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Design Languages >> Verilog-AMS >> How to use a curve fit function to simulate MEMS transient response
https://designers-guide.org/forum/YaBB.pl?num=1333358899

Message started by sr1857 on Apr 2^nd, 2012, 2:28am

Title: How to use a curve fit function to simulate MEMS transient response
Post by sr1857 on Apr 2^nd, 2012, 2:28am

Dear All,,
I am trying to create a model of a MEMS switch in Verilog-A. I saw an example of Verilog-A MEMS switch model on this website which is applicable to a parallel plate capacitor MEMS.

http://www.designers-guide.org/VerilogAMS/mems-models/OHMIC_CANTILEVER_RF_MEMS_SWITCH.va

I have a MEMS design that is not a parallel plate capacitor device. I have simulated this device in ANSYS (good for transient MEMS simulation). From the ANSYS simulations I have the transient response of the MEMS structure i.e displacement vs time in the form of
z = A*t^2+B*t

where z is the displacement and t is the time.

I want to use this response function in the Verilog-A design but I don't know how to modify the non-linear state space equations for Pos(z) and Pos(velocity) for the above transient response.

Pos(velocity) is pretty straight forward I think and I could use the same one as given in the example (link above), i.e.

Pos(velocity):ddt(Pos(z))==Pos(velocity);

But I can't think of a way to express Pos(z); I tried something along the lines of the following:

Pos(z):idt(Pos(velocity),ic)==A*pow((Pos(z)/Pos(velocity)),2) + B*(Pos(z)/Pos(velocity));

The logic behind the above equation is t = Pos(z)/Pos(velocity)

Would anyone have any idea how to plug in the transient response into the state space equations?

I would really appreciate your help.

Many thanks,
Sunil.