engelbrl
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Oregon State University
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I have a question regarding ac small-signal simulation with magnetic fields. It may be more of a questio\ n concerning how Spectre actually works. I have written a compact model in Verilog-A which successfully \ describes the dynamics of a magnetic nanoparticle (abbreviated code shown below - Theta(Mpol) and Theta(M\ az) are the polar and azimuthal angles of magnetization respectively). I want to do an ac simulation to \ show ferromagnetic resonance at a particular frequency and have thus far been unsuccessful. The stimulus\ is the ac field and a DC bias field, both in the z-dir (perpendicular to the material plane), because I \ would like to see the magnetization rotate about the z-axis. The simulation runs but the output is extre\ mely small (zero really...) and without any resonant peak at the expected frequency.
I'm wondering if there is a reason why the small-signal analysis would not work with the system of equati\ ons I have developed for this magnetic system (I realize that I might not have yet all of the conditions \ just right to get a reasonable output). I had assumed that since I had a DC operating point from other t\ ransient simulations, Spectre would linearize the system of equations around that operating point in the \ same way that SPICE does. I don't think it should matter whether the system uses V and I or M and H - Doe\ s anyone know if there is a limitation to the kind of system in which a Spectre ac analysis can operate? \ Does anyone know if Spectre really does do a differential linearization of the system equations in the s\ ame way SPICE does?
Thank you, Linda
(partial code listing) ----------------------------- nature Magnetic_Induction abstol = 1e-6 ; access = H ; units = "A/m" ; endnature
discipline sig_flow_H potential Magnetic_Induction ; enddiscipline
module SW3D(hx, hy, hz,Mpol,Maz,Mea ); input hx, hy, hz ; inout Maz, Mpol, Mea ;
sig_flow_H hx, hy, hz, hMpol, hMaz ; // H-field vector components rotational Mea, Maz, Mpol, Anis; // port discipline for easy axis angle // and magnetization angles(spherical) : //parameters set : analog begin : H(hMpol) <+ ....eqn for H(hMpol).... H(hMaz) <+ ....eqn for H(hMaz)...
Theta(Mpol) <+ idt((C1*G0)*(H(hMaz) + alpha*H(hMpol)),`M_PI/2 ) ;
Theta(Maz) <+ idt(((C1*G0)/sin(Theta(Mpol)))*(alpha*H(hMaz)- H(hMpol)),`M_PI); end endmodule
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