moisiad
New Member
Offline
Posts: 5
Athens, Greece
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Hi
I am using Spectre in Cadence. I am trying to perform a PSS and Pnoise analysis of a veriloga behavioral model (given below) of a VCO with FM jitter . However i am getting the following error message:
"Distributed components and components with hidden state are not allowed with this analysis", which most probably refers to the line where dT is declared.
How can i overcome this problem
Thanks
// Voltage Controlled Oscillator with Jitter
‘include “discipline.h”
‘include “constants.h”
module vco (out, in);
input in; output out; electrical out, in;
parameter real Vmin=0;
parameter real Vmax=Vmin+1 from (Vmin:inf);
parameter real Fmin=1 from (0:inf);
parameter real Fmax=2*Fmin from (Fmin:inf);
parameter real Vlo=–1, Vhi=1;
parameter real tt=0.01/Fmax from (0:inf);
parameter real jitter=0 from [0:0.25/Fmax);
parameter real ttol=1u/Fmax from (0:1/Fmax);
real freq, phase, dT;
integer n, seed;
analog begin
@(initial_step) seed = –561;
// compute the freq from the input voltage
freq = (V(in) – Vmin)*(Fmax – Fmin)
/ (Vmax – Vmin) + Fmin;
// bound the frequency (this is optional)
if (freq > Fmax) freq = Fmax;
if (freq < Fmin) freq = Fmin;
// add the phase noise
freq = freq/(1 + dT*freq);
// phase is the integral of the freq modulo 2p
phase = 2*‘M_PI*idtmod(freq, 0.0, 1.0, –0.5);
// update jitter twice per period
// 1.414=sqrt(K), K=2 jitter updates/period
@(cross(phase + ‘M_PI/2, +1, ttol) or
cross(phase – ‘M_PI/2, +1, ttol)) begin
dT = 1.414*jitter*$dist_normal(seed,0, 1);
n = (phase >= –‘M_PI/2) && (phase < ‘M_PI/2);
end
endmodule
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Error in simulating a VCO in veriloga (Read 3993 times)