//VerilogA for ring,nefffilter,veriloga
//Xuanqi Chen, Zhifei Wang, Yi-Shing Chang, Jiang Xu, Jun Feng, Peng Yang, Zhehui Wang, Luan H. K. Duong, ”Modeling and Analysis of Optical Modulators Based on Free-Carrier Plasma Dispersion Effect,” IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems (TCAD), vol. 39, no. 5, pp. 977-990, May 2020.
`include "constants.vams"
`include "disciplines.vams"
`define MAX_TABLE_SIZE 300000
`define MAX_X_NUM 1000
//500*500=250000
module nefffilter(Ipow1,Iphase1,Ilam1,Opow1,Ophase1,Olam1,Ipow2,Iphase2,Ilam2,Opow2,Ophase2,Olam2,Vbias,Gnd);
//Parameters
parameter real r = 10u from (0:inf);
parameter real phaseshift_ratio = 0.8407 from (0:1);
parameter real nref_coupler = 3.02 from (0:inf);
parameter real kappa_coupler = 2.15e6 from (0:inf);
parameter real l_coupler = 0.1u from (0:inf);
parameter real alpha_phaseshift_ref = 80 from (0:inf);
parameter real alpha_absorp = 1 from (0:inf);
parameter real alpha_wd = 1 from (0:inf);
parameter real rib_width = 0.4u from (0:inf);
parameter real pn_offset = 0 from [0:inf);
parameter real ni = 1e16 from (0:inf);
parameter real N_A = 5e23 from (0:inf);
parameter real N_D = 1e24 from (0:inf);
parameter real Lp = 2u from (0:inf);
parameter real Ln = 1u from (0:inf);
parameter real epsr_Si = 11.7;
parameter real Is = 1e-14 from (0:inf);
parameter real IBV = 1000u from (0:inf);
parameter real BV = 40 from (0:inf);
parameter real V0 = 1 from [0:inf);
parameter real Cj0 = 1.5p from [0:inf);
parameter real tau = 0.5n from (0:inf);
parameter real Rs = 55 from (0:inf);
parameter real emi = 1 from (0:inf);
parameter real Vt = 0.0259 from (0:inf);
parameter string neff_ps_filename = "../../../data/EIM/outputPN1.54-1.56-500.txt";
parameter string neff_wg_filename = "../../../data/EIM/output-wg1.54-1.56-500.txt";
input Ipow1,Iphase1,Ilam1,Ipow2,Iphase2,Ilam2,Vbias;
output Opow1,Ophase1,Olam1,Opow2,Ophase2,Olam2;
inout Gnd;
electrical Ipow1,Iphase1,Ilam1,Ipow2,Iphase2,Ilam2,Vbias,Opow1,Ophase1,Olam1,Opow2,Ophase2,Olam2,Gnd;
electrical Nint;
branch (Gnd,Nint) Iint;
branch (Nint,Gnd) CCj,CCd,Idd,RRs;
//internal variables
real beta_cp;
real k_cp_r,k_cp_i;
real t_cp_r,t_cp_i;
real beta_wg;
real k_wg_r,k_wg_i;
real beta_ps;
real k_ps_r,k_ps_i;
real er,ei;
real p_mr_r,p_mr_i;
real E_in1_R,E_in1_I,E_in2_R,E_in2_I;
real E_out1_R,E_out1_I,E_out2_R,E_out2_I;
real t2r,t2i,p2r,p2i,k2r,k2i;
real c0r,c0i,c11r,c11i,c1r,c1i,c2r,c2i;
real cpr,cpi,cdr,cdi;
real alpha_phaseshift;
real W,Wdp,Wdn;
real eps,phi_bi,phi;
real N_avr;
