I understand the basic concepts behind amplitude modulation, frequency modulation, and pulse width modulation, but i have never really understood what is meant by the amount of modulation or modulation depth. Pwm is employed in a wide variety of applications, ranging from measurement and communications to power control and conversion. Principles of communication modulation tutorialspoint. Pulse width modulation, frequency modulation, demodulation, frequency to voltage converter 1. This shout can be heard only up to a certain distance. Pulse width demodulation theory with block diagram and. Pulse width modulation pwm is an alternative method of harmonic control. Principles of communication modulation a signal can be anything like a sound wave which comes out when you shout. This article gives the basic information on the difference between pam, pwm, and ppm. In telecommunications and signal processing, frequency modulation fm is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave in analog frequency modulation, such as fm radio broadcasting of an audio signal representing voice or music, the instantaneous frequency deviation, the difference between the frequency of the carrier and its center.
The average value of voltage and current fed to the load is controlled by turning the switch between supply and load on and off at a fast rate. Pulse position demodulation october 12, 20 by ashutosh bhatt the pulse position modulation ppm is a modulation technique designed to achieve the goals like simple transmitter and receiver circuitry, noise performance, constant bandwidth and the power efficiency and constant transmitter power. Pulse width modulation is a process that is used in many applications. Analog communication pulse modulation tutorialspoint. Pulse width modulation pwm, or pulseduration modulation pdm, is a method of reducing the average power delivered by an electrical signal, by effectively chopping it up into discrete parts. Demodulation of pwm and ppm block diagram and waveform pwm and ppm detection pulse modulation duration.
Printable pdf pulse width modulation pwm is a powerful technique for controlling analog circuits with a processors digital outputs. To study amplitude demodulation by linear diode detector 3. The changes in the carrier signal are chosen from a finite number of m alternative symbols the modulation alphabet. In demodulation, we need pwm detector and its related circuitry for demodulating the pwm signal.
Modulation to overcome equipment limitations modulation is used to place signals in a portion of the spectrum where equipment limitations are minimal or most easily met. Pwm circuitry is more cost effective than similar pcm digital circuitry on a percustomer basis at present whenever it is applicable. The coded message in the form of pwm can be easily decoded with the help of a synchronous pulse. In this chapter we will discuss ways of demodulating am, cw, fm, phase, and pulse modulation. To study pulse width modulation and pulse position modulation 9. The simulation for the same was carried out using ngspice. We have discussed pwm generator circuit using 741 op amp in previous articles. The pulse width demodulation circuit with the first order low pass filter used for the demodulation is given in the following figure. Digital phase modulation and demodulation request pdf. The simple pulse modulation technique called pulse amplitude modulation pam proved to be more power efficient than the pwm and consumes constant power for individual pulses like ppm. Modulating signal forms one of the input to the comparator and the other input is fed with a nonsinusoidal wave or sawtooth wave. Apr 07, 2015 pulse width modulation pwm is a modulation technique, which converts an analog signal into a digital signal for transmission. To study and perform pulse code modulation and demodulation. Demodulation for communications simulation matlab demod.
Pwm converts an audio signal into a sequence of pulses having constant amplitude, but the width is proportional to amplitude of an audio signal. This is divided into analog pulse modulation and digital pulse modulation. Modulation is the process of influencing data information on the carrier, while demodulation is the recovery of original information at the distant end from the carrier. To study and perform pulse width modulation and demodulation.
Circuit diagram of pulse width demodulation circuit with low pass filter. Aug 20, 2017 synchronous modulation and demodulation. A modem is an equipment that performs both modulation and demodulation. Many digital systems are powered by a 5volt power supply, so if you filter a signal that has a 50% duty cycle you get an average voltage of 2. Each channel sharing scheme a set of basis vectors. Can somebody please shed some light on the subject. Pulse width demodulation theory with block diagram and wave. Difference between pam, pwm, and ppm comparison of pwm. Synchronous modulation and demodulation photo optical modulator. The only thing that hasnt changed in all of this is the high voltage level, because on is always the same for the digital output. The pwm generation is explained with the help of the fig5 given below. Jun 22, 2009 lecture series on communication engineering by prof. Modulation for multiplexing this allows for multiple signals to be carried on a single transmission medium multiplexing is one form of modulation. Introduction to modulation and demodulation free download as powerpoint presentation.
