These values are used in the equations given in 'FR4 2-port equations.txt'. Also see slides 15 & 16 of 05-877v1.

   case {'stripline_200'}
    pcb_Z = 103.2
    pcb_vf = 0.515
    k_o = 0;
    k_sm = 4.55e-7;
    k_dm = 0.49e-11;
    k_sv = 0;
    k_dv = 1/(pcb_vf*3e8*39.37);
    
   case {'stripline_150'}
    pcb_Z = 103.1
    pcb_vf = 0.506
    k_o = 0;
    k_sm = 4.65e-7;
    k_dm = 0.49e-11;
    k_sv = 0;
    k_dv = 1/(pcb_vf*3e8*39.37);
    
   case {'microstrip_200'}
    pcb_Z = 106
    pcb_vf = 0.5765
    k_o = 0;
    k_sm = 2.4e-7;
    k_dm = 0.27e-11;
    k_sv = 3*k_sm;
    k_dv = 1/(pcb_vf*3e8*39.37);
    
   case {'microstrip_300'}
    pcb_Z = 105.8
    pcb_vf = 0.5772
    k_o = 0;
    k_sm = 0.75e-7;
    k_dm = 0.38e-11;
    k_sv = 0.12e-7;
    k_dv = 1/(pcb_vf*3e8*39.37);

The values for pcb_Z were determined while fitting return loss results. Other differential impedance values may be used to effect other S11 (and S22) return loss values.

Tom Lindsay, ClariPhy