real gd,Id,Cj,Cd;
real pn00,np00;
real lam;
real neff_waveguide,neff_phaseshift_ref,neff_phaseshift;
//1550nm
real sigma_ne=-8.8E-22;
real sigma_nh=-8.5E-18;
real sigma_ae=8.5E-18;
real sigma_ah=6.0E-18;
real xlength;//=0.6u;
integer xnum=`MAX_X_NUM+1;
integer xnum2=2*`MAX_X_NUM+1;
real x[0:`MAX_X_NUM];
real np[0:`MAX_X_NUM];
real pp[0:`MAX_X_NUM];
real pn[0:`MAX_X_NUM];
real nn[0:`MAX_X_NUM];
real xx[0:2*`MAX_X_NUM+1];
real n[0:2*`MAX_X_NUM+1];
real p[0:2*`MAX_X_NUM+1];
integer wi,wf;
real dalpha_e[0:2*`MAX_X_NUM+1];
real dalpha_h[0:2*`MAX_X_NUM+1];
real dalpha[0:2*`MAX_X_NUM+1];
real sum_dalpha,dalpha_avr;
integer ps_file, wg_file;
real width_start, width_end, width_step;
integer width_num;
real lam_start, lam_end, lam_step;
integer lam_num;
integer lam_near, width_near;
real tmp;
real lam_old=0;
real width_old=0;
real neff_table_ps[0:`MAX_TABLE_SIZE] = {0};
real neff_lamtable_ps[0:`MAX_TABLE_SIZE] = {0};
real neff_widthtable_ps[0:`MAX_TABLE_SIZE] = {0};
real neff_table_wg[0:`MAX_TABLE_SIZE] = {0};
real neff_lamtable_wg[0:`MAX_TABLE_SIZE] = {0};
integer read_table_ps=1;
integer read_table_wg=1;
integer i, j;
analog initial begin
pn00=pow(ni,2)/N_D;
np00=pow(ni,2)/N_A;
eps=epsr_Si*`P_EPS0;
phi_bi=`P_K*$temperature/`P_Q*ln(N_A*N_D/pow(ni,2));
N_avr=N_A*N_D/(N_A+N_D);
end
analog begin
lam=V(Ilam1);
gd=(-Is*(exp(5)-1)+IBV)/(-5*emi*Vt + BV);
Id=Is*(limexp(V(Nint)/(emi*Vt))-1)+V(Nint)*gd;
if (V(Nint) >= V0)
Cj=0;
else
Cj=Cj0/sqrt(1-V(Nint)/V0);
//Cd=Id*tau/(emi*Vt);
Cd=Is*(exp(V(Nint)/(emi*Vt))-1)*tau/(emi*Vt);
I(Iint) <+ V(Vbias)/Rs;
I(CCj) <+ Cj*ddt(V(CCj));
I(CCd) <+ Cd*ddt(V(CCd));
I(Idd) <+ Id;
V(RRs) <+ I(RRs)*Rs;
E_in1_R=sqrt(V(Ipow1))*cos(V(Iphase1)/360.0*2*`M_PI);
E_in1_I=sqrt(V(Ipow1))*sin(V(Iphase1)/360.0*2*`M_PI);
E_in2_R=sqrt(V(Ipow2))*cos(V(Iphase2)/360.0*2*`M_PI);
E_in2_I=sqrt(V(Ipow2))*sin(V(Iphase2)/360.0*2*`M_PI);
beta_cp = 2.0*`M_PI*nref_coupler/lam;
k_cp_r=-sin(kappa_coupler*l_coupler) * sin(l_coupler*beta_cp);
k_cp_i=sin(kappa_coupler*l_coupler) * cos(l_coupler*beta_cp);
t_cp_r=cos(kappa_coupler*l_coupler) * cos(l_coupler*beta_cp);
t_cp_i=cos(kappa_coupler*l_coupler) * sin(l_coupler*beta_cp);
phi=phi_bi-V(Nint);
if (phi<0)
phi=0;
W=alpha_wd * sqrt(2.0*eps*phi/(`P_Q*N_avr));
Wdp=N_D * W/(N_A+N_D);
Wdn=N_A * W/(N_A+N_D);
xlength=rib_width/2;
for (i=0; i<xnum; i=i+1) begin
x[i]=i*xlength/(xnum-1);
np[i]=np00*(exp(`P_Q*V(Nint)/(`P_K*$temperature))-1)*exp(-(x[i]-Wdp)/Ln)+np00;
if (x[i]>Wdp) begin
pp[i]=N_A;
end
else begin
pp[i]=0;
end
