Communication signal is modulated to the power signal with the backscatter modulation. 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. This chapter describes the essential principles behind modulation and demodulation, which we introduced briefly in chapter. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. On the contrary, demodulation is done in order to recover the original message signal from a modulated signal. Message power in st slide 6 powers in single tone case cont. Vectors and modulation cse 466 interfacing 3 spose m and n are orthogonal unit vectors. Pulsecode modulation pcm is a method used to digitally represent sampled analog signals.
Modulator vs demodulatordifference between modulator,demodulator. Phase modulation pm pm or phase modulation is the process of varying the instantaneous phase of carrier signal accordingly with instantaneous amplitude of message signal. Amplitude shift keying ask in the context of digital communications is a modulation process, which imparts to a sinusoid two or more discrete amplitude levels. Introduction frequency modulation is a form of modulation, which represents information. Using matlab m file and simulink to implement fm modulation and demodulation. An important consideration is the phase difference between the local oscillator and the carrier. Frequency modulation fm is a process in which the carrier frequency is varied by the amplitude of the modulating signal i. Althoughthereareanumberofwaysinwhicharadio signal may be modulated, one of the easiest is to change its amplitudeinlinewithvariationsofthesound. Based on your location, we recommend that you select. But if u use a stone or any other object to wind the paper, then the paper reaches more t. Pdf format this file type includes highresolution graphics and schematics when applicable. Difference between modulation and demodulation with. The principle of fsk modulation is to send binary data with two different frequencies and the resultant modulated signal is regarded as amplitude modulation am of different carrier frequencies. This is accomplished through modulation of radio signals.
In electronics and telecommunications, modulation is the process of varying one or more. The difference in the depth of modulation or ddm is used by instrument landing systems in conjunction with the associated airborne receiving equipment to define a position in airspace. Fsk modulation and demodulation technique file exchange. 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. Modulation indices are described for various forms of modulation. Demodulation is extracting the original informationbearing signal from a carrier wave. Amplitude modulation contents slide 1 amplitude modulation slide 2 the envelope and no overmodulation slide 3 example for single tone modulation slide 4 measuring the modulation index slide 5 transmitted vs. Matlab code for ask modulation and demodulation file. When input noise power is quite large we would be inclined to use fm and allows a sacrifice of bandwidth for the sake of improved output signaltonoise ratio. We can also get back our analog signal by demodulation. Describe phase demodulation circuit operation for the peak, lowpass filter, and conversion detectors. Modulation of a radio wave can be performed by varying one or more of its signal.
Difference between encoding and modulation compare the. Introduction to iq demodulation of rfdata september 15, 1999 page 3 of 1 introduction 1. Phase demodulation module consists of a circuit design and a digital design. Experiment 8 amplitude modulation, demodulation and signal. A demodulator is an electronic circuit or computer program in a softwaredefined radio that is used to recover the information content from the modulated carrier wave. Phase modulation pm is a different form of frequency modulation and the carrier is similar in appearance to a frequencymodulated carrier.
But the term demodulation tends to be used more widely when referring to the process of extracting the modulation from the signal. Choose a web site to get translated content where available and see local events and offers. Digital phase modulation and demodulation request pdf. The amplitude modulation, am, modulation index can be defined as the measure of extent of amplitude variation about an unmodulated carrier. Phase modulation and demodulation file exchange matlab. Thus it is amenable to demodulation by an envelope detector. Demodulation channel decoding is the corresponding process at the receiver of converting the received waveform into a. All about modulation part i basic concepts, signal space, constellations and phase shift keying modulations psk, qpsk, oqpsk, mpsk. Modulation and demodulation medium, it would be dif.
A demodulation that produces a scaled and delayed version of the original message is considered successful. 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. Frequency modulation fm frequency modulation is the process of varying the frequency of a carrier wave in proportion to the amplitude of a baseband signal. The signal output from a demodulator may represent sound an. Pulse code modulation is a method that is used to convert an analog signal into a digital signal so that a modified analog signal can be transmitted through the digital communication network. The amplitude of the carrier remains constant phase modulation pm another form of analog modulation technique which we will not discuss. Communication systemsamplitude modulation wikibooks. What is amplitude modulation in order that a radio signal can carry audio or other information for broadcasting or for two way radio communication,itmustbemodulatedorchangedinsome way. This demo gives the user sufficient freedom to vary the values of modulating and carrier signal amplitude and frequency.
