1. Chapter 4-Radio Frequency signal and Antenna Concepts
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)

2. Exam Essentials 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.

3. Exam Essentials 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.

4. Signal and Antenna Concepts
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 office
Complex-multiple semi-directional antennas
Pg 107

5. Active and Passive Gain
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

6. Passive Gain Focusing isotropic energy in a specific pattern
Created by the design of the antenna
Uses the magnify glass concept

7. Active Gain Providing an external power source Amplifier
High gain transmitters

8. Azimuth and Elevation Charts
Charts help you “see” how antennas focus energy
Polar charts or antenna radiation envelopes
Pg 109

9. Azimuth and Elevation Charts
In either chart, the antenna is placed at the middle of the chart.
Azimuth chart = H-plane = top-down view
Elevation chart = E-plane = side view
Like casting a shadow with your hand
Shape is same, but size grows with power.
Pg 109

10. Interpreting Polar Charts
Easy to misinterpret
The chart shows the DECIBEL mapping of coverage
Each line 5 dB!!
Normalized charts appear very different
Pg 110

11. Interpreting Polar Charts
Easy to misinterpret
The chart shows the DECIBEL mapping of coverage
Each line 5 dB!!
Normalized charts appear very different
Pg 110

12. Beamwidth
The measure of how broad or narrow the focus of an antenna is
Measured both horizontally and vertically
To the point where the signal decreases by half power (-3dB)
Pg 113

13. Reading a chart
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

14. Antenna Types Pg 115 Omnidirectional Semidirectional
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

15. Antenna Types
Antennas not only amplify transmitted signal, they amplify received signal
Pg 115

16. Omnidirectional Antennas
Common on many access Points
Dipole
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

17. The omni antenna is the most commonly used antenna type
Low Gain Omni-directional Antenna
High Gain Omni-directional Antenna
The omni antenna is the most commonly used antenna type
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.

18. Antennas
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 Point
Building to multiple building coverage
Beware of higher gain limiting the vertical coverage
Pg 117

19. Semidirectional Antennas
Designed to direct the signal in a specific direction
Point to point-outdoors about a mile
Down hallways
Three types
Planar Type
Patch
Panel
Yagi
Pg 118

20. Semidirectional Antennas
Multiple planar antennas can be used to cover multiple aisles
Libraries, Warehouses, Retail, etc
Yagi antennas are like old TV antennas
However, each element is fitted for wireless wavelengths
Even fraction or multiple of wavelength
Pg 119

21. Semidirectional Antennas
Also good on walls
Most have limited side lobe and vertical and can be pointed down for coverage
Pg 121

22. Semi-directional Antennas
Patch
Semi-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/Corridors
Wireless ISPs
PTP & PTMP Bridging
Patch
Multiple semi-directional antennas can be combined into an array to provide omni-directional coverage.

23. Highly Directional Antennas
For Point to Point
Generally between two buildings
Focused, narrow beamwidth
Two main types
Parabolic Dish
Grid Antenna
Since they are used outdoors, wind loading is an issue
Since they have narrow beamwidth, the wind can push them out of direction
Pg 121

24. Highly Directional Antennas
Highly focused energy
Most common type - parabolic

25. Phased Array Antennas
Multiple antennas connected to a signal processor
Different antennas can be fed different phases
Able to create very directed beams
Usually regulated differently
Not common in
802.11n has a PHY specification that supports it
Smart antenna technology
Pg 123

26. Sector Antennas Specialized high gain, semidirectional antenna
Multiple antennas with limited back lobe
Each 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

27. Line of Sight The “line” from source to destination
Visual LOS is not important on Wireless networks
RF line of sight is
Mostly for outdoor point to point connections
Should be unobstructed
Pg 124

28. Maintaining Clear Communications
Visual line of sight
RF line of sight
Fresnel zone

29. 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 transmissions
more than 40% will make link unrealiable
Keep it to less than 20%
Pg 125

30. Fresnel Zone
You need to understand how the calculations will affect placement when designing a point to point.
Can calculate the size of the zone in middle
Or at certain distances
Important for keeping out obstructions
Pg 125

31. Fresnel Zone Don’t mistake smaller beamwidth for smaller Fresnel zone
Fresnel zone is affected by the frequency of the transmission, not the antenna
Pg 128

32. Earth Bulge For longer Point to Point links-More than 7 miles
Important to calculate height requirements for towers
Pg 128

