差频

本文对小质量X射线双星的准周期振荡的差频模型做了修正和补充。

Some corrections and improvements to the beat frequency model for the quasi-periodic oscillation phenomenon in X-rays binaries have been made in this paper .

参量阵扬声器是一种新型的声场定向设备，所发射的差频声场具有强指向性而被称为音频聚光灯。

Its beat frequency sound field has a strong directivity so be called the Audio Spotlight .

利用各向同性半导体晶体差频产生可调谐THz辐射的理论研究

Study of tunable terahertz-wave generation via difference frequency mixing in isotropic semiconductor crystals

XLPE电缆的差频检测技术研究

Study on the Difference Frequency Detecting Technique for XLPE Cable

设计了利用量子阱共线差频产生THz波的实验装置。

At last , the experimental setup of difference-frequency generation of THz-wave in asymmetric quantum well was designed .

当α较小时（α≤1），系统的收敛系统决定于步长μ和主输入的两个正弦波的差频Δf；

The system convergence performance is relative to both step size and frequency separation of the two sinusoidal signals as primary inputs when the α is small (α≤ 1 ) .

在利用非线性光学差频方法产生THz波的关键技术中，研制新型的差频泵浦源是最为重要的。

Among the key technologies of THz generation by the nonlinear optical difference frequency , developing novel difference frequency pumping sources is the most important .

差频Ronchi光栅的频谱特性与在图象处理中的应用

The spectral characteristics of a double frequency Ronchi grating and the application in image processing

讨论了在GaSe晶体和GaAs晶体中，利用CO2激光差频产生THz波的相位匹配问题。

Phase-matching problem in the generation of terahertz radiation via difference frequency mixing of CO2 laser lines in GaSe and GaAs crystals has been discussed in detail .

本文主要工作概述如下：1、针对差频信号为正弦信号模型的多目标检测问题，讨论了几种经典的基于DFT的频率估计算法，仿真并比较了它们的估计性能；

With respect to the multiple targets detection the beat signal of which is sinusoid , some classical frequency estimation methods based on DFT are discussed and their performance is compared .

PPLN晶体差频测量飞秒激光脉冲的载波包络相移

Measurement of carrier-envelope phase of few cycles Ti : sapphire laser by difference frequency technique

LFMCW雷达目标检测问题最终可归结为对差频信号的处理。

The problem of LFMCW radar target detection , in essential , is the beat signal processing .

第五章讨论了THz波的产生机理，并对切伦科夫型差频产生THz波进行了理论分析。

In chapter five , the generation principle of THz-wave is introduced . The generation of THz-wave using Cerenkov-type difference frequency generation ( DFG ) is also discussed theoretically .

通过与固定振荡频率的信号进行混频、低通滤波得到差频信号来反映油水浓度的变化。对具有近似平稳特征的低频信号建立ARMA预测模型；

The frequency signal is mixed with a fixed frequency signal , and goes through a low-pass filter . Then the approximate stationary low frequency signal is predicted using ARMA model ;

三次实验中差频信号的信噪比均优于20dB。

The beat frequency signal - to-noise ratios are better than 20 dB .

静止、匀速运动和加速运动三类目标分别对应着正弦信号、线性调频（LFM）信号和多项式相位信号（PPS）三种差频信号模型。

The beat signal model of the stationary , uniform motion and accelerated motion target is sinusoid , Linear Frequency-Modulated ( LFM ) signal and polynomial-phase signal ( PPS ) respectively .

基于PPLN光波导和频与差频级联型全光波长转换的研究

All-Optical Wavelength Conversion Based on the Cascaded Sum and Difference Frequency Generation in a Periodically Poled Lithium-Niobate Waveguide

在利用光学与光子学原理产生THz波的方法中，利用非线性光学差频的办法可以获得结构紧凑、低成本、室温运转、可调谐的THz波辐射源。

Among the methods based on optics and photonics , the method by using nonlinear optical difference frequency mixing could obtain compact , low-cost , room-temperature , and tunable THz radiation sources .

当各向同性固体板中传播的SH型板波模式包含两个频率成分时，板材的非线性将导致二阶和频及差频声波的发生。

Generation of second order sum frequency and difference frequency acoustic waves due to the bulk nonlinearity of the plate material will occur once SH plate modes propagating in an isotropic plate include two frequencies .

