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1
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- Based on Cisco Wireless Material
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2
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- This module will cover basic antenna theory, including directional and
omnidirectional antenna selection. After discussing antenna theory and
types of antennas, cables, connectors and accessories for antennas will
be discussed. Additionally, important antenna design considerations,
such as link engineering, path planning, and installation are also
discussed.
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3
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- Define how an antenna is used to propagate an RF signal.
- Define basic facts of EIRP.
- Define facts on FCC regulations for UNII-1, UNII-2 and UNII-3.
- Identify what an isotropic antenna is and why it is used as a reference
for other antennas.
- Identify Cisco Aironet antennas, their coverage patterns, and the
proper polarization of each antenna.
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4
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- Lobes
- Directional
- Omnidirectional
- Beamwidth
- Bandwidth
- Polarization
- Vertical (Elevation)
- Horizontal (Azimuth)
- Diversity
- Plane (H and E)
- (H-Magnetic Field, E-Electric
Field)
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5
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- 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)
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6
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- FCC requires that ALL antennas sold by
a spread spectrum vendor be certified
with the radio they are to be sold with
- All Cisco Aironet 802.11b supplied cables, RF devices and antennas have
reverse polarity TNC
(RP-TNC) connectors
- Cisco Aironet supplied antennas meet all
FCC rules
- Wide variety of 802.11b antennas for most applications
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7
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- FCC requires that all radios utilizing the UNII-1 Band (5.15 GHz – 5.25
GHz) must have non-removable or integrated antennas
- FCC allows radios utilizing the UNII-2 Band (5.25 GHz – 5.35 GHz) to
have external or removable antennas
- The Cisco Aironet 802.11a radios utilize both UNII-1 and UNII-2 bands,
therefore cannot have external or removable antennas
- Cisco 802.11a antennas are integrated into the radio module
- Cisco 1400 radios utilize UNII-3 bands, therefore have external or
removable antennas
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8
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- 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
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9
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- Antennas have gain in particular directions
- Direction other than the main intended radiation pattern, are typically
related to the main lobe gain
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10
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- 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
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11
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- A theoretical isotropic antenna has a perfect 360º vertical
and horizontal beamwidth
- This is a reference for ALL antennas
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12
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- Energy lobes are ‘pushed in’ from the top and bottom
- Higher gain
- Smaller vertical beamwidth
- Larger horizontal lobe
- Typical dipole pattern
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13
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- More coverage area in a circular pattern
- Energy level directly above or below the antenna will become lower
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14
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- 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
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15
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- 802.11b antenna
- Must use a unique, or proprietary connector
- Cisco Aironet products use RP-TNC connector
- Part 15 standards
- Approved antenna may exceed
- Exceeding may lead to interference problems
- Penalties could result in fines
- FCC standards apply to Part 15 users in the United States
- Different countries will have similar standards
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16
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- Point-to-Multipoint
- FCC allows increasing the gain of an antenna/cable system if the
transmitter power is reduced below 30 dBm in a 1:1 ratio
- Reduce Transmit Power below maximum of 30 dBm by 1 dBm and increase
antenna/cable system gain by 1dBi
- Point-to-Point
- Maximum of 36 dBm EIRP
- Installations – 30 dBm maximum transmitter power with 6 dBi in gain
attributed to antenna and cable combination
- FCC allows exceeding the 36 dBm EIRP in Point-to-Point installations
using the 3:1 rule
- Reduce Transmit Power below maximum of 30 dBm by 1 dBm and increase
antenna/cable system gain by 3 dBi
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17
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18
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- Currently ETSI stipulates a maximum of 20 dBm EIRP on
Point-to-Multipoint and Point-to-Point installations –17 dBm maximum
transmitter power with 3 dBi in gain attributed to antenna and cable
combination
- Professional installers are allowed to increase the gain of an
antenna/cable system if the transmitter power is reduced below 17 dBm in
a 1:1 ratio
- Reduce Transmit Power below maximum of 17 dBm by 1 dBm and increase
antenna/cable system gain by 1 dBi
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19
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20
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- FCC regulations for UNII-1 and UNII-2
- UNII-1
- FCC max 50 mW
- 802.11a max 40 mW
- With max 6 dBi antenna gain
- 802.11a max of 40 mW complies with all countries except Singapore (20
mW)
- UNII-2
- FCC max 250 mW
- 802.11a max 200 mW
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21
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- FCC requires that all radios utilizing the UNII-1 Band (5.15 GHz – 5.25
GHz) must have non-removable or integrated antennas
- FCC allows radios utilizing the UNII-2 Band (5.25 GHz – 5.35 GHz) to
have external or removable antennas
- FCC requires radios operating in both UNII-1 and UNII-2 bands must
comply with antenna rules regulating UNII-1 band (including indoor use
only)
- The Cisco Aironet 802.11a radios utilize both UNII-1 and UNII-2 bands,
therefore cannot have external or removable antennas and must be used
indoors only
- Cisco 802.11a antennas are integrated into the radio module
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22
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- 2 dBi Dipole "Standard Rubber Duck"
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23
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- 5.2 dBi Mast Mount Vertical
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24
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25
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- 5.2 dBi Pillar Mount Diversity
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26
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- 2 dBi Diversity Omni-Directional
Ceiling Mount
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27
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- 12 dBi Omni-Directional (Outdoor
only)
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28
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- 9 dBi omni (Vertical polarization)
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29
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- 9.5 dBi sector (H or V polarization)
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30
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- 6.5 dBi Diversity Patch Wall Mount – 55 degree
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31
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- 6 dBi Patch Antenna – 65 degree
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32
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- 8.5 dBi Patch Antenna – 60 degree
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33
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- 13.5 dBi Yagi Antenna – 25 degree
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34
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35
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- 21 dBi Parabolic Dish Antenna – 12 degree
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36
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- 28 dBi dish (H or V polarization)
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37
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- 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
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38
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39
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40
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41
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42
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43
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44
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- 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
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45
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46
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- Radio line of sight
- Earth bulge
- Fresnel zone
- Antenna and cabling
- Data rate
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47
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- The following obstructions might obscure a visual link:
- Topographic features, such as
mountains
- Curvature of the Earth
- Buildings and other man-made
objects
- Trees
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48
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- Line of Sight disappears at 6 miles
(9.7 Km) due to the earth curve
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49
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50
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51
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- Antenna Height
- Fresnel zone consideration
- Line-of-Sight over 25 miles (40 Km) hard to implement
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52
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53
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54
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55
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- Omni-directional antennas provide 3600 coverage
- Also accepts interference from all directions
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56
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57
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58
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59
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60
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- Aironet Client Utility
- Site Survey Utility for antenna alignment
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Notes