查询词典 pulse-code modulation

Based on surveying the development of variable frequency power supply and analyzing its development tendency, and considering the practical features of the assignment, the conversion system is designed as follows: it selects the 3-phase Pulse Width Modulation Engine SA4828 as the PWM control signals generator; it chooses the single-chip-computer PIC16F877 as the microcontroller, which integrated the A/D modulation, which cuts down the complexity of the hardware system and strengthens the dependability of the system.

在论述和分析了变频电源及其控制技术发展的概况和趋势的基础上，结合本课题任务的实际要求，设计了一套中小功率的逆变电源。系统中PWM控制信号采用专用集成芯片SA4828生成，减轻了控制器的工作量也提高了系统的可靠性。控制器选用集成了A/D转换器的单片机，使得系统的硬件复杂性降低，提高了可靠性。

A system and method for providing overvoltage protection during a pulse width modulation dimming of a liquid crystal display backlight inverter are provided.

提供了一种系统和方法，用于在液晶显示器背光反向器的脉宽调制调光期间提供过压保护。

One of the most important issues of pulse position modulation for optical wireless communications is the receiver symbol synchronization subsystem, in this paper, the basic principle of symbol synchronization for PPM sequence is discussed, and the upper limit of exact synchronization probability for random PPM sequence is analyzed.

讨论了PPM序列的符号同步原理；在分析随机PPM序列的精确符号同步概率上限的基础上，给出了一种在PPM序列中插入同步信号来实现PPM精确符号同步的方案及其数字逻辑电路实现。

To detect the carrier signal in the background of strong interference, a Duffing chaotic oscillator was applied to the triple-state pulse position modulation signal detection.

为了检测在强干扰背景下的载波信号，提出了将 Duffing 混沌振子应用到三态脉冲位置调制信号检测中。

Digital signal processor; space-voltage vector pulse width modulation; pressure closed-loop control system

数字信号处理器；电压空间矢量脉宽调制；压力闭环控制系统

Inverter ; pulse width modulation/common-mode voltage ; control strategy

逆变器；脉宽调制/共模电压；控制策略

The results show the temporal pulse shape modulation is affected by the broadening factor and the delay time, as spectrum modulation is only affected by the delay time, and the intensity factor changes similarly with the cosine function of the phase factor.

研究结果表明，时间调制与基元脉冲的展宽量及相邻脉冲之间的延迟时间有关，光谱调制只与相邻脉冲之间的延迟时间有关，而强度的演化则与相位因子的余弦函数演化具有一定的相似性。

Single-phase Sinusoidal Pulse Width Modulation Inverter Power Supply in this paper belongs to AC power supply (AC-DC-AC convert). Control mode adopts feedback of voltage control. The methods of intermitting power flux and changing duty-cycle can change pulse width of drive voltage that adjust and rectify output voltage ultimately.

本文设计的单相脉宽调制逆变电源属于交流电源，采用电压反馈控制，通过中断功率通量和调节占空比的方法来改变驱动电压脉冲宽度来调整和稳定输出电压。

At first, this paper gives the brief introduction of the history and present status of accelerometer and its testing technology, the working principium and math model of the liquid floated pendu-lous accelerometer, and then, decides the binary width pulse force retrim loop as the design proposal of testing system, researches the transfer function of every part in the system emphasizly, analyses the stability of the whole accelerometer testing system from the angle of control theoretics by the open loop transfer function of system, and designed the correcting net, analyses the basal problems such as resolution, sampling restraint, precision and so on, designs the hardware testing circuits such as preamplification, band-pass filter, alternating amplifier, phase sensitive demodulatorn, pulse-width modulation, frequency scale circuit, moment current generator. Finally, using the graphics program language LabV-IEW which is designed for testing field especially by NI accomplishes the solfware design of testing system,realized the testing functions.

首先对加速度计及其测试技术的发展历史和现状，液浮摆式加速度计的工作原理和数学模型等作了简要的介绍，然后确定了以二元调宽脉冲再平衡测试回路为设计方案，并从控制理论的角度进行了分析，着重研究了系统中各部分的传递函数，利用系统开环传递函数分析了系统的稳定性，同时设计了系统的校正网络；分析了二元调宽脉冲再平衡测试回路的分辨率、采样约束以及测试精度等基本问题，并按照系统分析的结果设计了包括前置放大、带通滤波、交流放大、相敏解调、脉宽调制、频标电路以及力矩电流发生器等测试系统各部分硬件电路，验证了电路的正确性，最后按照测试系统的要求，采用了美国NI公司专为测试领域所开发的虚拟仪器工具——LabVIEW作为测试软件开发工具，利用该图形化编程语言完成了测试系统软件部分的设计，实现了测试功能。

In consideration of the in-pulse phase modulation and Doppler frequency rate-of-change's subtleness, a fast and accurate algorithm is proposed. The influence to parameter estimation with phase modulation is dismissed by time domain correlation between neighboring pulses. Signal noise ratio is increased by frequency domain accumulation.

该文针对信号脉内相位调制和多普勒频率变化率信息非常微弱的特点，提出了一种快速高精度估计算法，通过相邻脉冲间的时域相关消除了相位调制对参数估计的影响，频域积累增强了信噪比，利用脉冲间的相参特性进行频谱相关消除了相位模糊，并放大了多普勒频率变化率信息。

I didn't watch TV last night, because it .

昨晚我没有看电视，因为电视机坏了。

Since this year, in a lot of villages of Beijing, TV of elevator liquid crystal was removed.

今年以来，在北京的很多小区里，电梯液晶电视被撤了下来。