At last we introduce the realization of all the parts , the problem in the circuit design and the measured data . the results show that the designed system has met the requirement . in this dissertation , direct digital synthesis technology has been used in the phase - locked frequency synthesizer , which can make full use of the characteristics of direct digital synthesis technology such as flexible output wave shape and continuous 本课题将直接数字式合成技术用于锁相频率合成器中,该方法将直接数字合成的特点,如输出波形灵活且相位连续、频率稳定度高、输出频率分辨率高、频率转换速度快、输出相位噪声低、集成度高、功耗低、体积小等与锁相环路的频带宽、工作频率高、频谱质量好等优点有机的结合起来,从而在宽带的条件下实现了比较好的杂散性能和相噪。
In chapter 3 , we studied the effect of gaussian transverse profile for the driving and laser fields on lasing without population inversion ( lwi ) in a closed v - type system and an open v - type system . moreover , we discussed also the effect of the unsaturated gain coefficient , the cavity - damping rate , the ratio of the atomic injection rates and atomic exit rate on the corresponding systems . in chapter 4 , we mainly discussed the effect of doppler broadening on the gain , dispersion and the frequency up - conversion of the open v - type lwi system and compared the differences and the same between the open system and the corresponding closed system 发现： ( 1 )在考虑doppler展宽的情况下，通过选取合适的实验室条件(比如合适的原子环境温度等)可得到合适doppler展宽值，从而使系统获得最佳增益； ( 2 )要想实现系统的频率上转换，同时又要获得足够强的无反转激光增益，则系统频率转换比不能选取的太大； ( 3 )对于开放系统，比较小的粒子注入速率比与退出速率对产生无反转激光是有利硕士学位论文摘要的： （ 4 ）由于dopp1oy展宽的存在，当探测场与驱动场的传播方向相反时，增益在探测场失谐的某一段区域产生振荡，且振荡的振幅、频率失谐范围的大小与dopper展宽的取值有关。
Based on the dds technology , the waveform generator first stored data in high speed ram , then used dac to synthesize waveform by the data . many waveforms could then be generated easily . besides , the wave generator could get high performance on frequence resolution and stability , phase continuum , relative bandwidth etc . the dds technology was widely used in frequence synthesis field 基于dds技术的波形发生器以高速存储器作为波形数据查找表、通过高速d / a转换器对存储器的波形进行合成,可以灵活产生多种波形,同时具有频率分辨率高、频率稳定性好、频率转换快、相位连续性好以及相对带宽较宽等特点。
Its specifications show that the system have basically realized within the range of 2 ~ 12ghz : the phase noise is superior to - 72dbc / hz @ 10khz , spurious is superior to - 55dbc , harmonic restrain is superior to 30dbc , step is 10mhz , hopping time is 14 s . so the feasibility has been verified 测试结果表明系统在2 ~ 12ghz范围内基本实现了相位噪声优于- 72dbc / hz @ 10khz ,杂散抑制大于- 55dbc ,谐波抑制大于30dbc ,跳频间隔10mhz ,频率转换速度14 s ,验证了该方案的可行性。
At present , people usually use birefrigence and quasi - phase - matching methods to achieve higher effiency in the process of conversion . a significant advantage of quasi - phase - matching method is that the interaction is occurred through the largest element of the x ( 2 ) tensor ; the period of optical superlattice can be designed randomly , and any interaction can be matched without walk - off angle ; they are fitted to be used in frequency conversion of lower power especially . the quasi - phase - matching method has some advantages over birefrigence method , improving the efficiency of frequency conversion ; the range of frequency conversion covers its whole transperant wavelength 由于准相位匹配技术有其独特的优势，可以利用非线性光学晶体的最大二阶极化张量，如ppln 、 pplt 、 ppktp用的非线性极化张量都是d _ ( 33 ) ,其有效非线性系数高出普通非线性光学介质(如bbo 、 lbo 、 ktp )一个数量级，而且可以人为灵活设计调制周期，通过周期设计其频率变换范围可以覆盖准相位匹配介质的整个透明波段，选择无走离效应，解决了常规pm难以解决的问题，拓宽了非线性晶体的应用范围，极大地提高了频率转换效率，已成为非线性光学材料和固体激光器的研究热点之一。
