Active and Passive Gain Azimuth and elevation charts (antenna radiation

envelopes) Interpreting polar charts Beamwidth Antenna types

Omnidirectional antennas Semidirectional antennas Highly directional antennas Phased array antennas Sector antennas

Visual line of sight RF line of sight Fresnel zone Earth bulge Antenna polarization Antenna diversity Multiple-input multiple-output (MIMO)

Understand passive and active gain Understand how antennas provide passive gain and

how transceivers and amplifiers provide active gain. Know the different categories and types of

antennas, how they radiate signals, and what type of environment they are used in. Make sure you know the three main categories of

antennas and the different types of antennas. know the similarities and differences between them, and understand when and why you would use one antenna over another. Make sure that you understand azimuth and elevation charts, beamwidth, antenna polarization, and antenna diversity.

Fully understand the Fresnel zone. Make sure you understand all of the issues and

variables involved with installing point-to-point communications. You are not required to memorize the Fresnel zone or earth bulge formulas; however, you will need to know the principles regarding these topics and when and why you would use the formulas.

Understand the concerns associated with connecting and installing antennas and the antenna accessories. Every cable, connector, and device between the

transceiver and the antenna affects the signal that gets radiated from the antenna. Understand which devices provide gain and which devices provide loss. Understand what vSWR is and what values are good or bad. know the different antenna accessories, what they do, and why and when you would use them.

Signal must be radiate with enough power so that is will be understood by the receiver

Antenna installation will have a great effect.Simple-omni-directional in middle of officeComplex-multiple semi-directional antennas

Pg 107

Measurements of the increase in signal from the Antenna (EIRP) If gain is from an amplifier or increased

power at the transmitter-it is ACTIVE Gain If from shaping or focusing the power with

an antenna,-PASSIVE Gain

Passive gain from focusing existing Power

Active Gain by adding more power

Pg 107

Focusing isotropic energy in a specific pattern

Created by the design of the antennaUses the magnify glass concept

Providing an external power sourceAmplifierHigh gain transmitters

Charts help you “see” how antennas focus energyPolar charts or antenna radiation envelopes

Pg 109

In either chart, the antenna is placed at the middle of the chart.Azimuth chart = H-plane = top-down viewElevation chart = E-plane = side view

Like casting a shadow with your handShape is same, but size grows with power.

Pg 109

Easy to misinterpretThe chart shows the DECIBEL mapping of

coverage Each line 5 dB!!

Normalized charts appear very different

Pg 110

Easy to misinterpretThe chart shows the DECIBEL mapping of

coverage Each line 5 dB!!

Normalized charts appear very different

Pg 110

The measure of how broad or narrow the focus of an antenna isMeasured both horizontally and verticallyTo the point where the signal decreases by

half power (-3dB)

Pg 113

First determine the scale of the polar chart. On this chart, you can see that the solid circles represent the –10, –20, and –30 dB lines, and the dotted circles therefore represent the –5, –15, and –25 dB line

Now to determine the beamwidth of this antenna, frst locate the point on the chart where the antenna signal is the strongest. In this example, the signal is strongest where the number 1 arrow is pointing. Move along the antenna pattern away from the peak signal (as shown by the two number 2 arrows) until you reach the point where the antenna pattern is 3 dB closer to the center of the diagram (as shown by the two number 3 arrows).

This is why you needed to know the scale of the chart first. Draw a line from each of these points to the middle of the polar chart (as shown by the dark dotted lines) and measure the distance in degrees between these lines to calculate the beamwidth of the antenna. In this example, the beamwidth of this antenna is about 30 degrees.

Pg 113

Omnidirectional Omnidirectional antennas radiate RF in a fashion similar to the way a table or

foor lamp radiates light. They are designed to provide general coverage in all directions.

Semidirectional Semidirectional antennas radiate RF in a fashion similar to the way a wall

sconce radiates light away from the wall or the way a street lamp shines light down on a street or a parking lot, providing a directional light across a large area.

