For the sake of simplicity, ka 1 and ar ac have been chosen lowpass. Pulse amplitude modulation pam is used extensively in telecommunications as an intermediate step of other techniques such as phase shift keying psk. 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 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. Note that this is on the very low end of the recommended voltage range.
To study and perform pulse width modulation and demodulation. To study amplitude demodulation by linear diode detector. In the case of analog pulse amplitude modulation signals, the number of pulse amplitudes can be infinite. Figure 321 includes a simplified circuit view a for this demodulator and its waveforms views b and c. 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. Dutton ee3 winter 2004 1 ee3 lab 1 amplitude modulation and demodulation 1 lab notes a word about power. Commutator determines the synchronization and sequence of the channels signals to be sampled.
Fm is mostly used in highfrequency radio broadcasting, and. In pulse amplitude modulation pam technique, the amplitude of the pulse carrier varies, which is proportional to the instantaneous amplitude of. Pam pulse amplitude modulated modulation ve demodulation sample and hold flat top mode hacettepe university ee telecommunication lab. To study frequency modulation and determine its modulation factor 4.
In the positive half cycle of pam signal, diode conducts and current flows through r, whereas in negative half. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. The pulse may take any real voltage value that is proportional to the value of the original waveform. In this chapter we will discuss ways of demodulating am, cw, fm, phase, and pulse modulation. To study sampling and reconstruction of pulse amplitude modulation system. Channels, modulation, and demodulation of binary pam where the basic pulse shape pt is a sinc function. Pulse amplitude modulation pam the actual amplitude of the pulse represents the number being transmitted. Remember, neither yt, nor the oscillator signal, appears at the multiplier output. Pulse amplitude demodulation peak detection is used to detect pam.
The term demodulator is used because the demodulation process is considered to be the opposite of modulation. The output amplitude for each of data1 to data4 is set. Sampling theorem and pulse amplitude modulation pam reference stremler, communication systems, chapter 3. The pulse amplitude modulated signal, will follow the amplitude of the original signal, as. Mcnames portland state university ece 223 communications. Quadrature amplitude modulation qam pam signals occupy. 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 phase and quadrature demodulation. 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. Hence, pam is continuous in amplitude but discrete in time. Laboratory manual principles of communication system lab ee226f ivth semester. In general, amplitude modulation definition is given as a type of modulation where the amplitude of the carrier wave is varied in some proportion with respect to the modulating data or the signal. Simply put, the transmission of data takes place by the variation of the amplitude of pulse according to the modulating signal. What is amplitude modulation, am electronics notes.
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. To study and perform pulse amplitude modulation and demodulation. 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. To study and perform amplitude modulation and demodulation. Pam pulse amplitude modulated modulation ve demodulation. The low pass filter eliminates high frequency ripples and generates the demodulated signal which has its amplitude proportional to pam signal at all time instant. In pam the amplitude of the individual pulses are varied according to the amplitude of the modulating signals. This means that their ratio is unity at the output of the adder, which forces m to a magnitude of exactly unity. Amplitude modulation definition, types, solved examples. It is often called as am and is commonly used in transmitting a piece of information through a radio carrier wave. In a pcm stream, the amplitude of the analog signal is sampled regularly at uniform intervals, and each sample is quantized to the nearest value within a range of digital steps. Amplitude modulation and demodulation 1 lab notes a word about power. Pulse modulation timedivision multiplex tdm timedivision multiplexing is the method of combining several sampled signals in a definite time sequence. 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.
Pulsecode modulation pcm is a method used to digitally represent sampled analog signals. In particular, we consider pam signal demodulation and detection and give a. Laboratory exercise on demodulation of pam signal asee peer. As for the mechanism, when amplitude modulation is used there is a variation in the amplitude of the carrier. Repeat the experiment for different input signal and sampling. 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. Demodulation is the process by which the original information bearing signal, i.
