Principles of communication systems 20022003 8 chapter 7. Sampling theorem determines the necessary conditions which allow us to change an analog signal to a discrete one. Pulse width modulation pwm pulse train with fixed frequency modulation of the duty cycle periodtime pulse time. Pulse amplitude modulation and quadrature amplitude modulation and their demodulation. Cr1 is the input diode which allows capacitor c1 to charge to the peak value of the pam input pulse. Pcm will be explored in this experiment in three manners. Pulse amplitude modulation and demodulation objectives. Explain generation and demodulation of pam, ppm and pwm.
Dutton ee3 winter 2004 1 ee3 lab 1 amplitude modulation and demodulation 1 lab notes a word about power. Pulse amplitude modulation pam the actual amplitude of the pulse represents the number being transmitted. 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. 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. In pam the amplitude of the individual pulses are varied according to the. To study sampling and reconstruction of pulse amplitude modulation system. Decision maker preparation generation amplitude shift keying ask in the context of digital communications is a modulation process which imparts to a sinusoid two or more discrete amplitude levels 1. Pulse pileup correction method for gammaray spectroscopy. Power amplifiers and the use of pulse modulation amplifier types. The possible number of amplitudes can be infinite, but mostly it is some power of two. To study the effect of pam for varying width of carrier pulse train. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. This experiment will be comprised of simulation steps only, due to its complexity. Pulse amplitude modulated signal and demodulated signals are observed.
Pam, pwm, and ppm modulations belong to analog modulation and the pcm modulation belongs to the digital modulation. 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. Overmodulated am signals and its requirement for coherent detection are also considered. Quadrature amplitude modulation qam pam signals occupy. Hence, pam is continuous in amplitude but discrete in time.
Pam pulse amplitude modulated modulation ve demodulation. The purpose of this experiment is to introduce pulse code modulation pcm by approaching this technique from two fronts. Constellation diagrams, and eye patterns for signals with multiple pulse amplitudes. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. Amplitude modulation am is defined as a process in which the amplitude of the.
Sampling theorem and pulse amplitude modulation pam. If you continue browsing the site, you agree to the use of cookies on this website. Department of electronics and communication engineering. In experiment 3, dsb signals were generated by the multiplication of a message signal with a carrier waveform. Pulse modulation timedivision multiplex tdm timedivision multiplexing is the method of combining several sampled signals in a definite time sequence. Sampling theorem and pulse amplitude modulation pam reference stremler, communication systems, chapter 3. The standard form of an amplitude modulated am wave is defined by st a c 1 k a mt cos2f c t where k a is a constant called the amplitude sensitivity of the modulator. 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. 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. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. To study sampling and reconstruction of pulse amplitude modulation system 6. To study pulse amplitude modulation and demodulation. Amplitude modulation is defined as a process in which the amplitude of the carrier wave ct is varied linearly with the instantaneous amplitude of the message signal mt.
Note that this is on the very low end of the recommended voltage range. Amplitude modulated signal can be represented by the following equation. Pulse amplitude modulation pam theory of and its applications. Pdf experimental comparison of pulse amplitude modulation. Amplitude modulation is a process by which the wave signal is transmitted by modulating the amplitude of the signal. Each channel sharing scheme a set of basis vectors. Matlab, simulink, and a communications example 1 introduction linear systems are very often used for signal and information processing. Pulse amplitude modulation pam is used extensively in telecommunications as an. Pam pulse amplitude modulated modulation ve demodulation sample and hold flat top mode hacettepe university ee telecommunication lab. This experiment examines the characteristics of the amplitude modulation am process. Bandwidths limit is also big advantage for amplitude modulation, which doesnt have in frequency modulation. Amplitude modulation definition, types, solved examples. Fig2 shows the spectrum of pulse amplitude modulated signal along with the message signal and the sampling signal which is the carrier train of pulses with the help of the waveform plotted in time domain. Details of the point source used in this experiment are.
