差频

As walk-off angle and acceptance angle of beam limit the conversion efficiency and the tunable wavelength range of difference frequency generation, research include effective nonlinear coefficient, walk-off angle and acceptance angle as functions of wavelength, the relationship between conversion efficiency and acceptance angle, and the impact of crystals length on the process of frequency conversion.

由于光束的走离角、允许角限制了转换效率和差频调谐波长范围，研究内容还涉及了有效非线性系数、走离角和允许角与波长的关系，转换效率与允许角的关系，以及晶体长度在频率变换过程中产生的影响。

This paper analyzes the LFMCW signal used in HF radar,then deduces the expression of its beat frequency phase which indicates physics meanings of quantities to be detected,and it supplies theoretical bases for detection methods.

就LFMCW信号在高频雷达中的应用作了具体分析，并导出了其差频相位的具体表达式，它表现出了要检测的各量的物理意义，对检测的方法提供了理论依据。

In the aspect of Opto—electrical signal processing, because the heterodyne interference signal is a high frequency fringe signal, how to measure the phases change of this signal——including the integer part of phases change over 2π and decimal part of phases change within 2π, is a difficult problem in electrical circuit technique.

一方面，该电路能同时测量出相位改变量的2π整数部分和2π以内的小数部分，从而实现了大量程和高精度的统一；另一方面，由于该电路是模拟电路，其最高工作频率可以远大于由数字集成电路组成的条纹计数电路，故在实际应用中，其工作频率的设计范围能够适应较宽的外差干涉差频范围，这就为高速激光外差干涉测量打下了基础。

The paper presents a new method for measuring magnetizing rate of weak magnetic material- differential frequency method.

本文介绍了一种测量弱磁性物质磁化率的新方法──差频法。

A simultaneous dual-wavelength continuous wave, quasi-cw or linearly polarized wave diode-end-pumped Nd:YAG laser operating at 1319nm and 1338nm is demonstrated. To the best of our knowledge, our experimental results achieve the highest level in the domestic domain. The simultaneous dual-wavelength laser provides an experimental basis for generating highly coherent THz wave radiation of 3.23THz by nonlinear optical difference frequency method.2. A diode-end-pumped Nd:YAG crystal, type-I critical phase matching LBO crystal intra-cavity frequency doubled, simultaneous multi-wavelength red laser at 659.5nm, 664nm and 669nm is firstly realized.

本论文主要围绕用于差频产生THz辐射源的多波长激光器及THz光子晶体的带隙特性分析而展开，论文的主要内容包括：一、从LD端面泵浦固体激光器的激光阈值公式出发，理论计算了腔镜对于两个波长的透过率关系，实现了LD端面泵浦Nd：YAG 1319nm/1338nm双波长激光连续、准连续及线偏振稳定输出。

Under the small-signal approximation, the effects of the waveguide length and the response flatness on DFG-based wavelength conversion are investigated by use of matrix operator, and then a feasible scheme to expand conversion bandwidth and pump bandwidth is proposed.

在小信号近似条件下，利用矩阵计算的方法分析了波导长度和转换效率的波动性对基于差频效应的波长转换器带宽的影响，给出了扩展信号光转换带宽和抽运带宽的优化设计方案。

An automatic balancing head employing permanent magnetic difference frequency motor is designed in the paper, to realize a non-contact transmission of control signal and driving energy between a control element and the balancing head.

李勇设计了使用永磁差频电动机的自动平衡头，实现了控制单元和平衡头之间控制信号和驱动能量的无接触传递。

An automatic balancing head employing permanent magnetic difference frequency motor is designed in the paper, to realize a non contact transmission of control signal and driving energy between a control element and the balancing head.

设计了使用永磁差频电动机的自动平衡头，实现了控制单元和平衡头之间控制信号和驱动能量的无接触传递。

Throughout the research on on-line monitoring system of power cable insulation, the working principle, systemic structure and procedure of data of on-line monitoringbased on the different frequency method is presented, and favorable principle foundation and practice experience are provided for on-line monitoring technology for cable insulation which can well apply into practice and safe, convenient and rapid obviating cable fault in power system.

本文通过对电力电缆绝缘在线监测系统的研究，提出了基于差频法的在线监测的工作原理、系统结构以及数据处理方案，从而为更好的实际运用电缆绝缘故障在线监测技术，为电力系统安全、方便、迅捷的排除电缆故障提供有利的理论依据和实际经验。

At first, setting up the arith relation between the signal input and the signal output of the generalized multi-carrier system of the Discrete Fourier Test spread-spectrum; then setting equilibria parameters of the frequency field equilibria subcarrier of the generalized multi-carrier system of the DFT spread-spectrum according to channel frequency response, channel noise variance and equilibria method; then calculating average power of useful signal, interferential average power between signals as well as noise variance of the generalized multi-carrier system receiving terminal of the DFT spread-spectrum according to the arith relation as well as the frequency field equilibria parameter, and recomputing available signal information noise ratio, so as to calculate the available signal information noise ratio of the generalized multi-carrier transmission system accurately, the method for estimating the available signal information noise ratio can be used for link self-adapting transmission solution of the generalized multi-carrier system based on Discrete Fourier Test spread-spectrum and radio material management.

一种DFT扩频的广义多载波系统的SINR估计方法，其通过首先建立所述离散傅立叶变换扩频的广义多载波传输系统的信号输入输出之间的数学关系，然后根据信道频率响应、信道噪声方差和均衡方法，设定所述DFT扩频的广义多载波传输系统的频域均衡子载波的均衡系数，再根据所述数学关系及所述频域均衡系数分别计算所述DFT扩频的广义多载波传输系统接收端有用信号的平均功率、信号间干扰的平均功率以及噪声方差，再计算有效信干噪比，如此以实现对广义多载波传输系统的有效信干噪比的准确计算，该有效信干噪比估计方法可用于基于离散傅立叶变换扩频的广义多载波传输系统的链路自适应传输方案和无线资源管理方面。

I am sure after a few weeks of adaptation and familiarization I will have no difficulty in functioning on a daily basis in an English speaking society or in participating fully in graduate studies.

在大学的三年的学习生活不仅给予我自身的充实，更重要的是磨练和培养了我较强的自觉能力和严谨，踏实的作风以及不怕困难的精神，对未来充满了信心！

As the first volcanoes erupted, one of the gases that bellowed out was steam.

在第一批火山喷发时，喷出的气体之一就是水蒸汽。