Modulation and demodulation does not catch any channel noise. Those light waves may be sent through a transparent medium as a laser beam, or contained within a fiber optic cable. Modulation is the process of superimposing a low frequency signal on a high frequency carrier signal. A demodulator is an electronic circuit that is mainly used to recover the information content from the modulated carrier wave. 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. Digital modulation and power spectrum modulation is the process whereby message information is embedded into the radio frequency carrier. At time t1, the amplitude of mt increases from zero to e1. Request pdf generalized carrier based pulse width modulation technique for a three to n phase dual matrix converter this paper presents a novel topology for a dual three to phase direct matrix. These digital modulation techniques are discussed in our digital. Phase modulation pm changes only the phase of the signal. Phase modulation is similar to frequency modulation and is an important technique in digital communication systems. If we were to implement every possible combination of demodulation algorithm, carrierrecovery technique, and clock regeneration as a distinct model, the combinatorial explosion of different models would become unmanageable. Angle modulation is the process in which the frequency or the phase of the carrier varies according to the message signal.
Modulation schemes coherent and incoherent systems. This is further divided into frequency and phase modulation. So, for this reason, this modulation is also comes under the frequency modulation. Chapter 5 traditional analog modulation techniques mikael olofsson 20022007 modulation techniques are mainly used to transmit information in a given frequency band. In phase modulation of an analog signal, the phase change. However, they provide the benefit of higher data rates for the amount of bandwidth consumed. All these modulation types are analog modulation techniques. Carrier modulation and demodulation types of analog modulation technique i. Communications toolbox provides modulators and demodulators for these phase modulation techniques. An overview of prior art and recent approaches for phase modulation is presented in this paper. Modulation techniques are roughly divided into four types. Spectra have a typical trapezoidal shape in linear frequency and amplitude in decibels. The application of the heterodyne principle to modulation is shown schematically in figure 143.
After continuous wave modulation, the next division is pulse modulation. Therefore, at t1, the phase modulated carrier also changes corresponding to e1, as shown in figure a. Quadrature amplitude modulation with amplitude modulation. Phase modulation equation of phase modulation pm wave. In pulse amplitude modulation pam technique, the amplitude of the pulse carrier varies, which is proportional to the instantaneous amplitude of the message signal. Phase modulation is another type of angle modulation in which the phase of the carrier wave is changed according to the amplitude magnitude of the message modulating signal. Phase modulation pm phase shift keying psk digital modulation amplitude shift keying ask. Phase modulation is one of the two principal forms of angle modulation, together with frequency modulation the phase of a carrier signal is modulated to follow the changing. Practicing all modulation and demodulation tnpsc entrance exam questions and answers in online helps you to improve your ability to attend the real time maths, chemistry, physics entrance exams. Interference when two or more optical waves are present simultaneously. Quadrature amplitude modulation advantages and disadvantages quadrature amplitude modulation is a combination of simple amplitude modulation and simple phase modulation. As the resultant is a coded pulse train, this is called as pcm. Frequency modulation fm looks similar to phase modulation, though frequency is the controlled parameter, rather than relative phase. Fm signals have the same peak frequency deviation, then when mt is a sinusoidal signal set such that the pm and note.
Message information can be transmitted in either the amplitude, frequency, or phase of the carrier, or. We begin our discussion of digital modulation by starting with the three basic types of digital modulation techniques. Bandpass modulation and demodulation techniques communication systems, dept. Generalized carrier based pulse width modulation technique. The continuous analog signal st is a baseband signal with the information content voice or music to be transmitted. Both fm and pm are forms of angle modulation and are related by the transfer function of the modulating signal. Modulationtypesamplitude,frequency,phase modulation. Xpminduced phase modulation can be measured with phase sensitive techniques such as coherent detection which will be discussed in details in the following chapter. Phase modulation is defined as the process in which the instantaneous phase of the carrier signal is varied in accordance with the instantaneous amplitude of the modulating signal. Linear modulation one scheme is to simply square the received dsb signal x2 r. Amplitude and phase modulation can be used together. Measurements of phase noise and am noise are performed in thefrequency domain using a spectrum.
All communications toolbox demodulator functions, system objects and blocks can demodulate binary data using either hard decisions or soft decisions. Superheterodyne receiver modulation techniques youtube. Another way of expressing the modulation index is in terms of the maximum and minimum values of the amplitude of the modulated carrier wave. Depending upon the modulation techniques used, they are classified as shown in the following figure. It encodes a message signal as variations in the instantaneous phase of a carrier wave. Openloop phase modulation presents a viable solution for achieving widebandwidth operation.
