Podcast
Questions and Answers
Who invented Pulse Code Modulation (PCM) in 1937?
Who invented Pulse Code Modulation (PCM) in 1937?
What is a limitation of PPM and PWM that PCM can overcome?
What is a limitation of PPM and PWM that PCM can overcome?
Why is it necessary for the voltage to be relatively constant during ADC conversion in a PCM transmitter?
Why is it necessary for the voltage to be relatively constant during ADC conversion in a PCM transmitter?
What is the main function of a sampling circuit in a PCM transmitter?
What is the main function of a sampling circuit in a PCM transmitter?
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What is a characteristic of Pulse Code Modulation (PCM) signals?
What is a characteristic of Pulse Code Modulation (PCM) signals?
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Why is PCM the most preferred method in telecommunications?
Why is PCM the most preferred method in telecommunications?
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What is the main limitation of natural sampling?
What is the main limitation of natural sampling?
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What is the primary function of a sample-and-hold circuit?
What is the primary function of a sample-and-hold circuit?
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What is the advantage of flat-top sampling over natural sampling?
What is the advantage of flat-top sampling over natural sampling?
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What is the primary method used for sampling voice signals in PCM systems?
What is the primary method used for sampling voice signals in PCM systems?
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What is the result of the sampling process in natural sampling?
What is the result of the sampling process in natural sampling?
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What is the purpose of the sample-and-hold circuit in PCM systems?
What is the purpose of the sample-and-hold circuit in PCM systems?
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Study Notes
Pulse Code Modulation (PCM)
- A digital encoding modulation technique that converts an analog signal into a digital signal via sampling.
- PCM signal consists of a group of pulses that represent the inputted analog data.
History of PCM
- Invented by Alec H. Reeves in 1937 while working for AT&T.
Advantages of PCM
- Most preferred method in tele-communications for digitizing voice and digital data.
- Offers ease of digitizing voice and digital data with high-speed signal transmission through metallic and optic-fiber cables.
Limitations of Other Modulation Techniques
- PPM and PWM have bandwidth limitations due to resolution requirements in transmitting 16-bits and beyond.
- PAM is susceptible to noise, affecting the recovered signal.
PCM Transmitter and Receiver
- Function of a sampling circuit in a PCM transmitter is to periodically sample the continually changing analog input voltage and convert those samples to a series of constant amplitude pulses.
- Sampling circuit allows for accurate conversion of voltage to a binary code by the ADC.
Sampling Techniques
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Natural Sampling
- Retains natural shape of sample pulses during the sample interval.
- Makes it difficult for an ADC to convert the sample to a PCM code.
- Alters the frequency spectrum of the sampled output.
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Flat-top Sampling
- Most common method used for sampling voice signals in PCM systems.
- Accomplished in a sample-and-hold circuit.
- Introduces less aperture distortion than natural sampling.
- Can operate with a slower analog-to-digital converter.
Sample-and-Hold Circuit
- Periodically samples the continually changing analog input voltage and converts those samples to a series of constant-amplitude PAM voltage-levels.
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Description
Learn about the basics of Pulse Code Modulation, a digital encoding technique used to convert analog signals into digital signals. This quiz covers the concept of PCM, its history, and its applications in tele-communications.
