Transfer matrix about nonlinear network

If one circuit network contains some nonlinear devices, such as varactor diodes, can we still make use of the transfer matrix(ABCD matrix)?

The usual network matrices, including the ABCD matrix, are for linear operation. If you have nonlinear devices, each set of parameters is valid for small signal operation with a given bias point.

Recently, Agilent had introduced the non-linear X Parameters. These are an extension of S-parameters and add nonlinear terms.

http://en.wikipedia.org/wiki/X-parameters

If your interest is a behavior of small signal around oeration point determined periodical large signal drive, you can use small signal matrix including frequency conversion effect.

If you use Cadence Spectre, use PSS/PSP or QPSS/QPSP.
If you use Agilent GoldenGate, use SSNA.

Here these analyses give you S-parameters including frequency conversion effects.
If you want to get chain-matrix(ABCD), convert this S-parameter to chain-matrix.

If you use Agilent ADSsim, invoke HB analysis with small signal.
Here you have to run two simulations to get {A,B,C,D}.

Also see the followings.
http://www.designers-guide.org/Forum...1239997125/1#1
https://www.edaboard.com/viewtopic.php?t=380636