CHAPTER 2 - Conveying Power at Radio Frequency
90
2.8.5 Mismatched line, Z
L
> Z
0
When Z
L
> Z
0
some of the power is reflected back to the source and hence a standing wave is
created along the line. Note that, in this case, the incident and reflected voltages DO NOT have the
same amplitude as in the short and open circuit cases. Instead of peaks and nulls we will therefore
observe minima and maxima. This is because part of the wave will indeed be transmitted to the load
and its amplitude will be equal to the amplitude of the incident voltage minus the amplitude of the
reflected voltage. The phase of the load voltage will be identical to that of the incident voltage.
In this section the line is terminated with a 100Ω load.
Incident and reflected voltages are 180⁰ out of phase and hence the standing wave amplitude is at a
minimum
Incident and reflected voltages are in phase and hence they add constructively to maximise the
amplitude of the standing wave
t= 0s
t=0.25T
Conquer Radio Frequency
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