## Coping with multipath fading

### Directional antenna

#### One logical way to reduce the effect of multipath fading is to reduce the number of paths seen by the receiver. This in practice means using a directional antenna on either the transmitting unit or receiving unit, or both.Unfortunately, it is very difficult to make an antenna directive at low radio frequencies (below a few hundred MHz), without requiring a very large physical structure. #### As the frequency of operation increases, the physical size of the antenna can be reduced in line with the reducing wavelength, and directivity is much more easily realized. |
| #### For example, television aerials achieve modest directivity by having several elements in an array and this leads to a significant reduction in ghosting (caused by multipath echoes) of the signal on the television screen. Microwave links achieve very good directivity by using a parabolic reflector. It is clearly not sensible to put a fixed directional antenna on a moving object, the orientation of which will change with time, and under these circumstances, the only solution is to try to implement an adaptive directional antenna that can track the wanted signal over time.