Cr1 is the input diode which allows capacitor c1 to charge to the peak value of the pam input pulse. Basic concept of modulation the information source typically a low frequency signal referred to as the baseband signal carrier a higher frequency sinusoid example. The output of a sampling circuit with a zeroorder hold zoh is one example of a pam signal. Pulse amplitude modulation is a technique in which the amplitude of each pulse is controlled by the instantaneous amplitude of the modulation signal. 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. Amplitude modulation, am frequency modulation, fm double and single sideband, dsb and ssb digital modulation phase shift keying. The ideal modulated signal should have a minimum euclidean distance of 2. Pulse amplitude modulation pam theory of and its applications. No information is lost, but the energy is redistributed in the frequency domain.
Pulse amplitude modulation pam, quadrature amplitude modulation qam 12. Overview of communication topics 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 j. Pwm converts an audio signal into a sequence of pulses having constant amplitude, but the width is proportional to amplitude of. Pulse amplitude modulation request pdf researchgate. Pulseamplitude demodulation peak detection is used to detect pam. It reacts to all amplitude changes needs a limiter. Pulse amplitude demodulation september 4, 20 by ashutosh bhatt 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. Amplitude modulation, am, is one of the most straightforward ways of modulating a radio signal or carrier. Classification and types of analog modulation double sideband suppressed carrierdsb sc introduction.
The pulse amplitude modulated signal, will follow the amplitude of the original signal, as the signal traces out the path of the whole wave. For example, am is used in shortwave and radio wave broadcasting. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. If you continue browsing the site, you agree to the use of cookies on this website. 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.
Amplitude modulation is a process by which the wave signal is transmitted by modulating the amplitude of the signal. The low pass filter eliminates high frequency ripples and generates the demodulated signal which has. 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. 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. Explain generation and demodulation of pam, ppm and pwm with. 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. 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. The original waveform amplitude is quantized with a resulting loss of information. The process of demodulation for signals using amplitude modulation can be achieved in a number of different. Even though there are different methods for modulation and demodulation processes, each has its own advantages and disadvantages. To study amplitude demodulation by linear diode detector 3. Request pdf pulse amplitude modulation pulse amplitude modulation pam. Analog communication pulse modulation tutorialspoint.
Pulse amplitude modulation pam is an analog modulating scheme in which the amplitude of the pulse carrier varies proportional to the instantaneous amplitude of the message signal. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. There is a simple pulse modulation technique called pulse amplitude modulation pam which is proved to be more power efficient than the pwm and consumes constant power for individual pulses. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. Sampling theorem and pulse amplitude modulation pam. For demodulation of the pulse amplitude modulated signal, pam is fed to the low pass filter as shown in fig3 below. Pam pulse amplitude modulation signal generation for qam transmission mp1800a s eries. In this circuit diode d is the detector diode, the resistance r is the load resistance and c is the filter capacitor. Pulseamplitude modulation pam, is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. Pdf pulseposition and pulseamplitude modulation interface for. Oct 22, 2017 pam pulse amplitude modulated modulation ve demodulation sample and hold flat top mode hacettepe university ee telecommunication lab.
It requires that the amplitude of the dc a part of a t is equal to the amplitude of the ac part a. Observe the pulse amplitude demodulated signal at fil out, which is same as the input signal. From the diagram, it can be seen that the envelope of the signal follows the contours of the modulating signal. The circuit in which restoration is achieved is called the detector or demodulator both of these terms are used in neets. Pulse width modulation pwm is a modulation technique, which converts an analog signal into a digital signal for transmission. In this chapter, let us discuss the following analog pulse modulation techniques. It is relatively difficult to tune, as tuned circuit must be tuned to different frequency than carrier frequency. Sinusoidal amplitude modulation amplitude demodulation. Explain generation and demodulation of pam, ppm and pwm. If the negative symbol is transmitted, the pdf for z will be as sketched below. After continuous wave modulation, the next division is pulse modulation. Communication fundamentals envelope of a bandpass signal a signals gt is a bandpass signal if its fourier transform is nonnegligible only in a band of frequencies of total extent 2w centered about fc.
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