IV) A transmission line is loaded by a 96 % efficiency antenna that radiates 35

Question

IV) A transmission line is loaded by a 96 % efficiency antenna that radiates 35 Watts into space. The antenna has a 30 dB gain and has a radiation resistance of 85 ?. This line is loaded by a matched source TX. The receiver antenna is located 5 Km from the transmitter antenna and the frequency is 900 MHz. 1. What is the total power absorbed by the transmitting antenna? 2. What is the total resistance of the antenna? 3. What is the Loss in Free Space in ratio value and in dB? 4. What is the received power induced in the receiver antenna? 5. What is the effective area of the receiver antenna? 6. What is the electric field around the receiver antenna?

Explanation / Answer

Photophone Main article: Photophone Bell and Tainter's photophone, of 1880. The world's first wireless telephone conversation occurred in 1880, when Alexander Graham Bell and Charles Sumner Tainter invented and patented the photophone, a telephone that conducted audio conversations wirelessly over modulated light beams (which are narrow projections of electromagnetic waves). In that distant era, when utilities did not yet exist to provide electricity and lasers had not even been imagined in science fiction, there were no practical applications for their invention, which was highly limited by the availability of both sunlight and good weather. Similar to free space optical communication, the photophone also required a clear line of sight between its transmitter and its receiver. It would be several decades before the photophone's principles found their first practical applications in military communications and later in fiber-optic communications. [edit]Early wireless work Main article: Wireless telegraphy David E. Hughes transmitted radio signals over a few hundred yards by means of a clockwork keyed transmitter in 1879. As this was before Maxwell's work was understood, Hughes' contemporaries dismissed his achievement as mere "Induction". In 1885, Thomas Edison used a vibrator magnet for induction transmission. In 1888, Edison deployed a system of signaling on the Lehigh Valley Railroad. In 1891, Edison obtained the wireless patent for this method using inductance (U.S. Patent 465,971). In 1888, Heinrich Hertz demonstrated the existence of electromagnetic waves, the underlying basis of most wireless technology.[3][4] The theory of electromagnetic waves was predicted from the research of James Clerk Maxwell and Michael Faraday. Hertz demonstrated that electromagnetic waves traveled through space in straight lines, could be transmitted, and could be received by an experimental apparatus.[3][4] Hertz did not follow up on the experiments. Jagadish Chandra Bose around this time developed an early wireless detection device and helped increase the knowledge of millimeter-length electromagnetic waves.[5] Practical applications of wireless radio communication and radio remote control technology were implemented by later inventors, such as Nikola Tesla. Further information: Invention of radio [edit]Radio Main article: History of radio Marconi did transmit the first radio signal across the Atlantic. The term "wireless" came into public use to refer to a radio receiver or transceiver (a dual purpose receiver and transmitter device), establishing its usage in the field of wireless telegraphy early on; now the term is used to describe modern wireless connections such as in cellular networks and wireless broadband Internet. It is also used in a general sense to refer to any type of operation that is implemented without the use of wires, such as "wireless remote control" or "wireless energy transfer", regardless of the specific technology (e.g. radio, infrared, ultrasonic) used. Guglielmo Marconi and Karl Ferdinand Braun were awarded the 1909 Nobel Prize for Physics for their contribution to wireless telegraphy. [edit]Electromagnetic spectrum Wireless data communications are an essential component of mobile computing.[7] The various available technologies differ in local availability, coverage range and performance,[8][9] and in some circumstances, users must be able to employ multiple connection types and switch between them. To simplify the experience for the user, connection manager software can be used,[10][11] or a mobile VPN deployed to handle the multiple connections as a secure, single virtual network.[12] Supporting technologies include: Wi-Fi is a wireless local area network that enables portable computing devices to connect easily to the Internet.[13] Standardized as IEEE 802.11 a,b,g,n, Wi-Fi approaches speeds of some types of wired Ethernet. Wi-Fi has become the de facto standard for access in private homes, within offices, and at public hotspots.[14] Some businesses charge customers a monthly fee for service, while others have begun offering it for free in an effort to increase the sales of their goods.[15] Cellular data service offers coverage within a range of 10-15 miles from the nearest cell site.[8] Speeds have increased as technologies have evolved, from earlier technologies such as GSM, CDMA and GPRS, to 3G networks such as W-CDMA, EDGE or CDMA2000.[16][17] Mobile Satellite Communications may be used where other wireless connections are unavailable, such as in largely rural areas[18] or remote locations.[8] Satellite communications are especially important for transportation, aviation, maritime and military use.[19]

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