Virtual Labs

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

In flat-top PAM, what is the main purpose of maintaining a fixed pulse width with a constant amplitude level for the duration of the sample?

a: To simplify the demodulation process and allow for stable sampling by 'Sample and Hold' circuits. Explanation

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b: To increase the average transmitted power for better performance over long distances. Explanation

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c: To encode additional information into the width of the pulse (Pulse Width Modulation). Explanation

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d: To eliminate the 'Aperture Effect' and frequency distortion in the recovered signal. Explanation

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In Pulse Amplitude Modulation (PAM), what is a key trade-off when increasing the signal bandwidth to reduce inter-symbol interference (ISI)?

a: Improved ISI performance but increased noise susceptibility Explanation

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b: Reduced quantization error but higher latency Explanation

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c: Lower amplitude distortion but reduced dynamic range Explanation

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d: Better noise immunity but higher bit error rate Explanation

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In PWM circuits, how does adjusting the duty cycle control the average power delivered to a load?

a: By changing the width of each pulse, which alters the average voltage over time Explanation

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b: By increasing the pulse amplitude to deliver more energy Explanation

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c: By varying the pulse frequency to control power Explanation

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d: By shifting the pulse position in time without changing width Explanation

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In Pulse Position Modulation (PPM), how does timing jitter affect symbol detection in a non-ideal receiver?

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

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b: It causes overlapping of adjacent symbols Explanation

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

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

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Why is PWM more suitable for motor control than PAM?

a: Because it minimizes power loss and allows precise control of average voltage Explanation

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b: Because it provides higher resolution at low voltages Explanation

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c: Because it reduces electromagnetic interference Explanation

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d: Because PWM signals are easier to encode digitally Explanation

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Why does Pulse Position Modulation (PPM) generally require more bandwidth than PAM or PWM for the same data rate?

a: Because narrow pulses must be accurately resolved in time, requiring higher sampling frequency Explanation

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b: Because pulse amplitudes vary widely, increasing spectral spread Explanation

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c: Because longer pulses overlap adjacent symbols Explanation

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d: Because phase modulation is also applied to each pulse Explanation

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