Pulse Amplitude Modulation Questions

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Very Short Answers Questions [1 Mark Questions]

Ques. What is the full form of PAM?

Ans. The full form of PAM is Pulse Amplitude Modulation.

Ques. Which filter is used to detect the PAM signal?

1. Low Pass Filter
2. High Pass Filter
3. Bandpass Filter
4. All-Band Pass Filter

Ans. The correct answer is a. Low Pass Filter

Explanation: Low Pass Filter is used to detect a Pulse Amplitude Modulation (PAM) signal. A low-pass filter is used during the demodulation process to get the original baseband signal from the modulated PAM signal.

Ques. Which of the following systems is analog?

1. PCM
2. DM
3. DPCM
4. PAM

Ans. The correct answer is d. PAM

Explanation: Pulse amplitude modulation (PAM) is an analog modulation technique in which the amplitude of the analog signal changes to represent the information to be transmitted.

Ques. Define amplitude.

Ans. Amplitude is defined as the maximum displacement of a particle from its mean position. The SI unit of amplitude is meter (m). It is denoted by the letter ‘A’.

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Short Answers Questions [2 Marks Questions]

Ques. What are the different types of amplitude modulation?

Ans. There are five different types of amplitude modulation

• Double sideband-suppressed carrier modulation
• Single sideband modulation
• Vestigial sideband modulation
• Double sideband full carrier modulation
• Quadrature amplitude modulation

Ques. What is amplitude modulation?

Ans. Amplitude Modulation is a technique used in communication systems to transfer voice or data over a carrier signal. In this technique, the amplitude of the carrier signal changes according to the amplitude of the modulating signal. The modulating signal is the signal which contains the information to be transmitted.

Ques. How is the Pulse Amplitude Modulated wave generated?

Ans. The pulse amplitude modulated wave is generated by the following process

• Sampling: The continuous analog modulating signal is converted into discrete amplitude samples through the sampling process.
• Quantization: The discrete samples are then quantized into a finite number of amplitude levels.
• Amplitude modulation: The amplitude of the carrier signal is then converted according to the modulating signal.

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Long Answers Questions [3 Marks Questions]

Ques. What factors affect pulse amplitude modulation?

Ans. The factors affecting the pulse amplitude modulation are

• The distance through which a PAM signal is transmitted affects the quality of the signal.
• It depends on the Signal-to-Noise ratio (SNR). A higher SNR means better signal quality.
• The data rate of the PAM signal is determined by the frequency at which the pulse repeats itself. A higher repetition rate allows more data to be transmitted per unit of time.

Ques. What is frequency modulation?

Ans. Frequency Modulation is a technique used in communication systems to transfer voice or data over a carrier signal. In this technique, the frequency of the carrier signal changes in accordance with the characteristics of the modulating signal. This technology is used in

• Telecommunications
• Radio Broadcasting
• Signal Processing
• Signal Computing

Ques. State and explain the types of pulse amplitude modulation.

Ans. Pulse amplitude modulation is of two types

1. Single Polarity PAM: In this type, the amplitude of the pulse train of the PAM signal varied only in one direction and have only positive values.
2. Double Polarity PAM: In this type, the amplitude of the pulse train of the PAM signal varies in both direction and have both negative and positive values.

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Very Long Answers Questions [5 Marks Questions]

Ques. What are the applications of Pulse amplitude modulation?

Ans. The applications of Pulse amplitude modulation are

• PAM is used to transmit digital data over analog channels in digital communication systems.
• Graphic cards and high-speed networking also use pulse amplitude modulation to reduce the signal-to-noise ratio.
• In some power line communication systems, PAM is used for data transmission over existing power lines.
• It is also used in LED (Light emitting diodes) drivers for efficiency in the energy of the lighting.
• PAM is also used in some RADAR systems.
• PAM is used in remote sensing applications to carry information about the environment.

Ques. What are the advantages of PAM or pulse amplitude modulation?

Ans. The followings are the advantages of pulse amplitude modulation

• It is cost-effective and easy to implement.
• It is bandwidth-efficient. As compared to other modulation techniques it can achieve a higher data rate using less bandwidth.
• Demodulation of the PAM signal is less complex as compared to other modulation techniques.
• PAM has high SNR (Signal-to-Noise ratio) because the amplitude of the pulse of the PAM signal directly represents the signal level.
• As compared to other modulation techniques, a PAM signal generates a relatively low level of electromagnetic interference.

Ques. What are the disadvantages of pulse amplitude modulation?

Ans. The followings are the disadvantages of pulse amplitude modulation

• It is highly sensitive to noise, any noise in the communication channel produces errors in the demodulated PAM signals.
• The performance of PAM is characterized by SNR, as the noise level increases the quality of the demodulated signal decreases.
• This modulation technique is not efficient for transmitting analog signals with continuous values.
• It is not suitable for applications where frequency information is important.
• A PAM-based system offers only amplitude modulation, so it is incompatible with applications such as quadrature amplitude modulation (QAM) or resonant amplitude modulation (RAM).

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