Modulation techniques pwm and pulse code modulation. Where as digital modulations are with bit streams or symbols from computing vevices as base band signals. Reduced distortion and improvement in signal to noise ratios. 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. Before starting the topic, it is important to understand the basic difference between continuous wave modulation and pulse modulation. Here you can download the free lecture notes of analog communication system pdf notes ac notes pdf materials with multiple file links to download. Ti precision designs are analog solutions created by tis analog experts. After continuous wave modulation, the next division is pulse modulation. The microcontroller is the most efficient tool for generating various pulse width modulation techniques. The am and fm radios are examples of analog data over analog medium. We use modulation technique to alter signals in time and frequency to accomplish desired objectives. Modulation techniques are roughly divided into four types.
In fm, the amplitude of the modulating carrier is kept constant while its frequency is varied by the modulating message signal. Pam is pulse modulation system in which the signal is sampled at regular intervals and each sample is made proportional to amplitude of signal at instant of sampling pamfm demodulation pam. Digital signals pcm pulse code modulation based on the nyquists sampling theorem. Pulse amplitude modulation is the simplest form of modulation. The original waveform amplitude is quantized with a resulting loss of information. Goal of modulation techniques lmodulation is difficult task given the hostile mobile radio channels lsmallscale fading and multipath conditions. 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. What is the difference between pulseamplitude modulation. Modulation is the process by which we map information on to a carrier. In analog modulation, the modulation is applied continuously in. The application of the heterodyne principle to modulation is shown schematically in figure 143. Digital modulation involves transmission of binary signals 0 and 1. The analog signal is represented by a series of pulses and nonpulses. Pdf analog communication system pdf notes ac notes sw.
The changes in the carrier signal are chosen from a finite number of m alternative symbols the modulation alphabet. Ee4512 analog and digital communications chapter 3 chapter 3 digital baseband modulation techniques goals in communication system design pages 7576. 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. So now lets discuss different types of pulse modulation techniques in detailpulse modulation can be categorized broadly into two types.
Pwm pulse width modulation apwm analog pulse width modulation dpwm digital pulse width modulation fpga fieldprogrammable gate array msb most significant bit lsb least significant bit v volts. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. Common digital modulation techniques and pulse modulation methods. Usually high frequency sine wave is used as a carrier wave signal. In analog modulation, analog signal sinusoidal signal is used as a carrier signal that modulates the message signal or data signal. Digital modulation methods can be considered as digitaltoanalog conversion and the corresponding demodulation or detection as analogtodigital conversion. Sep 30, 2017 this ezed video explains modulation techniques types of modulation analog modulation digital modulation analog modulation amplitude modulation frequency modulation phase modulation. Lpf pulse time modulation ptm in this sample amplitude is kept. Prior to discussing further about the different types of modulation techniques, let us. Rectangular pulse amplitude modulation pam analog comparator token 5 removes the uneven output signal level. Frequency modulation fm is the most popular analog modulation technique used in mobile communications systems. Pulse code modulation pcm was pioneered by the british engineer alec reeves in 1937.
The pulse may take any real voltage value that is proportional to the value of the original waveform. Murat torlak introduction in a digital communication system, the source to be transmitted is discrete both in time and amplitude digital information carrying signals must be first converted to an analog waveform prior to transmission. Analog digital modulation lanalog modulation l the input is continues signal l used in first generation mobile radio systems such as amps in usa. The process of varying any of the three characteristics as the amplitude, frequency or the phase of a carrier signal is called as modulation we know that the information signal to be transmitted can be of any form such as data, music, video etc. Hence pulse shaping techniques are used to reduce isi and spectral bw. 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. Ee4512 analog and digital communications chapter 3 rectangular pulse amplitude modulation pam. Pulsecode modulation pcm is a method used to digitally represent sampled analog signals. Types of analog pulse modulation systems are options.
Analog communications 2 outline baseband communication. These are not modulation schemes in the conventional sense since they are not channel coding schemes, but should be considered as source coding schemes, and in some cases analog todigital conversion techniques. Since pcm is a very complex technique, other techniques have been developed to reduce the. Analog modulation, digital modulation, pulse modulation, and spread spectrum method. Pulse code modulation is the heart of technology in communications in todays digital world.
There are two types of modulation analog and digital. Digital modulation can then be defined as the process. Pulse amplitude modulation pam theory of and its applications. These modulation techniques are classified into two major types. Digital modulation relies on digital signal processing, such as digitaltoanalog converters dacs at a receiver and analogtodigital converters adcs at a transmitter to transform analog information e. In this chapter, let us discuss the following analog pulse modulation techniques. Modulation, analog modulation, digital modulation, am,fm,pm. Pulse amplitude modulation the pulse amplitude modulated signal, will follow the amplitude of the original signal, as the signal traces out the path of the whole wave.
