查询词典 frequency modulation

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 performances of noise jamming, pulse jamming, shift-frequency jamming, range pull off jamming on pulse compression radar signals are analyzed in this paper, which include the linear frequency modulation signal, the binary phase-coded signal and the compound signal of LFM and BC.

针对线性调频信号，二相编码信号以及由线性调频信号和二相编码信号构成的混合信号这几种脉冲压缩雷达信号，分析了噪声干扰、脉冲干扰、移频干扰和距离拖引干扰对它们的干扰性能，并给出了仿真模型和仿真结果

Optimal methods are also presented on system control methodology (current control and pulse frequency modulation) and frequency compensation.

根据研究结果提出系统在控制方法选择（电流控制和脉冲频率调制）和频率补偿方面的优化办法。

Abstrac t : The emissive frequency of the general frequency modulation broadcast transmitter is fixed.

一般的调频广播发射机，发射频率是固定的。

Differential modulation is also a widely used method to the case of no knowledge of the channels in the receiver. Here we propose noncoherent sequence detection for differential space-frequency modulation, which can be used to alleviate the error floor that occurs in a multipath channel with long time delay expansion.

在接收端不知道信道状态信息的情况下，差分调制也是一种被广泛采用的技术，论文提出了应用于差分空频调制的非相干序列检测方法，该方法通过积累多个符号上的信道信息来完成发送符号的检测，可以消除由于长的信道延迟扩展带来的误码平层。

Modulation offers the advantage of spreading out a frequency selective fading over many symbols, which effectively randomizes burst errors caused by fading or impulse noise, so that instead of several adjacent symbols being completely destroyed; many symbols are only slightly distorted.

modulation提供延长一频率有选择性退色的好处在许多标志，有效地随机化退色或脉冲噪声造成的猝发错误，因此而不是完全地被毁坏的几个毗邻标志；许多标志少许被变形。

Multi-carrier modulation offers the advantage of spreading out a frequency selective fading over many symbols, which effectively randomizes burst errors caused by fading or impulse noise, so that instead of several adjacent symbols being completely destroyed; many symbols are only slightly distorted.

多载体 modulation提供延长一频率有选择性退色的好处在许多标志，有效地随机化退色或脉冲噪声造成的猝发错误，因此而不是完全地被毁坏的几个毗邻标志；许多标志少许被变形。

The mathematical model and working modes of a novel three-phase two-arm three-level neutral-point-clamped pulse width modulation rectifier suitable for direct-driving wind power system are analyzed in detail, and the constant frequency control strategies based on space voltage vectors are proposed and applied to the rectification conversion of direct-driven power generation system.

系统分析了新型三相两桥臂三电平中性点箝位脉宽调制(pulse width modulation，PWM)整流器的数学模型和工作模式，提出了基于空间电压矢量的恒频控制策略，并将其应用于直驱风力发电系统整流变换中。

As thebiggest hydropower station of two-row placed units in the world, LijiaxiaHydropower Stationinstalled capacity 1600(4×400MWof Yellow River upstreamis the chief station for hump modulation and frequency modulation in northwest area.

李家峡水电站是目前世界上最大的双排机水电站，装机1600(4×400)MW，是西北电网中的骨干调频、调峰电厂。

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％。