Finally, the basic components of the spectrum analyzer will be examined. Frequency modulation consists of encoding information onto a carrier signal by varying the frequency of the carrier. Amplitude modulation or am is the process of varying the instantaneous amplitude of carrier signal accordingly with instantaneous amplitude of message signal. Lecture 2829 fm frequency modulation pm phase modulation. Frequency modulation and phase modulation are the two complementary principal methods of angle modulation. Early investigators thought that narrowband fm could have arbitrar ily narrow bandwidth, allowing more channels than am. The equations for the simple example of the a single tone used for modulation can be expanded to show how the signal will appear of a typical sound consisting of many frequencies is used to modulated the carrier. Even for the pure tone modulation, the fm spectrum consists of.
Once a signal has been modulated, information is retrieved through a demodulation process. In am the amplitude of the modulated signal represents the message. The goal of this experiment is to become familiar with fm modulation and demodulation. In this experiment, you will examine the characteristics of amplitude modulation am. Am or amplitude modulation and fm or frequency modulation are ways of broadcasting radio signals. Amplitude modulation am is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. We can use the above formula to calculate the power of am wave, when the carrier power and the modulation index are known. 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. 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.
In fm however, the frequency of the modulated signal characterizes. Amplitude modulation definition, types, solved examples. Modulation, analog modulation, digital modulation, am,fm. Am is widely used for the transmission of data in everything from short range wireless links such as wifi to cellular telecommunications and much more. Fm has poorer spectral efficiency than some other modulation formats. The carrier frequency, fc, should be larger than the highest spectral component. Pdf on jan 1, 1997, alexandros potamianos and others published speech analysis and synthesis using an amfm modulation model. Its main advantage is that it is more resistant to additive noise than am. Therefore, both fm and pm are often referred to as angle modulation. We will get the percentage of modulation, just by multiplying the modulation index value with 100. Frequency modulation frequency modulation is a change in the carrier frequency fc with all other factors remaining constant. 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.
Similarly, it can be frequency modulation and phase modulation also in other words modulation is the phenomenon of superimposition of modulating signal input signal into the. The process of amplitude modulation consists of the amplitude of the. Amplitude modulation am frequency modulation fm phase modulation pm amplitude modulation. This shout can be heard only up to a certain distance. The left and right channels each limited to 15khz are multiplexed into a single baseband signal using amplitude modulation using frequency modulation to shift the baseband. Instantaneous frequency the instantaneousfrequencyof cos. The phase angle cannot change without also affecting a change in frequency. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. Amplitude and frequencyphase modulation zurich instruments. Amplitude modulation, commonly abbreviated as am, is a common method of broadcasting radio signals.
Or modulation is defined as the precess by which some characteristics, usually amplitude, frequency or phase. Principles of communication modulation tutorialspoint. These form some of the main uses of amplitude modulation. This detector demodulates fm signals and suppresses amplitude noise without the need of limiter stages. Amplitude modulation, am, is one of the most straightforward ways of modulating a radio signal or carrier. Modulation and demodulation this chapter describes the essential principles behind modulation and demodulation, which. Glavieux a, thitimajshima p 2010 near shannon limit errorcorrecting pdf. Most radio systems in the 20th century used frequency modulation fm or amplitude modulation am for radio broadcast. This video lecture explains different types of continuous wave modulation like amplitude modulation am, frequency modulation fm and phase modulation pm. I always had difficulties in understanding frequency modulation fm and its frequency spectrum.
Overmodulated am signals and its requirement for coherent detection are also considered. Am bandwidth bandwidth of an am signal 2x bandwidth of modulating signal, and covers a range centered on carrier. Some phase modulation and quadrature amplitude modulation formats have a higher spectral efficiency for data transmission than frequency shift keying, a form of frequency modulation. The idea is simple, though the notion that it can be used to modulate signals for transmission was hardly obvious before its discovery. Nbfmblockdiagram in practice, this modulation will not be perfect, and there will be some amplitude modulation remaining. In analog modulation technique, if the amplitude or duration or position of a pulse is varied in accordance with the instantaneous values of the baseband modulating signal, then such a technique is called as pulse amplitude modulation pam or pulse durationwidth modulation pdmpwm, or pulse position modulation ppm.
