The main difference between a transmission line and a wave guide is −
· A two conductor structure that can support a TEM wave is a transmission line.
· A one conductor structure that can support a TE wave or a TM wave but not a TEM wave is called as a waveguide.
The following table brings out the differences between transmission lines and waveguides.
| Transmission Lines | Waveguides |
| Supports TEM wave | Cannot support TEM wave |
| All frequencies can pass through | Only the frequencies that are greater than cut-off frequency can pass through |
| One conductor transmission | Two conductor transmission |
| Reflections are less | Wave travels through reflections from the walls of waveguide |
| It has characteristic impedance | It has wave impedance |
| Propagation of waves is according to “Circuit theory” | Propagation of waves is according to “Field theory” |
| It has a return conductor to earth | Return conductor is not required as the body of the waveguide acts as earth |
| Bandwidth is not limited | Bandwidth is limited |
| Waves do not disperse | Waves get dispersed |
