© Javier Araque, this material cannot be used outside the course where it was obtained without author's written consent.

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Transmission Lines and AntennasIntroduction and Motivation

Javier Leonardo Araque QuijanoOf: 453 – 204

Ext. 14083jlaraqueq@unal.edu.co

© Javier Araque, this material cannot be used outside the course where it was obtained without author's written consent.

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Image from www.wikipedia.org: EM spectrumTable from [1]

v = f λv = f λ

© Javier Araque, this material cannot be used outside the course where it was obtained without author's written consent.

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EM Waves and the Atmosphere

Image from http://mynasadata.larc.nasa.gov/

© Javier Araque, this material cannot be used outside the course where it was obtained without author's written consent.

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Field and Circuit Quantities

dl

+

V

-

Harmonic Maxwell's equations(complex vector/scalar fields)

Harmonic circuit quantities(complex scalars)

I

ds

© Javier Araque, this material cannot be used outside the course where it was obtained without author's written consent.

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Frequency and Operation Regimesλ

Low frequency → phase is constant

throughout the componentλ >> system dims

Quantities depend on time but not on space

CIRCUIT REGIME

λ

Medium frequency → phase changes over the

system's extentλ ~ system dims

Quantities depend both on time and space

MICROWAVE REGIME

λ

High frequency → phase changes considerably

over the system's extentλ << system dims

The main interest is in frequency and amplitude

OPTICAL REGIME

© Javier Araque, this material cannot be used outside the course where it was obtained without author's written consent.

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Microwave Frequenciesμwaves: 300MHz­30GHz (Collin)

RF: 30MHz­3GHz / μwaves: 3GHz­300GHz (Pozar)

Microwave application motivated by:

● Large bandwidth available

● Satellite communications (μwaves do not interact significantly with atmosphere)

● Better performance of antennas at high frequencies (for fixed dimensions)

● Resolution of EM imaging equipment scales with λ = c/f

Applications in: RADAR, remote sensing, medicine, communications, etc.

© Javier Araque, this material cannot be used outside the course where it was obtained without author's written consent.

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Limitations of Circuit Analysis

- What is the current on the generator? - on the load?

v(t) ~ R

l

© Javier Araque, this material cannot be used outside the course where it was obtained without author's written consent.

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Limitations of Circuit Analysis

- What is the current on the generator? - on the load?

v(t) ~ R

l

= (l/c) f

© Javier Araque, this material cannot be used outside the course where it was obtained without author's written consent.

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References

[1] R. E. Collin, “Foundations of Microwave Engineering”. IEEE press, 2001.

[2] R. Harrington, “Time Harmonic Electromagnetic Waves”, IEEE press, 2001.

[3] www.wikipedia.org

[4] http://mynasadata.larc.nasa.gov