Notes on the Text

Part I

1. For example, in the photoelectric effect—the emission of electrons from metallic surfaces by electromagnetic radiation—it is found that increasing the intensity of the incident radiation has no effect, and that only the frequency of the radiation is relevant in ejecting electrons.

例如，在光电效应（即因电磁辐射而从金属表面发射电子的现象）中，我们发现入射辐射强度的增强是没有影响的，只有辐射频率与发射的电子有关。

2. Over time, it was realized that the electric and magnetic fields are better thought of as two parts of a greater whole—the electromagnetic field.

随着时间的推移，电场和磁场可以更好地被认为是电磁场这一整体的两个部分。

3. If these other charges and currents are comparable in size to the sources producing the above electromagnetic field, then a new net electromagnetic field will be produced.

如果另外这些电荷和电流的大小与产生上述电磁场的源是可比的，那么将产生一个新的净电磁场。

Part Ⅱ

1. A patch antenna is a narrowband, wide-beam antenna fabricated by etching the antenna element pattern in metal trace bonded to an insulating dielectric substrate with a continuous metal layer bonded to the opposite side of the substrate which forms a ground plane.

片状天线是一种窄带宽波束的天线，通过将天线单元图样蚀刻到粘贴在绝缘基底上的金属轨迹而制成，基底的另一面则粘贴连续的金属层形成接地平面。

2. Because such antennas have a very low profile, are mechanically rugged and can be conformable, they are often mounted on the exterior of aircraft and spacecraft, or are incorporated into mobile radio communications devices.

因为这种天线外形低矮，机械强度大，并且形状上适应性强，通常装在飞机或太空飞行器外表，或组合在移动无线电通信设备上。

·conformable，有适应性的，指能适应形状。

3. As the dielectric constant of the substrate increases, the antenna bandwidth decreases which increases the Q factor of the antenna and therefore decreases the impedance bandwidth.

随着基底介电常数的增大，天线的带宽减小，其Q值提高，因而阻抗带宽减小。

4. Patch antennas can easily be designed to have various polarizations, using multiple feed points, or a single feed point with asymmetric patch structures.

片状天线能很容易地通过多个馈点或在非对称片结构上采用单一馈点设计成具有各种偏振特性。

·various polarizations：包括vertical polarization（垂直偏振）, horizontal polarization（水平偏振）, right hand circular polarization（RHCP，右旋圆偏振）, left hand circular polarization（LHCP，左旋圆偏振）。

Part Ⅲ

1. This range of wavelengths has led many to question the naming convention used for microwaves as the name suggests a micrometer wavelength.

这个波长范围令人对命名习惯提出了疑问，因为微波使人联想到微米波长。

2. Vacuum tube based devices operate on the ballistic motion of electrons in a vacuum under the influence of controlling electric or magnetic fields, and include the magnetron, klystron, traveling wave tube (TWT), and gyrotron.

基于电子管的器件是在受控制电场和磁场影响的真空内由电子的冲击运动而工作的，包括磁控管、速调管、行波管和振动陀螺仪。

3. This means that they work on the basis of clumps of electrons flying ballistically through them, rather than using a continuous stream.

这意味着它们是基于真空管发出的电子簇工作的，而不是用连续的电子流。

4. Starting in the early 1950's, frequency division multiplex was used to send up to 5,400 telephone channels on each microwave radio channel, with as many as ten radio channels combined into one antenna for the hop to the next site, up to 70 km away.

从20世纪50年代开始，人们用频分复用在每一个微波无线电信道中传送多达5400路电话，将10路无线电信道组合起来送到一个天线，发送到70 km以外的下一个中继站。

·hop to the next site：直译“跳到下一个地点”，指传送到下一个中继站。

5. NASA worked in the 1970s and early 1980s to research the possibilities of using Solar Power Satellite (SPS) systems with large solar arrays that would beam power down to the Earth's surface via microwaves.

美国宇航局在20世纪70年代和80年代初期研究利用太阳能卫星系统SPS的可能性，这种系统装有大型太阳能阵列，通过微波向地球表面送回发射能量。

·beam power down to the Earth's surface：将功率（电能）波束射向地球表面。