- 7.1 Forget the Word Ground
- 7.2 The Signal
- 7.3 Uniform Transmission Lines
- 7.4 The Speed of Electrons in Copper
- 7.5 The Speed of a Signal in a Transmission Line
- 7.6 Spatial Extent of the Leading Edge
- 7.7 “Be the Signal”
- 7.8 The Instantaneous Impedance of a Transmission Line
- 7.9 Characteristic Impedance and Controlled Impedance
- 7.10 Famous Characteristic Impedances
- 7.11 The Impedance of a Transmission Line
- 7.12 Driving a Transmission Line
- 7.13 Return Paths
- 7.14 When Return Paths Switch Reference Planes
- 7.15 A First-Order Model of a Transmission Line
- 7.16 Calculating Characteristic Impedance with Approximations
- 7.17 Calculating the Characteristic Impedance with a 2D Field Solver
- 7.18 An n-Section Lumped-Circuit Model
- 7.19 Frequency Variation of the Characteristic Impedance
- 7.20 The Bottom Line
- End-of-Chapter Review Questions
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?