The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. Amplitude modulation and frequency modulation youtube. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. Ee4512 analog and digital communications chapter 6 the analytical signal for double sideband, large carrier amplitude modulation dsblc am is. Principles of communication modulation a signal can be anything like a sound wave which comes out when you shout. Fm wave does not look at all like the modulating waveform. Audio signals transmitted by fm radio communications are the most common. Amplitude modulation am is a process by which the wave signal is transmitted by modulating the amplitude of the signal. Am modulation where the amplitude of the carrier does not depend on the value of the modulating signal. Am works by modulating varying the amplitude of the signal or carrier transmitted according to the information being sent, while the frequency remains constant. Oct 08, 2017 am and fm are two of the most popular modulation techniques. Modulation is the process of superimposing a low frequency signal on a high frequency carrier signal.
Effectively it is formed by having two carriers 90 out of phase. Amplitude modulation am frequency modulation fm phase modulation pm amplitute modulation. Frequency versus amplitude modulation l amplitude modulation am l changes the amplitude of the carrier signal according to the amplitude of the message signal. Thus, if mt is the message signal and ctacosw c t then am signal ft is written as. May 09, 2015 these videos explain you what is modulation, different kinds of modulations like amplitude modulation am and frequency modulation fm,qpsk,qam,phase modulat. Amplitude modulation this experiment examines the characteristics of the amplitude modulation am process.
Also, the process of retrieving information from encoded signals will be discussed. For a perfect modulation, the value of modulation index should be 1, which implies the percentage of modulation should be 100%. The idea is simple, though the notion that it can be used to modulate signals. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the. While this is the simplest technique available, it is nonlinear since a first order lowpass filter response falls as. Amplitude modulation a1 49 you will see in this experiment, and in others to follow, that there is no problem in generating an am signal with a depth of modulation exceeding 100%, and without. Phase modulation phase modulation is a change in the carrier phase angle. Pdf speech analysis and synthesis using an amfm modulation. Pdf modulation comparison of fm and am alaa warrag. The power transmission of fm waves is better than that of the am signals. Anglemodulation,ii lecturetopics fmbandwidthandcarsonsrule. There is another way of modulating a, sinusoidal carrier wave, namely, angle modulation in which the angle of the carrier wave is varied according to the baseband signal. Using amplitude modulation to shift the baseband signal fm radio 88mhz108 mhz.
Fm basics frequency modulation is a form of analog angle modulation in which the baseband informationcarrying signal, typically called the message or information signal mt, varies the frequency of a carrier wave. This type of modulation technique is used in electronic communication. The modulation index or modulation depth is often denoted in percentage called as percentage of modulation. What is amplitude modulation, am electronics notes. Modulation fm, amplitude shift keying ask, phase shift keying psk, etc.
Both transmit the information in the form of electromagnetic waves. Frequency modulation is that from of angle modulation in which the instantaneous frequency if t. Aug 26, 2016 analog modulation comes in three types. It was the earliest modulation technique used to transmit voice by radio. If the carrier frequency is khz, the am signal spectrum. Frequency modulationfm fm was invented and commercialized after am. Dec 05, 2014 types of modulation sine wave carrier described by 3 parameters. In chapter1, we investigated the way of modulating a sinusoidal carrier wave using am technique. Frequency modulation fm is a process in which the carrier frequency is varied by the amplitude of the modulating signal i. Fm signals have the same peak frequency deviation, then. Amplitude modulation was developed in the beginning of the 20th century. What is fm, frequency modulation electronics notes. This differs from fm technology in which information sound is.
Or modulation is defined as the precess by which some characteristics, usually amplitude, frequency or phase, of a carrier is varied in. In this article, were going to talk about the former two, due to their immense popularity in radio communication. Fm frequency modulation pm phase modulation continued ee44510 22 narrowband fm only the j o and j 1 terms are significant same bandwidth as am using eulers identity, and. Modulation, analog modulation, digital modulation, am,fm,pm. It can be achieved in a number of ways, but the simplest. Each radio station is assigned 200 khz, to transmit a stereo audio. 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. The phase of the carrier fm varies with the integral of the modulating signal. The demodulation is performed by an envelope detector. So, the power required for transmitting an am wave is 1. 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. As a result, most data transmission system use psk. These methods contrast with amplitude modulation, in which the amplitude of the carrier wave varies, while the frequency and phase remain constant.
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