Pulse Code Modulation

Parth Chitre Ayush Jaiswal Karan Panikatti

2022200022 2023201009 2021200082

Introduction Circuit Details Simulation Results: (PCM modulator) Conclusion

The PCM modulator circuit was designed as follows: Circuit for PCM modulator:
Pulse Code Modulation (PCM) is a digital In this experiment, we explored Pulse Code
1. Key Components:
modulation technique by which an analog signal ○ IC CD4016: Quad bilateral switch IC Modulation (PCM), a key technique for converting
○ LM324: Quad op-amp IC with low power consumption
is converted to an equivalent sequence of binary analog signals into a digital format. PCM involves
○ IC 7493: 4-bit binary ripple counter IC used for
codes. frequency division and counting applications. sampling an analog signal at regular intervals,
○ IC 7400: Quad 2-input NAND gate IC quantizing these samples into predefined levels,
The analog signal is first sampled at regular ○ Resistors: 2.2 kΩ and 1 kΩ
2. Circuit Parameters: and then converting them into binary codes using
intervals and these samples are then quantized ○ Input Signal: 2 Vpp, 100 Hz unipolar sine wave an Analog-to-Digital Converter (ADC). Through
to predefined levels. ○ Sampling Clock: 4Vpp, 500Hz square wave with 20%
duty cycle setting up the PCM modulator circuit, we observed
An analog to digital convertor converts these ○ Clock input as counter: 5V, 5KHz square wave how an analog signal is sampled and converted
quantized symbols to their corresponding binary The circuit was implemented in Multisim Desktop, providing into a series of binary codes, which can be
a visual and functional representation of PCM modulation.
codes. Output of IC 7493 (4-bit binary ripple counter) transmitted or stored digitally.
Methodology The experiment demonstrated the importance of
the sampling clock and counter in generating
The project methodology involved the following steps:
Objectives accurate PCM outputs, with the oscilloscope
Setup the Circuit - Assemble the PCM modulator circuit on a
breadboard according to the given schematic, ensuring all revealing the input signal, the sampled output, and
components and connections are correctly made.
The primary goals of this project are: the resulting staircase waveform from the DAC.
Input Signal - Provide a 2Vpp, 100Hz unipolar sine wave as the
1. To demonstrate the conversion of an analog analog input with a DC offset of 2V to ensure a range of +1V to The proper timing and signal conditioning were
+3V.
input signal into a PCM (Pulse Code crucial for obtaining optimal results, highlighting
Sampling Clock - Use a 4Vpp, 500Hz square wave with 20% duty
Modulation) encoded digital output. cycle as the sampling clock (clock 1), and a 5V, 5KHz square wave
how the modulation process works in real-world
as the clock input of the counter (clock 2). applications.
2. To observe the process of sampling, Sampling Process - Employ an analog switch to sample the input
quantization, and binary encoding of an signal, which is then compared with the DAC output. The PCM is essential in modern communication
comparator triggers the counter clock when the sampled signal systems, such as telephony, audio and video
analog signal. exceeds the DAC output. Circuit Simulation result:
3. To analyze the staircase waveform produced Observe & Analyze - Use an oscilloscope (CRO) to observe the
compression, and digital storage, as it allows
input sine wave, the sampled output, and the staircase waveform analog signals to be transmitted in a digital form.
by the DAC as part of the PCM encoding of the PCM output. Adjust input and clock signal levels to obtain
optimum results. This experiment reinforced the role of PCM in
process.
Applications ensuring efficient and reliable digital signal
4. To understand and visualize the role of
transmission, providing a deeper understanding of
sampling and clock signals in the PCM The practical implications of this project extend to several
real-world applications:
its practical applications in telecommunications and
modulation process using a CRO.
Telecommunications: Used for encoding audio signals in digital media.
digital form for long-distance transmission in digital
telephony and voice communication.
Digital Audio and Video: Applied in digital broadcasting,
audio streaming, and video compression for high-quality
media transmission.
Digital Storage: Utilized in formats like CDs and DVDs for
storing audio and video data in a precise digital format.
Medical Systems: Employed in devices like ECGs and
EEGs to convert analog biological signals into digital data
for better monitoring and analysis.

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