What is amplitude modulation, am electronics notes. Infrared remote control techniques on mc9s08rcrdrerg family. Adaptation of the information signal to the transmission channel. Vestigial sideband amplitude modulation vsbam is a modulation that improves the spectral e.
In this project, we have generated ten different types of pulse width modulation techniques for inverters. Modulation generalities the carrier is a pure sinusoidal signal of constant amplitude, frequency and phase. To understand amplitude and phase modulation, we change to the rotating frame of reference with. Amplitude modulation refers to the process in which amplitude of the carrier wave is varied with the message signal. Modulation not only transforms informationbearing signals into a format that is. In this chapter, let us discuss the following analog pulse modulation techniques.
Because of amplitude modulation wavelength, am signals can propagate longer distances. If the baseband signal is bandlimited, then there is a. Process by which a property or a parameter of a signal is varied in proportion to a second signal. Amplitude modulation am is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. Amplitude modulation the amplitude of the carrier signal is controlled by the modulating signal pitfall of am. Other methods of demodulating an am signal use synchronous techniques and provide much lower levels of distortion and improved reception where.
For binary modulation, the bit rate and symbol rate are identical. It can be achieved in a number of ways, but the simplest uses a single diode rectifier circuit. Analog modulation techniques am modulation, fm modulation, single side band modulation, ssb, bandwith of fm signals, phase modulation, angle modulation, pdf file. The receivers used to listen to amdsbc are perhaps the simplest receivers of any radio modulation technique. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that. Each part may be of any convenient amplitude at the input to an adder. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. Rc audio generator, oscilloscope, and spectrum analyzer demonstrations with speech and radio. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. Linear modulation techniques vary the amplitude of a high frequency carrier. Pdf modulation is an integral part of every modern communication systems and.
Another way to think is to realize that we are really plotting the amplitude. The measurement and definition of amplitude modulations. Digital modulation can then be defined as the process whereby the amplitude, frequency. Why modulation is used suitable for signal transmission distanceetc. 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 depth of modulation can be varied using the variable knob provided at a. This conforms to the expectation as the maximum and minimum peak of the modulated signal waveform varies proportional to the amplitude of the modulating signal. After continuous wave modulation, the next division is pulse modulation. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. This means that each rf symbol represents one of 256 possible combinations of amplitude the signal power versus phase a shift. Both modulated carriers are summed to result in a signal with amplitude and phase modulation. Basic concept of modulation the information source typically a low frequency signal referred to as the baseband signal carrier a higher frequency sinusoid example.
The amsc technique essentially translates the frequency spectrum of the mod. The idea is simple, though the notion that it can be used to modulate signals for transmission was hardly obvious before its discovery. However, as a consequence of the low current bias necessary for gainlever modulation, the modulation bandwidth decreases and nonlinear distortion increases. Changing the amplitude using different levels m ary phase shift keying m ary psk. Vary the modulating frequency and amplitude and observe the effects on the modulated waveform. What is modulation 2 modulation in the modulation process, some characteristic of a highfrequency carrier signal bandpass, is changed according to the instantaneous amplitude of the information baseband signal. For am this quantity is also known as modulation depth. The amplitude modulation am modulation index can be defined as a measure of the amplitude variation upon a carrier. The microcontroller is the most efficient tool for generating various pulse width modulation techniques. Frequency modulation fm was the modulation of choice and frequency division multiplexing fdm was used to combine hundreds or thousands.
In pulse amplitude modulation pam technique, the amplitude of the pulse carrier varies, which is proportional to the instantaneous amplitude of the message signal. When expressed as a percentage it is the same as the depth of modulation. As illustrated in figure 5, the amplifier is biased class c and the output rf signal amplitude is modulated by causing the collector supply voltage to vary with the modulation voltage. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. Chapter 6modulation techniques shandong university. Bandpass modulation and demodulation techniques communication systems, dept. He developed the principle of pole amplitude modulation, enabling induction motors to run at different speeds with his fellowresearchers, he filed more than nstruction, and our pole amplitude. 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. Frequency modulation is a type of angle modulation. Multiple choice questions and answers on modulation and. The history of amplitude modulation bright hub engineering.
The components of each carrier are called inphase and quadrature. Learn the concise history of amplitude modulation or am broadcasting technique. The power efficiency is the ability of a modulation technique to preserve the fidelity. Amplitude modulation early radio ee 442 spring semester. We wish to use the carrier wave to carry the message signal, so that the message signal can appropriately be transmitted over a bandpass channel. The resonance frequency of the laser is decreased from 5 ghz to 3 ghz. It is often called as am and is commonly used in transmitting a piece of information through a radio carrier wave. Amplitude modulation is a modulation system in which the carrier wave has its instan taneous amplitude varied. Any baseband signal can be broken up into a weighted sum of sinusoids using fourier decomposition chapter. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. Am, fm, pm, pdf file analog modulation techniques a tip. This type of amplitude modulation is called single side.
Types of modulation sine wave carrier described by 3 parameters. There are a variety of modulation schemes available for both analog and digital modulation. 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. The same possible carrier modifications are available. Amplitude modulation response and linearity improvement of.
