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We have the following path.

enter image description here

I tried to create the gain with Mason's formula, which lead me to the following:

Forward Path 1: 1
Loop 1: (1/s)*(2/s)*2
Loop 2: (-1)*(2/s)*2

When I put them together I get:

(1/1 - ((1/s)*(2/s)*2) - ((2/s)*2)) * (-1)*(2/s)*2

If I multiply it with s^2 I get 

(-4s)/(s^2+4s+4)

But according to the solution it should be 

(s^2 + 4s)/(s^2+4s+4)

So my upper part does not match. Do I use Mason's Gain Formula wrong?

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  • \$\begingroup\$ Can you offer a better picture that more easily distinguishes between the characters 2,Z and S. \$\endgroup\$ – Andy aka Apr 18 '17 at 8:25
  • \$\begingroup\$ I added a better one. \$\endgroup\$ – Pascal Apr 18 '17 at 8:30
  • \$\begingroup\$ Isn't loop 1 (1/s)*(2/s)*2? You seem to be using 1/2 instead of 1/s. \$\endgroup\$ – Andy aka Apr 18 '17 at 8:38
  • \$\begingroup\$ ah sorry, I typed it wrong \$\endgroup\$ – Pascal Apr 18 '17 at 8:39
  • \$\begingroup\$ So was that your error? \$\endgroup\$ – Andy aka Apr 18 '17 at 8:40

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