antenna concepts © 2001, cisco aironet systems, inc. chapter5-1
TRANSCRIPT
Antenna ConceptsAntenna Concepts
© 2001, Cisco Aironet Systems, Inc. Chapter5-1
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-3
ObjectivesObjectivesObjectivesObjectives
Upon completion of this chapter, you should be able to:
• Understand how an antenna is used to propagate an RF signal
• Explain 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
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-4
Cisco Aironet AntennasCisco Aironet AntennasCisco Aironet AntennasCisco Aironet Antennas
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-supplied cables, RF devices and antennas have reverse TNC (RP-TNC) connectors
Cisco Aironet-supplied antennas meet all FCC rules
Wide variety antennas for most applications
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-5
Antenna ConceptsAntenna ConceptsAntenna ConceptsAntenna Concepts
Directionality• Omni (360º coverage) directional
• Directional (limited range of coverage)
Gain• Measured in dBi and dBd. (0dBd = 2.14dBi)
• More gain means more coverage - in certain directions
Polarization• Antennas are used in the vertical polarization
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-6
Antenna GainAntenna GainAntenna GainAntenna Gain
In life you never get “something for nothing;” the same is true in 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.
These angles are referred to as beamwidth, and have a horizontal and vertical measurement.
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-7
Antenna TheoryAntenna TheoryAntenna TheoryAntenna Theory
A theoretical isotropic antenna has a perfect 360º vertical and horizontal beamwidth.
This is a reference for ALL antennas
Side View(Vertical Pattern)
Top View(Horizontal Pattern)
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-8
Antenna Theory- DipoleAntenna Theory- DipoleAntenna Theory- DipoleAntenna Theory- Dipole
To obtain omni-directional gain from an isotropic antenna, the energy lobes are ‘pushed in’ from the top and bottom, and forced out in a doughnut type pattern.
The higher the gain, the smaller the vertical beamwidth, and the larger the horizontal lobe area
This is the typical dipole pattern. Gain of a dipoleis 2.14dBi (0dBd)
Side View(Vertical Pattern)
Top View(Horizontal Pattern)
New Pattern (with Gain)
Vertical Beamwidth
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-9
High Gain Omni-DirectionalsHigh Gain Omni-DirectionalsHigh Gain Omni-DirectionalsHigh Gain Omni-Directionals
High gain omni-directional antennas will create more coverage area in away from the antenna, but the energy level directly below the antenna will become lower. Coverage here may be poor.
Area of poor coverage directly under the antenna
Beamwidth
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-10
Directional AntennasDirectional AntennasDirectional AntennasDirectional Antennas
For directional antennas the 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.
Side View(Vertical Pattern)
Top View(Horizontal Pattern)
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-11
FCC Part 15 Antenna FCC Part 15 Antenna RequirementsRequirements
FCC Part 15 Antenna FCC Part 15 Antenna RequirementsRequirements
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-12
EIRPEIRPEIRPEIRP
Effective Isotropic Radiated PowerPower Setting dBm
100 mW 20 dBm
50 mW 17 dBm
30 mW 15 dBm20 mW 13 dBm
15 mW 12 dBm
5 mW 7 dBm
1 mW 0 dBm
w/ 6 dBi Patch EIRP
6 dBi 26 dBm
6 dBi 23 dBm
6 dBi 21 dBm6 dBi 19 dBm
6 dBi 18 dBm
6 dBi 13 dBm
6 dBi 6 dBm
Cisco Aironet Cisco Aironet AntennasAntennas
Cisco Aironet Cisco Aironet AntennasAntennas
© 2001, Cisco Systems, Inc. www.cisco.com AWLF 1.0—Chapter5-13
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-14
2.4Ghz Omni-Directional 2.4Ghz Omni-Directional AntennasAntennas
2.2dBi Dipole “Standard Rubber Duck”
Cisco Aironet Part # AIR-ANT4941
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-15
2.4Ghz Omni-Directional 2.4Ghz Omni-Directional AntennasAntennas
2.2dBi Ceiling Mount
Cisco Aironet Part # AIR-ANT3194
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-16
2.4Ghz Omni-Directional 2.4Ghz Omni-Directional AntennasAntennas
5.2dBi Ceiling Mount
Cisco Aironet Part # AIR-ANT1728
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-17
2.4Ghz Omni-Directional 2.4Ghz Omni-Directional AntennasAntennas
5.2dBi Mast Mount Vertical
Cisco Aironet Part # AIR-ANT2506
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-18
2.4Ghz Omni-Directional 2.4Ghz Omni-Directional AntennasAntennas
5.2dBi Pillar Mount Diversity
Cisco Aironet Part # AIR-ANT3213
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-19
2.4Ghz Omni-Directional 2.4Ghz Omni-Directional AntennasAntennas
5.2dBi Ground Plane
Cisco Aironet Part # AIR-ANT2561
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-20
2.4Ghz Omni-Directional 2.4Ghz Omni-Directional AntennasAntennas
12dBi Omni Directional (Outdoor only)
Cisco Aironet Part # AIR-ANT4121
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-21
2.4Ghz Directional 2.4Ghz Directional AntennasAntennas
3dBi Patch Antenna – 65 degree
Cisco Aironet Part # AIR-ANT3195
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-22
2.4Ghz Directional 2.4Ghz Directional AntennasAntennas
6dBi Patch Antenna – 65 degree
Cisco Aironet Part # AIR-ANT1729
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-23
2.4Ghz Directional 2.4Ghz Directional AntennasAntennas
8.5dBi Patch Antenna – 55 degree
Cisco Aironet Part # AIR-ANT3549
H Plane
E Plane
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-24
2.4Ghz Directional 2.4Ghz Directional AntennasAntennas
13.5dBi Yagi Antenna – 25 degree
Cisco Aironet Part # AIR-ANT1949
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-25
2.4Ghz Directional 2.4Ghz Directional AntennasAntennas
21dBi Parabolic Dish Antenna – 12 degree
Cisco Part # AIR-ANT3338
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-26
SummarySummarySummarySummary
Upon completion of this chapter you should be able to perform the following tasks:
•How different antennas can affect the propagation of the RF signal
•Compare antenna ratings in dBi vs. dBd
•Assist the customer in choosing the right antenna for their installation
© 2001, Cisco Systems, Inc. AWLF1.0—Chapter5-27
Review QuestionsReview QuestionsReview QuestionsReview Questions
1. A 2.14 dBi antenna is the same as a 3.28 dBd antenna (True/False)?
2. An antenna with more gain is always a better antenna? Why or why not?
3. Ceiling mount antennas are always the best choice for an indoor installation? Why or why not?
4. A higher gain antenna adds more output power to the access point’s output (True/False)?
Cisco Aironet Wireless Training© 2000, Cisco Aironet Systems, Inc.