The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. Principles of communication systems 20022003 8 chapter 7. Pulse amplitude modulation pam the actual amplitude of the pulse represents the number being transmitted. Three kinds of modulations modulation is the process of facilitating the transfer of information over a. Pulsecode modulation pcm is a method used to digitally represent sampled analog signals. Pulse coded modulation pcm is a form of modulation where there is no carrier, so that makes it a pure digital system. Outline l frequency versus amplitude modulation l amplitude modulation am l angle modulation ldigital modulation l line coding l pulse shaping techniques l geometric representation of modulation signal l linear modulation techniques. In this paper, a full analysis is presented on digitaltoanalog conversion for pulse amplitude modulated pam systems. In the case of analog pulse amplitude modulation signals, the number of pulse amplitudes can be infinite. Pulse amplitude modulation matlab pammod mathworks. High frequency signals are desirable for transmission. Amplitude modulation definition, types, solved examples. Question pulse width modulation pwm pulse position.
Modulation is the use of one electrical signal to control a primary variable of another. Modulation techniques for mobile radio school of information science and engineering, sdu. Amplitude modulation this experiment examines the characteristics of the amplitude modulation am process. Digitaltoanalog conversion of pulse amplitude modulated. Pulse modulated signals, such as pam, pwm, ppm, pm and dm. 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. To convert a 10khz sinusoidal signal to digital form, the minimum sampling frequency is 20khz. By analyzing the cyclostationary nature of pulseamplitude modulation pam systems, two methods of quantization are proposed. Pdf on may 1, 2016, waleed madany and others published pulseposition and pulseamplitude modulation interface for serial. It is the standard form of digital audio in computers, cds, digital telephony and other digital audio applications. The modulation processisprobablyeasier tounderstand whenviewed fromthe perspective of amplitude modulation.
The output of a sampling circuit with a zeroorder hold zoh is one example of a pam signal. The alldigital transmitter uses pulse width modulation pwm. Toward digital transmitters with amplitude shift keying and quadrature amplitude modulators implementation examples. The amplitude of the analog signal is sampled at uniform intervals and each sample is quantized to its nearest. Pulse amplitude modulation pulse code modulation sampling. It is the type of modulation in which we sample the signals at each interval and we make sure that the samples are directly proportional to the signals amplitude at that particular instance. The amplitude modulation am modulation index can be defined as the ratio of the peak. 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. Dm is the simplest form of pulse code modulation pcm where the difference between successive samples is encoded into nbit data streams. The pulse amplitude modulated signal, will follow the amplitude of the original signal, as.
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. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. Pcm is by far the most prevalent form of pulse 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. Amplitude modulation early radio ee 442 spring semester. Pulse amplitude modulation is a technique in which the amplitude of each pulse is controlled by the instantaneous amplitude of the modulation signal. For the example above, the carrier signal is p es cos2. 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. For an introduction to the basics of matlab, see appendix a. The original waveform amplitude is quantized with a resulting loss of information. 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. Denoting the modulating signal as mt, pulse amplitude modulation is achieved by multiplying the carrier with the mt. M amplitude modulation the first amplitude modulated signal was transmitted in 1901. The particular form of pulse amplitude modulation is referred to as natural pam, because the tops of the pulses follow the.
In this chapter, let us discuss the following analog pulse modulation techniques. Pulse amplitude modulation has some applications, but it is not used by itself in data communication. A sample symbol sequence and corresponding continuoustime signal are also. 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. Pulse modulation and pulse modulation techniques like pulse amplitude modulation pam, pulse width modulation pwm, pulse position modulation ppm and pulse code. A 65nm cmos example of a 6bit 9gbs pamdts link has been designed and simulated using 1. Commutator determines the synchronization and sequence of the channels signals to be sampled. Pulse amplitude modulation pam is defined as the data transmission by altering the amplitudes of every pulse in a regular time sequence of electromagnetic pulses. With no modulation, the am carrier is transmitted by itself. Pulse position modulation ppm a pulse of fixed width and. Overmodulated am signals and its requirement for coherent detection are also considered. Hence, pam is continuous in amplitude but discrete in time.
