Radio System Co
Radio System Co-existence
Standards
Certification
Education & Training
Publishing
Conferences & Exhibits
Brian Cunningham
Cooper Bussmann
September, 2012
Agenda
• Frequencies
– Frequency choices
– ISM bands
– Filters
• Antenna Gain
– Omni and Yagi antennas
• Antenna Aiming and Mounting
– Suitable locations
– Polarization
• Signal-to-Noise Ratios
– Measurements and numbers
– Bandwidth implications
• Antenna Guidelines Conclusion
2
Frequencies – as long as
different, can co-exist
• Lower Frequencies:
– propagate further
– penetrate objects better
– 900 band is 26MHz wide
• 2.4GHz:
– used by microwave ovens
(rain fade on longer links)
– is license free around the
world
– 2.4 band is 81MHz wide
• 5.8GHz
– brand new ISM band
900MHz
2.4GHz
5.8GHz
3
Spread Spectrum Introduction
• FCC allocated a portion of the 900MHz band, then later
2.4GHz and later 5GHz.
• Created Rules Manufacturers Must Adhere to:
–
–
–
–
1W of Transmit Power
FH or DS or OFDM
FCC will not referee in case of interference from others
Many other technical requirements
• Manufacturers Must Submit Prototype for Testing
• FCC then Certifies, and Assigns ID to Appear on Label
• Radio can then be Used by Anyone, Anywhere (in the
US)
4
Filters – A measure of quality
Ideal filter
characteristics
Real world filter
characteristics
• Filters work better the greater the
frequency difference
• Radios with multiple levels of filtering offer
better performance but at a higher cost
5
Antenna Gain - Defined
• The higher the Gain, the greater the Range and the
greater the Directivity
• Gain is analogous to a Telescope’s Lenses - a High
Gain antenna does not add energy, it just focus’s
energy in a specific direction
• Gain is Expressed in dB (0dBd = 2.15dBi) (dBd
abbreviated as dB)
• 1 Watt 900MHz Transmitters are Limited to 6dBi net
gain
• Net Gain = (Antenna Gain - Cable Losses)
• Rule of thumb: for every 6dB “gained” the distance a
signal will travel doubles
6
There are 2 Types of Antennas
• OMNI Directional
– Antenna Points (mounts)
Vertically
– Radiates energy (mostly)
in Horizontal Plane
– Radiates energy 360
degrees
• Directional
– Yagi Antenna is a Type
of Directional Antenna
• Yagi Antenna
– Radiates energy in a
specific direction
– Must be aimed towards
transmitter/receiver
– Named after one of 2
Japanese inventors (Yagi
and Uda)
7
Omni Directional Antenna Radiation
Patterns
3dB Omni
5dB Omni
Vertical Beamwidth = 40º
Vertical Beamwidth = 17º
(with MaxRad 3dB Antenna)
(with Radial Larsen 5dB
Antenna)
8
Yagi Antenna Gain - Aiming and
Radiation Patterns
6dB Yagi Antenna
94 degree horizontal beamwidth
58 degree vertical beamwidth
(with Radial Larsen 6dB yagi)
10dB Yagi Antenna
50 degree horizontal beamwidth
50 degree vertical beamwidth
(with Radial Larsen 10dB yagi)
9
Omni vs. Yagi Antenna - Which
to Use?
• Omni Recommended:
– Multiple Transmitters/
Receivers in different
directions
– No Line-of-sight and lots
of Metal Structures
– Generally best for
Industrial Plant
Applications
• Yagi Recommended:
– Long Range needed Yagi’s offer higher gain
– No Line-of-sight and
Trees, Brick or Concrete
obstructions (nonmetallic)
– Generally best for
Municipal Applications
10
900 MHz Antenna Examples
6dB Gain
3dB Gain
6dB Gain
10dB Gain
0dB Gain
3dB Gain
5dB Gain
11
Fiberglass Radome
• Some antennas have a
fiberglass radome
enclosing the metal
radiating elements
• Protects internal metal
radiating element from
corrosion, snow build-up, in
some cases reduced wind
loading
• Inside the radome, the
antenna looks the same as
one without
13
Antenna Polarization
•
Vertical Polarization
– Must be used with omni
antennas
– Minimizes snow build up
– By far, most common and
popular installation method
•
Horizontal Polarization
– Only used with yagi-to-yagi
– Only used to minimize
interference from nearby radio
system using vertical
polarization
– Problem with snow build-up
(except when antenna has
fiberglass radome)
14
Background Noise vs Signal
Typical industrial plant
noise floor
Signal/Noise
Level
Strong signal from
much closer transmitter
-40dBm
Distant transmitter signal, must
be minimum 10dB above noise
floor
-60dBm
-80dBm
Background noise from distant
transmitters
-100dBm
-120dBm
902MHz
Bandwidth (MHz)
928MHz
15
Occupied Band Width of your Radio
Wider Channels allow
greater throughput
BUT…
Wider Channels mean the filters
must be set wider, allowing more
interference through
40MHz Turbo Channel
20MHz Channel
250KHz Channel
40MHz = 108Mbps
20MHz = 54Mbps
250KHz = 200Kbps
16
Practical Recommendations
• Use a high gain antenna
– Narrow beam width excludes interference
– Will boost signal (to noise) level
– Make sure you do not violate FCC’s rules
• Locate your antenna far from others
– Vertical separation is most effective
– Rule of thumb – 10’ (3m) vertical
• Mount the antennas outside, up high
– Metal electrical enclosures and steel corrugated
buildings will contain radio waves
– Height increases propagation distance
17
Conclusion – Questions?
Contact Info:
Brian Cunningham
Applications Engineer
Port Coquitlam BC
866 713 4409 x 298
Brian.Cunningham@Cooperindustries.com
18
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