Pavel -
You have two things across (A,B) that are both trying to set the voltage:

inductor #(.l(50u)) L1 (A,B);

and

V(A, B) <+ ddt(flux);

At time=0, both are shorts (V=0), and you can't put two 0-volt voltage sources in parallel (physically, any arbitrary current can flow in the loop created by the two of them; mathematically, you have a singular matrix).

I generally work with the electrical discipline, that is, with voltage and current, rather than with flux and charge.  I suppose you could define a flux source and a module that had a flux input and converted it to a voltage.

Code:

module flux_source(out);
  inout out;
  magnetic out;
  parameter real FREQ = 100;
  parameter real AMPL = 10;

  analog begin
    Phi(out) <+ AMPL*sin(`M_TWO_PI*FREQ*$abstime);
    $bound_step(0.05/FREQ);
  end
endmodule

module flux_recv(in, vout);
  inout in, vout;
  magnetic in;
  electrical vout;

  analog
    V(vout) <+ ddt(Phi(in));
endmodule
 

Pavel wrote on Nov 10^th, 2006, 6:50am:


You did miss something.  The creation of different natures allows you to set different tolerances on the variables: if the simulator applied ABSTOL (which usually runs around 1e-12 in Spice-like simulators) to charge variables (which in modern MOSFETs runs in the 1e-18 range, then you could never expect the charge to give accurate results, because any answer would be below the tolerance.

Also, there's some mention about compatible disciplines -- a good simulator will warn you (or give an error) if you accidentally connect a magnetic port to one that is really supposed to be electrical.  I heard a story once about a designer who accidentally connected the "thermal terminal" of a bipolar model with self-heating to an electrical wire in a Spice simulator; he thought Kirchoff's current law was being violated because current was disappearing into the "thermal ground" of the BJT model (and he must have been getting the wrong answer because his BJT was incorrectly computing its temperature).

Quote:


I think you'd need to write your own inductor with the usual two electrical ports and a magnetic port to bring in the RF:

Code:

module fluc_recv(a,b,rf_in);
  inout a, b, rf_in;
  electrical a, b;
  magnetic rf_in;
  parameter real L = 1n from (0:inf);

  analog
    V(a,b) <+ ddt(L * I(a,b) + Phi(rf_in));

endmodule
 

Quote:


The LRM says that idt() without an initial condition has to be used in a feedback loop that forces its inputs to zero.  I would suggest you look into that, or convert to ddt() as I used in my module.