Frequency modulation is used in different applications like radar, radio and telemetry, seismic prospecting. The two common forms of analog modulation are amplitude modulation. Design different modulators for amplitude modulation. In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal that typically contains information to be transmitted. Free space optical using different modulation techniques. This video lecture discusses different types of modulation techniques. Modulation is necessary in all of the above scenarios. Comparison of different modulation techniques for free. The message signal is, for example, a function of the sound to be reproduced by a. It is often called as am and is commonly used in transmitting a piece of information through a radio carrier wave. In both the techniques, the baseband information is converted to radio frequency signals, but in analog modulation these rf communication signals are continuous range of values, whereas in digital modulation these are prearranged discrete states. Analog modulation and demodulation amplitude modulation pages 306309.
Understanding modern digital modulation techniques. Freespace optical communication has gained a lot of popularity as an alternative to. Free space optical fso communication is the system of transmission of data using a wireless medium, which uses modulated near infrared light beams as carrier wave. The modulation technique aims at adapting the frequency band of the useful signal to. The idea is simple, though the notion that it can be used to modulate signals for transmission was hardly obvious before its discovery. The different types of modulation techniques can be classified into continuous. The analog modulation techniques are mainly classified into pulse amplitude modulation, pulse duration modulationpulse width modulation, and pulse position modulation. This type of modulation technique is used in electronic communication. One popular technique is quadrature amplitude modulation qam involves splitting the signal into eight different phases, and two different amplitude for a total of 16 different possible values, giving us lg16 or 4 bits per value. Pdf a comparative study of various digital modulation. Phase modulation pm changes only the phase of the signal. Mimo system for different modulation techniques using alamouti stbc coding and zf, mmse equalizer receivers r bhagya1, dr.
Additional info pulse wave modulation pam, pwm, ppm do not convert baseband msg signal to bandpass, whereas continuos wave modulation am, fm, pm converts baseband into bandpass msg signal. Chapter 7 amplitude modulation techniquesgeneration and. This ezed video explains modulation techniques types of modulation analog modulation digital modulation analog modulation amplitude modulation frequency modulation phase modulation. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. The different types of amplitude modulations include the following. It was the earliest modulation technique used to transmit voice by radio. When we take the pulse digital modulation, we use a periodic sequence of rectangular pulses as the carrier signal. Types of modulation techniques am, fm, pm, pam, pwm, ppm. Ee4512 analog and digital communications chapter 6 the analytical signal for double sideband, large carrier amplitude modulation dsblc am is.
Other methods of demodulating an am signal use synchronous techniques and provide. Includes both frequency modulation and phase modulation some have an amplitude modulation component bpsk qpsk offset qpsk some are constant envelope binary fm fsk, msk, premod filtered msk, gmsk mary fsk soqpsk multih continuous phase modulation no amplitude variation. Pulse digital modulation is also used in both analog and digital communications. Other feedback variables such as the shift in cantilever resonance frequency in frequencymodula tion afm or the phase shift in phase. The main difference between both modulations is that in frequency modulation, the frequency of the carrier wave is modified as per the transmit data, while in amplitude modulation, the carrier. Digital modulation and demodulation fsk,psk,bpsk,qpsk techniques. However, it is the first step for another popular conversion method called pulse coding modulation pcm. Amplitude and phase modulation can be used together. In this project, we have generated ten different types of pulse width modulation techniques for inverters. This principle is at the heart of amplitude modulation. Modulation techniques lmodulation can be done by varying the l amplitude l phase, or. 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.
Free propagation of signals requires it to posses considerable power. Therefore one performs modulation of signals where a characteristic of a high frequency signal called carrier is modified w. The modulated signal is shown in the below figure, and its spectrum consists of the lower frequency band, upper frequency band and carrier frequency components. Magnitude is represented as the distance from the center and phase is represented as the angle. In pulse width modulation, there are different types of modulation for analog and digital as shown below. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. These techniques all claim a degree of optimality and have been derived from basic. Chapter 7 amplitude modulation techniques generation and detection chapter outline 7. A sinusoid has three different parameters than can be varied. Amplitude modulation is a process by which the wave signal is transmitted by modulating the amplitude of the signal. The modulated signal at carrier frequency of fc can be constructed by. Modulation, analog modulation, digital modulation, am,fm.
