Amplitude modulation a continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. Demodulation is the process by which the original information bearing signal, i. Ee4512 analog and digital communications chapter 6 chapter 6 analog modulation and demodulation amplitude modulation pages 306309. Amplitude modulation, am, is one of the most straightforward ways of modulating a radio signal or carrier. Amplitude modulation is a process by which the wave signal is transmitted by modulating the amplitude of the signal. Pulseamplitude demodulation peak detection is used to detect pam. The input signal is pulse width modulated, so the on time of the signal is changing according to the modulating signal. The modulation index can be used to make the carrier amplitude more or less sensitive to the variations in the value of the baseband signal. There are no amplitude scales shown, but you should be able to deduce the depth of modulation 1 by inspection. Request pdf pulse amplitude modulation pulse amplitude modulation pam. Amplitude modulation in wind turbine noise valeri v. What is amplitude modulation, am electronics notes.
Pulse amplitude modulation is the basic form of pulse modulation. An am wave may thus be dscribed, in the most general form, as a function of time. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. With amplitude modulation, the carrier signal is alternately driven above and below its resting unmodulated value. Sampling theorem and pulse amplitude modulation pam. Modulation is broadly classified into continuouswave modulation and pulse modulation. Sampling theorem determines the necessary conditions which allow us to change an analog signal to a discrete one. Hsu analog and digital communication summary equation message general mt monotone am. To study frequency modulation and determine its modulation factor 4. 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modulation is widely used in baseband transmission of digital data, with nonbaseband applications having been largely superseded by pulsecode modulation, and, more recently, by pulse position modulation. Pulse width modulation and in position ppm, pulse position. In part i you will learn how to design an amplitude modulator am and in part ii you will be able to demodulate an am signal.
In this experiment, a carrier signal and an audio modulating signal are applied to the modulator ic mc 1496 and the produced modulated waveform is observed. Pulse amplitude modulation pam theory of and its applications. 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. Pulse amplitude modulation pam, quadrature amplitude modulation qam. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. At 100% modulation, the peaks will be driven to twice the resting power, and the valleys will reach zero. Communications i amplitude modulations and demodulations. Each channel sharing scheme a set of basis vectors. To improve the spectral efficiency of the amplitude modulation, two schemes can be used to either utilize or remove the 100% spectra redundancy. As we mentioned before, well use dsbc modulation because of its ease in demodulation.
A modem is an equipment that performs both modulation and demodulation. Introduction what is communication transmitter channel receiver a communication system process of conveying message or information transmitter modifies the message signal into a form which is suitable for transmission over channel which is achieved by modulation information source. Before we study in detail about pam lets know the concepts of modulation. Most radio systems in the 20th century used frequency modulation fm or amplitude modulation am for radio broadcast. In the frequency domain, amplitude modulation corresponds to translating the baseband spectrum to a band. 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.
Sinusoidal amplitude modulation amplitude demodulation. 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. Pulse amplitude modulation request pdf researchgate. To study and perform pulse width modulation and demodulation. In this modulation, the signal is sampled at regular intervals and each sample is made proportional to the amplitude of the modulating signal. To study and perform frequency modulation and demodulation. Here well use the example of a square law fet as illustrated in figure 9.
Cr1 is the input diode which allows capacitor c1 to charge to the peak value of the pam input pulse. Laboratory manual principles of communication system lab ee226f ivth semester prepared by. The demonstration centers around a number of signals displayed in both the time domain and the frequency domain using a signal generator, an oscilloscope to view the signal. Modulation is a technique to transmit information via radio carrier waveform. This gives us something to modulate and carry the information pattern from.
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. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. To study amplitude demodulation by linear diode detector 3. Amplitude modulation am, demodulation and their circuit. The process of demodulation for signals using amplitude modulation can be achieved in a number of different techniques, each of which has its own advantage. We will discuss these two types of detectors in this experiment. To study sampling and reconstruction of pulse amplitude modulation system 6. Sampling theorem and pulse amplitude modulation pam reference stremler, communication systems, chapter 3. 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. To study sampling and reconstruction of pulse amplitude modulation. Hsu analog and digital communication summary equation message general mt monotone am cos. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. To generate the pulse amplitude modulated and demodulated signals.
