11 Sampling and Periodic Signals 278 Figurc 11.18: Spectrim of t,he sampled real signal it is multiplied by another cosine funct,ion: h.(t) = si (g) ( cos (WO + $)t ) (1 1.44) Figurc 11.19 depicts the irnpulse respoiise for W O = 3.Aw, ( n = ) It can clearly be seen that the envelopes in Figtire 11.19 agree with the curve in Figure 11.11 when the time axis is scaled by a factor of (11.44) is also valid for the case wg = in the lowpass case (11.35) (Exercise 11.22) Figure 11.1% Impulse response of art interpolation filter for a critically sampled real band-pass signal with wg = 39w The sampling frequencies deterrriiiled for the three cases of critical sampling arc