Explain generation and demodulation of pam, ppm and pwm. This application note will look at what pulse width modulation is and will also explain how to perform pulse width modulation using two different methods. We use modulation technique to alter signals in time and frequency to accomplish desired objectives. Other duty cycles produce any voltage in the range of 0 to 100. Although an inductive type transformation process is required, the output dc may be obtained without rectifying devices. Although pwm is also used in communications, its main purpose is actually to. To understand the theoretical foundations of analog communications as well as of doublesideband amplitude modulation and demodulation dsbam to design the simulink model of the dsbam to analyze each signal in time and frequency domains using time scope and spectrum analyzer. In pulse amplitude modulation pam technique, the amplitude of the pulse carrier varies, which. In pam the amplitude of the individual pulses are varied according to the amplitude of the modulating signals. January 1987 pulse width modulation for analog fiber. Am modulation in order to transfer signals we need to transfer the frequency to higher level one approach is using modulation modulation. If you continue browsing the site, you agree to the use of cookies on this website. To study frequency modulation and determine its modulation factor.
The demodulated signal might require amplification and further filtering to achieve good quality message signal. Surendra prasad, department of electrical engineering,iit delhi. Describe phase demodulation circuit operation for the peak, lowpass filter, and conversion detectors. Source called v1 generates the message to be transmitted. Pulse width modulation an overview sciencedirect topics. Synchronous modulation and demodulation photo optical. Changing the amplitude of the carrier am modulation is one type of modulation easy, cheap, lowquality. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. Introduction in chapters 1 and 2 you studied how to apply intelligence modulation to an rfcarrier wave. Amplitude modulation early radio ee 442 spring semester. One approach to reduce this interference, known as frequencydivision multiplexing, allocates. Pulse width modulating signal can be generated using a comparator as shown in the figure 4 a. In this article we will learn about what is pwm, pwm signals and some parameters associated with it, so that we will be confident in using them in our designs. As we mentioned before, well use dsbc modulation because of its ease in demodulation.
If the received carrier phase is assumed to be constant, each of the seven reference values will have to be shifted only once at the beginning of the simulation. In practice, problems arise in baseband transmissions. How to detect or demodulate a pulse width modulated signal. Radio waves can carry audio, video, and digital information over great distances by using changes in a carrier waves amplitude, frequency, or phase to represent the information being transmitted. One of the easiest ways to implement this is by using an arduino. Demodulation channel decoding is the corresponding process at the receiver of converting the received waveform into a. Mar 28, 2016 demodulation of pwm and ppm block diagram and waveform pwm and ppm detection pulse modulation duration.
Abstract this document gives an overview of how pulse width modulation and demodulation can be performed using bipolar junction transistors and operational amplifiers. Ee4512 analog and digital communications chapter 6 chapter 6 analog modulation and demodulation amplitude modulation pages 306309. To study and perform pulse position 6 to study and perform pulse code modulation and demodulation. Modulation and demodulation medium, it would be dif. As the resultant is a coded pulse train, this is called as pcm. A pwm signal consists of two main components that define its behavior.
The results obtained have been presented at the end of this document. In the double polarity pulse amplitude modulation, the output of modulating signal will have both positive and negative ends. The pam modulator and demodulator circuits simple compared to other kinds of modulation and demodulation techniques. This lecture introduces phase characteristic in the frequency response, and the derivation of dtft for a rectangular pulse. Modulation and demodulation pdf modulation and demodulation ch16 modulator demodulation 16. In digital modulation, the modulation technique used is pulse code modulation pcm where the analog signal is converted into digital form of 1s and 0s. The pam modulator and demodulator circuits simple compared to other kind of modulation. Explain generation and demodulation of pam, ppm and pwm with. Pulse modulation timedivision multiplex tdm timedivision multiplexing is the method of combining several sampled signals in a definite time sequence. This paper provides a new look at the mechanisms underlying pulse width modulation pwm.
Pulse modulation is a technique in which the signal is transmitted with the information by pulses. Finds the pulse widths of a pulsewidth modulated signal y. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. Synchronous modulation and demodulation low dc current may be transformed into a high voltage dc by simple chopper action. Introduction pwm, or pulseduration modulation pdm, is a technique used to encode a message into a pulsing signal. Amplitude modulation am, demodulation and their circuit. Chapter 5 digital bandpass modulation and demodulation. Pwm signal can be generated by using a comparator, where modulating signal and sawtooth signal form the input of the comparator. Pulse width modulation using digital pulses to create some analog value other than just high and low signal levels. Laboratory manual principles of communication system lab ee226f ivth semester prepared by.
