get2PortResponseModel

      get2PortResponseModel   returns a model for a 2x2 Frequency Response model:
                              Sijm = Hij(w)Sij
          H = get2PortResponseModel(G1,G1m,G2,G2m,T,Tm)
          input:
              G1,G2: [num_pts] actual, listed, or ideal reflection coefficient
                  at port 1 and port 2
              Gm1,Gm2: [num_pts] measured reflection coefficient at port 1 and port 2
              T,Tm: [2,2,num_pts] actual, listed, or ideal thru measurement (T)
                  and measured thru (Tm)
          output:
              H: [2,2,num_pts] 2x2 Frequency Response model (channel)