Digital modulation in digital communications, the modulation process corresponds to switching or keying the amplitude, frequency, or phase of a sinusoidal carrier wave according to incoming digital data three basic digital modulation techniques amplitudeshift keying ask special case of. Modulation is the process of converting data into electrical signals optimized for transmission. Phase modulation is a linear baseband modulation technique in which the message modulates the phase of a constant amplitude signal. Modulation techniques lmodulation can be done by varying the l amplitude l phase, or l frequency of a high frequency carrier in accordance with the amplitude of the message signal. Where as digital modulations are with bit streams or symbols from computing vevices as base band signals. Signal is defined as the useful information which is sanded by the transmitter and received by the receiver. Modulation, analog modulation, digital modulation, am,fm. All about modulation basic concepts, signal space, constellations and phase shift keying modulations psk, qpsk, oqpsk, mpsk.
Reasons for choosing encoding techniques digital data, digital signal equipment less complex and expensive than digital toanalog modulation equipment. This allows for more data to transfer over the same. The two processes are closely related because phase cannot be changed. In phase 2, a compatible qpsk modulation scheme is used to achieve a similar data rate in a 6. Polar view of digital iq modulation contd transmission signal is sine wave at frequency f 0 with information encoded in discrete values of amplitude and phase. Optical modulation a tutorial introduction to optical modulation techniques by gary breed editorial director t his article introduces the subject of optical modulation, the process of applying information to a light wave. Other articles where phase modulation is discussed.
Analog modulation delas with the voice, video and regular waves of base band signals. Phase modulation the phase of a carrier wave is varied in response to the vibrations of the sound source in phase modulation pm. Or the process of modulation can be defined as varying the rf carrier wave in accordance with the intelligence or information in a low frequency signal. Phase noise is the term most widely used to describe the characteristic randomness of frequency stability. Principles of communication modulation tutorialspoint. Phase modulation is the basis for many digital modulation formats, in which a. Modulation efficiency an overview sciencedirect topics. 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.
There are two types of modulation analog and digital. Phase modulation is one of the two principal forms of angle modulation, together with frequency modulation the phase of a carrier signal is modulated to follow the changing signal level amplitude of the. Modulation techniques pwm and pulse code modulation. A tutorial introduction to optical modulation techniques. Analog modulation, digital modulation, pulse modulation, and spread spectrum method. Phase modulation and demodulation techniques are more complex than modulation and demodulation based on amplitude and frequency. This page on amplitude modulation am vs frequency modulation fm vs phase modulation pm describes difference between amplitude modulation,frequency modulation and phase modulation types. Phase modulation works by modulating the phase of the signal, i. Phase modulation has been of wide interest to industry be cause of its simplicity. In this type of modulation, the amplitude and frequency of the carrier signal remains unaltered after pm. Therefore we only consider the case where the message signal mtis a sinusoidal signal. If the frequency is varied, the phase will also be varied. Phase shift keying psk is a digital modulation process which conveys data by changing modulating the phase of a constant frequency reference signal the carrier wave. In this chapter, let us discuss the following analog pulse modulation techniques.
Besides, there is a fourth mechanism and better that combines changes in phase and amplitude and is called quadrature amplitude modulation qam. This changes the phase of the signal from what it would have been if no modulation was applied. In other words the speed of rotation around the circle is modulated about the mean value. Pdf openloop widebandwidth phase modulation techniques. Amplitude modulation quadrature amplitude modulation other modulation techniques. 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. All the modulation types are used to transmit information from one place to the distant place.
Phase modulation weichih wang southern taiwan university of technology. Digital phase modulation and demodulation request pdf. Understanding modern digital modulation techniques. The term spectral purity refers to the ratio of signal power to phase noise sideband power.
