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161_1_Class9 - EE161 Electromagnetic Waves Spring 2010 Prof...

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Unformatted text preview: EE161 Electromagnetic Waves Spring, 2010 Prof. Y. Ethan Wang Electrical Engineering Dept. UCLA Lesson 9 • Striplines & Microstrip lines • General Waveguide Solutions • Longitudinal-Transverse Relationship Striplines •“Sandwich” of two wide thin conducting plates, bonded to a dielectric slab in which is buried a narrow thin conducting plate (“a flatten coax”). •The first type of “planar” transmission line •It can support a pure TEM wave, also higher order TM and TE modes (try to avoid in practice most of the time) If the inner strip is wide enough, the fringing field can be ignored and it can be approximated by two parallel-plate waveguides stacked back to back How to analyze? Stripline – Parallel Plate Waveguide Model x x y z Two parallel plate waveguides back to back a W d jkz t e d V y − = 2 ˆ E jkz TEM t e d V Z x − − = 2 1 ˆ H Upper half jkz t e d V y − − = 2 ˆ E jkz TEM t e d V Z x − = 2 1 ˆ H Bottom half , ) ( jkz e V z V − = jkz TEM e d W Z V z I − = 4 ) ( We then have voltage and current given by, r TEM W d Z W d z I z V Z ε η 4 4 ) ( ) ( = = = The characteristic impedance is thus given by, A Stripline Circuit Assembly Example (courtesy of M/A-COM Inc) Fringing Effects - Striplines •The fringing effects cause the strip width “virtually increase” ⇒ > W W eff •In reality, the fields spread out from the area bound by the center strip and the upper and bottom plates, this is so-called fringing effects. r eff W d Z ε η , 4 < Conclusion: The fringing effects will cause the characteristic impedance of stripline lower than the predicted value using the parallel plate waveguide model Ideally W Reality W eff Microstrip Lines...
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  • Spring '10
  • YuanxunEthanWang
  • Transmission line, parallel plate waveguide, Longitudinal Components, General Waveguide Field Solutions, General Waveguide Solutions, plate waveguide model

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161_1_Class9 - EE161 Electromagnetic Waves Spring 2010 Prof...

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