Adjacent-band aliasing cancels by opposite phase when bands are unmodified

Evidence

The necessary criteria for the prototype low-pass filter response hp(n) are that energy is preserved between the adjacent bands and that sufficient attenuation in non-adjacent bands is obtained to suppress the aliasing components (Creusere and Mitra, 1995; Cruz-Roldán et al., 2002). … The analysis and synthesis filters have the same magnitude spectrum, and thus the amplitudes are preserved in total between the adjacent bands. The downsampling– upsampling process is necessary because it reduces redundancy, but it also generates aliasing frequency components that remain after the synthesis filter. These aliasing components between the adjacent bands have opposite phases with respect to each other and cancel each other out if the frequency-band signals are not modified. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 2129

Categorization

Category: Causal Relationships

• DEFINE: Explains the mechanism by which near-perfect reconstruction PQMF banks cancel aliasing: opposite-phase adjacent components.