di2599.txt 
;**************************************************************************************************
; LISTING 1 - PSPICE MODEL FOR DIFFERENTIAL STRIPLINE
;
; "Spice models differential stripline," EDN, Oct 12, 2000, pg 190
;
; http://www.ednmag.com/ednmag/reg/2000/10122000/designideas.htm#21di2
;
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.SUBCKT diff_stripline a1 a2 b1 b2 params: W=1u D=1u T=1u L=1u P=1 kc=1 
+ er=4.6 LEN=1
.func Pi() {4*atan(1)}
.func A(x) {1+log(1+1/tanh(Pi()*D/(4*x+2*T)))/log(2)}
.func C(x) {2*log(2+T/(2*x))-(T/(2*x+T))*log(T*(4*x+T)/(4*x**2))}
.func Z1(x) {60*Pi()*x/((sqrt(kc*er))*(W+(2*x+T)*C(x)*A(x)/(2*Pi())))}
T_T1         a1 0 b1 0
+Z0={2*Z1(L)*Z1(P-T)/(Z1(L)+Z1(P-T))} 
+TD={(sqrt(er)/3.0e8)*LEN}
T_T2         a2 0 b2 0 
+Z0={2*Z1(L)*Z1(P-T)/(Z1(L)+Z1(P-T))} 
+TD={(sqrt(er)/3.0e8)*LEN}
.ENDS diff_stripline