3 basic types of pulse modulation pdf

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 modulation definition, types, block diagrams, pulse. In the intermediate dc circuit, the dc voltage is filtered in a lc lowpass filter. Analog communication pdf notes book starts with the topics covering introduction ac, dsb modulation, ssb modulation, angle modulation concepts, angle modulation methods, noise etc. 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. Null at 3 pam and pcm pam pulse amplitude modulation.

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. This video discusses digital modulation techniques ask, fsk and psk. The pulse may take any real voltage value that is proportional to the value of the original waveform. 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.

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. This choice of key determines the scale you use, how many sharps and flats there are and what chords you can use. No information is lost, but the energy is redistributed in the frequency domain. Modulation, analog modulation, digital modulation, am,fm. The bit rate defines the rate at which information is passed. Our study begins with the pulseamplitude modulation pam scheme. 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. A brief discussion about pulse code modulation and. So, this drawback can be overcome by the digital modulation technique.

Pulse amplitude modulation has some applications, but it is not used by itself in data communication. The baud or signalling rate defines the number of symbols per. Modulation modulation is the process whereby some characteristic of one wave is v aried in accordance with some characteristic of another wave. If noise enters into a system, it persists and gets carried up to the end receiver. When we take the pulse digital modulation, we use a periodic sequence of rectangular pulses as the carrier signal. Figure 2 pulse before pwm figure 3 pulse after pwm 3. Double polarity pam is a situation where the pulses are both positive and negative. For the baseband digital transmission, pulse amplitude modulation pam is the most efficient in terms of power and bandwidth utilization.

In these formats, the message waveforms are linecodes with symbols representing multiple bits. The tail edge can be fixed and the lead edge modulated. For bpsk this is just a rectangular pulse of duration t. 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 width modulation the most popular power devices for motor control applications are power mosfets and igbts. 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.

Pulse digital modulation is also used in both analog and digital communications. Modulation is the process of superimposing a low frequency signal on a high frequency carrier signal. There are two types of modulation analog and digital. 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. Modulation for ease of radiation antennas must be greater than onetenth of the wavelength 10. 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 this type of drive, a diode bridge rectifier provides the intermediate dc circuit voltage. The lead edge can be held at the lead edge of the window and the tail edge modulated. However, it is the first step in another very popular conversion method called pulse code modulation. These three types are shown in the above given figure, with timing slots. We can also get back our analog signal by demodulation. Amplitude modulation early radio ee 442 spring semester.

Pulse modulation, october 1960 popular electronics rf cafe. Analog modulation delas with the voice, video and regular waves of base band signals. Basic concept of modulation the information source typically a low frequency signal referred to as the baseband signal carrier a higher frequency sinusoid example. Pdf analog communication system pdf notes ac notes sw. All about modulation basic concepts, signal space, constellations and phase shift keying modulations psk, qpsk, oqpsk, mpsk. Pulse amplitude modulation an overview sciencedirect. Modulation is the process of changing the characteristics of the carrier signal in accordance with the instantaneous values of the modulating signal message signal. 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 analog modulation techniques are mainly classified into pulse amplitude. Before we study in detail about pam lets know the concepts of modulation. There are several types of modulation according to the nature. The waveforms, definition and basic concepts of each digital modulation techniques are discussed here. Pulse width modulated pwm drives rockwell automation.

Sampling is common in all pulse modulation techniques. Sampling theorem and pulse amplitude modulation pam. For a better quality and efficient communication, digital modulation technique. Modulationtypesamplitude,frequency,phase modulation. The impulse response is h t pt t the output of the low pass. The basic types of modulation are angular mo dulation including the special cases of phase and frequency modulation and amplitude modulation. Pulseamplitude modulation pam, is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses. 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. Percentage modulation, %m m100 v m v c 100 the percentage modulation lies between 0 and 80%. A signal is pulse code modulated to convert its analog information into a binary sequence, i. There are many modulation techniques, which are classified according to the type of modulation employed. Pulse amplitude modulation pulse code modulation sampling. The nice thing about a pulse is that theres another.

In this article we will see an introduction of pulse width modulation. 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. Channels, modulation, and demodulation of binary pam where the basic pulse shape pt is a sinc function. The following safety and common symbols may be used in this manual and on.

Analog and digital pulse modulation techniques gate study. 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. It is designed for highfrequency operation and has a low. A pulsecode modulation pcm system, as shown in figure 5. This sampled variable amplitude pulse is then digitalized by the analog to digital converter. When we modulate a carrier wave, we ordinarily alter its amplitude am, its frequency fm, or its phase pm. Analog communication pulse modulation tutorialspoint. Sampling theorem and pulse amplitude modulation pam reference stremler, communication systems, chapter 3. The analog pulse modulation is again classified as, 1. Modulation techniques pwm and pulse code modulation. Pulse amplitude modulation is categorized into two types. What is different in ppm is that ppm uses pulse positions to carry information. Pulse modulation communications university of toronto. Another basic concept in pulse modulation is the modulation itself.

Or modulation is defined as the precess by which some characteristics, usually amplitude, frequency or phase, of a carrier is varied in. All about modulation part i basic concepts, signal space, constellations and phase shift keying modulations psk, qpsk, oqpsk, mpsk. Its main features can be summarized as sinetriangle wave comparison. Sampling theorem determines the necessary conditions which allow us to change an analog signal to a discrete one. The pulse code modulator technique samples the input signal xt at a sampling frequency. Pulse amplitude modulation is the basic form of pulse modulation.

Demodulation is the opposite process of modulation. The output of a pcm will resemble a binary sequence. Analog communication pulse modulation after continuous wave modulation, the next division is pulse modulation. Pulse code modulation is a technique, which is used to convert an analog signal into digital signal. Of them all, the digital modulation technique used is pulse code modulation pcm. This way pulse time modulation can be classified into three types. Pcm is the preferred method of communication within the public switched telephone network pstn. Where as digital modulations are with bit streams or symbols from computing vevices as base band signals. In pulse width modulation, there are different types of modulation for analog and digital as shown below. Modulation is broadly classified into two categories namely analog modulation a. Pulse code modulation an overview sciencedirect topics. Therefore, analog modulation includes am, fm and pm and these are more sensitive to noise.

The pulse amplitude modulation is the modulation of signals by. We use modulation technique to alter signals in time and frequency to accomplish desired objectives. So now lets discuss different types of pulse modulation techniques in detailpulse modulation can be categorized broadly into two types. In this chapter, let us discuss the following analog pulse modulation techniques. 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. There are three types of pulse width modulation pwm. Pdf generation of pulse width modulation pwm signals. The second class of digital modulation format is called multilevel signaling formats.