Chapter 6modulation techniques shandong university. 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. 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. By varying the amplitude of the pulses the carrier signal in proportion to the instantaneous values of the analog. Pulse digital modulation is also used in both analog and digital communications. Pulse amplitude modulation pam theory of and its applications. Digitaltoanalog conversion of pulse amplitude modulated. Pulse code modulation pcm now we will discuss the digital form of pulse modulation technique. Many long distance facilities, particularly of the analog variety. Oct 03, 2011 this is a ppt for pulse modulation for final year ej diploma slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Pulse width modulation pwm technology benefits of deltas advance pwm control.
Jan 10, 2011 analog pulse modulation digital pulse modulation pulse amplitude pam pulse width pwm pulse position ppm pulse code pcm delta dm pulse modulation pulse amplitude modulation pam. Modulation, analog modulation, digital modulation, am,fm,pm. The main difference between analog and digital modulation is that an analog modulated signal can take up any value in a possible range whereas a digitally modulated signal can only take up one of a discrete set of values. 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. Using pwm to dim a lamp would produce less heat than an analog control that converts some of the current to heat. Although ptm has many advantages over analogue and. Calculate the pulse width of each bit to support the multiplex of these 20 signals. Pdf analog communication system pdf notes ac notes sw. However, it is the first step in another very popular conversion method called pulse code modulation. The signal is sampled at regular intervals such that each sample is proportional to the amplitude of the signal at that sampling instant. The output frequency is determined by this master oscillator. As the resultant is a coded pulse train, this is called as pcm. Reduced distortion and improvement in signal to noise ratios. Digital pulse width modulation dpwm provides a digital to time domain conversion.
In this chapter, let us discuss the following analog pulse modulation techniques. Sampling theorem and pulse amplitude modulation pam. Pulse modulation definition is modulation of a radio wave or signal by pulses. Analog and digital pulse modulation techniques gate study. Analog todigital converter analog signal mt analog samples pcm digital encoded signal. In general when we talk about a digital system, we are usually talking about digital information over an analog medium. A technique by which analog signal gets converted into digital form in order to have signal transmission through a digital network is known as pulse code modulation. It is basically signal coders also known as waveform coders. Analog and digital pulse modulation techniques need. 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. The same filter will do better on a low or high duty cycle pulse compared to a 50% duty cycle pulse. Pwm is employed in a wide variety of applications, ranging from measurement and communications to power control and conversion. Ee4512 analog and digital communications chapter 6 the analytical signal for double sideband, large carrier amplitude modulation dsblc am is. In amplitude modulation, the amplitude of the carrier signal changes instantaneously with respect to the amplitude of the modulating signal.
Pulse code modulation is a technique to convert analog signals into digital signals. Pulse amplitude modulation pulse code modulation sampling. Modulation is the process of changing the characteristics of the carrier signal in accordance with the instantaneous values of the modulating signal message signal. Aug 28, 2015 when we take the pulse digital modulation, we use a periodic sequence of rectangular pulses as the carrier signal.
The principle and design of a costeffective optical fiber communication system are proposed to support hybrid digital analog signal transmissions, by simultaneously using pulse width modulation. Complete notes download link ac notes analog communication pdf free download unit i introduction. Pulse width modulation pwm technique becomes popular and uses in many analog electronic devices and also in power electronics. Amplitude modulation is a type of analog modulation in which the amplitude of the highfrequency carrier signal is changing with respect to the instantaneous amplitude of the modulating signal. Pulse code modulation is the heart of technology in communications in todays. Pulse coded modulation pcm is a form of modulation where there is no carrier, so. Modulation, analog modulation, digital modulation, am,fm. Pwm is the poor mans digitalto analog converter dac. Because the wider pulse has more time to integrate to a stable filter voltage and the smaller pulse has less time to disturb it. The first transmission of a message using pcm was in 1943 during the world war ii. In this post, we are going to learn working, application, and advantages of the pulse width.
Modulation techniques pwm and pulse code modulation. The significant characteristics of a pulse are pulse amplitude, pulse duration or pulse width, and pulse position denoting the time of the rise or the fall of the pulse amplitude. Advance soft switching control available on certain models wide pwm frequency input range 30hz30khz flexible speed control prevent current spikes low switching noise low vibration high power efficiency web. These instances correspond to having analog channels that require the transmitted signal to be continuous in time, and to also be compatible with the bandwidth. Introduction pulse amplitude modulation pam is a common transmission method used for digital communications. 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. If you continue browsing the site, you agree to the use of cookies on this website. Pulse width modulation sensors raspberry pi python pwm control shaft encoders ultrasonic sensors v to f and f to v converters.
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. Also, if you use pwm, the entire control circuit can be digital, eliminating the need for digitalto analog converters. 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.
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. Modulation techniques for mobile radio school of information science and engineering, sdu. When we take the pulse digital modulation, we use a periodic sequence of rectangular pulses as the carrier signal. In analog pulse modulation some parameter of each pulse. Pulse code modulation pcm was pioneered by the british engineer alec reeves in 1937. Sep 28, 2015 analog and digital modulation refers to how a carrier signal is modified in order to transmit information. Terry sturtevant electronics pulse width modulation sensors. 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.
