EE3113_A2009_L3

EE3113_A2009_L3 - not apply anymore ECE3113_L3 6 Kirchhoffs...

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ECE 3113 INTRODUCTION TO RF CIRCUIT DESIGN Lecture Notes for A-term 2009 LECTURE 3 Prof. R. Ludwig Department of Electrical and Computer Engineering Worcester Polytechnic Institute Worcester, MA 01619 copyright © 2009, R. Ludwig Copyright, 1998 © R. Ludwig
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ECE3113_L3 2 Objectives • How do voltages and currents propagate at high frequency? • What is a transmission line? • What is the electric circuit representation of a transmission line?
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ECE3113_L3 3 Transmission Line Analysis • Propagating electric field • Phase velocity • Traveling voltage wave ) cos( 0 z t E E X X  Time factor Space factor r p c f v  1 ) sin( ) , ( 0 z t E t z V X Non-magnetic medium
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ECE3113_L3 4 High frequency implies spatial voltage distribution • Voltage has a time and space behavior • Space is neglected for low frequency applications • For RF there can be a large spatial variation
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ECE3113_L3 5 Generic way to measure spatial voltage variations • For low frequency (1MHz) Kirchhoff’s laws apply • For high frequency (1GHz) Kirchhoff’s laws do
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Unformatted text preview: not apply anymore ECE3113_L3 6 Kirchhoffs laws on a microscopic level Over a differential section we can again use basic circuit theory Model takes into account line losses and dielectric losses Ideal line involves only L and C ECE3113_L3 7 Example of transmission line: Two-wire line Alternating electric field between conductors alternating magnetic field surrounding conductors dielectric medium tends to confine field inside material ECE3113_L3 8 Example of transmission line: Coaxial cable Electric field is completely contained within both conductors Perfect shielding of magnetic field TEM modes up to a certain cut-off frequency E H ECE3113_L3 9 Example of transmission line: Microstrip line Cross-sectional view Low dielectric medium High dielectric medium ECE3113_L3 10 Triple-layer transmission line Conductor is completely shielded between two ground planes Cross-sectional view...
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EE3113_A2009_L3 - not apply anymore ECE3113_L3 6 Kirchhoffs...

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