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Unformatted text preview: Antennas
40504050-403 Concepts of Wireless Data Networks bxyics 1 Antenna
Radio frequency signals exert at the surface of the conductive materials Convert electrical energy into RF energy or waves, vice gy gy , versa The physical dimension are directly related to the p y y performance of an antenna Any conductive object will behave as an antenna bxyics 2 How does an antenna work?
At the transmitter end
Oscillating charger particles emit electromagnetic waves. http://www.colorado.edu/physics/2000/applets/fieldwaves. p p y pp html At the receiver end
Different voltage levels force charged particles bounce back and forth between two ends of the antenna forming current bxyics 3 Antenna bxyics 4 Dipole bxyics 5 Radiation Patterns
Antennas do not radiate power evenly in all direction. p y A graphical representation of the radiation properties of an antenna such as amplitude as a function of the angular space coordinates coordinates. Power pattern
A plot of the power (proportional to either the electric or magnetic fields) on a linear or decibel (dB) scale i fi ld ) li d ib l l E-plane or H-plane H- bxyics 6 Power Pattern
Normalized to the largest power level Linear scale Linear Array antenna y Beamwidth = 38.64 degree measured at the half power point p Main lobe: typically the focus of the beam Side lobes Linear plot suppresses side lobes bxyics 7 Power Pattern
Normalized dB scale Emphasis on side lobes bxyics 8 A 3D view
Linear scale Array antenna bxyics 9 Dipole Radiation Pattern bxyics 10 Dipole Radiation Pattern bxyics 11 Monopole bxyics 12 Monopole Radiation Pattern bxyics 13 Folded dipole bxyics 14 Array Antenna: Yagi-Uda Yagi- bxyics 15 bxyics 16 bxyics 17 bxyics 18 SemiSemi-directional: Yagi bxyics 19 Patch Antenna bxyics 20 SemiSemi-directional: Patch bxyics 21 Parabolic Reflector: with front feed
Directional bxyics 22 Parabolic Reflector: with cassegrain feed
Directional bxyics 23 HighlyHighly-directional
Parabolic dish Grid dish bxyics 24 Radiation Pattern of a Directional Antenna bxyics 25 Directional Parabolic
http://www.seattlewireless.net/index.cgi/Direct http://www seattlewireless net/index cgi/Direct ionalParabolic bxyics 26 Other antennas bxyics 27 Cantenna bxyics 28 Cantenna: parts
A N-Female chassis mount connector. NFour small nuts and bolts A thick wire A can N-male to pigtail Goldcrest Electronics, 700 South Goodman at South Clinton, 546546-8464 http://www.turnpoint.net/wireless/cantennahowto.html bxyics 29 Images bxyics 30 N Connectors
Usually found on external antenna and antenna cabling. bxyics 31 TNC connectors
Usually found on access points such as the Linksys WAP11. bxyics 32 SMA connectors
Usually found on PCI wireless cards, such as the cards Belkin F5D6001 or the Netgear MA311 bxyics 33 MC (Lucent) Connectors (Pigtails)
Usually found on pcmcia cards like the Buffalo WLI-PCMWLI-PCM-L11G and Lucent Orinoco cards bxyics 34 References
Constantine Balanis "Antenna Theory: Analysis Balanis, Antenna and Design", Wiley, 2005 Daniel Dobkin "RF Engineering for Wireless Dobkin, RF Networks: Hardware, Antennas, and Propagation Elsevier, Propagation", Elsevier 2005 bxyics 35 ...
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This note was uploaded on 04/21/2008 for the course VNSA 403 taught by Professor Yuan during the Winter '07 term at RIT.
- Winter '07