Amplitude shift keying ask frequencyshift keying fsk phaseshift keying psk all of these techniques vary a parameter of a sinusoid to represent the information which we wish to send. As for the mechanism, when amplitude modulation is used there is a variation in the amplitude of the carrier. Quadrature amplitude modulation qam is a combination of ask and psk two different signals sent simultaneously on the same carrier frequency change phase. Modulation techniques for mobile radio school of information science and engineering, sdu. Qam is used in almost all digital communication methods, including telephone. Amplitude modulation with modulation factor 1 or 100%. Space modulation is a radio amplitude modulation technique used in instrument landing systems that incorporates the use of multiple antennas fed with various radio frequency powers and phases to create different depths of modulation within various volumes of threedimensional airspace. Amplitude modulation definition, types, solved examples. Amplitude modulation is mostly used in the form of electronic communication. 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. The output of a sampling circuit with a zeroorder hold zoh is one example of a pam signal.
Basic concept of modulation the information source typically a low frequency signal referred to as the baseband signal carrier a higher frequency sinusoid example. Different types of modulation techniques in communication. Pulse amplitude modulation pam has some applications, but it not used in itself for data transmission. Pulse amplitude modulation pam the actual amplitude of the pulse represents the number being transmitted. Pulse amplitude modulation pam is an analog modulating scheme in which the amplitude of the pulse carrier varies proportional to the instantaneous. Amplitude shift keying, quadrature amplitude modulation, inphase component. Outline l frequency versus amplitude modulation l amplitude modulation am l angle modulation ldigital modulation l line coding l pulse shaping techniques. Amplitude modulation am frequency modulation fm phase modulation pm amplitude modulation. Understand different types of amplitude modulation. In amplitude modulation or am, the carrier signal has its amplitude.
Research article study of transmission characteristics of. Hence, digital modulation techniques have a greater demand, for their capacity to convey larger amounts of data than analog modulation techniques. But the channel bandwidth requirement is the same as before. Amplitude modulation, am, is one of the most straightforward ways of. What is the difference between pulseamplitude modulation. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. Difference between am and fm amplitude modulation and frequency modulation are used to transmit data using the method of modifying a carrier signal. This figure shows different forms of modulation in polar form. Amplitude modulation or am is the process of varying the instantaneous amplitude of carrier signal accordingly with instantaneous amplitude of message signal. Quadrature amplitude modulation with amplitude modulation. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. The microcontroller is the most efficient tool for generating various pulse width modulation techniques. The various parts of this lab unit will be used to explore and verify the operation of the two am modulation methods using four different am modulating circuits. Amplitude modulation am changes only the magnitude of the signal.
It explains what is modulation and classification of modulation. Introduction baseband term is used to designate the band of frequencies of the signal delivered by the source. Modulation techniques pwm and pulse code modulation. Chapter 6modulation techniques shandong university. Frequency modulation the frequency of the carrier signal is proportional to the modulating signal phase modulation. Understanding modern digital modulation techniques a tutorial on the most common digital modulation techniques used in both wireless and wired communications and how they compare to one another in. Amplitudeshift keying ask frequencyshift keying fsk phaseshift keying psk all of these techniques vary a parameter of a sinusoid to represent the information which we wish to send. Amplitude modulation was developed in the beginning of the 20th century. Most radio systems in the 20th century used frequency modulation fm or amplitude modulation am for radio broadcast a modulator is a device that performs modulation. The measurement and definition of amplitude modulations. Other modulation methods amplitude modulation the amplitude of the carrier signal is controlled by the modulating signal pitfall of am. Comparison of different modulation techniques for free space laser communication abstract.
Hence, pam is continuous in amplitude but discrete in time. In general, amplitude modulation definition is given as a type of modulation where the amplitude of the carrier wave is varied in some proportion with respect to the modulating data or the signal. Thus, if mt is the message signal and ctacosw c t then am signal ft is written as. There are many types of digital modulation techniques and also their combinations, depending upon the need. Amplitude modulation am frequency modulation fm phase modulation pm amplitute modulation. Process by which a property or a parameter of a signal is varied in proportion to a second signal. This is not possible for other signals, like video, that have strong.
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