid filter banks adc system , a kind of downsampler model based on bandpass sampling theorem is presented , and analyzed , proved in time and frequency domain , in addition a downsampler is designed according to the model . a class of high effective hybrid filter banks adc system which bases on the downsampler and radio frequency spectrum is proposed , of which digital signal rate falls m times as fast as the former 作者提出了一种基于带通采样定理的抽取器数学模型，对该数学模型进行了时域、频域的分析证明后，设计了一种基于该数学模型的抽取器，进而根据无线电射频信号频谱的特点，提出了高效混合滤波器组adc系统，其数字信号输出速率比高速混合滤波器组adc系统降低m - 1倍。
Abstract : it is the first time to use powder damping technique in reducing the vibration and noise of cold saw clamp . through measurement and analysls of the noise reduction effects and frequency spectrum , it is found that powder damping is a simple and practical technique , and influences on the strength and natural characteristics of the clamp are small 文摘:把粉体阻尼技术首次用于冷锯机夹盘的减振降噪，通过对其降噪效果及频谱的测量分析，发现粉体阻尼不但是一种简单实用的技术而且对夹盘的强度和固有特性影响小。
Chaotic switching signal obtained from chua ' s circuit was used to control buck dc / dc converter . by compared the power spectrum of input current between chaotic modulations and classical pwm , it demonstrate that chaotic switching modulations have good effect on spreading power spectrum , which can be used to reduce the level of emi and to improve emc of smps 通过对四种混沌调制模式下变换器输入电流与周期pwm模式下输入电流频谱的分析比较表明，混沌调制技术在扩展频谱方面有良好的效果，可以用于降低开关模式电源的电磁干扰( emi )水平，改善电磁兼容性( emc ) 。
In recent years , the worldwide researchers pay much attention to fourier telescopy . it is an active imaging technique that encodes the information in the temporal instead of spatial domain , then receives the speckle and deposed of it to reconstruction the object image . now , the high - resolution technique is under the condition of deeply researched 它是一种主动式干涉成像技术,这一技术通过时域内的相位的调制完成直线条纹对目标的扫描,从而达到对深空目标频谱的抽样,然后接收其散射回波,对回波信号进行处理,进而还原出目标的像。
The refinements made to the original methodology are based upon not only the abroad new research about noise evaluation , but also upon the thought of the domestic base of current noise evaluation . the procedure involves not only considering the noise sound pressure level , but also considering the speech interference level and noise spectrum balance problems , which offer enough information about building noise environment for engineer and owner 该评价方法借鉴了国外在噪声评价方面最新的研究成果，同时也考虑了国内目前的噪声评价状况，该方法不仅仅考虑了噪声声压级一个因素，同时还考虑了语言干扰级，以及噪声频谱的平衡性等问题，给工程人员以及建筑业主提供了建筑声环境方面充足的信息，这是很有意义的。
The emphasis of the thesis is base - band signal shaping and programmable interpolation algorithm . we introduce the basic theory of base - band signal shaping , and the effect of the digitizing of the ideal raised cosine rollof signal g ( t ) is attentioned . the shaping filter parameters are determined based on the system specifications , and the simulation results are given 首先从降低邻近码间干扰原则出发,讨论了基带成形的基本原理与升余弦滚降滤波器的时频特性,重点分析将理想的滚降波形g ( t )数字化后对频谱的影响,并且根据系统指标,确定了各项参数,给出了具体的设计举例和仿真结果。
At last , the evolution of gaussian pulse ’ s shape and spectrum in single - mode fiber with the existing of both the self phase modulation and the second - order dispersion is researched on the setting of coherent light array . on the basis of that , some conditions which should be met by the single - mode fiber used in the coherent light array system are given out 本文最后结合脉冲光相干合成的应用背景,对自相位调制和二阶色散共同作用下的高斯脉冲的演变过程进行了分析,并从相干并束所需要的脉冲波形和频谱的一致性出发,对相干并束系统中应用的单模光纤提出了要求。
In this paper the main work includes the analysis of the rotation of special angles , the range of rotation angles in cordic algorithm ; analysis on what condition should be fulfilled to reach any target angle ; analysis and simulation on error band and output spectrum ; imple - mentation of the architecture on fpga device 我所做的只是很小一部分,主要包括对cordic算法中特殊角的旋转和旋转角度范围;在何种条件下可以达到任意角度的分析;对许多问题比如误差上限和输出频谱的计算机仿真;这种结构在fpga器件上的实现。
But they have the disadvantages such as poor complexity , poor security and insufficient amount of sequence numbers among the family of codes , the chaotic signals have noise ? ike , broadband frequency spectrum , they can be used as spreading codes , furthermore , chaos system is extremely sensitive on initial conditions so that the various initial conditions given by chaos system can provide with large sum of spreading sequences and this can meet the demand of cdma , this thesis sets out to study on using chaos system to generate spreading sequence s , there are two parts is this paper : firstly , we study the basic theory of spread ? pectrum communication and the characteristics of chaos so as to prove the applicability of chaos system to be used in spread ? pectrum ii communication system 现在使用的扩频码有m序列， gold码和r - s码等，这些扩频码具有良好的随机性，但普遍存在着复杂度低、保密性差以及同一码族序列数目少等缺点。混沌信号具有类似噪声、宽带连续频谱的特征，正符合扩频通信中对扩频码的要求，而且混沌系统对初始值极其敏感，可以通过给混沌系统赋予不同的初始值得到为数众多、不相关的扩频序列，这正好满足码分多址的要求。本文对利用混沌系统应用于扩频通信作了一些研究工作，主要包括两部分：第一部分：探讨了扩频通信的基本理论和混沌的基本特性，说明将混沌系统应用于扩频通信系统的可行性。
