demodulator using adder with envelope detector

hello , I am trying to make a AM modualtor and a demodulator using a summer with envelope detector here is my code

clear close all;
clc;
A=1.5;
B=2;
f1=1;
f2=4;
RSZ=15;
P=7;
f0=100;
t=0:0.00001:1;
Fs=100000;
s1=A*cos(2*pi*f1*t);
s2=B*cos(2*pi*f2*t);
s=s1+s2;  
sp=P*cos(2*pi*f0*t);
figure(11), plot(t,s);
figure(1), plot(t,sp);

semnal_modulat=P*(1+s).*sp  
figure(2), plot(t,semnal_modulat);
iesire = awgn(semnal_modulat,RSZ); 

figure(3), plot(t,iesire);
spectru_iesire=fft(iesire);
figure(4), plot(abs(spectru_iesire));

demod=iesire+cos(2*pi*f0*t);
%detectorul de anvelopa
demod=2*demod.*demod;
demod=downsample(demod,15);
demod=sqrt(demod);
Wp=2*pi*1000 
Ws=2*pi*(2*f0-4)
[n,Wt]=buttord(Wp,Ws,1,40,'s');
[b,a]=butter(n,Wt,'s');
[bd,ad]=impinvar(b,a,Fs);
iesire_demod=filter(bd,ad,demod);
iesire_demod=iesire_demod-100;
figure(6),plot(iesire_demod)

the output is close to the original signal but not kind like it , can someone help me ?