查询词典 frequency bandwidth

One high-speed buffer circuit is added to the volume potentiometer to eliminate its influence on frequency bandwidth of the bridge circuit.

1，在音量电位器后增加一级高速缓冲电路，杜绝由于音量电位器对后级电路的频率带宽影响，音量控制方式使用并联型，有效提升音质，也降低了对电位器的要求，降低成本。

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。

Experiment results show that equiangular spiral antenna basked EBG structure has a wider frequency bandwidth, higher gain, and larger front-to-back ratio than a traditional spiral antenna with ground plate; and also the thickness of antenna is reduced obviously.

实验结果表明，背衬EBG材料的等角螺蜷天线与传统的带反射板的等角螺蜷天线（辐射器离反射板的高度为λ／4）相比能够同时提高增益、展宽带宽、改善前后辐射比，并且显著减薄天线的厚度。

The definition and transformation relationship of natural frequency, bandwidth fre quency and dualˉten index frequency were studied.

文中研究了转台自然频率、带宽频率和双十指标频带的定义与相互转换关系。

The main content of this dissertation includes: 1. Research on the theory of ultrasonic power supply, introduce its development process. On the basis of these, fix on the scheme of medical ultrasonic low-power supply. 2. According to the principle of modularized design, divide medical ultrasonic low-power supply into four parts. They are power amplify circuit, power control circuit, frequency automatic tracking circuit and matching circuit. Separately research on their theories and design their circuits and necessary programs, especially, effectively resolve the problem tracking the supersonic vibration system with a narrow syntony frequency bandwidth and a high swing. 3. The matching experiments gain good result, and prove that medical ultrasonic low-power supply is entirely up to the mustard on intellectualization, wide band of working frequency, steady output and high efficiency.

本文工作的主要内容包括： 1、研究了超声功率电源的原理，并回顾了它的发展过程，在此基础之上确定本文医用小功率超声电源的设计方案； 2、按照模块化的设计原则，将医用小功率超声电源的设计分解为功率放大电路、功率控制电路、频率自动跟踪电路和匹配电路等四个部分，分别研究了各部分的原理，在此基础之上进行了具体的电路设计和程序设计，尤其是有效地解决了对谐振频率带宽窄振幅高的超声振动系统的频率跟踪问题； 3、通过与超声振动系统的各项配合实验，取得了很好的实验结果，验证了医用小功率超声电源完全满足智能化、工作频带宽、输出功率稳定、输出效率高的设计要求。

Ricker wavelet whose predominant frequency is 200Hz was chosen as the exciting wave, and the character parameters (predominant amplitude, predominant frequency and frequency bandwidth) of its reflected wave were calculated.

选择主频为200Hz的雷克子波，理论计算原始地震反射波的特征参数（主振幅、主频率、频带宽度）。

This compensation circuit can make the stability of the LDO linear regulator undependent on the effect of load capacitor's equivalent serial resistance, and it also makes the unit gain frequency bandwidth change slightly when the load is varying, thus greatly improving the performance of transient response, Furthermore, on the basis of dynamic frequency compensation, an overcurrent protection circuit is designed.

文章针对LDO稳定性的问题，提出了一种内部动态频率补偿电路，使LDO线性稳压器的稳定性不受负载电容的等效串联电阻的影响，其单位增益带宽也不随负载电流变化而改变，大大提高了瞬态响应特性；采用Hynix 0.5μm CMOS工艺模型对电路进行仿真；此外，该电路在实现动态频率补偿的基础上又加入了系统的过流保护功能，当负载电流大于限制电流时，LDO不能正常工作；当负载电流小于限制电流时，又自动恢复到正常工作状态。

In wireless broadband digital communication, Inter-Symbol Interference caused by time disperse of radio channel is one of main factors that limit bandwidth of communicated information and system performance of communication. In receiver, Orthogonal Frequency Division Multiplexing system can easily cancel ISI and equalize frequency-selective fadings that are both caused by time disperse of radio channel.

在这一系统中，无线信道时延扩展引起的符号间干扰是限制传输性能和信息速率的主要因素之一；而在消除符号间干扰和均衡由无线信道时延扩展引起的频率选择性衰落方面，正交频分复用(Orthogonal Frequency Division Multiplexing，OFDM)技术具有明显优势。

At last, the frequency spectrum analysis shows that the four-winged chaotic attractor has extremely wide frequency bandwidth compared with that of the Lorenz system and Chua circuit, which is important in practical applications in communication encryption etc.

最后，通过比较该四翼混沌吸引子的系统、Lorenz系统、Chua氏电路等混沌信号的频谱发现，四翼混沌吸引子的系统信号具有极宽的频谱带宽，该特性在通讯加密等工程应用中具有重要价值。

Pseudo-random multi-frequency signal is invented and named by academician He Jishan. The bandwidth of PRMF signal is controllable, it's energy concentrates on several frequencies, which are equally spaced on log scale coordinates. It is ideal excitation source for electrical exploration.

中文题名伪随机多频电磁法观测系统研究副题名外文题名 The study on pseudo-random multi-frequency electromagnetic prospecting system 论文作者陈儒军导师何继善学科专业地球探测与信息技术研究领域\研究方向学位级别博士学位授予单位中南大学学位授予日期2003 论文页码总数165页关键词电法勘探电磁法伪随机多频信号馆藏号BSLW /2003 /P631.3 /4 伪随机多频信号由何继善院士发明和命名，该信号带宽可控，其能量集中在数个在对数坐标上呈等间距分布的频率上，是电法勘探的理想场源。

Graf, without question, is the greatest women's player in history.

格拉芙，现在，毫无疑问是女子网坛历史上最伟大的选手。

If not, you will have to look around at all your important data.

如果没有，您将需要检查所有的重要数据。