Transmission Line and Termination
Transmission Line Analysis• Wavelength Versus Distance
– Lumped:– Distributed:
• 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
LL
Transmission Lines• Metallic
– Parallel Wire Pair• FM and TV antenna
– Twisted Wire Pair• Phone line• 10BaseT Ethernet• http://www.swhowto.com/C
AT5_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
– Loss• Frequency dependent• Skin depthhttp://www.ipm.virginia.edu/process/PVD/Pubs/thesis4/chapter2.pdf
– TEM mode– Unbalanced
LCV
dDC
L
CjG
LjRZ
dDL
dDC
p
1
)/log(138
)/ln(2
)/ln(
2
0
0
0
Skin Depth In Copper
0
1
2
3
4
5
6
7
8
9
10
0.E+00 1.E+09 2.E+09 3.E+09 4.E+09 5.E+09 6.E+09
Frequency, Hz
Sk
in D
ep
th, m
icro
ns
f
Coaxial Cables
CoaxAttenuation 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!
RG-8X (Mini-8) 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
http://www.rfcafe.com/references/electrical/coax_chart.htm
Coax Connectors• BNC
• Type N
• SMA
• APC7
• K
Coax Connectors
Twin Lead Cable
• Balanced– 300
• Balun– Balanced to unbalance transformer
)/log(2760 rDZ
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
– Surface roughness
'
'''''
Tanj
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
=2483
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_S04/lectures/Lect03_measurement.pdf
– http://literature.agilent.com/litweb/pdf/5988-6505EN.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/Transmissionline.pdf
• Exercise– http://courses.ece.uiuc.edu/ece450/
Homework/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