频率调制

From the view of increasing diffraction efficiency, the interaction between Gaussian beam and acoustic wave is experimentally studied.

实验测量了调制频率变化对声光调制器衍射效率的影响，并用波矢量匹配的概念对测量结果进行了分析。

By means of a linear array CCD lightintensity distribution measuring system, via the variation of the frequency and the power of ultrasonic wave, the direction control and the intensity modulation for the laser beam can be carried out. The relation curve between acoustooptic deflexion and modulation measurement is given.

在实验中，应用线阵CCD光强分布测量仪等，通过改变超声波的频率和功率，分别实现了对激光束方向的控制和强度的调制；定量给出了声光偏转量的关系曲线和声光调制测量的关系曲线。

The experimental results show that in the case of surface temperature of about 700 K,the energy conversion efficiency is about 5.58% in the spectrum range of 1.3-14.5 μm.

实验结果表明，该光源在表面温度约700 K时，1.3-14.5 μm波长内的能量转换效率约为5.58%，光源的调制频率在50%的调制深度下接近40 Hz。

The sending end when the use of pulse modulation approach will be a binary digital signal into a frequency modulation of the pulse sequence, and driver fired infrared tube to the form of light pulses sent receiver will receive the pulse of light conversion to electrical signals , and then, after amplification, filtering and other treatment to the demodulation circuit after demodulation, reduced to a binary digital signal after the output.

发送端采用脉时调制方式，将二进制数字信号调制成某一频率的脉冲序列，并驱动红外发射管以光脉冲的形式发送出去；接收端将接收到的光脉转换成电信号，再经过放大、滤波等处理后送给解调电路进行解调，还原为二进制数字信号后输出。

The method of multilevel parallel phase modulation was proposed, which means two parallel multilevel phase shift keying signals were transmitted with one frequency at the same symbol period.

提出了高阶并行相位调制的方法，即在同一调制符号周期，使用同一频率、并行发送2路携带不同信息的高阶相位调制信号。

Carrier suppression double sideband optical signal with 40 GHz repetitive frequency is generated by using an optical phase modulator along with optical filtering technique.

在中心站采用相位调制器结合滤波的方法产生重复频率为40 GHz的载波抑制双边带毫米波信号，利用交叉复用器分离开毫米波信号的上下边带，其中的一个边带强度调制数据速率为2.5 Gbit/s的下行基带信号，另一个边带被发送到基站调制上行传输的基带数据。

In one where the modulating signal is applied across a varactor to vary the oscillator frequency , the deviation produced is a function of the modulating signal amplitude only.

在直接FM调制器中（也就是，调制信号加到变容二极管上来改变振荡频率），产生的频偏只是调制信号幅度的函数。

The FLL+ features digital frequency locked loop hardware that, in conjunction with a digital modulator, stabilizes the DCO frequency to a programmable multiple of the watch crystal frequency.

FLL+以数字式频率，与一个数字式调制器一道，稳定DCO频率对表面皿频率的一个可编程序的倍数的被锁的圈硬件为特色。

But there was no current modulate circuit for TDLAS system.The design of modulation circuit for tunable diode laser based on DDS has been introduced.The main idea of design is using MCU to control DDS and D/A chips,so we can get sine wave and saw tooth signals.

DDS器件采用高速数字电路和高速D/A转换技术，具备了频率转换时间短、频率分辨率高、频率稳定度高、输出信号频率和相位可快速程控切换等优点，可以实现对信号的全数字式调制。

Using upper sideband also allow the actual carrier frequency to be determined easily simply by adding the dial frequency to the audio modulation frequency.

使用上边带还允许实际载波频率确定仅仅通过增加拨号频率的音频调制频率容易。

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。