Design-Pulse Amplitude Modulation
Pulse Amplitude Modulation
Communication is at the forefront of today’s technology. Signals are used to communicate between a transmitter and a receiver. The data is carried by modulation of these signals. One of the types of modulation techniques used in signal processing is pulse amplitude modulation. The simplest mode of modulation is pulse amplitude modulation. The message information is stored in the amplitude of a sequence of signal pulses in this analogue to digital conversion process. The aim of this article is to provide an overview of pulse amplitude modulation, also known as PAM.
What is Pulse Amplitude Modulation?
The most fundamental method of pulse modulation is pulse amplitude modulation. The signal is sampled at regular intervals and each sample is relative to the amplitude of the modulating signal in this modulation.
What is Modulation?
Modulation is the method of altering the properties of a carrier signal, such as its amplitude, frequency, and width, among other things. It refers to the method of applying data to a carrier signal. A carrier signal is a waveform that has the same amplitude and frequency all the time.
Electromagnetic signals, such as radio lasers and optical signals are commonly modulated. For transmitting over telecommunication, audio, video, photographs, and text data are applied to the carrier signal.
Types of Modulation
Based on the form of signal, there are two forms of modulation.
- Continuous-wave Modulation
- Pulse Modulation
Pulse Amplitude Modulation
The amplitude of each pulse is controlled by the instantaneous amplitude of the modulation signal in pulse amplitude modulation. It’s a modulation mechanism in which the signal is sampled at regular intervals, with each sample equal to the signal’s amplitude at the time of sampling. The data is encoded in the amplitude of a sequence of signal pulses and transmitted using this method.
When using PAM to relay a signal, there are two kinds of sampling techniques. They are:
- Flat Top PAM
- Natural PAM
How PAM Signal is generated?
The following block diagram of pulse amplitude modulation can be used to generate PAM.
PAM, or pulse amplitude modulation, is the most basic form of pulse modulation, in which the signal is sampled at regular intervals and each sample is rendered proportional to the modulating signal’s amplitude at the sampling moment.
The PAM signal is produced by the sampler, which has two inputs: sampling/carrier signal and modulating signal, as seen in the block diagram above. As a result, the signal amplitude is proportional to the modulating signal over which the data can be transmitted. This is the PAM signal, then. The above waveforms represent the distribution of the PAM signal, which includes the message and sampling signals, with the carrier train of signals plotted within the time region. Pulse Modulation is mostly used to relay analogue data such as data that would otherwise be sent as a continuous speech signal.
The aim of this project is to create a Pulse Amplitude Modulation Circuit.
To design circuit for PAM modulation we have used components listed below. The 555 IC is used to produce a square wave that will act the CMOS as an astable multi vibrator.
Components used:
IC 555 -
The 555 timer IC is an integrated circuit that can be used to create timers, delays, pulse generators, and oscillators. Two or four timing circuits are combined in a derivative. Signe tics first commercialised it in 1972.
4016 -
Each of the 4016’s four analogue bilateral switches has an active-high activate input (A) and two input/outputs (X and Y). The X and Y terminals are bound by a low impedance while the allow input is asserted (high); this is the on state. When the allow is big, the turn is off so there is a high impedance path between X and Y. With the support of a BJT, resistors, and capacitors, this IC can be used in flat top sampling.
Battery -
10 V DC Battery
Resistors -
A resistor is a two-terminal passive electrical component that acts as a circuit element by implementing electrical resistance. Resistors are used in electrical circuits for a variety of purposes, including reducing current flow, adjusting signal speeds, dividing voltages, biasing active components, and terminating transmission lines. Three resistors with the values mentioned below are used. 1k, 10k, and 4.5k.
Capacitor -
A capacitor is an electrical energy storage system that operates in an electric field. It’s a two-terminal passive electronic component. Capacitance is the term used to describe the effect of a capacitor. A 10nF capacitance is used.
Polarized capacitor -
An electrolytic capacitor is a polarized capacitor with an anode or positive plate consisting of a metal that has been anodized to form an insulating oxide sheet. This oxide layer serves as the capacitor’s dielectric. One 10uF polarized capacitor.
Diode -
A diode is an electrical component that allows the flow of current only in one-direction. Here we have used 1N4007 diode which is a rectifier diode, designed specially to for the circuits to convert alternating current to direct current.
Pulse Amplitude Modulation Circuit using 555IC
The circuit for pulse amplitude modulation with a 555IC i is shown below. By connecting one 4016IC to the output of the 555IC, pulse amplitude modulation can be produced. This IC can be connected in astable mode to generate a pulse train, allowing samples of the audio signal to be collected.
IC555 generates square wave which is used here as sampling signal. It is configured to generate pulse train to get samples of information (audio) signal. The output of IC555 is fed to 4016 which is quad bilateral switch IC that has 4 switches that can be controlled individual using a control pin. Here output of IC is given to pin13 which is control input and modulating signal input is given to pin1. The output from pin2 of 4016 shows the pulse amplitude modulation which is observed with the help of oscilloscope.
Circuit Design:
The 555 oscillating frequency is set by the resistor and capacitor connected with the IC 555. The 4016 IC has two switches, one of which is used as a gate in the PAM modulator circuit. To the signal input, apply a sine wave. The signal amplitude is adjusted with a 10k resistor. The output is routed into a 1k resistor.
Output:
Applications of PAM:
- It’s a protocol that’s used in Ethernet networking.
- It is used to generate control signals in many microcontrollers.
- It’s used in the field of photobiology.
- It is used as an LED lighting electronic engine.
- PAM is a protocol that is used in an Ethernet network to link two networks and pass data between them. As a result, PAM is employed in Ethernet communications.
PAM can be used to produce control signals in a variety of microcontrollers. PCM and PPM are two modulation techniques that are often used in optical data transfer and applications. QAM is used for almost all phone modems that are higher than 300 bits per second (quadrature amplitude modulation).
Conclusion:
The biggest benefit of pulse amplitude modulation (PAM) is that it is more noise resistant. Because of the short length of the transmitted pulse, PAM transmission places stringent conditions on the magnitude and phase responses of the channel.
References:
https://www.electronics-tutorial.net/Mini-Projects/PAM-MODULATION-AND-DEMODULATION/
https://www.elprocus.com/pulse-amplitude-modulation/
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