33. Antenna Polarization 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 diversity
Multiple 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

34. Antenna Diversity Helps compensate for multipath
An AP has multiple antennas
Compares the signal from each antenna and choose the best signal
802.11n uses switched diversity
Signal with the best amplitude is used
Also known as received diversity
Can also use measurement to choose the transmit antenna
Pg 130

35. Antenna Diversity
Don’t put the antennas in different locations or point in different directions
That defeats the purpose
Usually a single radio with multiple connections
Common inside laptops
Pg 130

36. Multiple In Multiple Out (MIMO)
More sophisticated type of antenna diversity
Takes advantage of multipath
Uses Space Time Coding
Send multiple signals simultaneously
Pg 132

37. Voltage Standing Wave Ratio (VSWR)
Measure of the change in impedances to an AC signal
When 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 connecting
Cable to transmitter
Cable to antenna
Pg 133

38. Voltage Standing Wave Ratio (VSWR)
Ratio of energy reflected is the voltage reflection coefficient
Return Loss
Ideally, there is no mismatch
A matched cable, 0 ratio, infinite return loss
VSWR is a measure between the maximum voltage and minimum voltage
VSWR=Vmax/Vmin
Pg 133

39. Voltage Standing Wave Ratio (VSWR)
Higher the return loss, the less broadcast power
Return voltage can also damage the transmitter
Pg 133

40. Signal Loss
The goal when connecting the antenna to transmitter is to reduce signal loss
Must pay attention to devices used
Cables and connectors
Pg 134

41. Antenna Mounting Placement Mounting Appropriate Use
Orientation and alignment
Safety
Maintenance
Pg 134

42. Placement Correct placement for type of antenna
Omnidirectional toward center
Semi-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 Zone
Pg 135

43. Mounting Outdoors Indoors
Masts or towers
Indoors
Wall or ceiling
Often want to hide or camouflage for aesthetics
Pg 135

44. Appropriate Use Indoor vs. Outdoor
Although they look the same, they are designed for correct temperature and environment
Pg 136

45. Orientation and Alignment
Pay attention to horizontal vs. vertical alignment
Polarization can make the difference between being able to communicate or not
Pg 136

46. Safety Be careful RF health and safety courses
FCC and OSHA regulations
If installing on a tower, pole, etc-get a professional.
Pg 135

47. Maintenance Preventative and diagnostic Don’t just set and forget
Especially not outdoors
Outdoors you need to be aware of wind and water damage
Wind
Properly mount
Water
Cold-shrink tubing, sealant, drip loops
Pg 137

48. Antenna Accessories
All devices attached in the RF system need to be checked for
Frequency response
Impedance
VSWR
Maximum input power
Insertion loss
Pg 137

49. Cables Choose the correct cable based on technology, frequency, etc
Some cables can’t be used with some frequencies
Match the impedance
Calculate the signal loss
Different for different frequencies
Purchase pre-cut of hire a professional
You want to measure loss in the connections
Pg 139

50. Connectors
FCC has mandated that manufacturers use unique connectors to limit the ability to use noncertified antennas
Pigtail adapters get around this requirement
Be careful of exceeding FCC regulations
Pg 139

51. RF Connectors Join cables and devices together AP to antenna
Antenna to cable
Cable to cable
Etc.

52. Splitters Signal splitter, RF splitter, Power Splitter
Used when you need the signal to go to more than one location
Multiple antennas
Will cause loss and degradation of signal
Power monitoring
Pg 139

53. Amplifiers For active gain Unidirectional Bi-directional Fixed output
transmit only
Bi-directional
Transmit and receive
Fixed output
Generate a signal equal to that of the amplifier
Fixed Gain
Adds amplifier to transmitter power
Pg 140

54. Attenuators In cases where you need to limit the range or power
If the minimum power setting isn’t small enough
Pg 140

55. Lightning Arrestors Protect from power surges due to nearby strikes
Direct strike will fry it
Protects the devices behind it on the circuit
Pg 141

56. Lightening Arrestors 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
Does not prevent equipment loss in cases of direct lightning strikes!

57. Lightning Arrestors
Pg 141

58. Grounding Rod and Wires
Important to have a common ground
Properly sunk copper rod and connectors
Tinned copper wire to connect tower legs
Pg 142

59. Exam Essentials 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.

60. Exam Essentials 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.