diff --git a/SPARAMS.m b/SPARAMS.m
index 4388d9b..3c16777 100644
--- a/SPARAMS.m
+++ b/SPARAMS.m
@@ -816,11 +816,11 @@ classdef SPARAMS < handle
 			S = [S11 S12;S21 S22];
         end
         
-        function [A, B, C, D] = s2abcd(S, Z0)
-			A = ((1 + S(1,1)).*(1 - S(2,2)) + S(1,2).*S(2,1))./(2.*S(2,1));
-			B = Z0*((1 + S(1,1)).*(1 + S(2,2)) - S(1,2).*S(2,1))./(2.*S(2,1));
-			C = (1/Z0)*((1 - S(1,1)).*(1 - S(2,2)) - S(1,2).*S(2,1))./(2*S(2,1));
-			D = ((1 - S(1,1)).*(1 + S(2,2)) + S(1,2).*S(2,1))./(2*S(2,1));
+        function [A, B, C, D] = s2abcd(S11, S12, S21, S22, Z0)
+			A = ((1 + S11).*(1 - S22) + S12.*S21)./(2.*S21);
+			B = Z0*((1 + S11).*(1 + S22) - S12.*S21)./(2.*S21);
+			C = (1/Z0)*((1 - S11).*(1 - S22) - S12.*S21)./(2*S21);
+			D = ((1 - S11).*(1 + S22) + S12.*S21)./(2*S21);
         end
         
         function [S11, S21, S12, S22] = abcd2s(A, B, C, D, Z0)