11.3 Sainpling 285 Figure 11.26 shows the periodic spectruni correspondilzg t o 24 irriagPs per second and the weighting by the interpolation functiori h ( t ) An image aigiial has a doniiizant frequency component at w = Tlie zero of the spectrnm at the sariipling frrquency 24 Hz extensively suppresses the first reoccurrence The second at 48 Hz is not, weakened significantly, hit the flickering becomes much ticeable Additionally, the flicker reduction only functions when both rec that form h ( t ) (Figure 11.25) a w shiftccl away from each other by exactly T/2 Reduction of the compoiients at both 24 Hz arid 48 Hz (*an1 ben be achicvetl using ion (Excrcisc 11.24) zero at 24 Hz suppresses annoying flicker 24Hz 48Hz U) 2.z Figure 11.26: Magoitudc response of the interpolation f i h r with a zero at 24 Ilz equency-Domain The sampling theorem states that band-limited signals can be reconstructed froin their sample values if the samptixrg frequency is high enough thal 110 overlappiiig occurs in the frec~i~cncy-domain Becaiisc of the duality between the time-domain and frcqucncy-domain, a dual of thc sariipliiig theorem can be foirriulated: Signals of finite duration can be unambiguously reconstructed from a sufficient number of samples from their spectrum Signals repeated in the time-domain may not overlap We can rxpress this matherna;tically with the transform pair Y(jw) = Y(JW) + -U 2n (c) - (I157) I I (11.58)