H ELECTRICITY
H04 ELECTRIC COMMUNICATION TECHNIQUE
H04B TRANSMISSION
10/00 Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
H04B10/61 Coherent receivers
H04B10/613 including phase diversity, e.g., having in-phase and quadrature branches, as in QPSK coherent receivers