1 Sampling and Pcriodic Signals 276 interpolation filter H(icn;l) Figiirc 11.15: Spcctrniri of the sampled complex signal (11.40) 'I'herr is no conjugate syrriinetrp licrt eithcr, so thc corresponding impiilsc response is tomplcs: (11.41) Figure 11.16 h i o ~ l sthe real and iniagiiiarv parts ol / I ( , ) for "'cl = 4Aw For the spparentlv simple case of a reid ban gn,il correct choice of- sample iimi fiecluency is not a s simplr as for the coiiiplex band-pass s i p a l T l i ~sp~('1 of tt real bad-pass signal is ihowii in Figure 11 17 The coiiditions ol conjugate ~j-mnwtryare hilfillecl in this case Crilicnl sampling rcquirei a sample rate of f hw , I.e., x -.=- " I T wa = 2Aw , In contrast to complex bancl-pass signals, in this C R S P , triticd sarnplirig is oiily possibltx if WO mid A d have i i particular rrlattionship with each other Continuation belwecn -wu arid of the band-pass sp I iirii witlront gaps requirvs that, u~in F'igure 11.17 can take exactly an even ririiribcr of half-bands of width AdL1