Basic concept of modulation the information source typically a low frequency signal referred to as the baseband signal carrier a higher frequency sinusoid example. 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. 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. Amplitude modulation can be produced in various ways. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors.
The gpu algorithm is easier to add new features than hardware implementation and reaches 57x speed up compared with the serial algorithm on cpu. Digital phase modulation and demodulation request pdf. Thus, we can think of amplitude modulation as shifting the original spectrum upward by f c and downward by f c. Abstract pulse amplitude modulation pam is used extensively in telecommunications as an intermediate step of other techniques such as phase shift keying psk, quadrature amplitude modulation qam and pulse code modulation pcm 1. Its simplest form is accomplished by the multiplication between a bandlimited message signal and a cosine called carrier, whose frequency is located at a much higher place in the spectrum. Both modulated carriers are summed to result in a signal with amplitude and phase modulation. Here well use the example of a square law fet as illustrated in figure 9. As we mentioned before, well use dsbc modulation because of its ease in demodulation.
When expressed as a percentage it is the same as the depth of modulation. Restoring or recovering the message signal from the received modulated waveform that is generally corrupted by noise types of am detectors. This principle is at the heart of amplitude modulation. Source called v1 generates the message to be transmitted. The binary signal when ask modulated, gives a zero value for low input while it gives the carrier output for high input the following figure represents ask modulated waveform along with its. Pam however is an amplitude modulated am form of a pulse carrier 2, and hence has all the advantages and. Hapter modulation and demodulation mit opencourseware. Digital demodulator of the quadrature amplitude modulation. Demodulation channel decoding is the corresponding process at the receiver of converting the received waveform into a. Abstract in this paper the notion of amplitude modula tion of chaotic signals is introduced, similar to ampli tude modulation of harmonic signal. Radio waves can carry audio, video, and digital information over great distances by using changes in a carrier waves amplitude, frequency, or phase to represent the information being transmitted. A demodulator is an electronic circuit that is mainly used to recover the information content from the modulated carrier wave. Note that this is on the very low end of the recommended voltage range. Introduction modulation is used in efficient radiation of signals.
Demodulation is defined as extracting the original informationcarrying signal from a modulated carrier wave. Amplitude modulation and demodulation abstract a single tone sinusoidal signal is transmitted using amplitude modulation and is demodulated at the receivers end using an envelope detector and the attenuated signal is amplified using common source bjt amplifer. A demodulation method called coherent demodulation will be explored in this experiment. Readers are presented with stepbystep derivations showing the operation of qpsk modulation and demodulation. Pulse modulation is yet another form of modulation, without a carrier, in which pulses with precisely known characteristics are transmitted and details can be learned. The traditional qam demodulation method was implemented in hardware. Pdf implementation of amplitude modulation on software defined. It requires that the amplitude of the dc a part of a t is equal to the amplitude of the ac part a. Implementation of amplitude modulation and demodulation using. So can have amplitude modulation am frequency modulation fm phase modulation pm frequency and phase combined are known as angle modulation 8. Modulation and demodulation hold dominant positions in communication. Index termssoftware radio, wireless communication, am. Types of modulation sine wave carrier described by 3 parameters.
There are no amplitude scales shown, but you should be able to deduce the depth of modulation 1 by inspection. What is amplitude modulation, am electronics notes. The frequency of the carrier remains constant frequency modulation fm frequency modulation is the process of varying the frequency of a carrier wave in proportion to the amplitude of a. Dec 05, 2014 types of modulation sine wave carrier described by 3 parameters. In the area of ssb telephony military, commercial and. Modulation and demodulation this chapter describes the essential principles behind modulation and demodulation, which. The modulation index of an fm signal you can observe the change of the spectral shape for various modulation indices, in this step, you will generate a series of line spectra. Modulation is defined as the process by which some characteristics of a carrier signal is varied in accordance with a modulating signal. These two signals, usually sinusoidal functions such as sine and cosine, are 90 degrees out of phase with each other and are therefore called quadrature carriers. Analog modulation and demodulation amplitude modulation pages 306309. Notice that the sine wave will move up and down as the dc is varied, its mean value equalling the dc value. The components of each carrier are called inphase and quadrature. Vectors and modulation cse 466 interfacing 3 spose m and n are orthogonal unit vectors.
