Multiple choice questions and answers on modulation and. Remember, neither yt, nor the oscillator signal, appears at the multiplier output. Pdf amfm demodulation methods for reconstruction, analysis. 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. Chapter 6 doublesideband suppressedcarrier amplitude. In addition to a variable bandpass filter, one auto notch and one manual notch filter can be utilized to eliminate interfering signals.
Amplitude modulation circuits am, demodulation amplitude modulation of a sine or cosine carrier results in a variation of the carrier amplitude that is proportional to the amplitude of the modulating signal. Hapter modulation and demodulation mit opencourseware. An envelope detector is called a noncoherent demodulator because it makes no use of the carrier phase and frequency. The following demodulators detectors are used for demodulating am wave. The carrier signal and y have sampling frequency fs.
Demodulation of amplitude modulated signal submitted to. Types of modulation sine wave carrier described by 3 parameters. 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. Pdf format this file type includes highresolution graphics and schematics when applicable. Discuss the requirements for recovery of intelligence from an am signal and describe the theory of operation of the following am demodulators. A noncoherent detector has only one input, namely, the modulated signal port. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. Connect the output of am modulator to the input of am signal ip2 of the product detector located on the. Students will explore the mathematical theory behind amplitude modulation and use the analog discovery 2 to visualize the effects of amplitude modulation in the time and frequency domains. Am modulation and demodulation cypress semiconductor. The type of modulation that will be studied in this chapter is called doublesideband suppressedcarrier amplitude modulation dsbsc am. Amplitude modulation, am, is one of the most straightforward ways of modulating a radio signal or carrier.
Am receivers are very cheap as no specialisedcomponents are needed. Pdf energy demodulation of twocomponent amfm signal. Amplitude modulation refers to any method of modulating an electromagnetic carrier frequency by varying its amplitude in accordance. There are many types of modulation so there are many types of demodulators. Spectrum of a dsbsc am signal the fourier transform of st is s. This principle is at the heart of amplitude modulation. Chapter amplitude modulation and demodulation, ppt, adc. The am demodulator can be implemented by utilizing a balanced modulator. Analog communication am demodulators tutorialspoint. 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 amplitude modulation and frequency modulation are graphically shown in. Basic concept of modulation the information source typically a low frequency signal referred to as the baseband signal carrier a higher frequency sinusoid example. Demodulation article about demodulation by the free. We call this type of modulator as synchronous detector or product detector.
The purpose of this lab is for you to gain familiarity with the concepts of amplitude. Example 5 shows the double side band suppressed carrier dsbsc am wave. From dsbsc to dsbwc am carrier recovery circuits, which are required for the operation of coherent demodulation, are sophisticated and could be quite costly. Demodulation is extracting the original informationbearing signal from a carrier wave. The input is a passband representation of the modulated signal. Description download laporan modulator demodulator am comments. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the.
Introduction to iq demodulation of rfdata september 15, 1999 page 3 of 1 introduction 1. The document is intended for users of the rf options on the system five. Hi, im a beginner in matlab and im just wondering whether the modulation constant. Report laporan modulator demodulator am please fill this form, we will try to respond as soon as possible. A demodulator is an electronic circuit that is mainly used to recover the information content from the modulated carrier wave. Set the input signals of am modulator for the carrier of 250mvpp, 500 khz sine wave, and the audio signal of 150mvpp, 3 khz sine wave. It is a system of modulation in which the amplitude of the carrier signal is made proportional to the instantaneous amplitude of the modulating message signal.
The coherent detection method is used for demodulation. Once the signal has been received, filtered and amplified, it is necessary to recover the. Square law demodulator is used to demodulate low level am wave. In fact, it can be shown that a coherent demodulator performs better than an envelope detector when the received signal is corrupted by additive noise. Describe fm demodulation circuit operation for the phaseshift and gatedbeam discriminators and the ratiodetector demodulator. 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. Pdf laporan modulator demodulator am free download pdf. A demodulation method called coherent demodulation will be explored in this experiment. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation.
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. Fm demodulation is also called fm detection and sometimes the phrase fm discrimination is used, although this term tends to be used with older circuits and technology. Vectors and modulation cse 466 interfacing 3 spose m and n are orthogonal unit vectors. In addition to reading the questions and answers on my site, i would suggest you to check the following, on amazon, as well.
Then, students will use labview to program an am demodulator and use. Adjust the vr1 of am modulator to get the percent of modulation of 50%. Demodulation is the process by which the original information bearing signal, i. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information.
In chapter1, we investigated the way of modulating a sinusoidal carrier wave using am technique. The modulated signal y has zero initial phase and zero carrier amplitude, resulting from a suppressedcarrier modulation. Existing multicomponent am fm demodulation algorithms either assume spectrally distinct components or components separable via linear filtering and break down when the. Doublesideband suppressedcarrier amplitude modulation. The process of extracting an original message signal from the modulated wave is known as detection or demodulation. Amfm demodulation methods for reconstruction, analysis and motion. The singlesided spectrum of the modulated signal replicates the baseband. Fm demodulation is a key process in the reception of a frequency modulated signal. This lab introduces students to communications theory with amplitude modulation and demodulation.
Demodulation is a key process in the reception of any amplitude modulated signals whether used for broadcast or two way radio communication systems. The dsb am demodulator passband block demodulates a signal that was modulated using doublesideband amplitude modulation. Standard ordinary am the disadvantage of high cost receiver circuit of the dsbsc system can be solved by use of am, but at the price of a less efficient transmitter an am system transmits a large power carrier wave, acos. The message signal is, for example, a function of the sound to be. To investigate amplitude modulated signal in the time domain and the frequency domain. There are different types of modulation and so are demodulators. Restoring or recovering the message signal from the received modulated waveform that is generally corrupted by noise types of am detectors. If we can let mt be the envelope of the modulated signal, then a much simpler circuit, the envelope detector, can be used for demodulation noncoherent demodulation. Therefore, it is a common practice to implement the demodulation. Multiple choice questions and answers on modulation and demodulation. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave.
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