Basic Principle:
It exploits all available signal copies of〖 𝑵〗_𝒓 signal.
Each signal copy is multiplied by a complex weight, and then added up
Complex weight = Phase correction + Real weight of the amplitude.
Phase correction causes the signal amplitudes to add up, otherwise noise is added incoherently, so that noise powers add up.
For amplitude weighting, two methods are used.
Maximum Ratio Combining (MRC) – weighs all signal copies by their amplitude.
Equal Gain combining (EGC) – Signals are not weighted, but undergo a phase correction
MRC compensates for the phases and weights of the signals from different antenna branches according to their SNR.
It is an optimum method.
Channel is assumed as slow fading and fast fading.
Equal gain combining is similar to maximal ratio combining except that the weighting circuits are omitted.
The branch weights are all set of unity but the signals from each branch are co-phased to provide equal gain combining diversity.