In the absence of noise and isi, the mth bit is correctly decoded into am, and in turn, into bm. Pdf pulseposition and pulseamplitude modulation interface for. Pulse width modulation axiomatic technologies corporation. 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.
Linear modulation we are typically interested in locating a messagesignal to some new frequency location, where it can be ef. Pcm pulse code modulation quantized pam signal pcm modifies the pulses created by pam to create a completely digital signal. Sampling theorem and pulse amplitude modulation pam. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. As examples of the communication of dt information over ct channels, consider transmitting a binary sequence of 1s and 0s from one computer to another over a. The pulse code modulation pcm can transmit all the bits which are used to code sample. 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. However, it is the first step in another very popular conversion method called pulse code modulation. Sampling rate 4000 x 2 8000 sampless bit rate sampling rate x number of bits per sample 8000 x 8 64,000 bps 64 kbps.
In pulse amplitude modulation pam technique, the amplitude of the pulse carrier varies, which is proportional to the instantaneous amplitude of. The pulse may take any real voltage value that is proportional to the value of the original waveform. Before going to discuss the difference between pam, pwm, and ppm, let us discuss individually each. Amplitude modulation qam where both the amplitude and the phase are. The modulated signal has a minimum euclidean distance of 2. While the bit streams we wish to transmit are inherently discretetime, all physical media are continuoustime in nature. Which method listed in question 2 is the only form of pulse modulation that is used in a digital transmission system. The human voice normally contains frequencies from 0 to 4000 hz. The pulse code modulator technique samples the input signal xt at a sampling frequency. So now lets discuss different types of pulse modulation techniques in detailpulse modulation can be categorized broadly into two types. Pdf toward digital transmitters with amplitude shift. Analog communication pulse modulation tutorialspoint.
This sampled variable amplitude pulse is then digitalized by the analog to digital converter. For example, if an audio signal voltage is used to control the amplitude of a carrier signal, the result is amplitude modulation. 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 an overview sciencedirect topics. In pulseamplitude modulation pam, the amplitudes of regularly spaced pulses are varied in proportion to the corresponding sample values of a continuous. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. To convert an audio signal 020khz to digital form, the minimum sampling frequency is 40khz. Pam, pwm and ppm modulations are used for the analogical. The message signal must consist of integers between 0 and m1. 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. Pdf differentialtime and pulseamplitude modulation signaling.
Amplitude modulation with modulation factor 1 or 100%. 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. After continuous wave modulation, the next division is pulse modulation. Pulse position modulation ppm pulse amplitude modulation pam pulse code modulation pcm 3. The demodulation is performed by an envelope detector. We use modulation technique to alter signals in time and frequency to accomplish desired objectives. Sampling theorem and pulse amplitude modulation pam reference stremler, communication systems, chapter 3. Pulse modulation timedivision multiplex tdm timedivision multiplexing is the method of combining several sampled signals in a definite time sequence. Chapter 6modulation techniques shandong university. Pulse amplitude modulation pam, quadrature amplitude modulation qam 12. In this video, i have explained amplitude modulation by following outlines.
An informationbearing signal must conform to the limitations of its channel. If the negative symbol is transmitted, the pdf for z will be as sketched below. Sampling theorem determines the necessary conditions which allow us to change an analog signal to a discrete one. Figure 34 demodulation of a pam signal naturally sampled. By varying the amplitude of the pulses the carrier signal in proportion to the instantaneous values of. 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. Feedback can be used to achieve an output that matches exactly the control signal. Modulation addition of information or the signal to an electronic or optical signal carrier. 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. Amplitude modulation involves the transferring of information. The output is a series of pulses, the amplitudes of which vary in proportion to the modulating signal.