ECE3025_Fall2010_Example_Final_Questions

ECE3025_Fall2010_Example_Final_Questions - ECE 3025C...

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ECE 3025C -- Electromagnetics FINAL EXAM EXAMPLE QUESTIONS Problem 1. Consider the transmission line configuration shown above where the switch is closed at time 0 t = . You must use the following terms when requested in giving your answers: 2 actual voltage of first wave launched into line L1 after the switch is closed reflection coefficient for positive going waves in line L1 at the junction of lines L1, L2 and R , V IN F + = = Γ 2 i.e, percentage of positive going wave in L1 that is reflected back into line L1 reflection coefficient for negative going waves in line L3 at the junction of R in series R = Γ with the parallel combination of lines L1 and L2, i.e, percentage of negative going wave in L3 that is reflected back into line L1 reflection coefficie L = Γ 2 nt for positive going waves in line L3 at the load resistor R i.e, percentage of positive going wave in L3 that is reflected back into line L3 percentage of positive going L F L τ - = 2 3 wave in L1 that is transmitted into both line L2 and the series connection of resistor R and line L3 percentage of positive going wave in L1 that is transmitted into line L F L - = 1 1 3 percentage of negative going wave in L3 that is transmitted into line L1 steady state voltage expected in line L1 after 600T, i.e. over 100 reverberations in lines L1 R L SS L t V - - = = > and L3 steady state voltage expected across the load resistor R after 600T L SS L t V - = >

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2 Problem 1. (Continued) A. Find the numerical values of 2 1 3 1 V , , , , , , , IN F R L F L R L F L SS L V τ + - - - - Γ Γ Γ and SS L V - , and place your answers in the table provided below for grading? Only answers written in the table will be accepted! Your answers must be accurate through 4 significant digits to receive any points. Place the appropriate units on your answers. V IN + = F Γ = R Γ = L Γ = 2 F L - = 3 F L - = 1 R L - = 1 SS L V - = SS L V - =
3 L1 L3 V IN + V IN F + Γ 0 T 2 T 3 T 4 T 5 T 6 T 7 T 8 T Problem 1. (Continued) B. Complete the reflection diagram below showing all waves in lines L1 and L3 through a time of 7 . t T = Place the appropriate product of factors above each wave component from the list provided on page 2. For example, the first wave component launched into line L1 is properly labeled as V , IN + and the first wave component reflected back into L1 is labeled V IN F + Γ . You must sketch in the remaining wave components on the reflection diagram and the proper factors above each wave component. Numerical answers are not required and will not be counted in tabulating the points for this problem.

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4 Problem 2. The transmission line shown below is a fan-out configuration, i.e., one input line drives three output lines. Classically, a resistor network is used at the junction between the cables to match impedances.
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ECE3025_Fall2010_Example_Final_Questions - ECE 3025C...

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