pn[i]=pn00*(exp(`P_Q*V(Nint)/(`P_K*$temperature))-1)*exp(-(x[i]-Wdn)/Lp)+pn00;
if (x[i]>Wdn) begin
nn[i]=N_D;
end
else begin
nn[i]=0;
end
if (np[i]<0) np[i]=0;
if (pn[i]<0) pn[i]=0;
end
for (i=0; i<2*xnum; i=i+1) begin
if (i<xnum) begin
xx[i]=-x[xnum-1-i];
n[i]=np[xnum-1-i];
p[i]=pp[xnum-1-i];
end
else begin
xx[i]=x[i-xnum];
n[i]=nn[i-xnum];
p[i]=pn[i-xnum];
end
// if (abs(xx[i]+rib_width/2) < 0.001u) begin
// wi=i;
// $display("wi=%d",wi);
// end
// if (abs(xx[i]-rib_width/2) < 0.001u) begin
// wf=i;
// $display("wf=%d",wf);
// end
end
for (i=0; i<xnum2; i=i+1) begin
dalpha_e[i]=n[i]*sigma_ae*1e-4;
dalpha_h[i]=p[i]*sigma_ah*1e-4;
dalpha[i]=dalpha_e[i] + dalpha_h[i];
end
sum_dalpha=0;
for (i=0; i<xnum2; i=i+1) begin
sum_dalpha=sum_dalpha+dalpha[i];
end
dalpha_avr=sum_dalpha/(xnum2);
alpha_phaseshift = alpha_phaseshift_ref + dalpha_avr;
if (read_table_ps==0 || lam_old==0 || width_old==0) begin
read_table_ps=1;
end
if (read_table_ps == 1) begin
ps_file=$fopen(neff_ps_filename,"r");
if (ps_file==0) begin
$display("Error: cannot open ps_file %s",neff_ps_filename);
$finish;
end
// else
// $display("ps_file %s opened successfully",neff_ps_filename);
$fscanf(ps_file,"%f",width_start);
$fscanf(ps_file,"%f",width_end);
$fscanf(ps_file,"%d",width_num);
width_step = (width_end-width_start)/(width_num-1);
// $display("width_start=%f, width_end=%f, width_num=%f, width_step=%f",width_start,width_end,width_num,width_step);
$fscanf(ps_file,"%f",lam_start);
$fscanf(ps_file,"%f",lam_end);
$fscanf(ps_file,"%d",lam_num);
lam_step = (lam_end-lam_start)/(lam_num-1);
// for (i=0; i<width_num; i=i+1) begin
// $fscanf(ps_file,"%f",tmp);
// end
for (i=0; i<width_num; i=i+1) begin
for (j=0; j<lam_num; j=j+1) begin
$fscanf(ps_file,"%f",tmp);
neff_widthtable_ps[i*lam_num+j] = width_start+i*width_step;
neff_lamtable_ps[i*lam_num+j] = lam_start+j*lam_step;
neff_table_ps[i*lam_num+j] = tmp;
//$display("neff_widthtable_ps[%d]=%f, neff_lamtable_ps[%d]=%f, neff_table_ps[%d]=%f",i*lam_num+j,neff_widthtable_ps[i*lam_num+j],i*lam_num+j,neff_lamtable_ps[i*lam_num+j],i*lam_num+j,neff_table_ps[i*lam_num+j]);
end
end
$fclose(ps_file);
neff_widthtable_ps[width_num*lam_num+1] = 0;
neff_lamtable_ps[width_num*lam_num+1] = 0;
neff_table_ps[width_num*lam_num+1] = 0;
neff_widthtable_ps[width_num*lam_num+2] = 0;
neff_lamtable_ps[width_num*lam_num+2] = -1;
neff_table_ps[width_num*lam_num+2] = 0;
read_table_ps=2;
end
if (read_table_ps == 2) begin
if (lam*1e6<lam_start || lam*1e6>lam_end) begin
$display("Warning: lam=%f is out of range [%f,%f]",lam*1e6,lam_start,lam_end);
