英文翻譯外文文獻(xiàn)翻譯23畢業(yè)設(shè)計(jì)外文英文翻譯射頻與微波應(yīng)用(編輯修改稿)
2025-01-06 20:00 本頁(yè)面
【文章內(nèi)容簡(jiǎn)介】 orbiting satellites around the globe are a necessity for local or global munications. A very important civilian as well as military instrument is radar. The concept of radar is based on radar crosssection which is the effective reflection area of the target. A target’s visibility greatly depends on the target’s electrical size, which is a function of the incident signal’s wavelength. Microwave frequency is the ideal signal band for radar applications. Of course, another important advantage of use of microwaves in radars is the availability of higher antenna gain as the frequency is increased for a given physical antenna size. This is because the antenna gain being proportional to the electrical size of the antenna bees larger as frequency is increased in the microwave band. The key factor in all this is that microwave signal wavelengths in radars are parable to the physical size of the transmitting antenna as well as the target. There is a fourth and yet very important property of microwaves。 the molecular, atomic, and nuclear resonance of conductive materials and substances when exposed to microwave fields. This property creates a wide variety of applications. For example, because almost all biological units are posed predominantly of water and water is a good conductor, microwave technology has tremendous importance in the fields of detection, diagnostics, and treatment of biological problems or medical investigations (., diathermy, scanning, etc.). There are other areas in which this basic property would create a variety of applications such as remote sensing, heating (., industrial purification and cooking) and many others are listed in a later section. Reasons for Using RF/Microwaves Over the past several decades, there has been a growing trend toward use of RF/microwaves in system applications. There are many reasons among which the following are prominent: Wider bandwidths due to higher frequency Smaller ponent size leading to smaller systems More available and less crowded frequency spectrum Lower interference due to lower signal crowding Higher speed of operation Higher antenna gain possible in a smaller space On the other hand, there are some disadvantages to using RF/microwaves, such as: more expensive ponents, availability of lower power levels, existence of higher signal losses, and use of highspeed semiconductors (such as GaAs or INP) along with their corresponding lessmature technology (relative to the traditional silicon technology, which is now quite mature and less expensive). In many RF/microwave applications the advantages of a system operating at these frequencies outweigh the disadvantages and propel engineers to a highfrequency design. RF/Microwave Applications The major applications of RF/microwave signals can be categorized as follows: Communication This application includes satellite, space, longdistance telephone, marine, cellular telephone, data, mobile phone, aircraft, vehicle, personal, and wireless local area work (WLAN), among others. Two important subcategories of applications need to be considered: TV and radio broadcast, and optical munications. TV and radio broadcast In this ap
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