What is the modulation index in amplitude modulation. Therefore, both fm and pm are often referred to as angle modulation. Then inner products dot products are 1 1 0 can interpret inner product as projection of vector 1 v1 onto vector 2 v2in other words, inner product of v1 and v2 tells us how much of vector 1 is there in the direction of vector 2. This page on modulator vs demodulator covers basics of modulator and demodulator and also mention difference between modulator and demodulator as we know in telecommunication, in order to send information to longer distance and to take care of high bit rate requirement of the system different modulation techniques. Terms like diode detector, synchronous detector and product detector are widely used. Theory shows that in order to transmit a wave effectively, the length of the. The difference between the modulation and demodulation is that modulation is to transfer the message signal by adding it with the carrier signal while demodulation is the process of filtering out the actual message signal from the carrier signal. Instrument landing system ground stations provide radio frequency signals that vary linearly in the depth of modulation from the. Basics of modulation and demodulation 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. Study the effect of phase difference between the modulation sinusoid and the demodulation sinusoid on the reconstructed signal. In this type of modulation scheme for twolevel pulses we always put out a pulse pt that is amplitude modulating a carrier frequency, whether the data digit is a 1 or a 0, but we distinguish between the two digits by using two slightly different carrier frequencies f1 and f 2.
Modulation allows us to transmit multiple signals in the same medium i. Study of am modulation and demodulation file exchange. In the usual development of data modulation techniques as presented in most communications. Modulation is the process of influencing data information on the carrier, while demodulation is. In fm modulation when the bandwidth becomes so large that the input noise power is relatively large, the performance of the fm system degrades rapidly and the system exhibits a threshold. Modulation and demodulation pdf on the various aspects of modulation and demodulation. Amplitude modulation is one of the earliest radio modulation techniques. Modulator vs demodulatordifference between modulator.
In addition to a variable bandpass filter, one auto notch and one manual notch filter can be utilized to eliminate interfering signals. These are related to the number of levels adopted by the digital message. Each channel sharing scheme a set of basis vectors. The term detection is the older term dating back to the early days of radio. The output signal via demodulator may describe the sound, images or binary data. Encoding is about converting digital or analog data to digital signal, whereas modulation is about converting digital or analog data to an analog signal. Circuit needed for fm modulation and demodulation is bit complicated than am. Modulation is the process of imposing data information on the carrier, while demodulation is the recovery of original information at the distant end from the carrier.
Ddm is usually expressed in percentage but may also be expressed in microamperes. The major difference between modulation and demodulation is that modulation is the act of altering the parameters of the carrier signal according to message signal for convenient data transmission. For example, the very lowspeed bell system 103 modem standard for 300. Modulation is about changing a signal, whereas encoding is about representing a signal. This page on modulator vs demodulator covers basics of modulator and demodulator and also mention difference between modulator and demodulator as we know in telecommunication, in order to send information to longer distance and to take care of high bit rate requirement of the system different modulation techniques are employed. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. Matlab code for fsk modulation and demodulation file.
The code of ask modulation and demodulation has been developed using matlab according to conventional theory. This article presents the problems which arise in implementation of a demodulation of this signal on an arm. First, just consider a simple example of throwing a paper for a much far distancecould u do that with ease. Pdf the modulation and demodulation module of a high.
Fm modulation and demodulation electrical and computer. What is the difference between encoding and modulation. A similar approach is then taken for developing models for multiple phase shift keying mpsk, minimum shift keying msk, and frequency shift. Pcm is in binary form, so there will be only two possible states high and low0 and 1. Insidepenton com electronic design adobe pdf logo tiny. The discussion then moves to binary phase shift keying bpsk and shows how this simpler format is modeled using the generic quadrature modulation models. 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. In this experiment, you will examine the characteristics of amplitude modulation am. Introduction in chapters 1 and 2 you studied how to apply intelligence modulation to an rfcarrier wave. The code of fsk modulation and demodulation has been developed using matlab according to conventional theory. Amplitude modulated am signal and four demodulation methods for fre quency. The goal of this experiment is to become familiar with fm modulation and demodulation. However, the only signal of real interest is the difference between the desired. This thesis reveals the pros and cons of five demodulation methods for.
There are many types of modulation so there are many types of demodulators. According to one definition of digital signal, the modulated signal is a digital. A modem is an equipment that performs both modulation and demodulation. Modulation, analog modulation, digital modulation, am,fm. Information can be sent from a transmitter to a receiver by means of modulation and demodulation, respectively, whether those signals are light waves moving through optical cables, radio waves through metallic cables, or radio. Carrier modulation allows the transmission of modulating frequencies without the use of transmission wire as a medium. One approach to reduce this interference, known as frequencydivision multiplexing, allocates different carrier frequencies to different users or for dif. Digital modulation and demodulation fsk,psk,bpsk,qpsk techniques.
The major difference between modulation and demodulation is that modulation is the act of altering the parameters of the carrier signal according to message. This is a matlab code for fsk modulation and demodulation scheme. Pdf a moems accelerometer with high precision based on grating. Modulation is the process of encoding information onto a carrier signal which has frequency fc. This carrier signal is called the modulated signal, while the information carrying, or baseband signal is referred to as the modulating signal. We will follow a common practice and offset the receivers oscillator frequency. Modem is the device that performs both modulation and demodulation. Difference between modulation and demodulation compare. Describe fm demodulation circuit operation for the phaseshift and gatedbeam discriminators and the ratiodetector demodulator. Accordingly it displays the time domain waveforms of both the signals. Frequency division multiplexing, fdma amplitude modulation and demodulation.
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