CWNA Certified Wireless Network Administrator

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CWNACertified Wireless Network Administrator

• Antennas

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RF Antennas

• Antenna - A metallic device for sending or
  receiving electromagnetic waves.
• Antenna Reciprocity The interchangeability of
  an antenna to be use as either a transmitting or
  receiving device. (Disclaimer Power-handling
  ability.)

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Radiation Patterns

• Isotropic Point Source, Sphere shaped
  pattern.
• Dipole 2 Element Half-Wave, Oblong
  doughnut shaped pattern.

Z
Z
Y
Y
Y
X
X
Z
Z
Y
Y
Y
X
X
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Radiation Patterns

• Arrays Yagi-Uda, Multi-lobe shaped pattern.

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Radiation Patterns

• Parabolic Dish, and Corner Reflectors, Lobe
  shaped pattern.

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Radiation Patterns
X
Omni-Directional
Y
X
Semi-Directional
Y
X
Highly-Directional
Y
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Polarization

• Polarization By convention the orientation of
  the electric field, (E) with respect to the
  earths surface. Vertical, Horizontal, and
  Circular/Elliptical polarization.

H
E
P
E
E
E
E
A
B
D
C
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Antenna Beamwidth

• Beam-width the angular separation between the
  two half-power points on the major lobe of one of
  the radiation planes of an antenna. The
  half-power points are -3 dB or 0.707 of the
  voltage maximum.

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Antenna Beamwidth
Azimuth (E-Plane)
dB
0
Major Lobe
0
0 dB
A
B
-3
-3 dB
-6
?
-9
-12
-?
-90
90
-12
-9
6-element Yagi 7 dBi, 2.4 2.5 GHz 50 Watts Max.
-6
-3
0
Beamwidth ? ____ degrees
180
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HyperGain HG2415Y

• 2.4 GHz 14.5 dBi Radome Enclosed Wireless LAN
  Yagi Antenna

BW 24?
BW 30?
?65.00
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Directional Antennas
Proxim, Yagi BW 30?, 15 dBi
Alvarion, Sector BW 90?, 16 dBi
BW Beam-width
Cisco, Parabolic Dish BW 12.4?, 21 dBi
D-Link, Panel BW 30?, 14 dBi
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Omni-Directional Antennas
Proxim, Omni BW 360?, 2.5 dBi
Alvarion, Omni BW 360?, 8 dBi
Cisco, Omni BW 360?, 5.2 dBi
D-Link, Omni BW 360?, 8 dBi
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Free Space Path Loss

• Free Space Path Loss Loss caused by an EM wave
  as it propagates in a straight path through a
  vacuum with no other losses.

EM Wave
Antenna and Tower
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Free Space Path Loss
4?Dm
Path LossdB LPdB 20 log10
?m
Dm 5000 meters
2.45 GHz Link
LPdB 114 dB
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Free Space Path Loss Table
Path Attenuation
Table 4-1
f 2.45 GHz
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Coaxial Cables
Attenuation of cables, dB/100 ft, (dB/100 m)
Table 5-2
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RF Connectors

• An RF device for mechanically terminating and
  providing electrical contact between devices
  and/or cables.

Cable
RF Plug Male
RF Jack Female
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RF Cables

• RF Cables Coaxial Cable - A cylindrical
  transmission line comprised of a conductor
  centered inside a metallic tube or shield,
  separated by a dielectric material, and usually
  covered by an insulating jacket.

Insulating Jacket
Metal Shield
Dielectric
Center Conductor
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Coaxial Cable
2
1
3
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RF Connector Types
BNC - Type, stands for Bayonet Neill, Concelman,
1940s 50 O and 75 O, up to 11 GHz.
N - Type, named after Paul Neill of Bell Labs,
1040s 50 O, up to 11 GHz.
TNC - Type, stands for Threaded Neill, Concelman,
1950s 50 O, up to 11 GHz, There are two types of
TNC connectors Standard and Reverse Polarity.
SMA - Type is an acronym for SubMiniature version
A, 1960's 50 O, up to 18 GHz.
UHF - Type, is an acronym for Ultra High
Frequency, 1930s 50 O, up to 300 MHz. Not a
good connector for wireless LANs!
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N-Type Connectors
Female / Jack
Male / Plug
Female / Jack Chassis
Inline Double Female
Right Angle Male to Female
T Adaptor 2 Female to Male
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Link Budget
Yagi 14 dBi
Path Loss -114 dB
Yagi 14 dBi
Cable -3 dB
Cable -3 dB
0 dB
Rx Input
Each N-Connector -0.5 dB
AP-B
AP-A
Rec -82 dBm
Xmitter 15 dBm
Rx Threshold
Graph A
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Fresnel Zone

• Fresnel Zone - one of a (theoretically infinite)
  number of a concentric ellipsoids of revolution
  centered around the LOS path. (Pronouced frA-nel)
  
• Provides a technique to determine the required
  clearance between the signal and any obstacles
  along the transmission path.

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Fresnel Zone
D3
D2
D1
WISP Building
Client Condos
Water Tower
(D1) (D2)
72.1
D3
f (D1 D2)
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Earth Curvature
D
A
H
B
D
D2

43.3
H
8
4F
H ? Feet D ? Miles F ? GHz
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Antenna Installation

• Correctly installed antenna systems are a
  crucial part of a wireless network.
• Site Survey.
• Create installation documentation.

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Antenna Installation

• Installation preparation and checklists.
• Install the antenna systems according to the
  safety regulations.
• Use the correct tools and instruments.

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RF External Amplifier
Antenna
Antenna Mount
RF Amplifier
Cable Standoffs
Antenna Mast
Antenna Ground Rod
Building
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Antenna Mounting Hardware
C
B
F
A
D
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Antenna/Cable Grounding
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RF Attenuators

• An RF attenuator is a device that reduces the
  level of an RF signal. RF attenuators can be
  fixed or adjustable.

Stepped Attenuator
Variable Attenuator
Fixed Attenuators
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Lightning Arrestor

• Lightning Arrestor A device used to allow a
  path to ground for unwanted static electricity,
  lightning-induced surges, or any abnormally high
  voltage or current.

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Lightning Arrestors
Antenna
To Access Point
To Antenna
GND Post
Ground Rod
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RF Splitter / Power Dividers

• RF Splitter - A passive or active device that
  divides one RF signal into multiple RF signals.

Test Antenna
mW
50
Power Meter
RFAmplifier
RFSplitter
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RF Splitters
Sector Panel Antennas
RF Splitter
Ant - 1
Ant - 2
Reduced Power Out1
Reduced Power Out2
A
Radiation Patterns
Power In
B
Mechanical Beam Tilt
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Test Kits / Instruments

• Digital Multimeter
• Power Meter
• RF Signal Generator
• Spectrum Analyzer
• Time Domain Reflectometer

100
mW
Power Meter