The outputs of a cross-polarized antenna can produce a pair of different
parallel frequency-selective channels. The optimum combining strategy is
derived from maximum likelihood principles and used to define an
equivalent discrete-time model. The simulated post-equalizer BER results
show that optimum combining produces the best results, selection
diversity can provide reasonably good results, and that both optimum
combining and selection diversity can be superior to linear equalizer
operating on the

channel obtained by combining the antenna outputs before applying a
channel matched filter.