The sketch in Figure P12.2 illustrates the power spectral densities of a PN spread spectrum signal and narrowband interference in an uncoded (trivial repetition code) digital communication system. Referring to Figure 12.2-6, which shows the demodulator for this signal, sketch the (approximate) spectral characteristics of the signal and the interference after the multiplication of r(t) with the output of the PN generator. Determine the fraction of the total interference that appears at the output of the correlator when the number of PN chips per bit is Lc.
