two pole passive low pass filters using transfer function in

C2=input ('value of the capacitor C2: ');
C1=input ('value of the capacitor C1: ');
R2=input ('value of the resistor R2: ');
R2C1=R2*C1;
C1_C2=C1+C2;
C1C2R2=C1*C2*R2;
b=[R2C1 1];
a=[C1C2R2 C1_C2 0];
[A,B,C,D] = tf2ss(b,a)
a2=[C1C2R2 C1_C2 0 0];
kvco=20e6;
kphi=5e-3;
RFout=900e6;
Fref=200e3;
N=RFout/Fref;
omegap=2*3.14*20e3;
T1=0.414/omegap;
T2=1/omegap^2*T1;
C1=T1/T2*(kphi*kvco/omegap^2*N)*sqrt(1+(omegap*T2)^2/1+(omegap*T1)^2);
C2=C1*(T2/T1-1);
R2=T2/C2;
gain=kvco*kphi/N;
s=tf('s');
Z=(s*(C2*R2)+1/s^2*(C1*C2*R2)+(s*C1)+(s*C2));
Bode(Z)
grid on



*****can some one code this two pole passive low pass filter using transfer in matlab ....im not gettin the phase margin as 45deg...bode plot is completely wrong...though im an intermediate level in matlab codin...im just freakin out...

Re: two pole passive low pass filters using transfer functio

What exactly is wrong? As far as I can tell, you don't have a "canonical" two pole low-pass filter because your transfer function has a pole at zero, another pole and a zero.