查询词典 frequency bandwidth

This article first antenna, microstrip theory, the circular polarization technology, the theoretical discussion, in this based on the microstrip antenna of circular polarization method - corner square microstrip antenna, and has done a design simulation , and then do the design and further research to improve and eventually get a resonant frequency (S11 reflection coefficient corresponding to the minimum frequency) for the 1.5GHz and 1.43GHz, the frequency of circular polarization for the 1.46GHz, S11 is less than -10dB relative bandwidth, the VSWR is less than 2 is about 8.8% relative bandwidth, axial ratio less than 3dB relative bandwidth of about 2.2% of the right circular polarization microstrip antenna design case, which proved very good the circular polarization microstrip antenna theory, also fully confirmed by a square corner design is a practical program, and select the appropriate regulation of sticks is indeed able to improve the performance of the antenna.

本文先对天线、微带理论、圆极化技术等进行了理论论述，在此基础上，提出圆极化微带天线的实现方法——切角方形微带天线，并对此做了设计仿真，后又对这一设计方案做了改进及进一步研究，最终得到一个谐振频率（反射系数S11 的最小值所对应的频率）为1.5GHz和1.43GHz，圆极化频率为1.46GHz，S11 小于-10dB 的相对带宽、驻波比小于2 的相对带宽约为8.8%，轴比小于3dB 的相对带宽约为2.2%的右旋圆极化微带天线的设计案例，从而很好的印证了圆极化微带天线理论，也充分证实了切角方形是一种切实可行的设计方案，而选取合适的调节枝则确能提高天线的性能。

Today, the resources of frequency bandwidth become more and more exiguous because of the high-speed development.

随着通信技术的高速发展，频率资源变得愈加宝贵。

A comparison of the communication frequency bandwidth and the calculated MUF have been made.

本文首先简要介绍了1985年12月至1986年3月南极长城站与新乡的短波通信效果，可通信的时段与频段，并将频段与计算的MUF进行了比较。

It is found that the upper limit of the operational frequency bandwidth along the short great circle path which crosses the south-polar, region is approximately in accord with the calculated MUF and the other one along the long great circle path which crosses the north- polar region is different from the calculated MUF.

结果表明，经过南极区的短大圆路径的通信频段上限与计算的MUF基本相符；经过北极的长大圆路径的通信频段上限与计算的MUF有偏差。

When the nonlinear layer which has weak nonlinearity is thin and far away from the seismic source which be low energy, compared with the corresponding results in linear antis, the medium nonlinearity produces abort 1/10~1/4 and 1/10~1/3 differences of instantaneous dominant frequency aid bandwidth. These instantaneous feature differences of seismic waves induced by the nonlinearity of media become weaker and weaker with the decrease of source energy. However, with the increase of the wave travel path within the mummer layer, the nonlinear accumulation effect could still keep such phenomena as the waveform distortion and instantaneous dominant frequency and bandwidth variations in records.

在本文给定的弱非线性介质中（非线性炽较薄且远离震源），在震源能量较低的情况下，介质的非线性效应会造成地震波瞬时主频和频宽相对于线性介质情况分别为1/10~1/14和1/10~1/3左右的变化量此外，随着入射波能量的下降，介质非线性所造成的地震波瞬时特征的变化量减小，但随着地震波在穿越非线性介质时路径的加长，非线性作用的累积效应使得波形畸变和频率分布特征的变化等现象得以维持。

In order to widen the frequency bandwidth of piezoelectric vibration based generator, the structure with multi-beams and single mass is designed.

本文针对压电式振动发电机频带宽度过窄的问题，设计了多悬臂梁-单质量块结构的微型压电式振动发电机。

The echolocation signals of Rhinolophidae and Hipposideridae are both long CF-FM with 1 harmonic and narrow FM bandwidth. But Rhinolophidae has longer duration, higher duty cycle and lower dominant frequency than Hipposideridae. All the echolocation signals of Vespertilionidae are short FM with 2-6 harmonics and wide FM bandwidth. Vespertilionidae has shorter duration and lower duty cycle than the other two families. There are obvious differences in dominant frequency between different species in this family.

菊头蝠科和蹄蝠科回声定位信号均为长CF-FM型，一般具有1个谐波，调频带很窄，但菊头蝠科的持续时间和能率环明显高于蹄蝠科，蹄蝠科能量最大处频率高于菊头蝠科；蝙蝠科回声定位信号均为短FM型，具有2～6个谐波，持续时间和能率环比其他两科低，调频带很宽，能量最大处频率在种间变化较大。

In this paper, based on a pill-box window model with a conical-shaped alumina ceramic and Ansoft HFSS software, the relation of VSWR with various electrical parameters in the window is simulated; the effects of variations of the output window structure on electrical field intensity, microwave power flow and quantity of heat are analyzed; the electrical characteristics of frequency bandwidth, power capability and heat dissipation for the pill-box window with conical-shaped or disk alumina ceramic are discussed, which shows that, with a rational structure of the window with conical-shaped alumina ceramic, the output capability of microwave peak and average power may greatly be increased, the secondary electron emission may effectively be suppressed, and heat dissipation may become more uniform and be easier for cooling.

本文在前人工作的基础上，基于圆锥形陶瓷盒形输出窗模型，采用Ansoft HFSS三维计算软件的优化模拟，对该输出窗模型的驻波频率特性与各种结构参量的关系进行了优化模拟，分析了该输出窗片结构变化对其表面的电场分布，功率流分布、热量分布的影响，得出最优模型参数。并且探讨了陶瓷窗片的形状和几何结构对改善输出窗的频带特性、提高峰值功率和平均功率、抑制二次电子倍增方面的作用。

But its frequency bandwidth is in the middle (5) Metal nanotubes were prepared by heating metal-coated carbon nanofibers inthe air to remove carbon nanofiber templates.

5将镀层纳米碳纤维在空气中热处理，可以去除纳米碳纤维，获得纳米金属管。

The results show that:(1)the low-noise source-follower circuit can be effectively used to measure the output of PVDF thin film;(2)the piezoelectric coefficient D33 of the PVDF is very sensitive on temperatures;(3)the value of D33 intensively fluctuate in initial loading stage,this means that a pre-load is needed in practice application to keep a constant piezoelectric coefficient D33 of the PVDF;(4)when the compressive load is imposed on the surface of the PVDF along a incline direction,D33 value is obvious changed with changing incline angle,and(5)the frequency bandwidth of the PVDF thin film is very wide,it is more suitable to measure strike or impact loading at various loading conditions.

结果表明：(1)低噪声源跟随电路可有效测量PVDF 薄膜输出；(2)PVDF压电薄膜的压电系数D33对温度很敏感；(3)D33值在加载初始阶段波动很大，所以实际应用中应给PVDF提供一个预压载荷，以确保有一恒定的压电系数D33；(4)当压载荷沿倾斜方向作用在PVDF 表面时，由于有剪切力作用，D33 值会随着倾斜角的变化发生显著改变；(5)PVDF 薄膜具有很宽的频响，更适用于测定不同载荷条件下的侵彻或冲击等动态载荷。

With Death guitarist Schuldiner adopting vocal duties, the band made a major impact on the scene.

随着死亡的吉他手Schuldiner接受主唱的职务，乐队在现实中树立了重要的影响。

But he could still end up breakfasting on Swiss-government issue muesli because all six are accused of nicking around 45 million pounds they should have paid to FIFA.

不过他最后仍有可能沦为瑞士政府&议事餐桌&上的一道早餐，因为这所有六个人都被指控把本应支付给国际足联的大约4500万英镑骗了个精光。