function [sig2] = varm(x,n,a,ip,b,iq,nexp) 
      
m=2^nexp;
aa(1)=1.;
bb(1)=1.;
for i=2:m 
      	if i > n
		x(i)=0.;
	end
      	if i <= ip+1
		aa(i)=a(i-1);
	else
		aa(i)=0.;
	end
      	if i <= iq+1
		bb(i)=b(i-1);
	else
		bb(i)=0.;
	end
end
invrs=1;
x = fft_my(x,nexp,invrs);
aa = fft_my(aa,nexp,invrs);
bb = fft_my(bb,nexp,invrs);
sig2=0.;
for i=1:m 
	sig2=sig2+(abs(x(i))^2)*(abs(aa(i))^2)/(abs(bb(i))^2);
end
sig2=sig2/(n*m);