Highly directional Highly directional antennas radiate RF in a fashion similar to the way a

spotlight focuses light on a fag or a sign. Pg 115

Antennas not only amplify transmitted signal, they amplify received signal

Pg 115

Common on many access PointsDipole

Rubber duck

Bagel shaped transmission Wide horizontal coverage Limited vertical coverage Low gain antennas are usually 2.14dB

Higher gain is more elongated

Pg 116

High Gain Omni-directional Antenna

Low 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.

The omni antenna is the most commonly used antenna type

Antennas are most effective when the element is an even fraction or a multiple of the wavelength (λ)¼, ½, 1, 2, etc.

Higher gain antennas are often made by stacking dipole antennas

Used in multipoint environments Indoor Access PointBuilding to multiple building coverage

Beware of higher gain limiting the vertical coverage

Pg 117

Designed to direct the signal in a specific directionPoint to point-outdoors about a mileDown hallways

Three typesPlanar Type

Patch Panel

Yagi

Pg 118

Multiple planar antennas can be used to cover multiple aislesLibraries, Warehouses, Retail, etc

Yagi antennas are like old TV antennasHowever, each element is fitted for wireless

wavelengths Even fraction or multiple of wavelength

Pg 119

Also good on walls Most have limited side lobe and vertical

and can be pointed down for coverage

Pg 121

PatchSemi-directional

Antennas

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/CorridorsWireless ISPsPTP & PTMP Bridging

Multiple semi-directional antennas can be combined into an array to provide omni-directional coverage.

Patch

For Point to PointGenerally between two buildings

Focused, narrow beamwidth Two main types

Parabolic DishGrid Antenna

Since they are used outdoors, wind loading is an issueSince they have narrow beamwidth, the

wind can push them out of direction

Pg 121

Highly focused energy Most common type - parabolic

Multiple antennas connected to a signal processor

Different antennas can be fed different phasesAble to create very directed beams

Usually regulated differently Not common in 802.11

802.11n has a PHY specification that supports it Smart antenna technology

Pg 123

Specialized high gain, semidirectional antenna

Multiple antennas with limited back lobeEach antenna can be on its on its own

transceiver Usually set up to provide 360 degree

coverage Used extensively in cellular phone

systems

Pg 123

The “line” from source to destinationVisual LOS is not important on Wireless

networks RF line of sight is

Mostly for outdoor point to point connections

Should be unobstructed

Pg 124

Visual line of sight RF line of sight Fresnel zone

Football shaped area around the “LOS” Actually multiple zones surrounding the

main line of sight If first Fresnel zone is obstructed, it will

affect the transmissionsmore than 40% will make link unrealiableKeep it to less than 20%

Pg 125

You need to understand how the calculations will affect placement when designing a point to point.

Can calculate the size of the zone in middleOr at certain distances

Important for keeping out obstructions

Pg 125

Don’t mistake smaller beamwidth for smaller Fresnel zone

Fresnel zone is affected by the frequency of the transmission, not the antenna

Pg 128

For longer Point to Point links-More than 7 miles

Important to calculate height requirements for towers

Pg 128

Alignment of the antenna can affect polarization

Doesn’t matter if it is horizontal or vertical, both transmitter and receiver need to be the same way

Most systems have antenna diversityMultiple antennas (more than one

wavelength away) If the Received Signal Level (RSL) is

10 to 15 dB less than expected, you may be linking to a side lobe

Pg 130

Helps compensate for multipath An AP has multiple antennas

Compares the signal from each antenna and choose the best signal

802.11n uses switched diversitySignal with the best amplitude is usedAlso known as received diversity

Can also use measurement to choose the transmit antenna

Pg 130

Don’t put the antennas in different locations or point in different directionsThat defeats the purpose