Multiple choice questions and answers on modulation and demodulation in addition to reading the questions and answers on my site, i would suggest you to check the following, on amazon, as well. Demodulation is defined as the process of extracting this information. Among them, amplitude modulation am is considered the oldest. There are two reasons why frequencydivision multiplexing works. 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. Here, we will implement the dsbam baseband modulator and demodulator using a music file as a source. Building on the rates up to 64 quadrature amplitude modulation qam of 802.
Amplitude modulation is a process by which the wave signal is transmitted by modulating the amplitude of the signal. This method is capable of producing nearly 100% modulation with reasonable linearity. Analog modulation techniques am modulation, fm modulation, single side band. There are no amplitude scales shown, but you should be able to deduce the depth of modulation 1 by inspection. Quadrature amplitude modulation with amplitude modulation. The information is considered as the modulating signal and it is superimposed on the carrier wave by applying both of them to the.
The demodulation is performed by an envelope detector. Am modulators base, collector, grid and plate modulators. In mind body dualism pdf digital communications, the modulation process corresponds to. Amplitude modulation is mostly used in the form of electronic communication. Classification of linear and nonlinear modulations using bayesian. Frequency division multiplexing, fdma amplitude modulation and demodulation.
This varying supply voltage is applied to the class c amplifier. For a perfect modulation, the value of modulation index should be 1, which implies the percentage of modulation should be 100%. Amplitude modulation a1 53 experiment aligning the model the low frequency term at to generate a voltage defined by eqn. Overmodulated am signals and its requirement for coherent detection are also considered.
Modulationtypesamplitude,frequency,phase modulation. Am works by varying the strength of the transmitted signal in relation to the information being sent. Amplitudeshift keying ask frequencyshift keying fsk phaseshift keying psk all of these techniques vary a parameter of a sinusoid to. 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. Angle modulation changes the phase of a signal as well as its amplitude, where amplitude modulation leaves the phase unchanged. The first discovered a method for amplifying very weak signals and basically developed the amplitude modulation technique. In a hybrid modulation with the following constellation pattern, the outlying signal sig2, has higher energy i. 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. Ee3 lab 1 amplitude modulation and demodulation broadcast analog television tv signals have a bandwidth of approximately 6mhz and this is achieved with a quadrature modulation.
You can publish your book online for free in a few minutes. The general form of a sinusoidal signal can be written as ft. Modulation index in modulation techniques a modulation index is usually defined such that it indicates how much the modulated variable varies around its original value. The modulation techniques currently employed in modern communication systems can be classified into three major categories. Amplitude modulation am is a modulation technique where the. A second technique is to filter the binary data prior to modulation. The first transmission however, was performed by fessenden in 1906 from brant rock, massachusetts. Phase modulation is another type of angle modulation very similar to frequency modulation. Modulation technique pdf we begin our discussion of digital modulation by starting with the three basic types of digital modulation techniques.
The percentage modulation can be calculated using the formula. 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. Amplitude modulation, am is being used less in its basic format, but it. The carrier is described by the equation y a sin 2.
We begin our discussion of digital modulation by starting with the three basic types of digital modulation techniques. Modulation allows us to transmit multiple signals in the same medium i. A type of single sideband amplitude modulation that uses techniques such as. Modulation techniques pdf 3 amplitude and angle modulation processes. The modulation and multiplexing techniques that were used at this time were analog, adapted from the technology developed for microwave links in the previous two decades. This carrier must be modified to carry the signal we want to transmit. The modulating signal contains the intended message or information sometimes consisting of audio data, as in am radio. So a longer vector has a larger amplitude and hence higher energy. Amplitude modulation am is an analog modulation scheme where the amplitude a of a fixedfrequency carrier signal is continuously modified to represent data in a message. When the modulation signal occurs, the ac voltage across the secondary of the modulation transformer will be added to and subtracted from the collector supply voltage.
Sep 03, 2012 digital modulation digital modulation is the process by which a sequence of pulses message of duration t is transformed into a sequence of sinusoidal waveforms, st of duration t. For amplitude modulation, we use simple and low cost circuit. Amplitude modulation is one of the earliest radio modulation techniques. Demonstration with professor sandy hill from the university of massachusetts at amherst. So can have amplitude modulation am frequency modulation fm phase modulation pm frequency and phase combined are known as angle modulation 8. Three basic digital modulation formats are still very popular with lowdatarate shortrange wireless applications. Amplitude modulation, am, is one of the most straightforward ways of modulating a radio signal or carrier. The method of varying amplitude of a highfrequency carrier wave in accordance with the information to be transmitted, keeping the frequency and phase of the carrier wave unchanged is called amplitude modulation. Modulation is defined as the process of transmission of information such as images or videos on an electrical signal. Naturally, the amplitude of the current pulses through transistor q1 will vary. Amplitude modulation this experiment examines the characteristics of the amplitude modulation am process. Amplitude modulation definition, types, solved examples.
1558 1101 1552 204 1313 1114 468 421 1522 1121 1358 1411 1452 1614 517 384 1586 1127 1174 972 440 528 1296 349 986 1078 707 900 1311 1299 587 74 1108 1399 1023 481 840 41 1262 477