Basic concepts of modulation three kinds of modulations modulation is the process of facilitating the transfer of information over a medium. Control of functional electrical stimulation systems using. Pulse modulation definition and meaning collins english. Analog communication pulse modulation tutorialspoint. Here we will discuss in details, pulse modulation and pulse modulation techniques like pulse amplitude modulation pam, pulse width modulation pwm, pulse position modulation ppm and pulse code. While the bit streams we wish to transmit are inherently discretetime, all physical media are continuoustime in nature. All pulse modulation systems boil down to two basic principles. Figure 36 spectrum of a pam waveform with flattop sampling. This page covers advantages and disadvantages of pam, pwm and ppm. Pulse amplitude modulation pam theory of and its applications. A very complex method of combining phase modulation and am to increase the bit density of digital pulse modulation on an rf carrier is called quadrature amplitude modulation qam. Types of modulation 6 flynnkatz 7810 analog modulation amplitude modulation, am frequency modulation, fm double and single sideband, dsb and ssb digital modulation phase shift keying.
Farshad lahouti january 20, 2003 winter 2003 uw, ece 318 lecture notes 2 information source signal modulator propagation channel signal demodulator information destination analog communication system analog signals may be transmitted directly via carrier modulat ion over. In this modulation, the signal is sampled at regular intervals and each sample is made proportional to the amplitude of the modulating signal. Additional info pulse wave modulation pam, pwm, ppm do not convert baseband msg signal to bandpass, whereas continuos wave modulation am, fm, pm converts baseband into bandpass msg signal. The pulse amplitude modulated signal, will follow the amplitude of the original signal, as. Feb 12, 2014 pulse amplitude modulation is widely used in baseband transmission of digital data, with nonbaseband applications having been largely superseded by pulsecode modulation, and, more recently, by pulse position modulation. For the baseband digital transmission, pulse amplitude modulation pam is the most efficient in terms of. A modulation technique in which the amplitude of the pulsed carrier signal is changed according to the amplitude of the message signal is known as pulse amplitude modulation pam. Oct 06, 2015 pulse amplitude modulation, is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses. Analog pulse modulation pam pwm ppm digital pulse modulation pcm dm adm 3.
Pm is a type of angle modulation and it is defined as the change in phase of the carrier signal in correspondence with the amplitude of the message signal. Pam stands for pulse amplitude modulation,pwm stands for pulse width modulation and ppm stands for pulse position modulation. The presented control method determines pulse width pw, amplitude, and frequency of the electrical stimulation signal, synchronously. Pulseamplitude modulation pam, is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses. Pulse amplitude demodulation matlab pamdemod mathworks india. This means that a pulse transmitter will have a longer range than an am transmitter of the same power. The output of a sampling circuit with a zeroorder hold zoh is one example of a pam signal. Jul 01, 2019 pulse modulation has another outstanding advantage. So you can observe here that, quadrature amplitude modulation qam is the combination of both amplitude modulation and phase modulation as phase change of carrier wave takes place here. The amplitude of the analog signal is sampled at uniform intervals and each sample is quantized to its nearest.
Pulse amplitude modulation request pdf researchgate. If the negative symbol is transmitted, the pdf for z will be as sketched below. Pulse amplitude modulation theory pulse amplitude modulation. Pulse amplitude modulation pulse amplitude modulation is a technique in which the amplitude of each pulse is controlled by the instantaneous amplitude of the modulation signal. Equation 17 shows clearly the effect of channel noise on the transmitted signal. Lec 20 principles of communicationii introduction to. We use modulation technique to alter signals in time and frequency to accomplish desired objectives. In pam the amplitude of the individual pulses are varied according to the.
Pulse amplitude modulation in pulse amplitude modulation pam technique, the amplitude of the pulse carrier varies, which is proportional to the instantaneous amplitude of the message signal. Figure 321 includes a simplified circuit view a for this demodulator and its waveforms views b and c. Difference between pam, pwm, and ppm comparison of pwm and pam. The original waveform amplitude is quantized with a resulting loss of information. To extend the range of sound, we need to transmit it through a medium other than air, such as a phone line or radio. Here, both the frequency and amplitude of the carrier signal stays as constant whereas phase varies in accordance.
Pulse amplitude modulation pam, is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses. Pulse amplitude modulation using matlab with waveforms. If x is a matrix with multiple rows, the function processes the columns. Help me understand how pulseamplitude modulation pam works. The significant characteristics of a pulse are pulse amplitude, pulse duration or pulse width, and pulse position denoting the time of the rise or the fall of the pulse amplitude. To convert an audio signal 020khz to digital form, the minimum sampling frequency is 40khz. Oct 03, 2011 this is a ppt for pulse modulation for final year ej diploma slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising.
