This chapter discusses common types of modulation and their variants. It was the earliest modulation technique used to transmit voice by radio. In digital modulation, an analog carrier signal is modulated by a discrete signal. The two common forms of analog modulation are amplitude modulation. With tdoct, the signal passes through demodulation logarithmic amplifiers which compress the data and make the large snr signal more assessable. Pdf simulation of analog modulation and demodulation. To extend the range of sound, we need to transmit it through a medium other than air, such as a phone. 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. The usrp 2901 is used to design as fm transceiver with different frequencies 28. 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. 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. Where as digital modulations are with bit streams or symbols from computing vevices as base band signals. Pdf an analog method to modulate and demodulate signals is presented in this short paper. On the receiver end of an rfid device, i need a demodulator that can identify and demodulate ask.
The first step in the receiver will be demodulation of the received signal. This chapter describes the essential principles behind. Docsis cable modems use 64qam, 256qam for downstream channel to home and qpsk, 16qam for the upstream channel from home example 2. This type of modulation technique is used in electronic communication. 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. 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.
Signal demodulation an overview sciencedirect topics. Analog and digital modulation techniques assignment 1. Quadratureamplitude modulation qam applications qam rhymes with guam and vietnam is commonly used in communications example1. Three kinds of modulations modulation is the process of facilitating the transfer of information over a medium. The message signal or the modulating signal can either be analog or digital. Demodulation channel decoding is the corresponding process at the receiver of converting the received waveform into a.
Basic concepts of modulation three kinds of modulations modulation is the process of facilitating the transfer of information over a medium. This shout can be heard only up to a certain distance. Each channel sharing scheme a set of basis vectors. Demodulation, single sideband suppressed carrier ssbsc, double sideband. Frequency demodulation algorithms january 10, 2011 embedded staff. To extend the range your voice can reach, we need to. G document feedback information furnished by analog devices is believed to be accurate and reliable. The term detection is the older term dating back to the early days of radio. One approach to reduce this interference, known as frequencydivision multiplexing, allocates. Analog modulation delas with the voice, video and regular waves of base band signals. Principles of communication modulation a signal can be anything like a sound wave which comes out when you shout. Balanced modulator demodulator data sheet ad630 rev.
Modulation, analog modulation, digital modulation, am,fm. Digital modulation methods can be considered as digitaltoanalog conversion and the corresponding demodulation or detection as analogtodigital conversion. How to design a single demodulation circuit for ask, psk. Terms like diode detector, synchronous detector and product detector are widely used.
Sound transmission in air has limited range for the amount of power your lungs can generate. The changes in the carrier signal are chosen from a finite number of m alternative symbols the modulation. It explores the spectral effects of modulation and explains why certain types of modulation are used in differing situations. 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. Dutton ee3 winter 2004 1 ee3 lab 1 amplitude modulation and demodulation 1 lab notes a word about power. 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. 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. Pulse shaping enables successful demodulation at the receiver side. How to design a single demodulation circuit for ask, psk and fsk. The simulation of analog modulation and demodulation schemes in virtual instrumentation are explained in 29.
There are two types of modulation analog and digital. Carrier modulation allows the transmission of modulating frequencies without the use of transmission wire as a medium. Describe phase demodulation circuit operation for the peak, lowpass filter, and conversion detectors. Note that this is on the very low end of the recommended voltage range. Principles of communication modulation tutorialspoint. 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.
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. A modem is an equipment that performs both modulation and demodulation. The singlesided positive frequency axis spectrum of the modulated signal replicates the baseband spectrum as a doublesided spectrum about the carrier. Hapter modulation and demodulation mit opencourseware. Modulation and demodulation the telecommunications. The settings for the result summary can be defined individually for the different modulation types fm, am, pm. 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. But the term demodulation tends to be used more widely when referring to the process of extracting the modulation from the signal.
Both processes aim to achieve transfer information with the minimum distortion, minimum loss and. Telo, chapter 9, modulation, demodulation, signal sampling. Modulation and demodulation medium, it would be dif. Introduction in chapters 1 and 2 you studied how to apply intelligence modulation to an rfcarrier wave. Due to the frequency shifting property of analog multiplier, it can be used to implement each am modulator and demodulator lowpass. 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. 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. The chapter also explains, using mathematical notation, the operation of modulators and demodulators. Analog demodulation xseries measurement app, traditional ui. 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. The primary purpose of demodulation is to remove the carrier frequency doppler shift.
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