Theory Antenna Cppaste | Antenna (Radio)

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teoria de antenas
Transcript Introduction to  Antennas In the 1890s, there were only a few antennas in the world. These rudimentary devices were primarly a part of eperiments that demonstrated the transmission of electroma!netic waves. y #orld #ar II, antennas had $ecome so u$i%uitous that their use had transformed the lives of the avera!e person via radio and television reception. The num$er of antennas in the &nited 'tates was on the order of one per household, representin! !rowth rivalin! the auto industry durin!the same period. y the early (1st century, than)s in lar!e part to mo$ile phones, the avera!e  person now carries one or more antennas on them wherever they !o *cell phones can have multiple antennas, if +' is used, for instance. This si!nificant rate of !rowth is not li)ely to slow, as wireless communication systems $ecome a lar!er  part of everyday life. In addition, the stron! !rowth in I devices su!!ests that the num$er of antennas in use may increase to one antenna per o$ect in the world *product, container, pet, $anana, toy, cd, etc.. This num$er would dwarf the num$er of antennas in use today. 2ence, learnin! a little *or a lar!e amount a$out of antennas couldn3t hurt, and will contri$ute to one3s overall understandin!of the modern world.  4 50-meter dish antenna. art of 64'43s 7et ropulsion a$oratory *7 communication system.  Antenna Theory History #hat is the ori!in of the antenna I3m rulin! out such early devices as compasses, $ecause while they in some sense receive a ma!netic field, it is not an electroma!netic field. en ran)lin3s )ite eperiment wasn3t %uite an antenna, as that captured li!htnin! dischar!e, which is a direct current path where the ener!y is not transferred independent of the medium it travels. The human eye of course receives hi!h fre%uency electroma!netic waves *li!ht, to the layman.  Technically the eye could $e classified as an antenna however since it can3t transmit waves, it is really a sensor, so I3ll eclude that as well. The first eperiments that involved the couplin! of electricity and ma!netism andshowed a definitive relationship was that done $y araday somewhere around the18;0s. 2e slid a ma!netic around the coils of a wire attached to a !alvanometer. In movin! the ma!net, he was in effect creatin! a time-varyin! ma!netic field, which as a result *from <awell3s =%uations, must have had a time-varyin! electric field. The coil acted as a loop antenna and received the electroma!netic radiation, which was received *detected $y the !alvanometer - the wor) of an antenna. Interestin!ly, the concept of electroma!netic waves had not even $een thou!ht up at this point. 4 paintin! of <ichael araday. ein! a !reat eperimentalist, he naturallyda$$led in chemistry, shown here.2einrich 2ert> developed a wireless communication system in which he forced an electrical spar) to occur in the !ap of a dipole antenna. 2e used a loop antennaas a receiver, and o$served a similar distur$ance. This was 188?. y 1901, <arconi was sendin! information across the atlantic. or a transmit antenna, he used several vertical wires attached to the !round. 4cross the 4tlantic @cean, the receive antenna was a (00 meter wire held up $y a )ite A1B.  In 190?, Colum$ia &niversity had an =perimental #ireless 'tation where they used a transmittin! aerial ca!e. This was a ca!e made up of wires and suspended in the air, resem$lin! a ca!e A(B. 4 rou!h outline of some maor antennas and their discovery/fa$rication dates are listed:   Da!i-&da 4ntenna, 19(0s   2orn antennas, 19;9. Interestin!, the early antenna literature discussed wave!uides as Ehollow metal pipesE.  4ntenna 4rrays, 19F0s   ara$olic eflectors, late 19F0s, early 19G0s 7ust a !uess.   atch 4ntennas, 1950s.    I4, 1980s.Current research on antennas involves metamaterials *materials that have en!ineered dielectric and ma!netic constants, that can $e simultaneously ne!ative, allowin! for interestin! properties li)e a ne!ative inde of refraction. @ther research focuses on ma)in! antennas smaller, particularly in communications for personal wireless communication devices *e.!. cell phones. 4 lot of wor) is $ein! performed on numerical modelin! of antennas, so that their properties can $e predicted $efore they are $uilt and tested. eferencesA1B alanis, Constantine. E4ntenna Theory: 4 eviewE, roceedin!s of the I===,vol. 80, 7anuary 199(.A(B #(4== 4ntenna 2istory. 4rthur <. Hay *, scanned $y 4lan Crosswell. http://www.w(aee.colum$  Antenna Basics Antenna Fundamentals ets !et ri!ht down to the study of antennas and Antenna Basics . 'uppose one day you3re wal)in! down the street and a )ind $ut impatient person runs up and as)s you to desi!n an antenna for them. E'ureE, you %uic)ly reply, addin! Ewhat is the desired fre%uency, !ain, $andwidth, impedance, and polari>ationE
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