Some new trajectory patterns and periodic behaviors of unstable second-order digital filter with two’s complement arithmetic

<p>This letter shows some counter-intuitive simulation results that for some filter parameters in the extended boundaries of the stability triangle, the state vector will converge to a periodic orbit after some iterations, no matter what the initial conditions are. Also, a new pattern, which looks like a rotated letter ‘X’, is found. The center of the rotated letter is located at the origin and the slopes of the ‘straight lines’ of the rotated letter are equal to the values of the pole locations.</p>