To study different amplitude modulation scheme to study generation and detection of am signals. This principle is at the heart of amplitude modulation. The output of the product modulator is given by, vt svsb t cos2 fc t 1 ii svsb f f c svsb f f c 2 substituting equation. In wireless communication, such as radio, broadcast television, or cellular telephone, the medium is air. Retain the modulator setup with upper sideband modulation and make the demodulator setup as shown in the figure a. Modulatorfree quadrature amplitude modulation signal synthesis. Rahul agarwal contents introduction to modulations amplitude modulation demodulation generation methods of am introduction a carrier signal is modulated only in amplitude value the modulating signal is the envelope of the carrier the required bandwidth is 2b, where b is the bandwidth of the modulating. Modulation is defined as the process by which some characteristics of a.
This technique contrasts with angle modulation, in which either the frequency of the carrier wave is varied as in frequency modulation, or its phase, as in phase modulation. Describe phase demodulation circuit operation for the peak, lowpass filter, and conversion detectors. Experiment 2 amplitude modulation and demodulationpdf free. Amplitude modulation is a modulation system in which the carrier wave has its instan. This can also be extended to frequency modulation fm and frequencyshift keying fsk, for these can be regarded as a special case of phase modulation. In amplitude modulation, the amplitude of the carrier wave is varied in proportion to that of the message signal, such as an audio signal.
The two common forms of analog modulation are amplitude modulation. Learn the definition of frequency modulation, and get answers to faqs. The purpose of this lab is for you to gain familiarity with the concepts of amplitude modulation and demodulation. Filling a gap in the literature, this book features indepth discussions on amplitude modulation afm, providing an overview of the theory, instrumental considerations and applications of the technique in both academia and industry. Ask modulation introductionthe aim of this laboratory is to describe the ask amplitude shift keying modulation and demodulation. Amplitude modulation am works by varying the amplitude strength of a carrier signal, in proportion to amplitude of a modulation signal that is to be transmitted to one or more receivers. Modulated signal in amplitude modulation is given by. The signal is said to be 50% modulated if the peak message signal amplitude is half the peak amplitude of the carrier signal. To understand the theoretical foundations of analog communications as well as of doublesideband amplitude modulation and demodulation dsbam to design the simulink model of the dsbam to analyze each signal in time and frequency domains using time scope and spectrum analyzer. Chapter 14 modulation school of computing and information. It conveys two analog message signals, or two digital bit streams, by changing modulating the amplitudes of two carrier waves, using the amplitude shift keying ask digital modulation. Amplitude modulation definition if the modulating signal is r t and the carrier signal is a c sin 2. Amplitude modulation formats vestigial side band vsb increases almost 50% effective bandwidth used in tv same as ssb but uses a practical bandpass filter quadrature amplitude modulation qam doubles the effective bandwidth uses in limited bandwidth channel applications.
Modulation and demodulation principle borrow from radio telecommunication take a wide band signal few hz to khz modulate it with a single frequency the carrier signal which is the frequency associated to a given station emit the signal given the station frequency, a receiver follows a demodulation. Pdf the ability to generate highspeed onoffkeyed telecommunication. Frequency and phase modulation are complementary principal methods of angle. Check pages 1 7 of lab 5 amplitude modulation and demodulation in the flip pdf version. Phase modulation analog pm and phaseshift keying digital psk can be regarded as a special case of qam, where the amplitude of the transmitted signal is a constant, but its phase varies. Lab 5 amplitude modulation and demodulation was published by on 20150405. Hapter modulation and demodulation free online course. Unfortunately this gives a rather poor resolution of the frequency, which is adequate only for slowly modulated wavetrains. Describe fm demodulation circuit operation for the phaseshift and gatedbeam discriminators and the ratiodetector demodulator. For a sinusoidal message signal modulating signal, r t a m s.
