RF101 - Multipath and Diversity
In telecommunications when a RF signal is transmitted, it gets reflected in all directions. It takes different paths, for example, it can hit a wall, ceiling, glass, etc. Signals get reflected or refracted or absorbed by these obstacles. During this process, multiple wavefronts of the signal are creating, therefore duplicating the original signal. This is called Multipath. At the receiver end, there will be duplicates of the original signals from different reflections. This is called Multipath Fading or Multipath distortion.
Multi-path fading cannot be avoided, so we started using diversity antennas in cellular base stations. With the tremendous advancement in Telecommunications and Mobile communications, we started using diversity antennas, to receive and reconstruct the single as fast as possible, to increase the probability of receiving a better/stronger signal. The goal also is to maintain diversity or in other words isolation between the antennas in order to reconstruct the original signal. To make sure that one antenna encounters less multipath propagation effects than the other, diversity between the antennas is needed. There are five different ways to achieve this –
- Special diversity
- Polarization diversity
- Temporal diversity
- Frequency diversity
- Pattern diversity
We can further study each of these techniques to see how antennas can be diversified.
Cisco Systems put together a good view of what diversity and mutlipath is: http://www.cisco.com/c/en/us/support/docs/wireless-mobility/wireless-lan...
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