Overview
Introduction to WLAN
Building our own antenna
Demonstration (next time)
Conclusion (next time)
Introduction to WLAN
Wireless LAN connection over 30-100m
Since 1997
Various standards (a,b,g,n) with different specifications
WiMax
Technology behind WLAN
Modulation: Orthogonal frequency-division multiplexing, Quadrature amplitude modulation
Frequencies: 2.4 and/or 5 GHz
Channels
No encryption per default
Building our antenna - Types
types
omnidirectional antenna
sector beam antenna
radiated beam antenna
Wlan-antenna-types
examples:
sources:
http://ecx.images-amazon.com/images/I/11NB6H3HJAL._AA240_.jpg
http://www.germes-online.com/direct/dbimage/50036375/Yagi_Antenna.jpg
~ 25°/25°~ 30°360° /30°angle
~10dBi~ 15dBi~ 5dBigain
BiQuadYagiStandard
Legal aspects
Construction is legal, running it maybe not
frequencies must be between: 2,4 - 2,48
Ghz
limitation: 100mW = 20dBm of transmitting power
BiQuad-Antenna
radiated beam
source: http://www.lecad.uni-lj.si/~leon/other/wlan/biquad/radiation-wire.html
BiQuad-Antenna
Distance radiator – reflector
best at H=0.1315 λ ~120*0.1315=16mm
source: http://www.lecad.uni-lj.si/~leon/other/wlan/biquad/radiation-wire.html
BiQuad-Antenna
Dimension of the radiator
Best at H=0.23 λ29~mm
source: http://www.lecad.uni-lj.si/~leon/other/wlan/biquad/radiation-wire.html
Building our antenna - Material
cd spindle
1 cd
copper wire (~50cm, cross-section: 2.5mm2)
a short antenna/coaxial-cable
some tools
Building our antenna - Construction
reflector
preparing the spindle
stick: 18mm (antenna 16mm over ground)
rasp a cross
Building our antenna - Construction
the cable
damping
short distance
Length theoretical:multipleofλ/2
practical: additional adapter,
unknown cable, etc.
► try and error
Building our antenna - Hints
copper oxidises ► use hairspray or similar
attach antenna cable on the back of the spindle aswell
Standard vs BiQuad Antenna
Short distance indoor:
Standard
-25dBm -20dBm -54dBm
-24dBm -29dBm
-25dBm -30dBm
-51dBm -48dBm -59dBm
-51dBm -54dBm
-50dBm -69dBm
Antenna BiQuad No Antenna
1m direct
1m sidewards
1m backwards
3m direct
3m sidewards
3m backwards
Standard vs BiQuad Antenna
Long distance outdoor:
1 3 6 10 14 28 32 39 44 50 60
0
10
20
30
40
50
60
70
80
90
Signal/Noise Ratio vs. Distance
Qualität BiQuad
Qualität Standard
Distance in meters
Sig
na
l/No
ise
Ra
tio in
dB
m
Standard vs BiQuad Antenna
Standard:
Indoor usage
Short distances
Multiple clients
Cheap
BiQuad:
Outdoor usage
Long and short distances
Point-to-point connection
Also cheap, but takes some effort to build it