function [ x, y, Ryy ] = tryit( NX, N, alpha )
%TRYIT a simple echo problem
x = randn(1, NX);
y = filter([1 zeros(1,N-1) alpha], 1, x);
Ryy = conv(y, fliplr(y));
figure;
plot([-NX+1:NX-1], Ryy);
