It is well known that the error model of the SMC algorithm has been expressed by the signal flow diagram, what is the error model of the X parameter (signal flow diagram)？Is it possible to provide relevant reference materials?

It is well known that the error model of the SMC algorithm has been expressed by the signal flow diagram, what is the error model of the X parameter (signal flow diagram)？Is it possible to provide relevant reference materials?

Essentially it is the same, but of course each error term has a fundamental and harmonics so each error term represents more than one frequency at the same time. Then also you can have multiple signals from the DUT, including the large signal non-linear element (XF(|a1|) and small signal linear elements (still dependent on |a1|) such as Xs22,21 which is the second harmonic emanating from port 2, due to a fundamental signal applied at port 2, which depends on a1, and Xt22,21 which is the same but depends on a1* (conjugate).

Very deep technical topic; need a good reference:

https://www.amazon.com/X-Parameters-Characterization-Nonlinear-Components-Engineering/dp/0521193230

Essentially it is the same, but of course each error term has a fundamental and harmonics so each error term represents more than one frequency at the same time. Then also you can have multiple signals from the DUT, including the large signal non-linear element (XF(|a1|) and small signal linear elements (still dependent on |a1|) such as Xs22,21 which is the second harmonic emanating from port 2, due to a fundamental signal applied at port 2, which depends on a1, and Xt22,21 which is the same but depends on a1* (conjugate).

Very deep technical topic; need a good reference:

https://www.amazon.com/X-Parameters-Characterization-Nonlinear-Components-Engineering/dp/0521193230