To generate amplitude modulated wave and determine the percentage modulation. Yet, am continues to be used today in many communication applications. Modulation factor, m 0a 0 or 0% ii when signal amplitude is equal to the carrier amplitude as shown in fig. Amplitude modulation definition, types, solved examples. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting messages with a radio carrier wave. The continuous wave modulation techniques are further divided into amplitude modulation and angle modulation. Experiment 1 amplitude modulation and demodulation 1 amplitude modulation and demodulation preliminary discussion in an a mplitude m odulation am communications system, speech and music are converted into an electrical signal using a device such as a microphone. In the case of bask, under noisefree conditions, z would be either. Be able to explain why am is limited to 33% efficiency and the consequence of. To understand amplitude and phase modulation, we change to the rotating frame of reference with. It can be demodulated using a circuit consisting of very few components. If you look at the envelopes closely youll notice that the upper envelope is the same shape as the message.
Message signal embed into the amplitude of carrier simple am is also called. This is accomplished by using a process known as demodulation, which is the reverse of the modulation process. Lab 5 amplitude modulation and demodulation pages 1 7. Toggle the on board switchfrequency range of the phase shifter at the. Free download in pdf modulation and demodulation objective type questions and answers for competitive exams. Chapter amplitude modulation and demodulation, ppt, adc. In modulation, one characteristic of a signal generally a sinusoidal wave known as the carrier is changed based on the information signal that we wish to transmit modulating signal.
Introduction in chapters 1 and 2 you studied how to apply intelligence modulation to an rfcarrier wave. We are also to carry out an ask connection, with and without manchester data coding. As ofdm incorporating a component of optical carrier is useful in demodulation, iq modulators are usually biased slightly away from v. Amplitude modulation atomic force microscopy wiley online books. No information is lost, but the energy is redistributed in the frequency domain. The envelope of st has essentially the same shape as the baseband signal mt provided that two requirements are satisfied. Pdf 4amplitude modulator and demodulator circuits appi t. Amplitude modulation definition, examples, diagrams. Department of electrical and computer engineering more practical bandwidth saving amplitude modulation formats vestigial side band vsb increases almost 50% effective bandwidth used in tv same as ssb but uses a practical bandpass filter quadrature amplitude modulation qam doubles the effective bandwidth uses in limited bandwidth channel applications. Amplitude modulation and demodulation 2017 frank dorenberg n4spp v1. The modulation index m is an indicator for the degree of the amplitude modulation and is sometimes indicated in percent. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. In fact, for 100% modulation, the power supplied by the modulator must be equal to onehalf the total class c amplifier input power.
Building simulink model of amplitude modulator and demodulator. Carrier phase ft modulates ct in either amplitude, frequency or phase. These short solved questions or quizzes are provided by gkseries. Without giving input measuref o free running frequency. For example, the wavelength of a 1 ghz electromagnetic wave in free space is 30. Modulation and demodulation 415 amplitude change of carrier 0 amplitude of normal carrier a. A noncoherent detector has only one input, namely, the modulated signal port. Pdf chapter 3 chapter 3 amplitude modulation amplitude. Amplitude modulators highlevel modulation produces the best type of am, but it requires an extremely high power modulator circuit. Experiment 2 amplitude modulation and demodulation pdf free download.
Modulation and demodulation based interview questions. Amplitude modulation this experiment examines the characteristics of the amplitude modulation am process. In effect, modulation converts ft to a bandpass form, in the neighborhood of the center frequency f c. And finally the noise effect on the connection is to be examined. Vsb signal can be demodulated by passing a vsb signal through a product modulator along with a carrier signal and then passing through a low pass filter. Communication is the process of transmitting a message from one location to another though some medium. 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. These short objective type questions with answers are very important for competitive exams. To avoid distortion in recovering the modulating signal with a simple demodulator, the modulation index, m, is constrained to lie in the range zero to one. Amplitude modulation is a modulation technique used in electronic communication, most commonly for transmitting messages with a radio carrier wave. After the demodulation, the amplitude of the demodulated signal is proportional to the modulation index.