The terms coherent and incoherent are frequently used when discussing the generation and reception of digital modulation. Pdf photonic measurement of microwave frequency based on. Complex modulation may be achieved by imposing multiple modulation techniques on a single carrier, as in quadriture phase shift key amplitude modulation qpskam and the use of the fm carrier for both the fm modulation and the subsidiary communication authorization sca modulation, or by using a. Phase shift discriminator quadrature detector very common in tv receivers it uses a phase shift circuit it converts the instantaneous frequency deviation in an fm signal to phase shift and then detects the changes of phase cs results in 90 deg. In tro duction the purp ose of analog mo dulation is to impress an informationb earing analog w a v eform on to a carrier for transmission. Chapter 6modulation techniques shandong university. Amplitudeshift keying ask frequencyshift keying fsk phase shift keying psk all of these techniques vary a parameter of a sinusoid to represent the information which we wish to send. Generally, phase modulation is used for transmitting waves. We shall focus more on frequency modulation in this course and less on phase modulation.
Amplitude modulation am frequency modulation fm phase modulation pm click on the links given above to know more. Pm is used for signal and waveform generation in digital synthesizers, such as the yamaha dx7, to implement fm synthesis. Qam is the most efficient of these options and is the mechanism used in all modern modems. Jan 18, 2017 i think the spelling need to be checked,as ppt hasnt a meaning, anyhow, modulation means to include a certain message from any type into another transmitted carrier signal, including it has three types,am,fm, and pm pm is phase modulation wh. Each symbol represents n bits, and has m signal states, where m 2n.
Phase modulation advantages and disadvantages phase. When linked to the process of modulation the term coherence relates to the ability of the modulator to control the phase of the signal, not just the frequency. Pm and digital modulation s p where 2 is the pkpk phase change in one symbol duration, t for digital signals the modulation index. Photonic measurement of microwave frequency based on phase modulation article pdf available in optics express 179. Phase modulation pm is a modulation pattern for conditioning communication signals for transmission. Modulation for analog communication yao wang, 2006 ee3414. Phase noise and am noise measurements in the frequency. Modulation, analog modulation, digital modulation, am,fm,pm. The types of modulations are broadly classified into continuouswave modulation and pulse modulation. Amplitude modulation l, in which the carrier frequency is near baseband. The modulation concept, baseband signal, bandpass signal, message signal, carrier signal, modulated signal, modulation, types of modulation, amplitude modulation am, angle modulation, frequency modulation fm, phase modulation pm. Amplitude shift modulation ask, frequency shift modulation fsk and phase shift modulation psk.
Apr 21, 2015 ask fsk psk modulation digital modulation techniques amplitude, frequency and phase shift keying duration. But phase modulation seems to be in a different categorypm radio is by no means a common term. Phase modulation is widely used for transmitting radio waves and is an integral part of many digital transmission coding schemes that underlie a wide range of technologies like wifi, gsm and satellite television. In this type of modulation, the phase of the carrier signal varies in accordance with the message signal. In the continuouswave modulation, a high frequency sine wave is used as a carrier wave. When the phase of the signal is changed, then it affects the frequency. Frequency modulation will result in phase modulation if the signal is differentiated first.
Demodulation is the opposite process of modulation. If none of the three parameters is modulated, then the carrier is a simple sign wave, as show in the top diagram in figure 1, and carries no information. Demodulation is defined as extracting the original informationcarrying signal from a modulated carrier wave. Modulation and demodulation tnpsc questions and answers. The modulation is accomplished by varying the sine and cosine inputs at a precise time. Amplitude modulation of a sine or cosine carrier results in a variation of the. There are different types of modulation and so are demodulators. Phase modulation needs more complex receiving hardware because of its transition method which is a second disadvantage. Since the three variables are the amplitude, frequency, and phase angle, the modulation can be done by varying any one of them. The reason for that may be that the channel is bandlimited, or that we are assigned a certain frequency band and frequencies outside that band is supposed to be used by others. Related videos 1 modulation techniques block diagram types of modulation 2 amplitude modu. Or modulation is defined as the precess by which some characteristics, usually amplitude, frequency or phase. Analog modulation is typically used for am, fm radio, and shortwave broadcasting. Phase modulation free download as powerpoint presentation.
It is widely used for wireless lans, rfid and bluetooth communication any digital modulation scheme. This form of modulation is often considered a variation of fm. If the amplitude of message or modulating signal is huge then the phase shift will also be greater. But frequency modulation and phase modulation are closely related. Analog communication pulse modulation tutorialspoint. Aug 04, 2015 where s is the signal to be transmitted, a is the amplitude of the carrier. The other type of modulation in continuouswave modulation is the angle modulation. In the phase modulation, we vary the carrier signal in accordance with the phase of the modulating signal or message signal by keeping the frequency constant. We therefore assume mta mcos2 f mtfor pm and mta msim2 f mtfor fm.
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