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WLAN Antennas and Accessories

WLAN Antennas and Accessories. Basic RF antenna concepts WLAN Antenna types RF cables and connectors Factors in antenna installation Combating effects of wind and lightning Installation safety Antenna mounting Maintaining clear communications. Exam Essentials.

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WLAN Antennas and Accessories

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  1. WLAN Antennas and Accessories • Basic RF antenna concepts • WLAN Antenna types • RF cables and connectors • Factors in antenna installation • Combating effects of wind and lightning • Installation safety • Antenna mounting • Maintaining clear communications

  2. Exam Essentials • Understand RF signal characteristics and basic RF concepts used with antennas • Know the different types of antennas used in WLAN • Indentify various RF cables, connectors, and accessories used in WLAN • Understand additional concepts regarding RF propagation

  3. Basic RF Antenna Concepts • RF lobes – shape of the RF patterns • Beamwidth – Horizontal and vertical measurement angles • Antenna charts – azimuth and elevation • Gains – Changing the RF coverage pattern • Polarization – Horizontal and vertical

  4. RF Lobes • Lobe – shape of the RF energy (signal) emitted • Type of antenna design determines lobe • Omnidirectional, Semidirectional, parabolic etc.

  5. Beamwidth • Angle of the measurement of the main RF lobe at half power • Measured horizontally and vertically • Azimuth view from above – “birds-eyes-view”

  6. Antenna Gain • Change in coverage by focusing the area of RF propagation

  7. Passive Gain • Focusing isotropic energy in a specific pattern • Created by the design of the antenna • Uses the magnify glass concept

  8. Active Gain • Providing an external power source • Amplifier • High gain transmitters

  9. Antenna Polarization • How the wave is emitted from and antenna • Horizontal • Vertical

  10. WLAN Antenna Types • Omnidirectional Antennas • Semidirectional Antennas • Highly Directional Antennas

  11. Antenna Specifications • Frequency range • Voltage standing wave ratio • Polarization • Cable length • Dimensions • Mounting

  12. Omnidirectional Antennas • Most common type of antenna • 360 degree pattern horizontal Beamwidth • Vertical Beamwidth dependent on antenna gain • Shape of pattern looks like a donut.

  13. Low Gain Omni-directional Antenna The omni antenna is the most commonly used antenna type High Gain Omni-directional Antenna • Provides 360º horizontal coverage pattern along a flat plane. • Gain of signal along the horizontal plane means less signal along the vertical plane • Omni-directional antennas are also known as dipoles.

  14. Semidirectional Antennas • More specific pattern antenna versus Omnidirectional • Patch • Panel • Sector • Yagi

  15. Semi-directional Antennas Patch • Patch, Panel, Yagi and Sector are the primary semi-directional antenna types on the market today • Semi-directional antennas have 180º or less of horizontal and vertical beam width • Primary coverage uses include: • Hallways/Corridors • Wireless ISPs • PTP & PTMP Bridging Patch Multiple semi-directional antennas can be combined into an array to provide omni-directional coverage.

  16. Highly Directional Antennas • Highly focused energy • Most common type - parabolic

  17. Highly-Directional Highly-directional Antennas • Parabolic dish and grid are the primary types of highly-directional antennas used in the market today • Grid antennas are often used in locations where wind is problematic • Very narrow horizontal and vertical beam widths • Primary coverage use: • Long-distance PTP bridge links With narrow beam widths, it is important to assure accurate antenna alignment

  18. RF Cables and Connectors • Type • Length • Cost • Impedance

  19. Cable Types • Measured in resistance (Ohms) • Coaxial • Twin axial • Thick • Thin

  20. Cable Length • Induces loss of signal even in short lengths of cable • Connectors add additional loss

  21. Cable Cost • You get what you pay for • Always specify quality cable

  22. Impedance and VSWR • Impedance is a measurement of alternating current resistance. • Measured in ohms • Mismatched impedance can cause voltage standing wave ratio (VSWR) and adversely impact the signal

  23. RF Connectors • Join cables and devices together • AP to antenna • Antenna to cable • Cable to cable • Etc.

  24. Factors in Antenna Installation • Addressing the Effects of Earth Curvature • Antenna Placement • Minimizing the Effects of Multipath Using Antenna Diversity

  25. Addressing the Effects of Earth Curvature • A factor after 7 miles • Affects point-to-point and direct line of sight • Addressed by antenna height and direction

  26. Antenna Placement • Omnidirectional placement • Directly to the AP • Indoor or outdoor • Semidirectional placement • Flat on a wall • Indoor or outdoor • Highly directional placement • Exclusively outdoors • Free from obstructions

  27. Minimizing the Effects of Multipath Using Antenna Diversity • Using two antennas from one radio source • Minimizes • Reflection • Refraction • Scattering • Diffraction

  28. Combating Effects of Wind and Lightning on Wireless Connections • Lightning arrestors • Surge protectors • For both antenna and equipment • Grounding rods • Direct power surges around equipment into ground

  29. Lightening Arrestors Lightning Arrestors • An in-line RF device that must be connected to Earth ground • Dissipates static electricity in the air • When objects near RF antennas are struck, electrical current is induced Does not prevent equipment loss in cases of direct lightning strikes!

  30. Antenna Mounting • Pole/mast mount • Ceiling mount • Wall mount

  31. Pole/Mast Mount • Attaches to a pole • L-shaped mounting bracket • U-bolt mounting hardware

  32. Ceiling Mount • Attaches to hard-ceiling • Concrete • Drywall ceiling joists • Omnidirectional

  33. Wall Mount • Mounts similar to ceiling mount only vertical • Semidirectional antennas

  34. Maintaining Clear Communications • Visual line of sight • RF line of sight • Fresnel zone

  35. Visual Line of Sight • Unobstructed view by each point

  36. RF Line of Sight • Clear path for the radio frequency • The premise of the Fresnel zone

  37. Fresnel Zone • Area of coverage surrounding the visual line of sight • Obstacles • Trees • Buildings • Earth curvature • Hills mountains

  38. Exam Essentials • Understand RF signal characteristics and basic RF concepts used with antennas • Know the different types of antennas used in WLAN • Indentify various RF cables, connectors, and accessories used in WLAN • Understand additional concepts regarding RF propagation

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