频率调制

This paper analyses the frequency characteristics of the gear meshing and the signals due to amplitude and frequency modulation.

本文分析了齿轮传动的频率特性和它所产生的频率和幅值调制信号。

It locks the frequency of the carrier-wave at 35MHz.The stabilization of the carrier-wave can be 4×10-5,the accuracy can be 3×10-5.The frequency modulation and the confection of the carrier-wave are realized by the capacity-changing diode V149 and the integration voltage-control oscillator MC1648 chip.The end power amplifier uses the audion 2SC1970 to make it work in the third magnifying state,it improves the efficiency of the magnifier and the power of the output reaches the design demand.

发射部分采用锁相环式频率合成器技术， MC145152和MC12022芯片组成锁相环，将载波频率精确锁定在35MHz，输出载波的稳定度达到4×10-5，准确度达到3×10-5，由变容二极管V149和集成压控振荡器芯片MC1648实现对载波的调频调制；末级功放选用三极管2SC1970，使其工作在丙类放大状态，提高了放大器的效率，输出功率达到设计要求。

The transmit part adopts the phase-locked loop pattern of frequency synthesizing technology and uses the MC145152 and MC12022 chips to compose the phase-locked loop.It locks the frequency of the carrier-wave at 35MHz.The stabilization of the carrier-wave can be 4×10-5,the accuracy can be 3×10-5.The frequency modulation and the confection of the carrier-wave are realized by the capacity-changing diode V149 and the integration voltage-control oscillator MC1648 chip.The end power amplifier uses the audion 2SC1970 to make it work in the third magnifying state,it improves the efficiency of the magnifier and the power of the output reaches the design demand.

发射部分采用锁相环式频率合成器技术， MC145152和MC12022芯片组成锁相环，将载波频率精确锁定在35MHz，输出载波的稳定度达到4×10-5，准确度达到3×10-5，由变容二极管V149和集成压控振荡器芯片MC1648实现对载波的调频调制；末级功放选用三极管2SC1970，使其工作在丙类放大状态，提高了放大器的效率，输出功率达到设计要求。

When signals under test are 单击此处编辑母版标题样式 weak, in order to realize signals transmission especially for long distance, direct current amplification or modulation and demodulation may be adopted.

传感器输出的电信号一般为较低频率分量(在直流至几十千赫兹之间)，当被测信号比较弱时，为了实现信号的传输尤其是远距离传输，的电信号一般为较低频率分量(在直流至几十千赫兹之间)，当被测信号比较弱时，为了实现信号的传输尤其是远距离传输，可，当被测信号比较弱时以采用直流放大或调制与解调。

The result of frequency response analysis shows that when the modulation frequency of incident radiation increases, the phenomenon that the response of detector lagging behind the variation of radiation becomes evident, the temperature variation range in pyroelectric thin film decreases, but the variation velocity increases, so the current resulting from pyroelectric effect increases.

频率响应分析表明：随着入射辐射调制频率的增大，可以观察到探测器响应的滞后现象越来越明显，热释电薄膜中的温度变化范围减小，但变化速率增大，因此探测器的热释电电流增大。

The experimental results show that the electron multiplication process significantly influences the system MTF, compared with non-EM, especially at high EM gain.

实验结果表明，与无倍增时相比，倍增对系统调制传递函数的影响很大，尤其是在高倍增增益时，在Nyquist频率处，调制传递函数平均下降达30%。

Spectral efficiency equations are derived for both systems with and without channel prediction. Numerical results show that systems with channel prediction can get maximum spectral efficiency while systems without channel prediction but chosen optimum packet length can get suboptimum frequency efficiency, which is inversely proportional to Doppler frequency.

推导了信道预测和没有信道预测的自适应调制系统的频谱效率公式，分析结果表明对于自适应调制系统，信道预测的系统频谱效率是最优的，非信道预测系统根据信道情况选择最优帧长可以获得该系统的最优系统频谱效率，但它是低于信道预测的频谱效率的，而且是随多普勒频率的增大而逐渐减小的。

The frequency of an unmodulated wave capable of being modulated or impressed with a second (information-carrying) signal.

未经调制的电磁波频率可以接受调制或加载第二信号。

The analysis of 3D noise indicates that the measurement is effective. Two MRC models of ICCD imaging system has been established based on system performance of energy and modulation transfer whose target is three-bar. One MRC model is under the condition of standard A lamp, and the other is under the condition of night photo-spectrum. Because the MRC models integrate sensitivity, noise, target spatial frequency, MTF and the performance of human eye all together, the MRC models can evaluate limit performance of photoelectric imaging system more roundly.

在系统能量传递特性和调制传递特性的基础上，以三条带图案为研究对象，从信号转换的角度出发，围绕每景象立体弧度角中ICCD的电子通量，建立了基于量子噪声和CCD噪声特性的微光ICCD成像系统MRC模型，MRC模型综合了系统灵敏度和噪声、目标空间频率、系统调制传递特性以及人眼视觉特性等因素，能更全面地反映光电成像系统的极限性能。

A form of modulation in which signals are pulsed directly on the transmission medium without frequency division.

基带 一种调制方式，信号在传输媒介上直接进行调制而不需要频率分解。

According to the clear water experiment, aeration performance of the new equipment is good with high total oxygen transfer coefficient and oxygen utilization ratio.

曝气设备的动力效率在叶轮转速为120rpm～150rpm时取得最大值，此时氧利用率和充氧能力也具有较高值。

The environmental stability of that world - including its crushing pressures and icy darkness - means that some of its most famous inhabitants have survived for eons as evolutionary throwbacks, their bodies undergoing little change.

稳定的海底环境─包括能把人压扁的压力和冰冷的黑暗─意谓海底某些最知名的栖居生物已以演化返祖的样态活了万世，形体几无变化。