Analog communication pulse modulation tutorialspoint. In pam the amplitude of the individual pulses are varied according to the amplitude of the modulating signals. It is often called as am and is commonly used in transmitting a piece of information through a radio carrier wave. Am is a relatively simple way to add audio information to a carrier wave so that sounds can be transmitted. Cr1 is the input diode which allows capacitor c1 to charge to the peak value of the pam input pulse. The time division multiplex system use pulse modulation. However, it is the first step in another very popular conversion method called pulse code modulation. Difference between pam, pwm, and ppm comparison of pwm and pam.
Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. Pulsedensity modulation, or pdm, is a form of modulation used to represent an analog signal with a binary signal. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. Pulse amplitude modulation has some applications, but it is not used by itself in data communication. The modulating signal contains the intended message or information sometimes consisting of audio data, as in am radio. It is another type of ptm, where the amplitude and width of the pulses are kept constant and only the position of the pulses is varied.
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. Thus in pulse modulation, a series of pulses carries the information instead of continuous modulated signal. In a pdm signal, specific amplitude values are not encoded into codewords of pulses of different weight as they would be in pulsecode modulation pcm. 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. A sine wave generator is used which is based on wien bridge oscillator circuit. Figure 321 includes a simplified circuit view a for this demodulator and its waveforms views b and c. No information is lost, but the energy is redistributed in the frequency domain.
Circuit design of pulse amplitude modulation a pam is generated from a pure sine wave modulating signal and a square wave generator which produces the carrier pulse and a pam modulator circuit. Pulse frequency modulation pfm is a modulation method for representing an analog signal using only two levels 1 and 0. How to simulate pam pulse amplitude modulation in matlab. Theory and applications by angel vladimirov peterchev a. 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. Explain generation and demodulation of pam, ppm and pwm with. Sampling theorem and pulse amplitude modulation pam reference stremler, communication systems, chapter 3.
Simple and dirty pulse width modulation pwm with 555. In pulse amplitude modulation pam, the a m are purely real, that is imam0 for m 1, 2, m. How to plot real time serial data on python gui duration. The pulse position modulation ppm varies the position of individual pulses from their mean pos. Explain briefly in your report how amplitude modulation is accomplished by this circuit. The depth of modulation can be varied using the variable knob provided at a. 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. Use fg1 as the message signal and fg2 as the carrier signal. Remember, for analysis purposes keep the modulation index and frequency the same as part 2, step 3. Pulse amplitude modulation pam theory of and its applications. Use the spectrum analyzer to compare this modulator to the one in part 2. Amplitude modulation definition, types, solved examples.
Pulsecode modulation or pcm is known as a digital pulse modulation technique. Pulse amplitude modulation pam is the simplest form of pulse modulation. Explain generation and demodulation of pam, ppm and pwm. Amplitude modulation and demodulation abstracta single tone sinusoidal signal is transmitted using amplitude modulation and is demodulated at the receivers end using an envelope detector and the attenuated signal is amplified using common source bjt amplifer i. 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 of pwm and ppm block diagram and waveform. Sampling theorem and pulse amplitude modulation pam. Principles of communication systems 20022003 8 chapter 7. Pulse amplitude modulation pam, quadrature amplitude modulation qam 12. The original method of electronically encoding sound information on radio waves is called amplitude modulation, or am. The percentage modulation can be calculated using the formula. 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.
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. Lan 10 mhz ref out modulation in 1, 2 agilent 81150a pulse function arbitrary noise generator, available at modulation frequencies up to 10 mhz. There are two kinds of pam one in which the pulses have the same polarity and the other in which the pulses can have both positive and negative polarity according to the amplitude of the modulating signal. 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. Notice that the pulses are wider where the amplitude of the sine wave is higher and narrower where the amplitude is lower. Connect channel 1 probe of the oscilloscope to the output of the modulator at pin 7. 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. Pam, pwm and ppm, in the sense that the message signal is subjected to a great number of operations. The original waveform amplitude is quantized with a resulting loss of information. Application note of pampulse amplitude modulation signal. 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.
There are different kinds of modulation technique based on varying the properties of a pulse train. In ppm modulation technique the power required for transmitting individual pulses are constant, but synchronization of transmitter and receiver are required. Amplitude modulation early radio ee 442 spring semester. We use modulation technique to alter signals in time and frequency to accomplish desired objectives. In this video you will learn the block diagram of pwm and ppm. Amplitude modulation is mostly used in the form of electronic communication. 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. University of california, berkeley 2002 a dissertation submitted in partial satisfaction of the requirements for the degree of doctor of philosophy in engineeringelectrical engineering. This video is about quadrature amplitude modulation qam. The pulse position modulation ppm varies the position of individual pulses from their mean position according to the amplitude of the modulating signal. The agilent 81150a pulse function arbitrary noise, 2nd channel or the internal modulation source of the modulated channel.
