Virtual Labs

Pulse Amplitude Modulation (PAM), Pulse Width Modulation (PWM), Pulse Position Modulation(PPM) & their Demodulation

Which statement best explains why Pulse Amplitude Modulation (PAM) is more susceptible to noise compared to digital modulation schemes?

a: Because it encodes information in continuous levels susceptible to amplitude distortion. Explanation

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b: Because it uses wide bandwidth. Explanation

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c: Because it relies on frequency variation, which is inherently noisy. Explanation

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d: Because timing synchronization is not used. Explanation

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In PWM systems, why can wider pulses cause intersymbol interference (ISI) if the system is not properly designed?

a: Because wide pulses can overlap adjacent symbols, causing ISI. Explanation

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b: Because amplitude fluctuations distort the pulse height. Explanation

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c: Because higher amplitudes cause frequency drift. Explanation

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d: Because signal reflection occurs at higher amplitudes. Explanation

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Which property of Pulse Position Modulation (PPM) makes it advantageous in low-power optical communication systems?

a: It transmits energy in short bursts, allowing efficient power usage. Explanation

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b: It has a constant pulse width for all signal levels. Explanation

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c: It requires no synchronization. Explanation

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d: It encodes amplitude variations efficiently. Explanation

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Why is PAM (Pulse Amplitude Modulation) often used as an intermediate step in digital modulation schemes such as QAM or OFDM?

a: Because it allows simple mapping from digital bits to discrete amplitude levels. Explanation

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b: Because it uses time division to reduce the required channel bandwidth. Explanation

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c: Because it is an asynchronous protocol and requires no clock synchronization. Explanation

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d: Because it is inherently robust against phase distortion and multipath fading. Explanation

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In PWM, which factor makes it more robust than PAM under varying channel gain conditions?

a: Information is encoded in time (width), not amplitude. Explanation

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b: It uses orthogonal frequency tones. Explanation

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c: Its pulses are less frequent than in PAM. Explanation

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d: It automatically adjusts pulse spacing. Explanation

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In PPM, what is the main challenge related to timing when compared to PAM or PWM?

a: PPM requires precise timing alignment to correctly detect the pulse position. Explanation

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b: PPM uses wider pulses, increasing bandwidth requirements. Explanation

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c: PPM encodes information in amplitude, making it noise-sensitive. Explanation

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d: PPM can only encode binary data. Explanation

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