Pulse amplitude modulation pam, quadrature amplitude modulation qam 12. Varying the amplitude, polarity, presence or absence, duration, or occurrence in time of the pulses gives rise to the four basic forms of pulse modulation. Pulse position modulation ppm is an analog modulation scheme where, the amplitude and the width of the pulses are kept constant, while the position of each pulse, and also the reference to the position of a reference pulse varies according to the instantaneous sampled value of the message signal. The ltc6992 is a silicon oscillator with an easytouse analog voltagecontrolled pulse width modulation pwm capability. How to represent an analog signal as digital pulses the foundations of pulse code modulation pcm. In pulseamplitude modulation pam a pulse signal is used to sample an analog signal.
In cw modulation schemes some parameter of modulated wave varies continuously with message. Jan 19, 2011 how to represent an analog signal as digital pulses the foundations of pulse code modulation pcm. Many signals in modern communication systems are digital also, analog signals are transmitted digitally. The microcontroller is the most efficient tool for generating various pulse width modulation techniques. Sampling theorem and pulse amplitude modulation pam reference stremler, communication systems, chapter 3.
Analog todigital converter analog signal mt analog samples. Analog communication pulse modulation in analog communication. The time is quantized into number of discrete slots and is selected by a. Before going to discuss the difference between pam, pwm, and ppm, let us discuss individually each. Pulse code modulation pcm is a method used to digitally represent sampled analog signals. Pulse modulation and pulse modulation techniques like pulse amplitude modulation pam, pulse width modulation pwm, pulse position modulation ppm and pulse. If the negative symbol is transmitted, the pdf for z will be as sketched below. Pulse modulation communications university of toronto. Jul 05, 2016 digital information can be generated from a computer but the information source can also be analog, as its the case of the voice.
Pam systems operate by passing informationbearing pulses through pulse. These digital modulation techniques are discussed in our digital. Analog communication of analog signals is done using continuous wave. Analog communications 26 other modulation methods amplitude modulation the amplitude of the carrier signal is controlled by the modulating signal pitfall of am. Demodulation channel decoding is the corresponding process at the receiver of converting the received waveform into a.
Using pulse width modulation has several advantages over analog control. The only thing that hasnt changed in all of this is the high voltage level, because on is always the same for the digital output. Pulse width modulation sensors analog information can be communicated over digital signals. Introduction to communication system, need for modulation, frequency division multiplexing, amplitude modulation. Pdf introduction to various signal modulation techniques to have effective transmission of signals and comparison among them find, read and cite all the. Digital modulation in somewhat similar to the analog modulation except base band signal is of discrete amplitude level. Pulse modulation accessscience from mcgrawhill education. Introducing pulse width modulation pwm what is pulse width modulation. It is the standard form of digital audio in computers, cds, digital telephony and other digital audio applications. Investigation of the pulse time modulation techniques for. Pdf analog,digital and pulse modulation techniques researchgate.
No information is lost, but the energy is redistributed in the frequency domain. A single resistor, rset, programs the ltc6992s internal master oscillator frequency. Digital information can be generated from a computer but the information source can also be analog, as its the case of the voice. In cw modulation schemes some parameter of modulated wave varies. Our study begins with the pulseamplitude modulation pam scheme. The amplitude of the analog signal is sampled at uniform intervals and each sample is quantized to its nearest. In analog pulse modulation some parameter of each pulse is modulated. Analog modulation refers to the process of transferring digital low frequency baseband signal, like digital bitstream from computers over a higher frequency carrier signal such as a radio frequency band. The time division multiplex system use pulse modulation. This form of pulse modulation technique is known as pulse code modulation pcm.
Pulse amplitude modulation is a technique in which the amplitude of each pulse is controlled by the instantaneous amplitude of the modulation signal. Sampling theorem determines the necessary conditions which allow us to change an analog signal to a discrete one. Frequency modulation the frequency of the carrier signal is proportional to the modulating. Pulse width modulation is a technique of creating modulated electronic pulses or the electronic pulses of the desired width. In this project, we have generated ten different types of pulse width modulation techniques for inverters. Pulse width modulation pwm is a simple method of using a rectangular digital waveform to control an analog variable pwm control is used in a variety of applications, ranging from communications to automatic control 3. More precisely, we consider analog pam where we wish to. Pulse amplitude modulation has some applications, but it is not used by itself in data communication. Next topic pulse code modulation pulsecode modulation pcm is used to digitally represent sampled analog signals. In analog modulation, analog signal sinusoidal signal is used as a carrier signal that modulates the message signal or data signal. We use modulation technique to alter signals in time and frequency to accomplish desired objectives. The am and fm radios are examples of analog data over analog medium. The radios are examples of analog data over analog medium.
The original waveform amplitude is quantized with a resulting loss of information. Pulse modulation definition of pulse modulation by merriam. Pulse width modulation pwm is a powerful technique for controlling analog circuits with a processors digital outputs. Cs 04 the basics of pulse code modulation pcm youtube. In digital modulation, the modulation technique used is pulse code modulation pcm where the analog signal is converted into digital form of 1s and 0s. It achieves this by rapidly toggling the pin from low to high. Some pulse modulation schemes also allow the narrowband analog signal to be transferred as a digital signal i. The ltc6992 is part of the timerblox family of versatile silicon timing devices.
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