Pam is also the first step in creating pulse code modulated digital signal. Quadrature amplitude modulation qam transmitter and receiver have been discussed here. Pulse amplitude modulation pam circuit eeweb community. Measure the output signal frequency and amplitude by connecting the output to cro. In the case of analog pulse amplitude modulation signals, the number of pulse amplitudes can be infinite. Classification and types of analog modulation double sideband suppressed carrierdsb sc introduction.
Pulse amplitude modulation is used in the popular ethernet communication standard. Circuit design of pulse amplitude modulation a pam is generated from a pure sine wave modulating the signal and a square wave generator which produces the carrier pulse and a pam modulator circuit. The pam modulator and demodulator circuits simple compared to other kind of modulation and demodulation techniques. Am modulators base, collector, grid and plate modulators. To study sampling and reconstruction of pulse amplitude modulation system 6. In this chapter we will discuss ways of demodulating am, cw, fm, phase, and pulse modulation. There are two categories of pam techniques, one is the pulses have the same polarity and the other in which the pulses can have both positive and. The circuit to create waveform like this is based upon a simple relay that is driven by a clock signal. Enough about modulation theory, lets get a more practical view of what pwm really is. Pam is a pulse modulation system in which the signal is sampled at regular intervals, with each sample proportional to the amplitude of the signal at the instant of sampling. The resulting plate flows in pulses, the amplitude of each pulse being proportional to the instantaneous bias and therefore to the instantaneous modulating voltage.
The application of these pulses to the tuned tank circuit will give amplitude modulation. The fig1 shows the generation of pam signal from the sampler which has two inputs i. Repeat the steps 3 and 4 by changing the applied input signal frequency to 100khz and 500 khz. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. Amplitude modulation is a process by which the wave signal is transmitted by modulating the amplitude of the signal. 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. Apply a 5 khz signal to both rf and af inputs of 0. Demodulation of pam for demodulation of the pulse amplitude modulated signal, pam is fed to the low pass filter as shown in fig3 below. 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 as a. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information.
Vary the modulating frequency and amplitude and observe the effects on the modulated waveform. The circuit in which restoration is achieved is called the detector or demodulator both of these terms are used in neets. Pulse amplitude modulation pulse code modulation sampling. To study frequency modulation and determine its modulation factor 4. The circuit shown above is actually a combination of a nonlin. The pam modulator and demodulator circuits simple compared to other kind of modulation and. Digital pulsewidth modulation control in power electronic. Pulse amplitude modulation pam the actual amplitude of the pulse represents the number being transmitted. Thus the amplitude of the signal is proportional to the modulating signal through which information is carried. Other articles where pulse position modulation is discussed. Pulse amplitude modulation pam converts an anlalog signal into a pulse type signal. The pulse may take any real voltage value that is proportional to the value of the original waveform.
Basic concept of modulation the information source typically a low frequency signal referred to as the baseband signal carrier a higher frequency sinusoid example. Oct 3, 2018 there are different kinds of modulation technique based on varying the properties of a pulse train. Consequently, the constellation points lie on the horizontal line. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. Oct 14, 2018 this video is about the demodulation detection of pulse width modulation pwm and pulse position modulation ppm. It was developed in the first few decades of the twentieth century. Amplitude modulation am is a modulation technique where the.
It is customary to arrange the points so that they are equally spaced and centered at zero. Demodulation channel decoding is the corresponding process at the receiver of converting the received waveform into a. The output of a sampling circuit with a zeroorder hold zoh is one example of a pam signal. It is another type of ptm, where the amplitude and width of the pulses are kept constant and only. Pulse width modulation pwm or pulse duration modulation pdm or pulse time modulation ptm is an analog modulating scheme in which the duration or width or time of the pulse carrier varies proportional to the instantaneous amplitude of the message signal.
For the baseband digital transmission, pulse amplitude modulation pam is the most efficient in terms of power and bandwidth utilization. Transmission pulse width or pulse duration modulation and pulse position modulation. Generation of pulse amplitude modulation pam duration. Introduction modulation is used in efficient radiation of signals. 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. In fact, the pulsecode modulation is quite complex as compared to the analog pulse modulation techniques i. The pulse width modulation pwm varies the width of individual pulses according to the amplitude of the modulating signal. Pcm pulse code modulation quantized pam signal pcm modifies the pulses created by pam to create a completely digital signal.
The pam modulator and demodulator circuits simple compared to other kinds of modulation and demodulation techniques. Simply put, the transmission of data takes place by the variation of the amplitude of pulse according to the modulating signal. Digital pulsewidth modulation control in power electronic circuits. 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. Pulse amplitude modulation an overview sciencedirect. Pulse amplitude modulation an overview sciencedirect topics. In the pulse modulation, the continuous signal is converted into a series of pulses, each proportional to the amplitude of the signal and corresponding in time to it. A modulation technique that allows variation in the position of the pulses according to the amplitude of the sampled modulating signal is known as pulse position modulation ppm. Sampling theorem determines the necessary conditions which allow us to change an analog signal to a discrete one. For an introduction to the basics of matlab, see appendix a. Commutator determines the synchronization and sequence of the channels signals to be sampled. Pulseamplitude demodulation peak detection is used to detect pam.
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