Chapter 6 modulation techniques shandong university frequency versus amplitude modulation l amplitude modulation am l changes the amplitude of the carrier signal according to the amplitude of the message signal. Pdf modulatorfree quadrature amplitude modulation signal. Analog communications lab manual bapatla engineering. The carrier frequency, fc, should be larger than the highest spectral component. Analogue modulation amplitude modulation v c t v c cos c t, peak amplitude v c, carrier frequency c radians per second. Amplitude modulation and demodulation objective amplitude modulation am is one of the simplest methods for modulating a sinusoidal carrier wave. It is a modulation on a different frequency from the original signal, to transfer out of f 1 noise fig. Quadrature amplitude modulation qam is the name of a family of digital modulation methods and a related family of analog modulation methods widely used in modern telecommunications to transmit information. Download lab 5 amplitude modulation and demodulation pdf for free. Modulation is a technique to transmit information via radio carrier waveform. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. Find more similar flip pdfs like lab 5 amplitude modulation and demodulation. Modulation is the process of transmitting data information in coded form, over. If the class c amplifier has an input power of w, the modulator must be.
Amplitude modulation am in am, the modulating signal the message signal mt is impressed on to the amplitude of the carrier. The scheme is power efficient in that it does not require the transmission of a separate carrier. Chapter 3 chapter 3 amplitude modulation amplitude modulation. Modulation and demodulation based interview questions and. Rahul agarwal contents introduction to modulations amplitude modulation demodulation generation methods of am introduction a carrier signal is modulated only in amplitude value the modulating signal is the envelope of the carrier the required bandwidth is 2b, where b is the bandwidth of the modulating signal since on both sides of the. Experiment 2 amplitude modulation and demodulationpdf. The pulse may take any real voltage value that is proportional to the value of the original waveform. A continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. That could be the amplitude, phase, or frequency, which result in amplitude modulation am, phase modulation pm, or frequency modulation fm.
The implementation complexity is qualita tively evaluated based on the maximum free running sample rate achieved by the digital signal. Dimension of the antennas is limited by the corresponding wavele ngth. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal, such as an audio signal. Theory of lock in modulation and demodulation 1 general scheme of lock in ring the synchronous moddemod is also called lock in modulation fig. In the case of bask, under noise free conditions, z would be either. Double sideband large carrier dsblc modultion for general message signal mt. Pdf channels modulation and demodulation evaluation channels modulation and demodulation what you in imitation of to read. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in.
It is a nonlinear process that generates additional frequencies, as we will see. A new technique is proposed for carrying out amplitude modulation demodulation. For a perfect modulation, the value of modulation index should be 1, which means the modulation depth should be 100%. Experiment 1 amplitude modulation and demodulation figure 2 below shows the am signal at the bottom of figure 1 but with a dotted line added to track the modulated carriers positive peaks and negative peaks. Frequency versus amplitude modulation l amplitude modulation am l changes the amplitude of the carrier signal according to the amplitude of the message signal.
When amplitude of carrier wave is changed according to information signal is called amplitude modulation. The original waveform amplitude is quantized with a resulting loss of information. Modulation is the process of altering the characteristics of the amplitude, frequency, or phase angle of the highfrequency signal in accordance with the instantaneous value of the modulating wave. Modulation is the process of varying some characteristics amplitude, frequency or phase of a high frequency carrier wave in accordance with the instantaneous value of the low frequency modulating signal. Digital communications lecture 6 modulation, demodulation. This means that their ratio is unity at the output of the adder, which forces m to a. Modulator free quadrature amplitude modulation signal synthesis. Amplitude modulation is done by the electronic circuit called modulator. 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.
1598 267 1212 402 706 22 1789 1329 460 682 566 270 1518 1375 571 641 1824 617 1823 551 879 487