Question 6.17: A 1 volt pulse propagates from z < 0 on a transmission li...
A 1 volt pulse propagates from z < 0 on a transmission line. The line is terminated in an open circuit @ z = 0. Four oscilloscopes are triggered by the same pulse generator and are located at:za = – 6 ; zb = -4 ; zc = -2 ; and zd = 0 (meters). Find the velocity of propagation and interpret the voltage signals on the oscilloscopes. Sketch the corresponding voltage signals if the transmission line is terminated in a short circuit.
From the traces on oscilloscopes a and b, we find the velocity of propagation to be v = ∆z / ∆t = 2 m / 1 µs = 2 x 106 m / s. Oscilloscope d is at the location of the open circuit and the incident and the reflected pulses add together. The signals that are detected after t = 4 µs are the reflected pulses that propagate toward the pulse generator.
The voltage signals detected by the oscilloscopes if the transmission line is terminated in a short circuit are depicted below. The voltage across the short circuit must be zero, hence the signal at oscilloscope d is zero.
It should be noted that the two oscilloscope pictures correspond to the voltage pulses. If the oscilloscope pictures would correspond to the current pulses, the first picture would correspond to a load impedance that was a shortcircuit and the second picture would correspond to an open circuit.
