Virtual Labs

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

1. 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

Explanation

b: Because it uses wide bandwidth. Explanation

Explanation

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

Explanation

d: Because timing synchronization is not used. Explanation

Explanation

2. In PWM systems, why can higher signal amplitudes lead to intersymbol interference if the system is not properly designed?

a: Because increased pulse width can overlap adjacent symbols. Explanation

Explanation

b: Because amplitude fluctuations distort the pulse height. Explanation

Explanation

c: Because higher amplitudes cause frequency drift. Explanation

Explanation

d: Because signal reflection occurs at higher amplitudes. Explanation

Explanation

3. 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

Explanation

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

Explanation

c: It requires no synchronization. Explanation

Explanation

d: It encodes amplitude variations efficiently. Explanation

Explanation

4. Why is PAM 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 amplitude levels. Explanation

Explanation

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

Explanation

c: Because it requires no synchronization. Explanation

Explanation

d: Because it is robust against phase distortion. Explanation

Explanation

5. 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

Explanation

b: It uses orthogonal frequency tones. Explanation

Explanation

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

Explanation

d: It automatically adjusts pulse spacing. Explanation

Explanation

6. In PPM, what is the key disadvantage when comparing synchronization requirements to PAM or PWM?

a: PPM requires precise timing alignment to decode correctly. Explanation

Explanation

b: PPM uses more bandwidth due to wider pulses. Explanation

Explanation

c: PPM encodes information in amplitude which is noise sensitive. Explanation

Explanation

d: PPM can only support binary encoding. Explanation

Explanation