Antennas Module 10B

CCRI J. Bernardini

AntennasModule 10B

Based on Cisco Wireless Material

CCRI J. Bernardini

Overview

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.

CCRI J. Bernardini

Learning Objectives

–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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Key terms

• 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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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)

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Cisco Aironet 802.11b 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 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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Cisco Aironet 802.11a Antennas

• 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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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

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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

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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

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Antenna Theory

• A theoretical isotropic antenna has a perfect 360º vertical and horizontal beamwidth

• This is a reference for ALL antennas

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Antenna Theory- Dipole

• Energy lobes are ‘pushed in’ from the top and bottom

• Higher gain– Smaller vertical

beamwidth– Larger horizontal lobe

• Typical dipole pattern

Side View(Vertical Pattern)

Top View(Horizontal Pattern)

New Pattern (with Gain)

Vertical Beamwidth

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High Gain Omni-Directionals

• More coverage area in a circular pattern

• Energy level directly above or below the antenna will become lower

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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

Side View(Vertical Pattern)

Top View(Horizontal Pattern)

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FCC Part 15 Antenna Requirements

• 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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2.4 GHz EIRP Rules for FCC Governed Areas

• 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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2.4 GHz EIRP Rules for FCC Governed Areas (cont.)

Transmitter Power

Transmitter Power

EIRPEIRP

Cisco MaximumCisco Maximum

6 dBi6 dBi 36 dBm36 dBm

100 mW100 mW 20 dBm20 dBm

FCC MaximumFCC Maximum

Maximum Gain

Maximum Gain

Transmitter dBm

Transmitter dBm

1 Watt1 Watt

Point-to-MultipointPoint-to-Multipoint

30 dBm30 dBm


Transmitter Power

Transmitter Power

EIRPEIRP

Cisco MaximumCisco Maximum


100 mW100 mW 20 dBm20 dBm

FCC MaximumFCC Maximum

Maximum Gain

Maximum Gain

Transmitter dBm

Transmitter dBm

1 Watt1 Watt

Point-to-PointPoint-to-Point

30 dBm30 dBm


The above values reflect the 1:1 rule


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2.4 GHz EIRP Rules for ETSI Governed Countries

• 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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2.4 GHz EIRP Rules for non-FCC Governed Bodies

Transmitter Power

Transmitter Power

EIRPEIRP

Cisco Integrated AntennasCisco Integrated Antennas

3 dBi 3 dBi 20 dBm20 dBm

Reduced TX PowerReduced TX Power 30 mW 30 mW 5 dBi 5 dBi15 dBm15 dBm

50 mW 50 mW 17 dBm17 dBm

7 dBi 7 dBi13 dBm13 dBm

20 dBi20 dBi


Gov. Body MaximumGov. Body Maximum

Maximum Gain

Maximum Gain

Transmitter dBm

Transmitter dBm

Reduced TX PowerReduced TX Power



50 mW 50 mW

20 mW 20 mW

5 mW 5 mW

1 mW 1 mW

Point-to-Multipoint and Point-to-PointPoint-to-Multipoint and Point-to-Point

17 dBm 17 dBm

7 dBm7 dBm

0 dBm0 dBm

2.2 dBi2.2 dBi 19.2 dBm19.2 dBm

20 dBm20 dBm

20 dBm20 dBm

20 dBm20 dBm


Governing bodies with 20 dBm ceiling on EIRP: ETSI, France/Singapore, Israel, Mexico

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802.11a and FCC 5 GHz Specifications

• 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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FCC Rules for 802.11a - Antennas

• 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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2.4 GHz Omni-Directional Antennas

• 2 dBi Dipole "Standard Rubber Duck"

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• 5.2 dBi Mast Mount Vertical

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• 5.2 dBi Ceiling Mount

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• 5.2 dBi Pillar Mount Diversity

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2.4 GHz Diversity Omni-Directional Antennas

• 2 dBi Diversity Omni-Directional Ceiling Mount

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• 12 dBi Omni-Directional (Outdoor only)

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5 GHz Omni-Directional Antennas

• 9 dBi omni (Vertical polarization)

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– 9.5 dBi sector (H or V polarization)

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

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2.4 GHz Directional Antennas (cont.)

• 6 dBi Patch Antenna – 65 degree

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• 8.5 dBi Patch Antenna – 60 degree

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• 13.5 dBi Yagi Antenna – 25 degree

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13.5 dBi Yagi Antenna—Inside view

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• 21 dBi Parabolic Dish Antenna – 12 degree

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– 28 dBi dish (H or V polarization)

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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 5 dBi omni position

In 6 dBi patch position

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5 GHz Radiation Pattern

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Mini-PCI RadioMini-PCI Radio

2.2 dBi Omni-Directional Diversity Antennas2.2 dBi Omni-Directional Diversity Antennas

•Option 1: 802.11b•Option 1: 802.11b

Cisco Aironet 1100 Series Internal View

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Cisco Aironet 1100 Series Antenna Details

Cone of reduced coverage


Sphere of influenceSphere of influence

Sphere of influenceSphere of influence



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H-Plane Pattern E-Plane Pattern

Top View Side View

Floor

H-Plane Pattern, Ivory Antenna = 90 degs Plane Cut (in x-y plane)

-20

-15

-10

-5

0

5

H-Plane Pattern, Ivory Antenna = 90 degs Plane Cut (in x-y plane)

-20

-15

-10

-5

0

5

E-Plane Pattern, Ivory Antenna = 0 degs Plane Cut (cut along x-z axis)

-25

-20

-15

-10

-5

0

5

E-Plane Pattern, Ivory Antenna = 0 degs Plane Cut (cut along x-z axis)

-25

-20

-15

-10

-5

0

5

Cisco Aironet 1100 Series Antenna Details (cont.)

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2.4 GHz Accessories

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RP-TNC Connectors

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Lightning Arrestor

• 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

To Antenna

Ground Wire

From RF Device

Lug

LockwasherNut

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Lightning Arrestor

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Path Considerations

• Radio line of sight• Earth bulge• Fresnel zone• Antenna and cabling• Data rate

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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

Line of sight!

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Longer Distances

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

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Fresnel Zone

Fresnel Zone

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Improving Fresnel Effect

Raise the antenna

New structure

Existing structure

Different mounting point

Remove trees

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Total Distance

Fresnel @ 60% (Value “F”)

Earth Curvature (Value “C”)

Antenna Height (Value “H”)

Site to Site Fresnel Zone

• Antenna Height– Fresnel zone consideration– Line-of-Sight over 25 miles (40 Km) hard to implement

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Antenna Alignment

Line of Sight

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Antenna Issues

•No Downtilt

•One-way communications

High gain omni-directional

Directional antenna

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8 Miles/13 Km

700 ft./213 m

8.50 downtilt

14.50

200

ft.

/61

m

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• Omni-directional antennas provide 3600 coverage• Also accepts interference from all directions

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Antenna Mounting

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Mounting (Cont.)

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Antenna Installation

Towers and antennas may require permits and must meet local regulations

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Antenna Installation (cont.)

• Antenna Alignment Tool

Id Name Address Signal Strength Signal Quality

18 Cisco Bridge #1 00409644fd35 100% -10 dBm 100%










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Antenna Installation (cont.)

• Aironet Client Utility• Site Survey Utility

for antenna alignment

Antennas Module 10B

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