3 basic types of pulse modulation pdf

There are many modulation techniques, which are classified according to the type of modulation employed. Figure 2 pulse before pwm figure 3 pulse after pwm 3. We can also get back our analog signal by demodulation. Sampling is common in all pulse modulation techniques. Pulse width modulated pwm drives rockwell automation. A pulsecode modulation pcm system, as shown in figure 5. This sampled variable amplitude pulse is then digitalized by the analog to digital converter. There are two types of modulation analog and digital.

Pulse amplitude modulation is categorized into two types. Our study begins with the pulseamplitude modulation pam scheme. There are several types of modulation according to the nature. Analog and digital pulse modulation techniques gate study. Another way of expressing the modulation index is in terms of the maximum and minimum values of the amplitude of the modulated carrier wave. The following safety and common symbols may be used in this manual and on. The impulse response is h t pt t the output of the low pass. Modulation modulation is the process whereby some characteristic of one wave is v aried in accordance with some characteristic of another wave. We use modulation technique to alter signals in time and frequency to accomplish desired objectives. Double polarity pam is a situation where the pulses are both positive and negative. 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.

Pulse code modulation an overview sciencedirect topics. The basic types of modulation are angular mo dulation including the special cases of phase and frequency modulation and amplitude modulation. The pulse amplitude modulation is the modulation of signals by. Pulse digital modulation is also used in both analog and digital communications. The lead edge can be held at the lead edge of the window and the tail edge modulated. Modulationtypesamplitude,frequency,phase modulation. All about modulation basic concepts, signal space, constellations and phase shift keying modulations psk, qpsk, oqpsk, mpsk. Ap1609710 different pwm for three phase acim 060803 for. The output of a pcm will resemble a binary sequence. 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 an overview sciencedirect. In this chapter, let us discuss the following analog pulse modulation techniques. 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.

Output frequency and voltage is controlled electronically by controlling the width of the pulses of voltage to the motor. Null at 3 pam and pcm pam pulse amplitude modulation. Sampling theorem and pulse amplitude modulation pam reference stremler, communication systems, chapter 3. Pulse amplitude modulation has some applications, but it is not used by itself in data communication. For the baseband digital transmission, pulse amplitude modulation pam is the most efficient in terms of power and bandwidth utilization.

Modulation is broadly classified into two categories namely analog modulation a. Pulse amplitude modulation pulse width modulation pulse position modulation pulse code modulation pulse modulation the process of transmitting signals in the form of pulses discontinuous signals by using special techniques. The second class of digital modulation format is called multilevel signaling formats. 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. Therefore, analog modulation includes am, fm and pm and these are more sensitive to noise. Pdf analog communication system pdf notes ac notes sw. The pulse code modulator technique samples the input signal xt at a sampling frequency. The pulse may take any real voltage value that is proportional to the value of the original waveform. It is a type of pulse time modulation ptm technique where the timing of the carrier pulse is varied according to the modulating signal in pulse duration modulation pdm, the amplitude of the pulse is kept constant and only the variation in width is noticed.

In pulse width modulation, there are different types of modulation for analog and digital as shown below. Another basic concept in pulse modulation is the modulation itself. Here you can download the free lecture notes of analog communication system pdf notes ac notes pdf materials with multiple file links to download. In these formats, the message waveforms are linecodes with symbols representing multiple bits. A brief discussion about pulse code modulation and. Sampling theorem determines the necessary conditions which allow us to change an analog signal to a discrete one. Modulation for ease of radiation antennas must be greater than onetenth of the wavelength 10. In the intermediate dc circuit, the dc voltage is filtered in a lc lowpass filter. Pulse code modulation is a method that is used to convert an analog signal into a digital signal so that a modified analog signal can be transmitted through the digital communication network. Single polarity pam is a situation where a suitable fixed dc bias is added to the signal to ensure that all the pulses are positive.

Modulation techniques pwm and pulse code modulation. When we modulate a carrier wave, we ordinarily alter its amplitude am, its frequency fm, or its phase pm. Where as digital modulations are with bit streams or symbols from computing vevices as base band signals. Pulse modulation, october 1960 popular electronics rf cafe. The nice thing about a pulse is that theres another. Analog communication pdf notes book starts with the topics covering introduction ac, dsb modulation, ssb modulation, angle modulation concepts, angle modulation methods, noise etc. When we take the pulse digital modulation, we use a periodic sequence of rectangular pulses as the carrier signal. Basic concept of modulation the information source typically a low frequency signal referred to as the baseband signal carrier a higher frequency sinusoid example. Sampling theorem and pulse amplitude modulation pam.

