Virtual Labs

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

1. In Pulse Amplitude Modulation (PAM), what is a critical trade-off encountered when increasing the signal bandwidth to mitigate inter-symbol interference (ISI)?

a: Improved spectral efficiency but increased noise susceptibility Explanation

Explanation

b: Reduced quantization error but higher transmission delay Explanation

Explanation

c: Lower distortion but reduced amplitude resolution Explanation

Explanation

d: Better noise immunity but higher bit error rate Explanation

Explanation

2. In high-frequency switching applications, what makes Pulse Width Modulation (PWM) inherently less power-efficient compared to other modulation schemes?

a: High-frequency harmonics result in greater switching losses Explanation

Explanation

b: The need for linear amplifiers increases energy demands Explanation

Explanation

c: PWM requires higher sampling rates than PAM Explanation

Explanation

d: Duty cycle variations distort the signal envelope Explanation

Explanation

3. In Pulse Position Modulation (PPM), how does timing jitter specifically impact the symbol detection process in a non-ideal receiver?

a: It randomly shifts the phase of the detected pulses Explanation

Explanation

b: It causes inter-symbol interference due to overlapping symbols Explanation

Explanation

c: It introduces uncertainty in pulse arrival times, increasing symbol error probability Explanation

Explanation

d: It reduces the amplitude of received pulses, causing clipping Explanation

Explanation

4. What is the primary non-ideality introduced by a nonlinear modulator in a PAM system from a frequency domain perspective?

a: Spectral nulls at harmonics of the pulse frequency Explanation

Explanation

b: Generation of intermodulation products and harmonic distortion Explanation

Explanation

c: Increase in channel noise floor Explanation

Explanation

d: Reduction in spectral efficiency due to pulse spreading Explanation

Explanation

5. Why is Pulse Width Modulation (PWM) more suitable for motor control applications compared to PAM?

a: PWM minimizes power loss during switching and allows efficient average voltage control Explanation

Explanation

b: PWM provides higher resolution of control at lower voltages Explanation

Explanation

c: PWM reduces electromagnetic interference compared to PAM Explanation

Explanation

d: PWM signals are easier to encode into digital logic levels Explanation

Explanation

6. In high-speed PPM systems, what is a key reason for preferring higher-order modulation despite its susceptibility to timing jitter?

a: It reduces symbol duration, increasing robustness to timing noise Explanation

Explanation

b: It allows higher data throughput without increasing pulse rate Explanation

Explanation

c: It mitigates phase noise in long-distance transmission Explanation

Explanation

d: It simplifies the demodulation circuitry by reducing synchronization requirements Explanation

Explanation