频带

There are all kinds of antennas used in EMC test such as biconical antennas, log periodic antenna, helical antenna, ridged horn antenna and etc.

用于电磁兼容试验的宽频带天线有很多类型，如双锥天线、对数周期天线、螺旋天线、喇叭天线等等。

Simulations based on finite integration method are carried out in a wide frequency range for a balanced feeding finite wide-angle biconical antenna and many results including input impedance and far fields are obtained.

利用基于有限积分法的电磁场仿真技术对平衡馈电的有限长宽角双锥天线作了计算，得到了天线在很宽频带内输入阻抗、远区辐射场与频率的关系曲线。

The antenna has a composite structure of a cage and an asymmetric biconical structure. The impedance bandwidth and radiation pattern bandwidth are enhanced, and the tilting and ripping of radiation patterns are eliminated.

将笼型与不对称双锥结构相结合，展宽了天线的阻抗和方向图带宽，抑制了天线辐射方向图在宽频带内上翘或裂瓣。

Because it is more superior than that of the binary scale FSK and OOK that the binary scale moves the looks key and accuses of the system in resisting noise performance and channel communication frequency band utilization ratio etc., widely used in digital communication.

二进制移相键控方式是受键控的载波相位按基带脉冲而改变的一种数字调制方式。由于二进制移相键控系统在抗噪声性能及信道通信频带利用率等方面比二进制FSK及OOK的优越，因而被广泛应用于数字通信中。

Because it is more superior than that of thebinary scale FSK and OOK that the binary scale moves the looks keyand accuses of the system in resisting noise performance andchannel communication frequency band utilization ratio etc., widelyused in digital communication.

二进制移相键控方式是受键控的载波相位按基带脉冲而改变的一种数字调制方式。由于二进制移相键控系统在抗噪声性能及信道通信频带利用率等方面比二进制FSK及OOK的优越，因而被广泛应用于数字通信中。

Digital TV is a bran-new broadcasting mode and a trend of TV development.

摘要数字电视，是一种全新的广播方式和电视未来发展的趋势，它具有图像质量好、频带利用率高和互动性的优势，必将取代模拟电视。

As the development of modern electronic technology, the high efficiency and broad band acoustic transmitter for the battery using equipments, such as acoustic buoyage, portable underwater acoustic communication equipment and small scale underwater detector is demanded.

随着现代电子技术的发展，一些使用电池供电的水声设备如水声浮标、便携式水声通信设备、便携式水下探测设备等对发射机高效率、宽频带的要求越来越高。

On plane carrier, the left hand MTL realizes series capacity and shunt inductance directly with features of compact structure, easy of manufacture, small size, low loss, and capability of applicable to microstrip IC. The MTL possesses symmetric structure, multiple adjustable parameters so as to suit requirements by different performances and different applications easily.

本发明的左手传输线在平面载体上直接实现了串联电容和并联电感，结构紧凑，易于加工，体积小，损耗低，能够直接应用于微带集成电路；且具有对称结构，可调参数多，可以容易地实现工作频带的调节以适合不同性能要求，实现不同应用。

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。

In this paper,finite-difference time-domain method was used to calculate the driving-point impedance of radial disk in circular groove guide.

引言圆形槽波导是一种新型波导，和传统波导相比，具有低损耗、高功率容量、低色散和宽频带等优良特性。

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。