end
if (Wdp*1e6<width_start || Wdp*1e6>width_end) begin
$display("Warning: Wdp=%f is out of range [%f,%f]",Wdp*1e6,width_start,width_end);
end
neff_phaseshift = $table_model(Wdp*1e6, lam*1e6, neff_widthtable_ps, neff_lamtable_ps, neff_table_ps, "3L,3L");
end
if (read_table_wg == 0|| lam_old==0 ) begin
read_table_wg=1;
end
if (read_table_wg == 1) begin
wg_file=$fopen(neff_wg_filename,"r");
if (wg_file==0) begin
$display("Error: cannot open wg_file %s",neff_wg_filename);
$finish;
end
$fscanf(wg_file,"%f",lam_start);
$fscanf(wg_file,"%f",lam_end);
$fscanf(wg_file,"%d",lam_num);
for (i=0; i<lam_num; i=i+1) begin
neff_lamtable_wg[i] = lam_start+i*lam_step;
end
for (j=0; j<lam_num; j=j+1) begin
$fscanf(wg_file,"%f",tmp);
neff_table_wg[j] = tmp;
end
read_table_wg=2;
$fclose(wg_file);
end
if (read_table_wg == 2) begin
if (lam*1e6<lam_start || lam*1e6>lam_end) begin
$display("Warning: lam=%f is out of range [%f,%f]",lam*1e6,lam_start,lam_end);
end
neff_waveguide = $table_model(lam*1e6, neff_lamtable_wg, neff_table_wg, "3E");
end
beta_wg = 2.0*`M_PI*neff_waveguide/lam;
beta_ps = 2.0*`M_PI*neff_phaseshift/lam;
k_wg_r=-alpha_phaseshift_ref;
k_wg_i=beta_wg;
k_ps_r=-alpha_phaseshift*alpha_absorp;
k_ps_i=beta_ps;
er = phaseshift_ratio*`M_PI*r*k_ps_r+(1.0-phaseshift_ratio)*`M_PI*r*k_wg_r;
ei = phaseshift_ratio*`M_PI*r*k_ps_i+(1.0-phaseshift_ratio)*`M_PI*r*k_wg_i;
p_mr_r = limexp(er)*cos(ei);
p_mr_i = limexp(er)*sin(ei);
t2r=t_cp_r*t_cp_r-t_cp_i*t_cp_i;
t2i=2*t_cp_r*t_cp_i;
p2r=p_mr_r*p_mr_r-p_mr_i*p_mr_i;
p2i=2*p_mr_r*p_mr_i;
k2r=k_cp_r*k_cp_r-k_cp_i*k_cp_i;
k2i=2*k_cp_r*k_cp_i;
c0r=1-t2r*p2r+t2i*p2i;
c0i=-t2r*p2i-t2i*p2r;
c11r=1+(k2r-t2r)*p2r-(k2i-t2i)*p2i;
c11i=(k2r-t2r)*p2i+(k2i-t2i)*p2r;
c1r=t_cp_r*c11r-t_cp_i*c11i;
c1i=t_cp_r*c11i+t_cp_i*c11r;
c2r=k2r*p_mr_r-k2i*p_mr_i;
c2i=k2r*p_mr_i+k2i*p_mr_r;
cpr=(c0r*c1r+c0i*c1i)/(c0r*c0r+c0i*c0i);
cpi=(c0r*c1i-c0i*c1r)/(c0r*c0r+c0i*c0i);
cdr=(c0r*c2r+c0i*c2i)/(c0r*c0r+c0i*c0i);
cdi=(c0r*c2i-c0i*c2r)/(c0r*c0r+c0i*c0i);
E_out1_R=cpr*E_in1_R-cpi*E_in1_I+cdr*E_in2_R-cdi*E_in2_I;
E_out1_I=cpi*E_in1_R+cpr*E_in1_I+cdi*E_in2_R+cdr*E_in2_I;
E_out2_R=cdr*E_in1_R-cdi*E_in1_I+cpr*E_in2_R-cpi*E_in2_I;
E_out2_I=cdi*E_in1_R+cdr*E_in1_I+cpi*E_in2_R+cpr*E_in2_I;
V(Opow1) <+ E_out1_R*E_out1_R+E_out1_I*E_out1_I;
V(Ophase1) <+ atan2(E_out1_I,E_out1_R)*360.0/(2*`M_PI);
V(Olam1) <+ V(Ilam1);
V(Opow2) <+ E_out2_R*E_out2_R+E_out2_I*E_out2_I;
V(Ophase2) <+ atan2(E_out2_I,E_out2_R)*360.0/(2*`M_PI);
V(Olam2) <+ V(Ilam2);
lam_old=lam;
width_old=Wdp;
end
endmodule