Amplitude modulation and demodulation objective amplitude modulation am is one of the simplest methods for modulating a sinusoidal carrier wave. What is analog modulation and state various techniques. Sinusoidal amplitude modulation amplitude demodulation synchronous and asynchronous double and singlesideband am modulation pulseamplitude modulation pulse code modulation frequencydivision multiplexing timedivision multiplexing narrowband frequency modulation. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that. In particular, we consider pam signal demodulation and detection and give a. In amplitude modulation or am, the carrier signal has its amplitude. Amplitude modulation is defined as the process in which the amplitude of the carrier wave ct is varied about a mean value, linearly with the baseband signal. If the negative symbol is transmitted, the pdf for z will be as sketched below. Amplitude modulation can be produced in various ways. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation.
Amplitude modulation am 9 t15 use speech or music from trunks as the message, and show that this also generates a trapezoid, and that setting the message amplitude so that the depth of modulation reaches unity on peaks a triangle is especially easy to do, using the gain control g of the adder. Both processes aim to achieve transfer information with the minimum distortion, minimum loss and. To study and perform pulse position modulation and demodulation. Pulse amplitude modulation pam, pulse shaping, and the nyquist criterion. The pulse may take any real voltage value that is proportional to the value of the original waveform. It is often called as am and is commonly used in transmitting a piece of information through a radio carrier wave. 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. 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. To study amplitude demodulation by linear diode detector.
Pulse amplitude modulation pam, quadrature amplitude modulation qam 12. Analog communication pulse modulation tutorialspoint. Figure 321 includes a simplified circuit view a for this demodulator and its waveforms views b and c. Feb 12, 2014 demodulation is performed by detecting the amplitude level of the carrier at every symbol period. 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. The channel noise is neglected in this lecture, and how to demodulate the.
In pam the amplitude of the individual pulses are varied according to the. The process of demodulation for signals using amplitude modulation can be achieved in a number of different. Amplitude modulation am 9 t15 use speech or music from trunks as the message, and show that this also generates a trapezoid, and that setting the message amplitude so that the depth of modulation reaches unity on peaks a triangle is especially easy. No information is lost, but the energy is redistributed in the frequency domain. From the diagram, it can be seen that the envelope of the signal follows the contours of the modulating signal. Demodulation is performed by detecting the amplitude level of the carrier at every symbol period.
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. Singlesideband ssb modulation, which removes either the lsb or usb so that for one message signal mt, there is only a bandwidth of b hz quadrature amplitude modulation qam, which. Amplitude modulation and demodulation 2017 frank dorenberg n4spp v1. Amplitude modulation ang man shun october 30, 2012 reference hwei p. It is a nonlinear process that generates additional frequencies, as we will see. We use modulation technique to alter signals in time and frequency to accomplish desired objectives. Pulse amplitude demodulation matlab pamdemod mathworks india. To study and perform pulse amplitude modulation and demodulation. Oct 30, 2017 amplitude modulation and demodulation. The ideal modulated signal should have a minimum euclidean distance of 2. Application note of pampulse amplitude modulation signal. To study and perform amplitude modulation and demodulation.
Source called v1 generates the message to be transmitted. Amplitude modulation definition, types, solved examples. The fact that rapidly modulating the amplitude of one wave results in a waveform identical to playing two notes of different frequencies is quite remarkable and for more information on such wave interference, please see our wave interference and beat frequency demo. Normally detector can be classified as synchronous detector and asynchronous detector. Here is the circuit used for modulation and its simulation. In the continuouswave modulation, a highfrequency sine wave is used as a carrier wave, whereas, in pulse modulation, a periodic sequence of rectangular pulses is used as a carrier wave. Why frequency modulation is better than amplitude modulation.
Pulseamplitude modulation is widely used in baseband transmission of digital data, with nonbaseband applications having been largely superseded by pulsecode modulation, and, more recently, by pulseposition modulation. Aly elosery october 25, 2010 this lab is divided into two parts. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. In amplitude modulation, the message signal mt is impressed on the amplitude of the carrier signal ct a c cos2 f c t there are several different ways of amplitude modulating the carrier signal by mt each results in different spectral characteristics for the transmitted signal we will describe these methods, which are. Before we study in detail about pam lets know the concepts of. The original waveform amplitude is quantized with a resulting loss of information. Amplitude modulation corresponds to multiplying the carrier by the shifted baseband signal. Process by which a property or a parameter of a signal is varied in proportion to a second signal. There is a mapping from the set of m 2b possible blocks into a signal constellation a a 1,a. Amplitude modulation is mostly used in the form of electronic communication.
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