Pulse Code Modulation PCM Questions and Answers for Viva

Answer-1: PCM stands for Pulse Code Modulation. It's a digital representation of an analog signal.

Answer-2: The purpose of PCM is to digitize analog signals for transmission and storage in digital systems.

Answer-3: PCM works by sampling the amplitude of an analog signal at regular intervals, quantizing each sample into a digital value, and then encoding these values into a binary format.

Answer-4: The sampling rate determines how frequently the analog signal is measured and converted into digital values. A higher sampling rate captures more details of the original analog signal.

Answer-5: Quantization is the process of converting the continuous amplitude of an analog signal into discrete digital values.

Answer-6: Quantization error can be minimized by increasing the number of quantization levels or using techniques such as dithering.

Answer-7: The Nyquist theorem states that the sampling rate must be at least twice the highest frequency component of the analog signal in order to accurately reconstruct the signal from its samples.

Answer-8: Advantages include improved signal-to-noise ratio, better resistance to noise and interference, and easier compatibility with digital systems.

Answer-9: Disadvantages include the potential for quantization noise, higher bandwidth requirements compared to analog signals, and complexity in implementation.

Answer-10: A codec (coder-decoder) is used to convert analog signals into PCM format for transmission or storage, and then decode PCM signals back into analog form.

Answer-11: Yes, PCM can handle multiple channels of audio by using multiple streams of PCM data, typically one stream per channel.

Answer-12: PCM quantizes the amplitude of each sample, while Delta Modulation quantizes the difference between consecutive samples.

Answer-13: Synchronization is typically achieved by including timing information in the PCM signal, allowing the receiver to sample the signal at the correct intervals.

Answer-14: Companding is a technique used in PCM to improve the signal-to-noise ratio by compressing the dynamic range of the input signal before quantization and expanding it back to the original range after decoding.

Answer-15: The PCM bit depth refers to the number of bits used to represent each sample. Common bit depths include 8-bit, 16-bit, and 24-bit.

Answer-16: Analog-to-digital conversion in PCM involves sampling the analog signal, quantizing each sample, and encoding the quantized values into binary format.

Answer-17: A low-pass filter is used in PCM to remove high-frequency components from the analog signal before sampling, in order to prevent aliasing.

Answer-18: Yes, PCM can be used for video transmission by sampling and quantizing the luminance and chrominance components of the video signal.

Answer-19: Applications include digital audio transmission, storage and playback systems, telecommunications, and medical imaging.

Answer-20: PCM is a type of PAM where the amplitude of the pulse is directly proportional to the amplitude of the analog signal being digitized. However, PCM adds quantization and encoding steps to convert the PAM signal into a digital format.