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

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'''''

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