查询词典 frequency modulation

Absolute frequency stabilization of diode lasers of wavelength nm grade are reported using the modulation transfer method .

阐述了利用调节及转换技术稳定激光二极管发射器的频率，这种发射器可以发射纳米波长的激光。

An expression for acoustic wave amplitude as a function of modulation frequency and relaxation time has been derived.

推导了光声信号振幅与入射光调制频率和样品分子振动－平动弛豫时间的函数关系。

The common equation of the evolution of spectrum caused by selfphase modulationis presented, which is the convolution of action spectrum and chirped spectrum caused by selfphase modulation when carrier frequency is single.

给出了由自相位调制引起的频谱演变的普遍表示，即单载频脉冲的SPM引起的啁啾频谱与光源的频谱的卷积，通过数值计算给出从相干脉冲到非相干脉冲的频谱演变规律。

NTSC uses a quadrature amplitude modulation with a suppressed color carrier and works with amotion frequency of approximately 30 Hz. A picture consists of 525 lines.

NTSC的色彩载波使用接近4.9MHz或3.57MHz的频率，它使用颜色载波进行正交调幅，画面运动频率约为30Hz，每幅画面有525线。

The frequency of the amplitude modulation signal is adjusted until a maximum lamp voltage is detected.

调节调幅信号的频率，直至检测到最大的灯电压为止。

Not only it is expediently to realize frequency, phase and amplitude modulation, but also it has well practicability.

采用FPGA设计的信号发生器，不仅可方便地实现各种比较复杂的调频、调相和调幅功能，而且具有良好的实用性。

The impact of the thickness of volume H-PDLC grating on the wavelength selectivity of Bragg diffraction are simulated numerically, as well as the theoretic relationships among the refractive index modulation, spatial frequency and the H-PDLC diffraction efficiency.

计算机模拟了体光栅厚度对于布拉格衍射波长选择性的影响，以及折射率调制深度、空间频率和H-PDLC光栅衍射效率的关系。

In communications, the frequency range of the information bearing signals prior to combination with carrier wave by modulation.

在通信技术中，未经调制使之和载波结合之前，携带信息的信号所占有的频率范围。

Later, it makes some comparison with four kinds of modulation technique, and finally, it implements the three-level PWM switching power amplifier with the PWM technique. The power of the amplifier is 2kVA, and the frequency bandwidth is 10～3kHz. In the thesis, the author designs and makes the hardwares of the switching power amplifier. The hardwares contain power inverter rank circuit, control system circuit based on DSP, drive and isolation circuit, and protective circuit. The thesis also analyses the potential safety problems and put forward some solutions for the problems. Furthermore, the thesis accomplishes the software design of the control system, and successfully debugs it. The methods of designing higher power ampilfier are also discussed in the thesis. It analyses the feasibility of the methods, outlines the way of how to design higher power switching power amplifier, and does some experiments with the method of switches-parallelling.

根据电动振动试验系统对开关功放的要求，提出了以电感电流瞬时值控制技术为基础的三电平脉宽调制开关功放的设计方案，并通过系统仿真进行了原理性论证；然后设计并制作了开关功放的硬件，包括功率转换电路，基于DSP的控制电路，驱动、隔离电路以及保护电路；针对开关功放数学模型不易得出的特点，细致分析了模糊自适应PID控制方法，在此基础上编写了控制程序；研制出一台功率为2kVA，通频带为10～3kHz的三电平脉宽调制开关功放；论文中还探讨了实现大功率开关功放的方法，分析了各种方法的可行性，给出了实现大功率开关功放的思路，并进行了并联开关管实现大功率开关功放的实验。

Based on the time-frequency analysis (continuous wavelet transform and short time Fourier transform), the arithmetic uses the modulus maximum characteristic on the phase scale and carry frequency scale to recognize phase modulation rule of signal. So without whole wavelet coefficient the signal mathematics model can be obtained quickly. It provides well condition for application of arithmetic in practice.

该算法基于信号的时频分析（小波分析和短时傅里叶变换），利用小波变换的相位尺度和载波尺度的模极大值特征辨识信号的相位调制规律，因而在无需计算全部小波系数的情况下，可快速地获得信号的数学模型，为算法在实际中的应用提供了良好的条件。

Breath, muscle contraction of the buttocks; arch body, as far as possible to hold his head, right leg straight towards the ceiling (peg-leg knee in order to avoid muscle tension).

呼气，收缩臀部肌肉；拱起身体，尽量抬起头来，右腿伸直朝向天花板（膝微屈，以避免肌肉紧张）。

The cost of moving grain food products was unchanged from May, but year over year are up 8%.

粮食产品的运输费用与5月份相比没有变化，但却比去年同期高8％。