ab2G

      ab2G   Returns reflection coefficient G (gamma) from a and b waves
          G = ab2G(rec,ports)
          Inputs:
              rec: [6,num_pts]
                  reciever recording returned by measure1Port()
              ports: map that associates a port number with each VNA Tx/Rx
                  possible keys: ['Tx1','Tx2','Rx1A','Rx1B','Rx2A','Rx2B']
                  possible values: [1, 2, 3, 4, 5, 6]
          Outputs:
              G = reflection coefficient (gamma) of the transmitting port