This was the case for analog modulation, but if we talk about qam with digital modulation, then, at the place of analog message signal, we use digital messages. Application note of pampulse amplitude modulation signal. Our pam pulseamplitudemodulation chlorophyll fluorometer consists of a basic pam101 system by walz. Linear modulation we are typically interested in locating a messagesignal to some new frequency location, where it can be ef. In practice, sampling frequency for encoding music into cd is 44. In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal that typically contains information to be transmitted.
In the case of analog pulse amplitude modulation signals, the number of pulse amplitudes can be infinite. It requires that the amplitude of the dc a part of a t is equal to the amplitude of the ac part a. Cr1 is the input diode which allows capacitor c1 to charge to the peak value of the pam input pulse. The modulated signal has a minimum euclidean distance of 2. It is a modulation system in which the signal is sampled at regular intervals and each sample is made proportional to the amplitude of the signal at the instant of sampling.
Sep 07, 2017 pulse amplitude modulation pam is a type of pulse modulation in which the signal is sampled at regular intervals, with each sample proportional to the amplitude of the signal at the time of sampling. In pam the amplitude of the message or modulating signal is mapped to a series of pulses with two possible variant. The basic types of modulation are angular mo dulation including the special cases of phase and frequency modulation and amplitude modulation. Pulse amplitude modulation pam is a one dimensional or in other words real modulation. Explain generation and demodulation of pam, ppm and pwm. Pam underlies the operation of a wide variety of modems. Sampling theorem determines the necessary conditions which allow us to change an analog signal to a discrete one.
It mentions pam advantages,pam disadvantages,pwm advantages,pwm disadvantages,ppm advantages and ppm disadvantages. Pulse width modulation axiomatic technologies corporation. Pulse position modulation ppm is an analog modulation scheme in which, the amplitude and the width of the pulses are kept constant, while the position of each pulse, with reference to the position of a reference pulse varies according to the instantaneous sampled value of the message signal. As we can see that unlike pam, in this technique the amplitude of the signal is constant and only the width is varying. The message signal must consist of integers between 0 and m1. Difference between pam, pwm and ppm with comparison chart. Pulse code modulation 251 of amplitude zi, the signal power a t. A two bit modulator pam4 will take two bits at a time and will map the signal amplitude to one of four possible levels, for example. Basic concept of modulation the information source typically a low frequency signal referred to as the baseband signal carrier a higher frequency sinusoid example. It is the standard form of digital audio in computers, cds, digital telephony and other digital audio applications.
The pulse code modulator technique samples the input signal xt at a sampling frequency. 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. The ideal modulated signal should have a minimum euclidean distance of 2. It uses transmitter energy more efficiently than either am or fm because of the simple onoff nature of the pulses. The input sequence b k consists of binary digits bits 1 and 0 with a bit duration of t b and a bit rate of r b 1 t b. It is an analog pulse modulation scheme in which the amplitudes of a train of carrier pulses are varied according to the sample value of the message signal. If you continue browsing the site, you agree to the use of cookies on this website. Pulse amplitude modulation is the basic form of pulse modulation. Amplitude modulation a1 49 you will see in this experiment, and in others to follow, that there is no problem in generating an am signal with a depth of modulation exceeding 100%, and without. An informationbearing signal must conform to the limitations of its channel. The analog pulse modulation is again classified as, 1.
Sampling theorem and pulse amplitude modulation pam reference stremler, communication systems, chapter 3. This can be a bit confusing because bpsk can be looked at as a phase modulation and its natural extension must be qpsk or 8psk modulations. A simultaneous modulation of the stimulation intensity and frequency is proposed to improve the joint controllability and muscle endurance. Simply put it is an extension of bpsk with m amplitude levels instead of two. The pulse amplitude modulated signal, will follow the amplitude of the original signal, as the signal traces out the path of the whole wave. Feedback can be used to achieve an output that matches exactly the control signal. The two common forms of analog modulation are amplitude modulation am and frequency modulation fm which is speci. Request pdf pulse amplitude modulation pulse amplitude modulation pam is a modulation method used in digital communication systems to facilitate. Pulse amplitude modulation an overview sciencedirect.
Matlab so ftware w hich is the language of technical computing. So now lets discuss different types of pulse modulation techniques in detail pulse modulation can be categorized broadly into two types. Pulse modulation, october 1960 popular electronics rf cafe. This sampled variable amplitude pulse is then digitalized by the analog to digital converter. Next topic pulse code modulation pulse code modulation pcm is used to digitally represent sampled analog signals. Simply put, the transmission of data takes place by the variation of the amplitude of pulse according to the modulating signal.