Usually a single radio with multiple connectionsCommon inside laptops

Pg 130

More sophisticated type of antenna diversity

Takes advantage of multipath Uses Space Time Coding

Send multiple signals simultaneously

Pg 132

Measure of the change in impedances to an AC signalWhen there is a difference or mismatch in

impedance between devices in a RF system Forward Energy is reflected backward to

the transmitter Usually at points where you are

connectingCable to transmitterCable to antenna

Pg 133

Ratio of energy reflected is the voltage reflection coefficientReturn Loss

Ideally, there is no mismatchA matched cable, 0 ratio, infinite return loss

VSWR is a measure between the maximum voltage and minimum voltage

VSWR=Vmax/Vmin

Pg 133

Higher the return loss, the less broadcast power Return voltage can also damage the transmitter

Pg 133

The goal when connecting the antenna to transmitter is to reduce signal loss

Must pay attention to devices usedCables and connectors

Pg 134

Placement Mounting Appropriate Use Orientation and alignment Safety Maintenance

Pg 134

Correct placement for type of antennaOmnidirectional toward centerSemi-direction at edge, pointed toward

center Pay attention to vertical and

horizontal coverage Also, power levels-

Too high a power will provide an overlarge coverage area Security risk

Outdoors-Watch the Fresnel ZonePg 135

OutdoorsMasts or towers

IndoorsWall or ceiling

Often want to hide or camouflage for aesthetics

Pg 135

Indoor vs. Outdoor Although they look the same, they are

designed for correct temperature and environment

Pg 136

Pay attention to horizontal vs. vertical alignment

Polarization can make the difference between being able to communicate or not

Pg 136

Be careful RF health and safety courses

FCC and OSHA regulations If installing on a tower, pole, etc-get a

professional.

Pg 135

Preventative and diagnostic Don’t just set and forget

Especially not outdoors Outdoors you need to be aware of wind

and water damageWind

Properly mountWater

Cold-shrink tubing, sealant, drip loops

Pg 137

All devices attached in the RF system need to be checked forFrequency response ImpedanceVSWRMaximum input power Insertion loss

Pg 137

Choose the correct cable based on technology, frequency, etcSome cables can’t be used with some

frequenciesMatch the impedanceCalculate the signal loss

Different for different frequenciesPurchase pre-cut of hire a professional

You want to measure loss in the connections

Pg 139

FCC has mandated that manufacturers use unique connectors to limit the ability to use noncertified antennasPigtail adapters get around this requirement

Be careful of exceeding FCC regulations

Pg 139

Join cables and devices togetherAP to antennaAntenna to cableCable to cableEtc.

Signal splitter, RF splitter, Power Splitter Used when you need the signal to go to

more than one locationMultiple antennas

Will cause loss and degradation of signalPower monitoring

Pg 139

For active gain Unidirectional

transmit only Bi-directional

Transmit and receive Fixed output

Generate a signal equal to that of the amplifier

Fixed GainAdds amplifier to transmitter power

Pg 140

In cases where you need to limit the range or power If the minimum power setting isn’t small

enough

Pg 140

Protect from power surges due to nearby strikesDirect strike will fry it

Protects the devices behind it on the circuit

Pg 141

Does not prevent equipment loss in cases of direct lightning strikes!

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

Pg 141

Important to have a common groundProperly sunk copper rod and connectorsTinned copper wire to connect tower legs

Pg 142

Understand passive and active gain Understand how antennas provide passive gain and

how transceivers and amplifiers provide active gain. Know the different categories and types of

antennas, how they radiate signals, and what type of environment they are used in. Make sure you know the three main categories of

antennas and the different types of antennas. know the similarities and differences between them, and understand when and why you would use one antenna over another. Make sure that you understand azimuth and elevation charts, beamwidth, antenna polarization, and antenna diversity.

Fully understand the Fresnel zone. Make sure you understand all of the issues and

variables involved with installing point-to-point communications. You are not required to memorize the Fresnel zone or earth bulge formulas; however, you will need to know the principles regarding these topics and when and why you would use the formulas.

Understand the concerns associated with connecting and installing antennas and the antenna accessories. Every cable, connector, and device between the

transceiver and the antenna affects the signal that gets radiated from the antenna. Understand which devices provide gain and which devices provide loss. Understand what vSWR is and what values are good or bad. know the different antenna accessories, what they do, and why and when you would use them.