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Antennas

Antennas. Olga Torstensson Halmstad University. Key terms. Lobes Directional Omnidirectional Beamwidth and Bandwidth Polarization Vertical Horizontal Diversity Plane (H and E) Fresnel Zone. Definition of Terms. dB- Decibel- Ratio of one value to another dBx where x =

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Antennas

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  1. Antennas Olga Torstensson Halmstad University

  2. Key terms • Lobes • Directional • Omnidirectional • Beamwidth and Bandwidth • Polarization • Vertical • Horizontal • Diversity • Plane (H and E) • Fresnel Zone

  3. Definition of Terms • dB- Decibel- Ratio of one value to another • dBx where x = • m = compared to 1 milliwatt (0 dBm=1 mW) • i = compare to isotropic antenna • d = compared to dipole antenna • w = compared to 1 watt (0 dBw = 1 watt)

  4. Important Antenna Concepts

  5. Beamwidth

  6. Antenna Concepts • Directionality • Omni (360º coverage) directional • Directional (limited range of coverage) • Gain • Measured in dBi and dBd (0 dBd = 2.14 dBi) • More gain means more coverage - in certain directions • Polarization • Antennas are used in the vertical polarization

  7. Antenna Issues (cont.) • Antennas have gain in particular directions • Direction other than the main intended radiation pattern, are typically related to the main lobe gain

  8. Antenna Gain • If the gain of an antenna goes up, the coverage area or angle goes down • Coverage areas or radiation patterns are measured in degrees • Angles are referred to as beamwidth • Horizontal measurement • Vertical measurement

  9. Beamwidth vs. Gain

  10. Antenna Theory • A theoretical isotropic antenna has a perfect 360º vertical and horizontal beamwidth • This is a reference for ALL antennas

  11. Side View (Vertical Pattern) Vertical Beamwidth New Pattern (with Gain) Top View (Horizontal Pattern) Antenna Theory- Dipole • Energy lobes are ‘pushed in’ from the top and bottom • Higher gain • Smaller vertical beamwidth • Larger horizontal lobe • Typical dipole pattern

  12. High Gain Omni-Directionals • More coverage area in a circular pattern • Energy level directly above or below the antenna will become lower

  13. Side View (Vertical Pattern) Top View (Horizontal Pattern) Directional Antennas • Lobes are pushed in a certain direction, causing the energy to be condensed in a particular area • Very little energy is in the back side of a directional antenna

  14. 2.4 GHz Omni-Directional Antennas • 2 dBi Dipole "Standard Rubber Duck"

  15. 2.4 GHz Omni-Directional Antennas • 5.2 dBi Mast Mount Vertical

  16. 2.4 GHz Omni-Directional Antennas • 5.2 dBi Ceiling Mount

  17. 2.4 GHz Omni-Directional Antennas • 5.2 dBi Pillar Mount Diversity

  18. 2.4 GHz Diversity Omni-Directional Antennas • 2 dBi Diversity Omni-Directional Ceiling Mount

  19. 2.4 GHz Omni-Directional Antennas • 12 dBi Omni-Directional (Outdoor only)

  20. 5 GHz Omni-Directional Antennas • 9 dBi omni (Vertical polarization)

  21. 5 GHz Integrated Antenna Innovative 5 GHz Combo Antenna: • Wall Mount: Fold antenna flat against access point housing for 6 dBi gain patch antenna • Ceiling Mount: Fold antenna out at a 90° angle for 5 dBi gain omni antenna In 6 dBi patch position In 5 dBi omni position

  22. 2.4 GHz Diversity Antennas • 6.5 dBi Diversity Patch Wall Mount – 55 degree

  23. 2.4 GHz Directional Antennas (cont.) • 6 dBi Patch Antenna – 65 degree

  24. 2.4 GHz Directional Antennas (cont.) • 8.5 dBi Patch Antenna – 60 degree

  25. 2.4 GHz Directional Antennas (cont.) • 13.5 dBi Yagi Antenna – 25 degree

  26. 13.5 dBi Yagi Antenna—Inside view

  27. 2.4 GHz Directional Antennas (cont.) • 21 dBi Parabolic Dish Antenna – 12 degree

  28. 5 GHz Omni-Directional Antennas • 28 dBi dish (H or V polarization)

  29. 5 GHz Antenna • 9.5 dBi sector (H or V polarization)

  30. Cable and Accessories2.4 GHz Accessories

  31. RP-TNC Connectors

  32. Lightning Arrestor To Antenna • Designed to protect LAN devices from static electricity and lightning surges that travel on coax transmission lines • RP-TNC connectors used on all Cisco Antennas Lug Lockwasher Nut Ground Wire From RF Device

  33. Lightning Arrestor

  34. Coax Connection Sealing • Number one problems with bridges - water in the connectors • Proper sealing is important • Coax Seal is one product that is inexpensive and works great • ces

  35. Link Engineering and RF Path Planning • Path Considerations Radio line of sight • Earth bulge • Fresnel zone • Antenna and cabling • Data rate

  36. Line of sight! Line of Sight • The following obstructions might obscure a visual link: • Topographic features, such as mountains • Curvature of the Earth • Buildings and other man-made objects • Trees

  37. Longer Distances • Line of Sight disappears at 6 miles (9.7 Km) due to the earth curve

  38. Fresnel Zone

  39. Improving Fresnel Effect Raise the antenna New structure Existing structure Different mounting point Remove trees

  40. Site to Site Fresnel Zone • Antenna Height • Fresnel zone consideration • Line-of-Sight over 25 miles (40 Km) hard to implement Antenna Height (Value “H”) Total Distance Fresnel @ 60% (Value “F”) Earth Curvature (Value “C”)

  41. Antenna Alignment Line of Sight

  42. Antenna Issues High gain omni-directional Directional antenna • No Downtilt • One-way communications

  43. Antenna Issues (cont.) 8.50 downtilt 200 ft./61 m 14.50 700 ft./213 m 8 Miles/13 Km

  44. Antenna Issues (cont.) • Omni-directional antennas provide 3600 coverage • Also accepts interference from all directions

  45. Antenna Mounting

  46. Mounting (Cont.)

  47. Interference • Carrier Detect Test (Spectrum Analyzer) • Built into Bridge • Run from Console Menu

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