The paper will give the results of modulation and demodulation circuit using. Here is the circuit used for modulation and its simulation. This way, the antenna size can be made small as well as more. Modulation of a radio wave can be performed by varying one or more of its signal componentsamplitude, frequency, or phasewhile keeping its other signal components constant. Modulation allows us to transmit multiple signals in the same medium i.
Amplitude modulated am signal and four demodulation methods for fre. The transition from analog communication to digital has advanced the use of qpsk. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. Amplitude modulation am, demodulation and their circuit. The idea is simple, though the notion that it can be used to modulate signals for transmission was hardly obvious before its discovery.
Chapter 6 doublesideband suppressedcarrier amplitude. Process by which a property or a parameter of a signal is varied in proportion to a second signal. Chapter 7 amplitude modulation techniquesgeneration and. However, a simpler demodulator for am signals is the envelope detector. Ee4512 analog and digital communications chapter 6 the analytical signal for double sideband, large carrier amplitude modulation dsblc am is. In continuouswave modulation, a high frequency sine wave is used as a carrier wave.
Amplitude modulation early radio ee 442 spring semester. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. 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. The idea is simple, though the notion that it can be used to modulate signals. Amplitude shift keying ask is a type of amplitude modulation which represents the binary data in the form of variations in the amplitude of a signal. Each channel sharing scheme a set of basis vectors. This form of modulation is essentially derived from two carriers that are 90 out of phase and adding information, either analogue or digital. This gives us something to modulate and carry the information pattern from. Farshad lahouti january 20, 2003 winter 2003 uw, ece 318 lecture notes 2 information source signal modulator propagation channel signal demodulator information destination analog communication system analog signals may be transmitted directly via carrier modulat ion over. Quadrature amplitude modulation is widely used for carrying many digital signals, everything from wifi to mobile phone communications and very much more. The amplitude modulation am modulation index can be defined as a measure of the amplitude variation upon a carrier. This paper proposes a demodulation algorithm using gpu. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. The message signal is, for example, a function of the sound to be reproduced by a.
It follows, then, that multiplying the modulated signal by the carrier frequency will transfer the spectrum back to its original positioni. There are different types of modulation and so are demodulators. Chapter 7 amplitude modulation techniques generation and detection chapter outline 7. Pdf in this paper, the digital algorithm and the device for the demodulation of the quadrature amplitude modulation signals are considered. Amplitude modulation am amplitude modulation is the process of varying the amplitude of a carrier wave in proportion to the amplitude of a baseband signal. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. Study how to perform the amplitude modulation and demodulation and to calculate the modulation index for various modulating voltages. Frequency division multiplexing, fdma amplitude modulation and demodulation.
A basic amplitudemodulated doublesideband full carrier signal is obtained by mixing a modulating signal y m t at a modulation index m and frequency. The fundamental advantages of our approach are simple hardware implementation, minimal number of arithmetic operations required over the signal period as well as the potential interference immunity. Set g so that the sinewave peaks just fall to zero. Mary quadrature amplitude modulation mqam is a modulation scheme that conveys data by modulating the data transmission onto the amplitude via two carrier signals. Dutton ee3 winter 2004 1 ee3 lab 1 amplitude modulation and demodulation 1 lab notes a word about power. If the amplitude of the high frequency carrier wave is varied in accordance with the instantaneous amplitude of the modulating signal, then such a technique is called as amplitude modulation. Modulation and demodulation are important aspects in communication. Group3 umang gupta 2010ee50564 indrabhushan 2010ee50548 vivekmangal 2010ee50566 jitendra kumar meena 2009ee50483 12912 experiment 2. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. This is further divided into amplitude and angle modulation. Accelerate demodulation of quadrature amplitude modulation. Amplitude modulation is defined as the process in which the amplitude of the carrier wave ct is varied about a mean value, linearly with the baseband signal. Spectrum of a dsbscam signal the fourier transform of st is s.
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