本文利用Nd∶YAG获取1.44μm激光，进行了理论研究、实验方案设计和实验结果分析；并对1.44μm激光在差频技术中的应用做了理论分析和研究。

In order to generate 1.44 μ rn with Nd : YAG , this paper has researched the basic theories , designed the experiment projects , analyzed the experiment results and introduced the application of 1.44 μ m laser in the DFG .

由于USAE信号和两束入射波非线性相互作用引起的差频波的存在，使得双频HIFU对共焦区组织的作用效果与常规单频HIFU有很大不同。

Due to existing the USAE signal and difference frequency signal brought by nonlinearity , dual-frequency HIFU has very different effect on the tissue of focal region compared with conventional single-frequency HIFU .

硬件部分给出了数字信号处理系统的原理图及PCB板图；软件部分根据探测系统对信号处理的要求，给出了数字信号的处理流程，完成了差频信号的采集、校正与FFT处理。

Schematic diagram and PCB figure of digital signal processing system are presented ; On the basis of the requirement of detection system , software gives the flow of digital signal processing . Different frequency signal is gathered , checked , disposed with FFT .

本文简略地叙述了低质量X射线双星中准周期振荡（QPO）现象的理论解释，对其中的差频模型（BFM）和它的一些发展作了较为详细的介绍。

The theory of Quasi-periodic Oscillation ( QPO ) in Low-mass X-ray Binaries ( LMXB ) is discussed in this paper . Beat-Frequency Models ( BFM ), including development , are presented in detail .

在运用改进的算法成像仿真，即对光外差探测后的差频信号用重拍WVD分布和Radon变换的方法来做时频分析对回波信号进行补偿。

After that , an improved arithmetic is proposed and in this arithmetic the echo signal is compensated through the time-frequency analysis of the detected beat signal , which is analyzed by retaking WVD distribution and radon transform .

方法二把差频处理后的传感器信号，送给单片机处理，研制了便携式QCM传感器频率检测仪，实现了传感器信号的采集、存储、液晶显示以及和计算机的串行通信。

Another processing way is to use the microchip to deal with the QCM sensor signals , and achieves sensor signal 's sampling 、 store 、 LCD display and serial communication with computers .

其中，差频晶体和差频波长的选择以及三波互作用的相位匹配等问题是非线性光学差频产生THz波的关键问题，应当着重考虑。

The choice of difference frequency crystal and wavelength as well as the phase-matching problem of the three-wave interaction are the key problems in the generation of THz wave via nonlinear optical difference frequency mixing , and it should be seriously considered .

在分析差频理论的基础上，得出转速转矩算法，并利用VC编程实现了计算机实时控制，对异步电动机在不同频率不同负载下的运行特性进行了实验研究。

Based on analyzing slip frequency theory , the torque speed control algorithm is obtained , and the computer real-time control has been realized by using the VC programming . The running characteristics of the asynchronous motor that it runs with different frequencies and different loads are researched by experiment .

对FBAR传感特性进行了测试和分析，在此基础上提出了一种双路计数差频方法采集处理FBAR质量传感信息的方法。

An in-depth analysis is made on FBAR tiny-mass sensor characteristics . Based on the analysis , we propose a dual-channel frequency difference counting method to acquire and process the information from FBAR tiny-mass sensor .

理论研究了利用剩余射线带色散补偿相位匹配原理，在Ⅲ-Ⅴ族和Ⅱ-Ⅳ族光学各向同性的半导体非线性晶体中差频产生可调谐THz波的可行性问题。

The tunable , coherent terahertz wave generation in a variety of isotropic semiconductor nonlinear crystals , such as ⅲ - ⅴ and ⅱ - ⅳ compounds , by difference frequency mixing is studied theoretically based on the theory of the cross-Reststrahlen band dispersion compensation phase-matching .

采取的方法是利用FFT得到FMCW雷达差频信号谱峰的粗略范围，再对这一范围进行频谱细化（Chirp-Z变换），从而实现频率（距离）高精度估计。

The method is getting the approximate range of frequency peak of FMCW radar 's beat frequency signal , using FFT . Then subdivide frequency in this range , by Chirp-Z transform . Thus we can get the high precision frequency estimation .