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，在光電效應（即因電磁輻射而從金屬表面發射電子的現象）中，我們發現入射輻射強度的增強是沒有影響的，只有輻射頻率與發射的電子有關。

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.

隨著時間的推移，電場和磁場可以更好地被認為是電磁場這一整體的兩個部分。

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.

如果另外這些電荷和電流的大小與產生上述電磁場的源是可比的，那么將產生一個新的凈電磁場。

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.

片狀天線是一種窄帶寬波束的天線，通過將天線單元圖樣蝕刻到粘貼在絕緣基底上的金屬軌跡而制成，基底的另一面則粘貼連續的金屬層形成接地平面。

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.

因為這種天線外形低矮，機械強度大，并且形狀上適應性強，通常裝在飛機或太空飛行器外表，或組合在移動無線電通信設備上。

·conformable，有適應性的，指能適應形狀。

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.

隨著基底介電常數的增大，天線的帶寬減小，其Q值提高，因而阻抗帶寬減小。

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

片狀天線能很容易地通過多個饋點或在非對稱片結構上采用單一饋點設計成具有各種偏振特性。

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

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.

這個波長范圍令人對命名習慣提出了疑問，因為微波使人聯想到微米波長。

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.

基于電子管的器件是在受控制電場和磁場影響的真空內由電子的沖擊運動而工作的，包括磁控管、速調管、行波管和振動陀螺儀。

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

這意味著它們是基于真空管發出的電子簇工作的，而不是用連續的電子流。

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.

從20世紀50年代開始，人們用頻分復用在每一個微波無線電信道中傳送多達5400路電話，將10路無線電信道組合起來送到一個天線，發送到70 km以外的下一個中繼站。

·hop to the next site：直譯“跳到下一個地點”，指傳送到下一個中繼站。

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.

美國宇航局在20世紀70年代和80年代初期研究利用太陽能衛星系統SPS的可能性，這種系統裝有大型太陽能陣列，通過微波向地球表面送回發射能量。

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