To study and perform pulse position 6 to study and perform pulse code modulation and demodulation. To study and perform pulse width modulation and demodulation. Pulse width modulation pwm is a form of pulse modulation where the width of the pulses in a carrier pulse train is made proportional to the instantaneous amplitude of the modulating signal. In each of these systems, a characteristic of the pulse such as amplitude, duration, or position is continuously varied in accordance with the modulating signal. 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 modulation pam, quadrature amplitude modulation qam 12. Pulse modulation may be used to transmitting analog information, such as continuous speech signal or data. The demod ulation is performed by an envelope detector. Because, atmospheric propagation is good for amplitude modulated signals. We have seen what an ask signal looks like in a previous chapter, repeated below. These are related to the number of levels adopted by the. This type of pulse modulation, where pulse amplitude is varied. Pulse position modulation ppm a pulse of fixed width and amplitude is used to transmit the information. It is deserved to pay attention that pcm modulation is a real digital signal that can be processed.
Amplitude modulation and demodulation objective amplitude modulation am is one of the simplest methods for modulating a sinusoidal carrier wave. Pulseamplitude modulation, is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses. An application of this is the simulation of a communication system that uses pulse amplitude modulation pam to transmit text messages over a bandlimited channel, such. To study frequency modulation and determine its modulation factor 4. This paper discusses a laboratory experiment used to supplement a. Indian institute of technology kanpur ee 381 electrical. The pulse amplitude modulation is the process in which the amplitudes of regularity spaced rectangular pulses vary with the instantaneous sample values of a. It is often called as am and is commonly used in transmitting a piece of information through a radio carrier wave. Pulse width and pulse position modulation and demodulation lab experiment vtu pulse amplitude modulation, pulse width modulation, pulse position modulation along with demodulation are all in this video.
Laboratory exercise on demodulation of pam signal asee peer. Laboratory manual principles of communication system lab ee226f ivth semester prepared by. Ask, fsk, and psk last time, we talked about two analog modulation methods. 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. Demodulation is performed by detecting the amplitude level of the carrier at every single period. To study amplitude demodulation by linear diode detector 3. The demodulation is performed by an envelope detector. 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. User manual for pulse amplitude modulation and demodulation trainer.
Quadrature amplitude modulation qam pam signals occupy twice the bandwidth required for the baseband transmit two pam signals using carriers of the same frequency but in. Pulse amplitude modulation is defined as the data transmission by altering the amplitudes power levels or voltage of every pulse in a regular time sequence of electromagnetic pulses. Communication is achieved over a transmitter and a receiver through signals. The amplitude of each pulse corresponds to the value of the message signal x t at the leading edge of the pulse.
The output of a sampling circuit with a zeroorder hold zoh is one example of a pam signal. Amplitude modulation this experiment examines the characteristics of the amplitude modulation am process. Thus the amplitude modulation and demodulation operation has been performed. Observation simulation of signal constellations of bpsk, qpsk and qam. Commutator determines the synchronization and sequence of the channels signals to be sampled. At the end of this experiment, you should have a better understanding of. Pcm is a technique widely used in communication systems, in particular in the conversion of analog signals into their digital representation. Pulse amplitude demodulation peak detection is used to detect pam. The experiment of rf modulation at the hls hefei light source is introduced. Amplitude modulation am refers to the modulation technique where the carriers amplitude is varied in accordance to the instantaneous value of the modulating or baseband signals amplitude. The amplitude at the corrected start point of the pileup pulse can be estimated by the peak time of the pileup pulse. Analog communication lab manual, prepared by nakka. The particular form of pulse amplitude modulation is referred to as natural pam, because the tops of the pulses follow the shape of the modulating signal.
The amplitude modulation receiver will be wider when compared to the fm receiver. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. To construct and study the pulse amplitude modulation technique. Analog communication pulse modulation tutorialspoint. These signals carry the information through modulation. Pdf pulse amplitude modulation pam and discrete multitone dmt technology are. A pulse width modulator circuit made up of 555 timer is shown in figure. Transmitter and receiver are simple in amplitude modulation. User manual for pulse amplitude modulation and demodulation. Pulse amplitude modulation is a technique in which the amplitude of each pulse is controlled by the instantaneous amplitude of the modulation signal.
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