Concatenate FRD models along frequency dimension
sys = fcat(sys1,sys2,...)
sys = fcat(sys1,sys2,...)frd models and merges their frequency
responses into a single frd model sys.
The resulting frequency vector is sorted by increasing frequency.
The frequency vectors of sys1, sys2,... should
not intersect. If the frequency vectors do intersect, use fdel to remove intersecting data from
one or more of the models.