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Lecture 6: Antennas

Lecture 6: Antennas. Anders Västberg vastberg@kth.se 08-790 44 55. L= l/2. I. I. Dipole antenna. Half-wave dipole Gain 1,64 = 2.15 dBi Linear Polarisation Quarter-wave dipole Conducting plane below a single quarter wave antenna. Acts like a half-wave dipole. L = l /4. I.

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Lecture 6: Antennas

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  1. Lecture 6: Antennas Anders Västberg vastberg@kth.se 08-790 44 55

  2. L=l/2 I I Dipole antenna • Half-wave dipole • Gain 1,64 = 2.15 dBi • Linear Polarisation • Quarter-wave dipole • Conducting plane below a single quarter wave antenna. Acts like a half-wave dipole L=l/4 I

  3. Corner Reflectors • Multiple images results in increased gain • Example:G=12 dBi Images l/2 Driven Element

  4. Yagi-antenna 3-30 element and a gain of 8-20 dBi http://www.urel.feec.vutbr.cz/~raida/multimedia_en/chapter-4/4_3A.html

  5. Loop-antenna • Linear Polarisation • Gain 1,76 dBi http://www.ycars.org/EFRA/Module%20C/AntLoop.htm

  6. Parabolic antenna • Effective area Ae =hp d2/4 h=0.56 [Stallings, 2005]

  7. Helical antenna • Normal mode • Axial mode http://hastingswireless.homeip.net/index.php?page=antennas&type=helical

  8. Characterization of Fading Small Scale Fading (Based on multipath time delay spread) Small Scale Fading (Based on Doppler spread) Frequency non-selective (Flat) Fading Frequency Selective Fading Fast Fading Slow Fading • BW of signal > BW of symbol • Tm > Ts • High Bd • Td < Ts • Channel variations faster than base band signal variations • Low Bd • Td > Ts • Channel variations slower than base band signal variations • BW of signal < BW of symbol • Tm < Ts [Rappaport, 1996]

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