Concatenate FRD models along frequency dimension
sys = fcat(sys1,sys2,...)
sys = fcat(sys1,sys2,...) takes two or more 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.