The two common forms of analog modulation are amplitude modulation. Telo, chapter 9, modulation, demodulation, signal sampling. Principles of communication modulation tutorialspoint. 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. Orthogonal frequency division multiplex ofdm and orthogonal frequency division multiple access ofdma are multiplexing and multiple access schemes, respectively, including a particular choice of pulse shape and modulation concept. This chapter describes the essential principles behind. The first step in the receiver will be demodulation of the received signal. The singlesided positive frequency axis spectrum of the modulated signal replicates the baseband spectrum as a doublesided spectrum about the carrier. Modulation and demodulation medium, it would be dif. This is an advantage over fdoct techniques, which are described in the next chapter. Digital modulation methods can be considered as digitaltoanalog conversion and the corresponding demodulation or detection as analogtodigital conversion.
Three kinds of modulations modulation is the process of facilitating the transfer of information over a medium. Carrier modulation allows the transmission of modulating frequencies without the use of transmission wire as a medium. But the term demodulation tends to be used more widely when referring to the process of extracting the modulation from the signal. It was the earliest modulation technique used to transmit voice by radio. Pdf simulation of analog modulation and demodulation. Each channel sharing scheme a set of basis vectors. Signal demodulation an overview sciencedirect topics. The simulation of analog modulation and demodulation schemes in virtual instrumentation are explained in 29. The message signal or the modulating signal can either be analog or digital. Introduction in chapters 1 and 2 you studied how to apply intelligence modulation to an rfcarrier wave. Describe phase demodulation circuit operation for the peak, lowpass filter, and conversion detectors. Analog modulation delas with the voice, video and regular waves of base band signals.
Balanced modulator demodulator data sheet ad630 rev. How to design a single demodulation circuit for ask, psk. Modulation and demodulation the telecommunications. Analog and digital modulation techniques assignment 1. Demodulation channel decoding is the corresponding process at the receiver of converting the received waveform into a. The changes in the carrier signal are chosen from a finite number of m alternative symbols the modulation. Basic concepts of modulation three kinds of modulations modulation is the process of facilitating the transfer of information over a medium. Principles of communication modulation a signal can be anything like a sound wave which comes out when you shout. The term detection is the older term dating back to the early days of radio. Hapter modulation and demodulation mit opencourseware. Modulation is the process of influencing data information on the carrier, while demodulation is the recovery of original information at the distant end from the carrier.
This type of modulation technique is used in electronic communication. This shout can be heard only up to a certain distance. This chapter discusses common types of modulation and their variants. The usrp 2901 is used to design as fm transceiver with different frequencies 28. Analog devices precision modulators and demodulators support balanced modulation and demodulation, synchronous detection, signal recovery, and a range of other applications in industrial, medical, and communications markets. To extend the range of sound, we need to transmit it through a medium other than air, such as a phone. Sound transmission in air has limited range for the amount of power your lungs can generate. In digital modulation, an analog carrier signal is modulated by a discrete signal. However, no responsibility is assumed by analog devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Pdf an analog method to modulate and demodulate signals is presented in this short paper. G document feedback information furnished by analog devices is believed to be accurate and reliable. How to design a single demodulation circuit for ask, psk and fsk.
Demodulation, single sideband suppressed carrier ssbsc, double sideband. Docsis cable modems use 64qam, 256qam for downstream channel to home and qpsk, 16qam for the upstream channel from home example 2. In this modulation, the amplitude of the carrier signal varies in accordance with the message signal, and other factors like phase and frequency remain constant. With tdoct, the signal passes through demodulation logarithmic amplifiers which compress the data and make the large snr signal more assessable. Due to the frequency shifting property of analog multiplier, it can be used to implement each am modulator and demodulator lowpass. A modem is an equipment that performs both modulation and demodulation. The chapter also explains, using mathematical notation, the operation of modulators and demodulators.
Where as digital modulations are with bit streams or symbols from computing vevices as base band signals. Quadratureamplitude modulation qam applications qam rhymes with guam and vietnam is commonly used in communications example1. The settings for the result summary can be defined individually for the different modulation types fm, am, pm. 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. On the receiver end of an rfid device, i need a demodulator that can identify and demodulate ask. Frequency demodulation algorithms january 10, 2011 embedded staff. Understand the principle of amplitude modulation know how to modulate a signal to a certain frequency know how to demodulate a signal back to the baseband can write the equation and draw block diagram for both modulation and demodulation can plot the signal spectrum after modulation and demodulation. The primary purpose of demodulation is to remove the carrier frequency doppler shift. Communication fundamentals envelope of a bandpass signal a signals gt is a bandpass signal if its fourier transform is nonnegligible only in a band of frequencies of total extent 2w centered about fc. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. Demodulation is the opposite process of modulation. Amplitude modulation is defined as the process in which the amplitude of the carrier wave ct is varied about a mean value, linearly with the baseband signal. One approach to reduce this interference, known as frequencydivision multiplexing, allocates. To extend the range your voice can reach, we need to.
Note that this is on the very low end of the recommended voltage range. Pulse shaping enables successful demodulation at the receiver side. Students will generate an ask signal using the switching method, recover the data using a simple envelope detector, and observe its distortion take online lab. Analog demodulation xseries measurement app, traditional ui. There are two types of modulation analog and digital. To understand the theoretical foundations of analog communications as well as of doublesideband amplitude modulation and demodulation dsbam to design the simulink model of the dsbam to analyze each signal in time and frequency domains using time scope and spectrum analyzer. Need of modulation and demodulation analog modulation and demodulation. It explores the spectral effects of modulation and explains why certain types of modulation are used in differing situations. Modulation, analog modulation, digital modulation, am,fm. Terms like diode detector, synchronous detector and product detector are widely used.
Dutton ee3 winter 2004 1 ee3 lab 1 amplitude modulation and demodulation 1 lab notes a word about power. Both processes aim to achieve transfer information with the minimum distortion, minimum loss and. Radio waves can carry audio, video, and digital information over great distances by using changes in a carrier waves amplitude, frequency, or phase to represent the information being transmitted. The main difference between modulation and demodulation is that the modulation is a process of varying one or more properties of a periodic waveform and demodulation is a process of extracting the original informationbearing signal from a carrier wave.
776 838 957 605 850 825 1148 897 472 598 404 554 318 418 798 931 452 483 1597 1200 1041 918 472 1264 95 17 74 1082 1594 1158 1606 369 491 906 1323 15 505 1474 122 772 544 15 217 1199 449 1439