A signal is pulse code modulated to convert its analog information into a binary sequence, i. Basic pulse width modulation pwm tutorials of cytron. Pdf generation of pulse width modulation pwm signals. Modulation describes the process where a piece of music changes from one key to another key when you start writing a piece of music one of the first things you do is choose a key to compose in. What is different in ppm is that ppm uses pulse positions to carry information. Analog communication pulse modulation after continuous wave modulation, the next division is pulse modulation. The pulse center may be fixed in the center of the time window and both edges of the pulse moved to compress or expand the width.

The analog pulse modulation is again classified as, 1. All about modulation part i basic concepts, signal space, constellations and phase shift keying modulations psk, qpsk, oqpsk, mpsk. Before we study in detail about pam lets know the concepts of modulation. Demodulation is the opposite process of modulation. Or the process of modulation can be defined as varying the rf carrier wave in accordance with the intelligence or information in a low frequency signal. No information is lost, but the energy is redistributed in the frequency domain. Most radio systems in the 20th century used frequency modulation fm or amplitude modulation am for radio broadcast a modulator is a device that performs modulation. It is designed for highfrequency operation and has a low. The tail edge can be fixed and the lead edge modulated. In this modulation, the signal is sampled at regular intervals and each sample is made proportional to the amplitude of the modulating signal. Pulse amplitude modulation is the basic form of pulse modulation.

Analog communication pulse modulation tutorialspoint. Analog modulation delas with the voice, video and regular waves of base band signals. Pcm is the preferred method of communication within the public switched telephone network pstn. 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. Pulse amplitude modulation pulse code modulation sampling. Pcm is in binary form, so there will be only two possible states high and low0 and 1. Lets us look at some of the different types of pulse modulation. For a better quality and efficient communication, digital modulation technique. The baud or signalling rate defines the number of symbols per. 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. This way pulse time modulation can be classified into three types.

The analog modulation techniques are mainly classified into pulse amplitude. There are three types of pulse width modulation pwm. These three types are shown in the above given figure, with timing slots. In this article we will see an introduction of pulse width modulation. Pulse modulation communications university of toronto. If noise enters into a system, it persists and gets carried up to the end receiver. The bit rate defines the rate at which information is passed. Channels, modulation, and demodulation of binary pam where the basic pulse shape pt is a sinc function. This video discusses digital modulation techniques ask, fsk and psk. So, this drawback can be overcome by the digital modulation technique. Modulation for frequency assignment the fcc assigns frequency bands to each radio application. Modulation, analog modulation, digital modulation, am,fm. However, it is the first step in another very popular conversion method called pulse code modulation.

The waveforms, definition and basic concepts of each digital modulation techniques are discussed here. This choice of key determines the scale you use, how many sharps and flats there are and what chords you can use. Amplitude modulation early radio ee 442 spring semester. A block diagram showing the basic classification of modulation techniques is given below. Percentage modulation, %m m100 v m v c 100 the percentage modulation lies between 0 and 80%. For bpsk this is just a rectangular pulse of duration t.

In this type of drive, a diode bridge rectifier provides the intermediate dc circuit voltage. Pulse modulation definition, types, block diagrams, pulse. Or modulation is defined as the precess by which some characteristics, usually amplitude, frequency or phase, of a carrier is varied in. Of them all, the digital modulation technique used is pulse code modulation pcm. Modulation is the process of changing the characteristics of the carrier signal in accordance with the instantaneous values of the modulating signal message signal. Its main features can be summarized as sinetriangle wave comparison. Pulse width modulation the most popular power devices for motor control applications are power mosfets and igbts. So now lets discuss different types of pulse modulation techniques in detailpulse modulation can be categorized broadly into two types. Modulation is the process of superimposing a low frequency signal on a high frequency carrier signal. Pulse width modulation has many application in digital communication, power electronics, auto intensity control of street lights, speed control of dc motor and variable pwm to generate analog signal from digital signals, digital to analog converter. Pulse code modulation is a technique, which is used to convert an analog signal into digital signal.