Transmission Line and Termination
Transmission Line Analysis
• Wavelength Versus Distance
– Lumped:   L
– Distributed:
L
• Pulse Transition Versus Propagation Delay
• Single Mode
–
–
–
–
Frequency response
Propagation (timing and phase) delay
Loss and dispersion
Pulse distortion
• Multimode
– Modal analysis
• Multi Lines
– Crosstalk
– Interference
• Metallic
Transmission Lines
– Parallel Wire Pair
• FM and TV antenna
– Twisted Wire Pair
• Phone line
• 10BaseT Ethernet
• http://www.swhowto.com
/CAT5_Ch1.htm
– Coaxial Cable
• RG58
– Metallic Conduit
– Planar Striplines
• Printed circuit board
• Hybrid IC carrier
• Dielectric
– Fiber
• Glass
• Polymer
Characteristic Impedance
• Impedance
– Z=V/I for an infinite cable
• Coaxial Cable
– CATV, lab, microwave
instrumentation
20
ln( D / d )
C
0
ln( D / d )
2
R  jL
L 138
Z0 


log( D / d )
G  jC
C

L
Vp 
1
LC
– Loss
• Frequency dependent
• Skin depth
http://www.ipm.virginia.edu/p
rocess/PVD/Pubs/thesis4/
chapter2.pdf
– TEM mode
– Unbalanced
Skin Depth In Copper
9
Skin Depth, microns


f 
10
8
7
6
5
4
3
2
1
0
0.E+00
1.E+09
2.E+09
3.E+09
4.E+09
Frequency, Hz
5.E+09
6.E+09
Coaxial Cables
Coax
Attenuation in
db per 100 feet
(On 27MHz)
Velocity
Factor
Description
RG-8
1.15 dB
.66
50 Ohm coax
RG-59
2.0 dB
.66
75 Ohm coax
RG-8/U Foam
0.85 dB
.80
50 Ohm coax, Foam Dielectric
RG-59/U Foam
1.5 dB
.79
75 Ohm coax, Foam Dielectric
Belden 9913
0.7 dB
.84
Premium 50 Ohm coax
1/2" Hardline
0.35 dB
.81
Special coax, expensive!
1.2 dB
.78
Small 50 Ohm coax. Preferred
over RG-58. Recommended for
mobile installations.
RG-58
2.35 dB
.66
50 Ohm coax
RG-213
1.35 dB
.66
50 Ohm coax.
RG-11/U Foam
0.85 dB
.80
75 Ohm coax.
RG-11/U
1.35 dB
.66
75 Ohm coax
RG-8X (Mini-8)
http://www.rfcafe.com/references/electrical/coax_chart.htm
Coax Connectors
•
•
•
•
•
BNC
Type N
SMA
APC7
K
Coax Connectors
Twin Lead Cable
• Balanced
– 300 
Z 0  276 log( D / r )
• Balun
– Balanced to unbalance transformer
Twisted Wire Pair
• Network Cables
– Cat 3, 4, 5, 5E, 6, ..
– DSL wiring at home
• http://www.smellyeyeball.com/dsl/
Striplines
• Micro Stripline
• Embedded Stripline
• Coplanar Stripline
• Loss
– Metallic
• Skin depth
• Localized current flow
– Dielectric
• Loss tangent    ' j ' '  Tan 
– Surface roughness
 ''
'
Transmission Line Termination
• Impedance Matching
– Termination
• Mismatch
– Reflection
• Time Domain Picture
– http://www.williamson-labs.com/xmission.htm
• Frequency Domain Analysis
Reflection and Transmission
• Reflection
• Standing Wave Ratio
• Wave Visualization
– http://www.educatorscorner.com/index.cgi?CONTENT_ID=2
483
Impedance Matching
• Effective Impedance
–
–
–
–
–
Load impedance
Cable in front of load
Frequency dependent
Bandwidth
Smith chart
• http://www.educatorscorner.com/index.cgi?CONTENT_ID=2482
• Impedance Matching
– Transformer
• www.minicircuits.com/pages/pdfs/tran14-2.pdf
– Stub
• http://www.ee.surrey.ac.uk/Personal/D.Jefferies/stubs.html
• Application
– http://www.sss-mag.com/pdf/arrl_circles.pdf
Time Domain Reflectometry
• Principle
–
–
–
–
Launch a pulse or a step waveform into the cable
Monitor reflected signal
Delay: location of mismatch
Magnitude: amount of mismatch
• Equipment
– http://www.tek.com/Measurement/App_Notes/55_14601/en
g/55W_14601_1.pdf
– Pulse generator
Time Domain Reflectometry
• Measurements
– http://bwrc.eecs.berkeley.edu/Classes/EE290C_S
04/lectures/Lect03_measurement.pdf
– http://literature.agilent.com/litweb/pdf/59886505EN.pdf
• Build Your Own TDR
– http://www.web-ee.com/Schematics/TDR/tdr.htm
Analysis for Digital Pulse
• Pulse Analysis
– http://www.mwrf.com/Articles/Print.cfm?ArticleID=5433
• Pulse Distortion
• EESoft Modeling
http://eesof.tm.agilent.com/pdf/asia_forum_2004_07.
pdf
Reading and Exercise
• Reading
– http://cktse.eie.polyu.edu.hk/eie403/Trans
missionline.pdf
• Exercise
– http://courses.ece.uiuc.edu/ece450/Home
work/HW3_F2004.pdf
• Reference
– http://www.connectorwizard.com/reference
/articles/pdfs/GoldenStandard_Part2.pdf
Chapter Review
• Transmission Lines
– balanced and unbalance
– Balum
•
•
•
•
•
•
Characteristic Impedance
Reflection Coefficient
Voltage Standing Wave Ratio
Smith Chart
Impedance Matching
Time Domain Reflectometry