Transcript Presentation Slides

Analysis of 2 Styles of
Homebrew Antennas
Electromagnetic theory basics
• Classic Dipole Analysis
How big should our antennas be?
• frequency range 2.45GHz
• Lambda * frequency = speed of light
– Lambda = (3e8m/s)/(2.45e9s^-1)
• Lambdba = 0.122m or 4.8in
The “Cantenna”
• The first type of antenna and very
common in the Homebrew world is the
can-based antenna or cantenna.
• Fabrication Parts
– Can
– Piece of standard 50ohm wire
– N-type connector
Fabrication leads to:
So what does a cantenna radiation
beam look like?
Printed Dipole Array
• This uses antenna strip idea as opposed
to hollow conductive waveguides to do its
work.
• Fabrication
– Glass substrate
– Adhesive copper roll
– Vinyl cutter
Fabrication leads to
Recognizing the dipole array
• multiple dipoles squeezing beam and
increasing gain
Dipole Array E&M field patterns
Why the tapered feed line (balun)?
• Balance/unbalance transmission line for
VSWR characteristics
The Printed Dipole Array Antenna
beam?
Which is the better antenna?
VS.
Field Testing
• Duplicate parameters of cantenna test
found online and compare results
– 1320ft Line of Sight distance
– Standard dipole on AP/Source/tx
– Laptop using plug-in card for destination/rcvr
Laptop
Top of vassar parking structure
w/card
1320 ft
Access
Point/source
Roof of my home
Cantenna test results
• http://home.carolina.rr.com/harothberg/Test2.htm
• Control: only using pc and wireless card
– Signal Level: -89dBm -> 1.26e-12W
• Actual test: using can design
– Signal Level: -68dBm -> 1.58e-10W
• dBi = log[base 10](P1/P2)
– 2.1dBi when compared to power from card
Printed Dipole Array Test Setup
•
Views from Source/AP and Destination/Laptop
1320 ft: laptop site
on Vassar parking
1320 ft: AP on
home roof
Printed Dipole Array Test Results
•
Control: only using pc and wireless card
–
•
Actual test: using printed dipole array design
–
•
Signal Strength Level: -91dB
Signal Strength Level: -65dB
dBi = log[base 10](P1/P2)
–
2.6dBi when compared to power from card
Wireless Card
Printed Dipole Array
Test Results Findings
• Absolutes [Cantenna vs. P.D.]
• Antenna Strength: 2.1dBi vs. 2.6dBi
• Surprise results of holding P.D antenna with and
without one’s hand:
– An unintended experiment happened as the antenna
was being tested. One test run involved me holding
the antenna with my hand (accidentally), while the
other involved me holding the antenna in a
nonconducting paper bag.
• Antenna gain showed a relative increase of +9dB in the
signal when no hands were used to hold the antenna. That
is a 3 time doubling of power in the signal. These results
simply stress the significant affect biological contact can have
on performance and points to better ways of insulating the
printed dipole antenna from conductive influences.
The better antenna, based on
analysis:
• Gain/power and coverage
– P.D.: 3 dipoles focused in 1D
• great gain and coverage, good for community setting
– Can: has 1 dipole that is focused in 2D
• okay on gain, low on coverage, good for point to point
• Fabrication
– P.D.: mass production easier
– Can: one-off production easier
• Portability
– P.D.: low profile(2D), lightweight, durable
– Can: bulky(3D), lightweight, durable