1. Standing waves
With a mismatched line there are
two EM waves travelling in opposite directions
at the same time (travelling waves). The two
waves set up an interference pattern known
as standing waves.

2. Standing waves

3. Standing Waves on an open line

4. Characteristics of transmission line
terminated in open
• Voltage incident wave is reflected back just as
if it were to continue
• Current incident wave is reflected back 180o
from how it would have continued
• The sum of incident and reflected current
waveform is minimum at the open.
• The sum of incident and reflected voltage
waveform is maximum at the open

5. Incident and Reflected waves on a transmission line
terminated in an open circuit

6. Incident and Reflected waves on a transmission
line terminated in an open circuit

7. Incident and Reflected waves on a transmission
line terminated in an open circuit

8. Incident and Reflected waves on a transmission
line terminated in an open circuit

9. Standing Waves on an open line
• Voltage and current standing Wave repeats every
one-half wavelength.
• Impedance at open end
Z= Vmax / Imin
and is maximum
• Impedance at one-quarter wavelength from open
end
Z= Vmin / Imax
and is minimum

10. Standing Waves on an shorted line

11. Characteristics of transmission line
terminated in short
• Voltage incident wave is reflected back 180o
from how it would have continued
• Current incident wave is reflected in same
manner as if it had continued.
• The sum of incident and reflected current
waveform is maximum at the short.
• The sum of incident and reflected voltage
waveform is minimum at the short.

12. Standing Waves on an short line
• Voltage and current standing Wave repeats every
one-half wavelength.
• Impedance at short end
Z= Vmin / Imax
and is minimum
• Impedance at one-quarter wavelength from short
end
Z= Vmax / Imin
and is maximum

13. Transmission line terminated in either
open or short circuit,
• reflection coefficient is 1
• SWR is infinity