Question:

Match List-I (modulation/generation techniques) with List-II (disadvantages/generated signal) and select the correct answer from the given codes:

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Associate key terms with modulation schemes: - PCM \(\leftrightarrow\) Quantization Noise - Delta Modulation \(\leftrightarrow\) Granular Noise \& Slope Overload - FM \(\leftrightarrow\) Threshold Effect - Ring Modulator \(\leftrightarrow\) DSB-SC

Updated On: Sep 19, 2025

A - II, B - IV, C - I, D - III
A - III, B - I, C - IV, D - II
A - IV, B - I, C - II, D - III
A - III, B - IV, C - I, D - II

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The Correct Option is D

Solution and Explanation

Step 1: Analyze each item in List-I.

(A) Ring Modulator: A ring modulator is a classic circuit used for generating a (III) DSB-SC (Double-Sideband Suppressed-Carrier) signal. It multiplies the carrier and the message signal.
(B) Pulse Code Modulation (PCM): PCM is a digital representation of an analog signal. The process involves sampling and then quantizing the samples. The error introduced by representing continuous amplitude levels with a finite set of discrete levels is called (IV) Quantization noise.
(C) Delta Modulation (DM): DM is a simpler form of digital modulation where only a 1-bit code is transmitted, indicating whether the signal has increased or decreased. A key issue with DM is slope overload distortion (when the signal changes too fast) and (I) Granular noise (when the signal is flat or changes slowly, the output toggles around it).
(D) Frequency Modulation (FM): A characteristic disadvantage of FM detection, particularly with simple detectors like discriminators, is the (II) Threshold effect. Below a certain carrier-to-noise ratio, the output signal-to-noise ratio degrades much more rapidly than the input, leading to a "threshold."

Step 2: Combine the matches. The correct matching is: A-III, B-IV, C-I, D-II.

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List-I (Modulation Schemes)	List-II (Wave Expressions)
(A) Amplitude Modulation	(I) \( x(t) = A\cos(\omega_c t + k m(t)) \)
(B) Phase Modulation	(II) \( x(t) = A\cos(\omega_c t + k \int m(t)dt) \)
(C) Frequency Modulation	(III) \( x(t) = A + m(t)\cos(\omega_c t) \)
(D) DSB-SC Modulation	(IV) \( x(t) = m(t)\cos(\omega_c t) \)