Discussion

Match List I with List II and select the correct answer using codes given below :

List I	List II
(a) DSB-SC modulation	(i) \(A \sin \left(w_{c}t + k\int_{-\infty}^{t} m(z)\, dz\right)\)
(b) Amplitude modulation	(ii) \(A \sin (w_{c}t + k_{m}(t))\)
(c) Frequency modulation	(iii) \(k.m(t)\, A \sin (w_{c}t)\)
(d) Phase modulation	(iv) \(\{1 + k_{m}(t)\}\, A \sin (w_{c}t)\)

Answer: B

The correct matching is a-iii, b-iv, c-i, d-ii.

(a) DSB-SC is the product of the message and the carrier, \(k\,m(t) A \sin(w_{c}t)\), with no carrier term (iii).
(b) AM adds a carrier: the amplitude is \(\{1 + k\,m(t)\}A\) (iv).
(c) FM makes the instantaneous frequency follow m(t), so the phase contains the integral of m(t) (i).
(d) PM makes the phase itself follow m(t): \(A \sin(w_{c}t + k\,m(t))\) (ii).

The other codes confuse AM with DSB-SC or FM with PM.

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