Pwm technique is similar to frequency modulation because, by the variation in the width of the pulses, the frequency of the pulses in the pwm signal shows variation. Pulse amplitude modulation pam is one of several forms of single modulation in which data is transmitted through varying the amplitude of the pulses in regular timed sequence of electrical or electromagnetic pulses. By varying the amplitude of the pulses the carrier signal in proportion to the instantaneous values of. What is the difference between pulseamplitude modulation. Figure 34 demodulation of a pam signal naturally sampled. Pulseamplitude modulation, acronym pam, is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses. Pulse position modulation ppm a pulse of fixed width and. What are the types of pulse amplitude modulation answers. Intelligence plus character that is the goal of true education. Pulse code modulation is a type of pulse modulation like pulse amplitude modulation, pulse width modulation, or pulse position modulation but there is an important difference between them pulse amplitude modulation, pulse width modulation, pulse position modulation are analog pulse modulation system where as pulse code modulation is a digital modulation. Dutton ee3 winter 2004 1 ee3 lab 1 amplitude modulation and demodulation 1 lab notes a word about power. Pulse modulation is the process in which signal is transmitted by pulses i.
Any possible signal amplitude x i a t the transmitter will be foundin a statistical sensewith a reduced amplitude q p. 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. By varying the amplitude of the pulses the carrier signal in proportion to the instantaneous values of the analog signal the message signal. The pulse position modulation ppm varies the position of individual pulses from their mean position according to the amplitude of the modulating signal. Before going to discuss the difference between pam, pwm, and ppm, let us discuss individually each. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. Pdf differentialtime and pulseamplitude modulation signaling.
The function of website is to teach one to think intensively and to think critically. The pwm is a kind of modulation technique indented for power efficiency, but the power required to transmit individual pulses varies significantly. To ensure accurate reproduction of an analog signal. The purpose of this paper is to analyze the concept of pulse amplitude modulation using. Pulse code modulation concepts of digital communication with pdf. No information is lost, but the energy is redistributed in the frequency domain. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. Pulse amplitude modulation pulse code modulation sampling. Sampling theorem and pulse amplitude modulation pam. The pulse amplitude modulated signal will follow the amplitude of the original signal, as the signal traces out the path of the whole wave. Pulse width modulation pwm, or pulse duration modulation pdm, is a method of reducing the average power delivered by an electrical signal, by effectively chopping it up into discrete parts. Pulse width modulation traditional solenoid driver electronics rely on linear control, which is the application of a constant voltage across a resistance to produce an output current that is directly proportional to the voltage. Amplitude shift keying ask modulation on mac where e pt is the energy contained in a bit duration.
Pulse amplitude modulation is the basic form of pulse modulation in which the signal is sampled at regular and each sample is made proportional to the amplitude of the modulating signal at the sampling instant. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. Explain generation and demodulation of pam, ppm and pwm with waveforms. The pulse may take any real voltage value that is proportional to the value of the original waveform. Introducing pulse width modulation pwm the period is normally kept constant, and the pulse width, or on time is varied the duty cycle is the proportion of time that the pulse is zon or high, and is expressed as a percentage. Pulse amplitude modulated pam fluorometry is a useful technique for identifying the amount of energy that is not used in photosynthesis but is reemitted as fluorescence or dissipated as heat in.
Pulseamplitude modulation pam, is a form of signal modulation where the message. The pulse modulation is classified as analog pulse modulation and digital pulse modulation. Pdf a pulseamplitudemodulated differentialtimesignaling pamdts architecture for serial communication links is presented in this paper. In continuous wave modulation amplitude modulation, frequency modulation, phase modulation the carrier wave used is continuous in nature, while in case of pulse modulation, the carrier wave is in the form of pulses. Pam is the simplest of all pulse modulation technique. Pulse amplitude demodulation peak detection is used to detect pam. In the positive half cycle of pam signal, diode conducts and current flows through r, whereas in negative half cycle, the diode is reversed biased and. Note that this is on the very low end of the recommended voltage range. Pulse amplitude modulation has some applications, but it is not used by itself in data communication. Modulation modulation is the process whereby some characteristic of one wave is v aried in accordance with some characteristic of another wave. The number of possible pulse amplitudes can be infinite in the case of analog pam, but it is usually some power of two so that the. Jagannatham of iit kanpur explains the following concepts in principles of digital communication system. Pulse amplitude modulation pam is the transmission of data by varying the amplitude s voltage or power levels of the individual pulses in a regularly timed sequence of electrical or electromagnetic pulses.