Glavieux a, thitimajshima p 2010 near shannon limit errorcorrecting pdf. Pulse code modulation is the heart of technology in communications in todays. Pdf implementation of analog modulation techniques using. Digital modulation relies on digital signal processing, such as digitalto analog converters dacs at a receiver and analog todigital converters adcs at a transmitter to transform analog information e. The changes in the carrier signal are chosen from a finite number of m alternative symbols the modulation alphabet. Frequency modulation fm is the most popular analog modulation technique used in mobile communications systems. Complete notes download link ac notes analog communication pdf free download unit i introduction. Modulation of analog data 2 why analog to analog modulation. Pulse coded modulation pcm is a form of modulation where there is no carrier, so.
Therefore, dm techniques have a huge demand due to their capacity for communicating superior amounts of information than am analog modulation techniques. This set of data communication and networking multiple choice questions and answers mcqs focuses on digital to analog to encoding modulation techniques amplitudeshift keying ask frequencyshift keying fsk phaseshift keying psk quadrature amplitude modulation qam. In pulse width modulation, there are different types of modulation for analog and digital as shown below. 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. The am modulation level of the rf carrier can be directly related to the power supply ripple by.
Pdf analog communication system pdf notes ac notes sw. Because of these relationships the pdf of the envelope is rayleigh. Hence info is carried in the phase or frequency of the carrier. This chapter describes the essential principles behind. Am and frequency modulation fm which is specific form of more general angle.
Preface progress in telecommunications over the past two decades has been nothing short of revolutionary, with communications taken for granted in modern society to the same extent as electricity. Analog to analog conversion analog to analog conversion, or modulation, is the representation of analog information by an analog signal. Analog communications 26 other modulation methods amplitude modulation the amplitude of the carrier signal is controlled by the modulating signal pitfall of am. The baseband power spectral density psd spectrum of the information signal st or sf for voice has significant components below 500 hz and a bandwidth of. Ds adcs are now ideal for converting analog signals. Chapter 6modulation techniques shandong university. Pradeep kshetrapal, tutorials point india private limited. Amplitude and phase can be modulated simultaneously and separately. We will get the percentage of modulation, just by multiplying the modulation index value with 100. Modulation avoids any interference between the two signals and also ensures that signal errors are avoided during transmission. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. The am and fm radios are examples of analog data over analog medium.
The digitization of the analog signal is done by the encoder. As the resultant is a coded pulse train, this is called as pcm. The first transmission of a message using pcm was in 1943 during the world war ii. Introduction to communication system, need for modulation, frequency division multiplexing, amplitude modulation.
Modulation, analog modulation, digital modulation, am,fm. For a perfect modulation, the value of modulation index should be 1, which implies the percentage of modulation should be 100%. Modern mobile communication systems use digital modulation techniques. Analog to analog conversion, or analog modulation, is the representation of analog information by an analog signal. 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. Amplitude modulation of a signal can be written as. 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. A single resistor, rset, programs the ltc6992s internal master oscillator frequency. In general when we talk about a digital system, we are usually talking about digital information over an analog medium. The modulation index or modulation depth is often denoted in percentage called as percentage of modulation.
Modulation is needed if the medium is bandpass in nature or if only a bandpass channel is available to us. 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. Analog to analog conversion techniques myreadingroom. The two common forms of analog modulation are amplitude modulation. The modulation signal influences the phase of the carrier. This ezed video explains modulation techniques types of modulation analog modulation digital modulation analog modulation amplitude modulation frequency modulation phase modulation. When we take the pulse digital modulation, we use a periodic sequence of rectangular pulses as the carrier signal. Amplitude modulation, normally abbreviated am, was the first modulation. Analog and digital modulation techniques assignment 1.
Chapter 6 principles of analog modulation analog and. The output frequency is determined by this master oscillator. Frequency modulation the frequency of the carrier signal is proportional to the modulating. The design of deltasigma ds analog todigital converters adcs is approximately threequarters digital and onequarter analog. Modulation techniques pwm and pulse code modulation. Digital modulation methods can be considered as digitalto analog conversion and the corresponding demodulation or detection as analog todigital conversion.
After each sample is quantized and the number of bits per sample is decided, each sample can be changed to an n bit code. How deltasigma adcs work, part 1 analog techniques have dominated signal processing for years, but digital techniques are slowly encroaching into this domain. Digital modulation dm gives more capacity of data, high information security, and accessibility of a faster system by enormous quality communication. We are all familiar with the common analog modulation techniques of amplitude modulation am and frequency modulation fm. We use modulation technique to alter signals in time and frequency to accomplish desired objectives. Digital modulation in somewhat similar to the analog modulation except base band signal is of discrete amplitude level. Pulse code modulation pcm was pioneered by the british engineer alec reeves in 1937.
It may come as a surprise for us to realise that the first modulation of. 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 amplitude modulation component mt can be written as. This paper discusses modulation techniques with the labviewbased rf communications package, developed for. Analog modulation uses mainly am amplitude and fm frequency modulations. An analog method to modulate and demodulate signals is presented in this short paper. Analog to analog conversion modulation geeksforgeeks. Types of modulation 6 flynnkatz 7810 analog modulation amplitude modulation, am frequency modulation, fm double and single sideband, dsb and ssb digital modulation phase shift keying.
An analog signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity i. Pdf simulation of analog modulation and demodulation. 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. Chapter 5 traditional analog modulation techniques commsys. Chapter 6 principles of analog modulation chapter outline 6.
Bandpass noise referring to the communication system diagram below, xt. The ltc6992 is a silicon oscillator with an easytouse analog voltagecontrolled pulse width modulation pwm capability. Pulse digital modulation is also used in both analog and digital communications. In digital modulation, an analog carrier signal is modulated by a discrete signal. Pdf on jul 1, 2017, vidyarani k r and others published implementation of analog modulation techniques using tms320c6748 and. Modulation, analog modulation, digital modulation, am,fm,pm, ask. Since pcm is a very complex technique, other techniques have been developed to reduce the. The government assigns a narrow bandwidth to each radio station. Digital to analog encoding modulation techniques ask. In analog modulation, analog signal sinusoidal signal is used as a carrier signal that modulates the message signal or data signal. In fm, the amplitude of the modulating carrier is kept constant while its frequency is varied by the modulating message signal. Modulation, analog modulation, digital modulation, amplitude, frequency, phase modulation, digital amplitute, frequency, phase shift keying, analog modulation. Modulation l frequency modulation fm l most popular analog modulation technique l amplitude of the carrier signal is kept constant constant envelope signal, the frequency of carrier is changed according to the amplitude of the modulating message signal. Analog and digital modulation refers to how a carrier signal is modified in order to transmit information.
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