查询词典 frequency band

An example of band-pass filter with center frequency in C band is given.

给出了一个中心频率在C波段的带通滤波器设计实例。

With internationally latest studies, the paper also proposes some biquadrate filters which are capable to perform the functions of second-order low pass、 high pass、 band pass、 band stop、 all pass filtering by selecting one of the three inputs or their proper combinations from the same configuration, furthermore whose natural frequency and the quality factor can be tuned independently. Then a continuous-time biquadratic filter using CCCII is proposed, which can be used in hearing aids and in other analog signal processing applications. Lastly a current mode and a voltage mode novel n-order filters of multifunction are presented. Not all both of the n-order filters are electronic tunable,but also they are integrated conveniently and compatible with VLSI technology.

尽量的全面归纳以电流控制传送器为有源器件的有源网络模拟电路、模拟信号处理电路，借鉴国内外最新研究成果，提出两种基于CCCⅡ的双二阶滤波器，这些电路在不需要改变电路结构的情况下，能同时实现低通、高通、带通、带阻或全通多种滤波功能，并且滤波器的特征频率ω_0和品质因数Q可实现独立调节；其中一种基于CCCⅡ的双二阶滤波器，首次提出将CCCⅡ应用于可编程助听器领域；最后设计了两种高阶滤波器，电压模式和电流模式各一种，这两种滤波电路均能实现多种滤波功能，能实现滤波器参数的电调谐，具有易于集成等优点。

For every ULA, the wide-band signals are sampled in spatial and temporal, then 2-D discrete Fourier transform is carried out. A projection operation on 2-D representation of wide-band signals is applied in the spatial-temporal frequency domain. The direction cosine relative to the ULA axes is estimated by MUSIC algorithm.

该方法采用3个共面的均匀线阵，每一均匀线阵对宽带信号空间采样，然后进行空时二维DFT变换，在空时频率域对宽带信号进行投影变换，用MUSIC算法实现宽带来波信号方向余弦的估计。

The impedance ratio and the meander could control the frequency of the second harmonic and the baseband ratio. According to that,we analyze several kinds of stepped impeedance resonator and use them to design the dual-band bandpass filters.In the thsis , The proposed bandpass filters and dual-band bandpass filters are designed for IEEE 802.11a/b wireless communicatuon system.

双频带带通滤波器是利用步阶阻抗谐振器之阻抗比与传输线之折线，可用来控制第二次谐波的频率与基频通带的比值，藉由改变阻抗比，来求得所要的第二次谐波，利用此特性，其中分析了几种不同形式的步阶阻抗谐振器，皆可用来设计双频带带通滤波器，带通滤波器与双频带带通滤波器是针对IEEE80211a与IEEE802.11b无线区域网路所设计。

On the basis of Raman and FTIR spectra research on melt structure and water solubility mechanism in albite glasses, we can make the following conclusions:(1) Higher pressure (1bar-2. 0GPa) can lead to below frequency region (50-650cm〓) shift to higher frequency and become narrower, and result in high frequency region (850-1300cm〓) move to lower wave number and become narrower at the same time. These are consistent with the decrease of average T-O-T angle and distribution scope of bond angles (0). In addition, the intensity of 580cm〓 band decrease with increase of pressure and the changes are obvious while pressure is in the range of 0.8-1. 0GPa. And these result from the"collapse"of the planar three membered -containing rings within the glass structure.

通过对高温高压下钠长石熔体结构及水在钠长石熔体中溶解机制的Raman和FTIR光谱实验研究，可以得出以下结论：(1)随着压力升高(1bar-2.0GPa)NaAlSi〓O〓熔体玻璃Raman光谱的低频区(50-650cm〓)不断变窄并向高频方向移动，同时高频区(850-1300cm〓)不断变窄且向低频区方向移动，这表明随着压力升高T-O-T键角不断减小，并且分布范围变窄，T-O-T键角这种变化从而可使T-O键的力常数减小，导致键强减弱；另外，580cm〓谱峰强度随着压力升高不断减弱，并在0.8-1.0GPa时最为显著，这是由于在0.8-1.0GPa时包含的平面三元环结构的"垮塌"造成的。

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。

It is indicated that: 1 at evidence level of 0.01, the chaffs dynamic RCS presents chi-square distribution at S-band and X-band; 2 the density of chaff cloud would decrease with time, which will result in lower RCS; and 3 with increasing of frequency and decreasing of wavelength, the coherence effect between different chaffs would get less, which will result in weaker fluctuation.

结果表明，当显著性水平为0.01时，该箔条云在S波段和X波段的动态RCS服从χ^2分布；箔条云形成之后，箔条密度随着时间的推移而下降，导致其RCS减小；随着频率升高而波长减小，箔条间互耦效应将减小，箔条云RCS的起伏也将减小。

A design and implementation method of the high speed modulation system, which adopted the new techniques of the FPGA and DAC based communication system,is presented in this paper. The effect of the key techniques of this system, such as the high speed digital signal processing for modulation, high speed based-band signal conversion, wide-band modulation, carrier suppression, high frequency and high precision system clock generation, is analyzed, and the solutions and performance analysis is also given. Finally, a high speed modulation system for space applications is implemented, can be used for high speed data transmission with QPSK, 8PSK, QAM or other kinds of digital modulation.

本论文依据正交调制原理，采用基于FPGA和DAC的设计技术，提出了一种高速、灵活的调制系统的设计方法，重点分析了系统组成的调制编码映射、基带脉冲信号转换、信号滤波、调制、系统时钟产生等关键技术环节的影响，解决了高速调制信号处理、高速数据转换、宽带调制、载波抑制、高频率高精度系统时钟的产生等关键技术问题，完成了一种适用于空间应用的高传输速率、多进制数字调制方式和调制体制灵活的数据传输调制系统的设计与实现，可在硬件设计不变的情况下，实现QPSK、8PSK和16QAM等多种调制方式的高速数据传输，QPSK调制速率达到500Mbps。

Refining a variety of high-frequency plastic welding machines, high-frequency fusing machine, high-frequency metal heat treatment machines, wide-band ultrasonic machine, blister sealing machine, heat shrink packaging machine and other packaging equipment!

精制各种高周波塑胶熔接机，高周波熔断机，高周波金属热处理机，全频段超声波机，吸塑封口机，热收缩包装机等各种包装设备！

Time-frequency analysis method is an effective method of identifying the narrow-band interference in the wide-band spread spectrum signal.

时频分析是识别宽带扩频信号中窄带干扰的有效方法。

On the other hand, the more important thing is because the urban housing is a kind of heterogeneity products.

另一方面，更重要的是由于城市住房是一种异质性产品。

Climate histogram is the fall that collects place measure calm value, cent serves as cross axle for a few equal interval, the area that the frequency that the value appears according to place is accumulated and becomes will be determined inside each interval, discharge the graph that rise with post, also be called histogram.

气候直方图是将所收集的降水量测定值，分为几个相等的区间作为横轴，并将各区间内所测定值依所出现的次数累积而成的面积，用柱子排起来的图形，也叫做柱状图。