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Published bySaul Gibbs Modified over 2 years ago

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EMLAB 1 Transmission line

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EMLAB 2 An apparatus to convey energy or signal from one place to another place. Transmitter to an antenna connections between computers in a network hydroelectric generating plant and a substation several miles away interconnect between components of a stereo system CATV service provider and your TV set Connections between devices on a circuit board Transmission line

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EMLAB 3 Example – Cable TV

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EMLAB 4 Example – Computer network

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EMLAB 5 Example – Electric power transmission line

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EMLAB 6 Example – Printed circuit board

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EMLAB 7 Example – Printed circuit board

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EMLAB 8 Types of transmission lines Microstrip line Coaxial cable Two-wire transmission line

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EMLAB 9 Distribution of electric field strengths of typical TEM lines E/H distributions vary as the structures of transmission lines change. For electromagnetic compatibility, E/H should be confined to small area. Microstrip Two-wire Parallel plate

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EMLAB 10 Field representation in waveguides

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EMLAB 11 Wave Solution TEM mode (Transverse electromagnetic mode)

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EMLAB 12 Parallel plate waveguide With a wide enough line trace, variation along y-axis can be ignored.

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EMLAB 13 i (z, t) v (z, t) + - zz L z C z i (z+ z, t) v (z+ z,t) + - i (z, t) zz v (z, t) + - Transmission line 등가 회로

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EMLAB 14 Transmission line eq. solution

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EMLAB 15 Transmission line 의 특징 H E Direction of propagation H 1.For a magnetic field and an electric field propagating in the same direction, the ratio of E and H (E + /H + ) is kept constant. 2.For a voltage and a current current propagating in the same direction, V + /I + ratio is equal to Z 0. 3.When the ratio is disturbed, reflected waves are generated.

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EMLAB 16 +V-+V- Reflection coefficient

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EMLAB 17 +V-+V- +V-+V- +V-+V- +V-+V- +V-+V- Z s = 20 Z 0 = 50 Z L = 1k 0.5m Influence of line length on load voltage Impedance mismatched VinVout R R2 R=1k Ohm MLIN R R1 R=20 Ohm VtPulse SRC1 t Z 0 = 50

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EMLAB 18

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EMLAB 19 Ringing : Time domain

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EMLAB 20 Signal source Load ~ Mismatched load Ringing

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EMLAB 21 Impedance matching – Digital logic ~ ~ Source matching Load matching

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EMLAB 22 Impedance matching topologies

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EMLAB 23 Frequency domain solution β : propagation constant, v p : speed of light

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EMLAB 24 Phasor representation +V-+V-

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EMLAB 25 Transmission line terminated with short, open Zs = Zo V refl V inc For reflection, a transmission line terminated in a short or open reflects all power back to source In phase (0 ) for open o Out of phase (180 ) for short V refl o

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EMLAB 26 Transmission Line Terminated with 25 Ω Zs = Zo Z L = 25 W V refl V inc Standing wave pattern does not go to zero as with short or open

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EMLAB 27 Equivalent input impedance

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EMLAB 28 Input impedance of short

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EMLAB 29 Input impedance of open

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EMLAB 30 Some transmission line examples case 1) matched load

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EMLAB 31 case 2) unmatched load

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EMLAB 32 Ringing : Time/frequency domain

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Transmission Line Theory

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