Analog communication pdf notes book starts with the topics covering introduction ac, dsb modulation, ssb modulation, angle modulation concepts, angle modulation methods, noise etc. Oct 03, 2017 pulse modulation techniques in this post, i will discuss different kinds of pulse modulation techniques. Oct 03, 2011 this is a ppt for pulse modulation for final year ej diploma. In pulse width modulation or pulse duration modulation, the width of the pulse carrier is varied in accordance with the sample values of message. Digital modulation is the process by which a sequence of pulses message of duration t is transformed into a sequence of sinusoidal waveforms, st of duration t. This ezed video explains modulation techniques types of modulation analog modulation digital modulation analog modulation amplitude modulation frequency modulation phase modulation. Pulse code modulation is the heart of technology in communications in todays. In pulse amplitude modulation pam technique, the amplitude of the pulse carrier varies, which is proportional to the instantaneous amplitude of the message signal. This carrier wave can be dc or ac or pulse chain depending on the application used. Its a process in which analog signals are converted to digital form.
As the resultant signal is a coded pulse train, this is called as pulse code modulation. Most pwm systems do not allow for 0% or 100% modulation because the output would be dc and may damage other components in the signal path. Additional info pulse wave modulation pam, pwm, ppm do not convert baseband msg signal to bandpass, whereas continuos wave modulation am, fm, pm converts baseband into bandpass msg signal. Pulse amplitude modulation pam pulse width modulation pwm and pulse depth modulation pdm. Demodulation is the opposite process of modulation. Pulseamplitude modulation pam pulsewidth modulation pwm pulseposition modulation ppm. Linear modulation one scheme is to simply square the received dsb signal x2 r.
In general when we talk about a digital system, we are usually talking about digital information over an analog medium. In this project, we have generated ten different types of pulse width modulation techniques for inverters. Sampling is common in all pulse modulation techniques. Digital information can be generated from a computer but the information source can also be analog, as its the case of the voice. In pulse modulation systems, the carrier is a train of pulses rather than a continuous signal. Pulse amplitude modulation is the basic form of pulse modulation. Analog and digital pulse modulation techniques need. Pulse duration modulation pdm or pulse width modulation pwm. Ee4512 analog and digital communications chapter 6 the dsbsc am coherent receiver has a bandpass filter centered at f c and with a bandwidth of twice the bandwidth of st because of the lsb and usb. Modulation definition need for modulation types of.
The first transmission of a message using pcm was in 1943 during the world war ii. The digitization of the analog signal is done by the encoder. In digital modulation, an analog carrier signal is modulated by a discrete signal. Analog modulation is typically used for am, fm radio, and shortwave broadcasting. The pulse code modulation is the method of converting an analog signal into a digital signal i. The analog modulation techniques are mainly classified into pulse amplitude modulation, pulse duration modulation pulse width modulation, and pulse position modulation. The general function sinusoidal waves is shown in the figure below, in which, three parameters can be altered to get modulation they are amplitude, frequency and phase. Jul 30, 2019 in analog modulation, analog signal sinusoidal signal is used as a carrier signal that modulates the message signal or data signal. Modulation is the process of changing the characteristics of the carrier signal in accordance with the instantaneous values of the modulating signal message signal. These are not modulation schemes in the conventional sense since they are not. Amplitude and phase can be modulated simultaneously and separately.
In digital modulation, the modulation technique used is pulse code modulation pcm. Analog modulation delas with the voice, video and regular waves of base band signals. Common digital modulation techniques and pulse modulation. Modulation is the process of converting data into electrical signals optimized for transmission. Chapter 6modulation techniques shandong university. Modulation, analog modulation, digital modulation, am,fm. Ee4512 analog and digital communications chapter 6 the analytical signal for double sideband, large carrier amplitude modulation dsblc am is. Analog data digital data digital signal encoding and. It is analog to digital conversion method where the message information is encoded in the amplitude of the series of signal pulses. Different types of modulation techniques in communication systems. Pulse amplitude modulation pam pulse width modulation pwm pulse position modulation ppm.
Pulse coded modulation pcm is a form of modulation where there is no carrier, so that makes it a pure digital system. 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. Analog communications 23 quadrature amplitude modulation with amplitude modulation. Analog communication pulse modulation tutorialspoint.
Many signals in modern communication systems are digital also, analog signals are transmitted digitally. Punjab edusat society sampling analog signal is sampled every ts secs. 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. In pulse amplitude modulation pam technique, the amplitude of the pulse carrier varies, which is proportional. In cw modulation schemes some parameter of modulated wave varies.
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