X(jw) 1 -π/4 π/4 ய Xp(jw) -π/4 π/4 No aliasing. ய Xp(jw) 1/2 s t s Λ No aliasing. -π/4 π/4 Xp(jw) 1/4 M -π/4 π/4 -π/2 No aliasing. Xp(jw) 1/81 XX -π/4 π/4 There is aliasing. π/2 Π 3 3 ய