The duty cycle describes the amount of time the signal is in a high on state as a percentage of the total time of it takes to complete. Ee4512 analog and digital communications chapter 5 chapter 5 digital bandpass modulation and demodulation techniques binary amplitude shift keying pages 212219. Lecture 39 pulse modulation schemes pwm and ppm youtube. Carrier modulation allows the transmission of modulating frequencies without the use of transmission wire as a medium. Watch the complete video lecture and written content about pulse modulation and pulse modulation techniques like pulse amplitude modulation pam, pulse width modulation pwm pulse duration modulation pdm, pulse position modulation ppm and pulse code modulation pcm. The circuit in which restoration is achieved is called the detector or demodulator both of these terms are used in neets.
A pwm can be considered as an exact opposite of it, pwm is used to produce analog signals from a digital device like microcontroller. The output signal via demodulator may describe the sound, images or binary data. After continuous wave modulation, the next division is pulse modulation. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. Introduction to modulation and demodulation modulation. Pwm pulse can be detected using ramp generator and some circuit combinations. In single polarity pulse amplitude modulation, there is fixed level of dc bias added to the message signal or modulating signal, so the output of modulating signal is always positive. Here is the circuit used for modulation and its simulation. In analog modulation technique, if the amplitude or duration or position of a pulse is varied in accordance with the instantaneous values of the baseband modulating signal, then such a technique is called as pulse amplitude modulation pam or pulse durationwidth modulation pdm pwm, or pulse position modulation ppm.
Angle modulation ch16 angle modulation digital modulation schemes ch16 angle modulation host modulation therapy detection estimation and modulation theory part i pdf sinusoidal pulse width modulation inverter arduino. An example of how to send a pulse over a lowpass and a bandpass channel opens discussion about modulation and demodulation. It is a type of pulse time modulation ptm technique where the timing of the carrier pulse is varied according to the modulating signal in pulse duration modulation pdm, the amplitude of the pulse is kept constant and only the variation in width is noticed. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. In this article, you will find the study notes on types of modulation and demodulation which will cover the topics such as introduction to communication systems, amplitude and demodulation, classification of am, angle modulation and demodulation, generation of fm and pulse modulation. The term demodulator is used because the demodulation process is considered to be the opposite of modulation. In this chapter, let us discuss the following analog pulse modulation techniques. To study and perform pulse position modulation and demodulation. A simple approach to analyze the behavior of a singlesided pulse width modulator is presented. Pulse amplitude modulation pam theory of and its applications. Digital modulation methods can be considered as digitaltoanalog conversion and the corresponding demodulation or detection as analogtodigital conversion. It is a type of modulation and therefore this modulation technique can be used to encode information for transmission.
As like pulse position modulation, noise interference is less due to amplitude has been made constant. Pulse width modulation for analog fiberoptic communications s. Pulse width modulation pwm generation, applications and. Many many digital systems are powered by a 5volt power supply, so if you filter a signal that has a 50% duty cycle you get an average. Principles of communication systems 20022003 8 chapter 7.
Quadrature amplitude modulation qam is the name of a family of digital modulation methods and a related family of analog modulation methods widely used in modern telecommunications to transmit information. Modulation techniques pwm and pulse code modulation. Introduction to modulation and demodulation the purpose of a communication system is to transfer information from a source to a destination. The power electronic switches are repetitively turned on and blocked several times during each half cycle. What is a pulse width modulation pwm signal and what is. A pulse width modulation pwm signal is a method for generating an analog signal using a digital source. Pulse width modulation pwm is a modulation technique, which converts an analog signal into a digital signal for transmission. Commutator determines the synchronization and sequence of the channels signals to be sampled. Y abstractthe pulse width modulation pwm technique has been. Pulsewidth modulation pwm is a modulation process or technique used in most communication systems for encoding the amplitude of a signal right into a pulse width or duration of another signal, usually a carrier signal, for transmission. Recall that our goal is to transmit data over a commu nication link, which we achieve by mapping the. The principle of fsk modulation is to send binary data with two different frequencies and the resultant modulated signal is regarded as amplitude modulation am of different carrier frequencies. Pulse amplitude modulation pam pulse width modulation pwm pulse position modulation ppm. If you do not specify the opt parameter, modulate uses a default of opt pimaxmaxx so the maximum phase excursion is.
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