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End-of-Chapter Review Questions

The answers to the following review questions can be found in Appendix D, “Review Questions and Answers.”

  • 7.1 What is a real transmission line?

  • 7.2 How is an ideal transmission line model different from an ideal R, L, or C model?

  • 7.3 What is ground? Why is it a confusing word for signal integrity applications?

  • 7.4 What is the difference between chassis and earth ground?

  • 7.5 What is the difference between the voltage on a line and the signal on a line?

  • 7.6 What is a uniform transmission line, and why is this the preferred interconnect design?

  • 7.7 How fast do electrons travel in a wire?

  • 7.8 What is the difference between conduction current, polarization current, and displacement current?

  • 7.9 What is a good rule of thumb for the speed of a signal on an interconnect?

  • 7.10 What is a good rule of thumb for the aspect ratio of a 50-Ohm microstrip?

  • 7.11 What is a good rule of thumb for the aspect ratio of a 50-Ohm stripline?

  • 7.12 What is the effect called when the dielectric constant and the speed of a signal are frequency dependent?

  • 7.13 What are two possible reasons the characteristic impedance of a transmission line would be frequency dependent?

  • 7.14 What is the difference between the instantaneous impedance and the characteristic impedance and the input impedance of a transmission line?

  • 7.15 What happens to the time delay of a transmission line if the length of the line increases by 3x?

  • 7.16 What is the wiring delay of a transmission line in FR4?

  • 7.17 If the line width of a transmission line increases, what happens to the instantaneous impedance?

  • 7.18 If the length of a transmission line increases, what happens to the instantaneous impedance in the middle of the line?

  • 7.19 Why is the characteristic impedance of a transmission line inversely proportional to the capacitance per length?

  • 7.20 What is the capacitance per length of a 50-Ohm transmission line in FR4? What happens to this capacitance per length if the impedance doubles?

  • 7.21 What is the inductance per length of a 50-Ohm transmission line in FR4? What if the impedance doubles?

  • 7.22 What can you say about the capacitance per length of an RG59 cable compared to an RG58 cable?

  • 7.23 What do we mean when we refer to “the impedance” of a transmission line?

  • 7.24 A TDR can measure the input impedance of a transmission line in a fraction of a nanosecond. What would it measure for a 50-Ohm transmission line, open at the end, that is 2 nsec long? What would it measure after 5 seconds?

  • 7.25 A driver has a 10-Ohm output resistance. If its open circuit output voltage is 1 V, what voltage is launched into a 65-Ohm transmission line?

  • 7.26 What three design features could be engineered to reduce the impedance of the return path when a signal changes return path planes?

  • 7.27 Which is a better starting model to use to describe an interconnect up to 100 MHz: an ideal transmission line, or a 2-section LC network?

  • 7.28 An interconnect on a board is 18 inches long. What is an estimate of the time delay of this transmission line?

  • 7.29 In a 50-Ohm microstrip, the line width is 5 mils. What is the approximate dielectric thickness?

  • 7.30 In a 50-Ohm stripline, the line width is 5 mils. What is the length of the transmission line?

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