Consider a message signal m(t) with the spectrum shown in Fig. 3.31. The message bandwidth W...

 

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Consider a message signal m(t) with the spectrum shown in Fig. 3.31. The message bandwidth W = 1 kHz. This signal is applied to a product modulator, together with a carrier wave A, cos(2nf4), producing the DSB-SC modulated wave s(t). This modulated wave is next applied to a coherent detector. Assuming perfect synchronism between the carrier waves in the modulator and detector, determine the spectrum of the detector output when: (a) the carrier fre- quency fe = 1.25 kHz and (b) the carrier frequency f. = 0.75 kHz. What is the lowest carrier frequency for which cach component of the modulated wave s(t) is uniquely determined by m(t)? M(f) FIGURE 3.31 Problem 3.23 Consider a message signal m(t) with the spectrum shown in Fig. 3.31. The message bandwidth W = 1 kHz. This signal is applied to a product modulator, together with a carrier wave A, cos(2nf4), producing the DSB-SC modulated wave s(t). This modulated wave is next applied to a coherent detector. Assuming perfect synchronism between the carrier waves in the modulator and detector, determine the spectrum of the detector output when: (a) the carrier fre- quency fe = 1.25 kHz and (b) the carrier frequency f. = 0.75 kHz. What is the lowest carrier frequency for which cach component of the modulated wave s(t) is uniquely determined by m(t)? M(f) FIGURE 3.31 Problem 3.23