ECE 540 Midterm I

January 23, 1998

 

Name ______________________

 

Open Notes, Open Book.

 

 

 

 

 

 

  1. (25 points) For the transmission line shown below:

 

  1. Find the input impedance to the line. Zin = _________________

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  2. Find the reflection coefficient of the load. G L = __________________

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  3. Find the VSWR = ______________

 

Plot the envelope of the standing wave on the line as a function of z. Clearly show the locations of the voltage minima and maxima, and their relative heights.

 

 

 

 

 

 

 

 

 

 

(d) Given Vg = 10.0 sin (w t) Volts, write expressions for Vo+ and Vo-

 

  2. (25 points) For the transmission line shown below Rg = 100 ohms, ZL = 25 ohms, Zo = 50 ohms, Length = 300 meters.

 

 

  1. Plot the voltage on the line at the center of the line (z=150m) as a function of time for 4 m s for the generator voltage shown below.

    2.  

     

     

    (b) Plot the current at the load as a function of time for 4 m s.

     

     

     

     

     

     

     

     

     

  2. Plot the voltage on the line as a function of distance at time t=2.5 m s.

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  3. Repeat part (a) for the generator voltage ( pulse wave form )shown below.

 

 

  2. (25 points) An RG 58 coaxial transmission line is used to transmit binary data at 1 GHz. The data pulses are 5 V peak, and the detector at the end will register a binary value of "1" when the received voltage is greater than or equal to 3.6 V.

 

Information about RG 58 coaxial line: a = 0.89 mm, b = 3.53 mm, filled with polyethylene with e r = 2.26, loss tangent = 0.00031 . [e '' = e o e r * losstan]. Conductors are made of copper.

 

 

  1. What are the values of R', L', C', G' for this cable?

    2.  

  2. What is the longest cable that can be used to send these signals accurately?

    3.  

  3. What will be the magnitude of the 5 V signal after it has propagated 10 meters down the line?

    4.  

  4. How long will it take for the wave to propagate 10 meters down the line?

 

 

  2. (25 points) For a rectangular transmission line shown below, the following fields are observed:

 

Ey = K a sin (mp x / a)

Hx = - Ey b / (w m )

 

(K is a constant.)

 

 

Write the integral equations to find R,L,G,C for this transmission line.

 

 

Name ________________________________

 

Problem 1 ___________ / 25 points

 

Problem 2 ___________ / 25 points

 

Problem 3 ___________ / 25 points

 

Problem 4 ___________ / 25 points

 

Total ___________ / 100 points