In this code, it is considered the default value of ma equal to 1 for hundred percent modulation. 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. What is amplitude modulation, am electronics notes. Ring modulation and tremolo audio effects are studied as special cases of am modulation. Amplitude modulation is mostly used in the form of electronic communication. The depth of modulation can be varied using the variable knob provided at a.
Basic concept of modulation the information source typically a low frequency signal referred to as the baseband signal carrier a higher frequency sinusoid example. Set g so that the sinewave peaks just fall to zero. Each part may be of any convenient amplitude at the input to an adder. Before coming to the lab, you are encouraged to read 1, and also the principles of operation of the diode envelope detector circuit shown below see, e. An interactive demo which enables you to both see and hear the result of multiplying a sine wave with a cosine amplitude envelope.
Denote the maximum amplitude of the am signal as v p, then the capacitor discharge will follow the following equation vp. Rapid amplitude and frequency modulation are characteristic of many songbird vocalizations. Indian institute of technology kanpur ee 381 electrical. Quadrature amplitude modulation is widely used for carrying many digital signals, everything from wifi to mobile phone communications and very much more. Hence balanced amplitude modulation can be described as. Note that this is on the very low end of the recommended voltage range.
Am is a relatively simple way to add audio information to a carrier wave so that sounds can be transmitted. Then, students will use labview to program an am demodulator and use it to explore and visualize the. Amplitude modulation am the process of combining the message signal with the carrier signal and the two sidebands. Repeat step iii and step iv, for modulation index of 0, 0. Notice that the sine wave will move up and down as the dc is varied, its mean value equalling the dc value. To study frequency modulation and determine its modulation factor 4. Frenzeljr, in handbook of serial communications interfaces, 2016. Amplitude modulation and frequency modulation youtube. Though it is theoretically possible to transmit baseband signals or information without modulating it, it is far more efficient to send data by modulating it onto a higher frequency carrier wave. Amplitude modulation am, variation of the amplitude of a carrier wave commonly a radio wave in accordance with the characteristics of a signal, such as a vocal or musical sound composed of audiofrequency waves. Learn to perform amplitude modulation with the agilent 33220a signal generator. The code for amplitude modulation am with control of modulation index ma has been developed using matlab according to conventional theory.
In amplitude modulation the carrier amplitude varies with the modulating amplitude, as shown in fig. Amplitude modulation is one type of continuouswave modulation, covered in 1. This modulation is the combination of two principal forms such as frequency modulation and angle modulation. Simulink implementation of amplitude modulation technique. Both pinnacle amplitude, as well as the carrier signals frequency, is maintained stable, although when the message signals amplitude changes. In this lab, we will be using a diode to convert the received signal into an audio signal. Consider the modulation of a simple waveform 2 cos4. Compare doublesideband and singlesideband amplitude modulation. The rate at which the amplitude of the carrier is changed is called the modulation rate. What happens when amessage signal is combine with a carrier. Aly elosery october 25, 2010 this lab is divided into two parts. The original method of electronically encoding sound information on radio waves is called amplitude modulation, or am. Varying these parameters in proportion to the baseband signal results in amplitude modulation am, frequency16 modulation fm, and phase modulation pm, respectively.
Analog communication lab manual, prepared by nakka. Dutton ee3 winter 2004 1 ee3 lab 1 amplitude modulation and demodulation 1 lab notes a word about power. 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. This form of modulation is essentially derived from two carriers that are 90 out of phase and adding information, either analogue or digital. Dutton ee3 winter 2004 1 ee3 prelab 1 amplitude modulation and demodulation 1 introduction this week we will be taking a look at the amplitude modulation am scheme. Vary the modulating frequency and amplitude and observe the effects on the modulated waveform. Amplitude modulation circuit implementation for use in.
Why modulation is used suitable for signal transmission distanceetc. 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. The resulting amplitude modulation am waveform is then demodulated. This lab gives you the opportunity to actually work on amplitude modulation and reinforce the theory taught in class. The standard form the amplitude modulated wave is defined as where carrier, modulating signal modulation index is defined as amplitude modulated signal. Amplitude modulation amplitude modulation is the process in which amplitude of the carrier wave will change in accordance with the modulating signal wave. For modulation index of 1, zoom around 0 hz to 5 khz to measure frequency of the demodulated message signal. The first is to gain a firsthand experience in programming the usrp to act as a transmitter and a receiver.
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. In amplitude modulation the amplitude of the carrier wave ct is varied linearly with the instantaneous amplitude of the message signal mt. Amplitude modulation and demodulation objective amplitude modulation am is one of the simplest methods for modulating a sinusoidal carrier wave. Amplitude, frequency and phase modulation can be applied directly by software to the generated signals, which gives great flexibility where complicated and precise waveforms are required. Lecture 14, demonstration of amplitude modulation mit res. The second is to investigate classical analog amplitude modulation and the envelope detector. It is still in use today in a variety of systems, including, of course, am broadcast radio. Phase modulation pm is a different form of frequency modulation and the carrier is similar in appearance to a frequencymodulated carrier. Amplitude modulation is used to encode information in a highfrequency carrier by varying the amplitude of the carrier. The various parts of this lab unit will be used to explore and verify the operation of the two am modulation methods using four different am modulating circuits. Onoff modulation change the message signal to a square wave 2 khz and with vpp 4v. In other words, amplitude modulation allows the original carrier waveform through the vca, and also creates two new signals called the sum and the difference signals.
To produce dsbsc and ssb change the carrier level to min. Therefore, both fm and pm are often referred to as angle modulation. Amplitude modulation is one of the earliest radio modulation techniques. The demonstration centers around a number of signals displayed in both the time domain and the frequency domain using a signal generator, an oscilloscope to view the signal.
The depth of modulation, defined below, can be adjusted with the adder gain control g. 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. The carrier is usually a radiofrequency rf signal such as the 1. 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.
Amplitude modulation refers to the process in which amplitude of the carrier wave is varied with the message signal. The message signal is, for example, a function of the sound to be reproduced by a. The demod ulation is performed by an envelope detector. Then as the audio signal amplitude is changed to 150 mvpp, the percentage modulation dropped to around 30%. T12 measure the peaktopeak amplitude of the am signal, with m 1, and confirm that this magnitude is as predicted, knowing the signal levels into the multiplier, and its k factor. The 9410 am dsb ssb generator controls and connectors carrier level changes the level of the carrier when using am. It was developed in the first few decades of the twentieth century. Phased array antennas combine signals from multiple radiators to form and steer a beam. The original waveform amplitude is quantized with a resulting loss of information. Teach online lab this is an online, interactive lab that contains instructions, multimedia, and assessments where students can learn at their own pace. In part i you will learn how to design an amplitude modulator am and in part ii you will be able to demodulate an am signal. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave.
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. The am generator, or exciter, as such a low power source of modulated signal is often called, is now set up. Lab 3 amplitude modulation sonoma state university. When you actually combine this tank circuit with the rest of your radio, the tunable frequency. Learn to perform amplitude modulation with the multiply function of the agilent 54622a oscilloscope. Among the types of modulation techniques, the main classification is continuouswave modulation and pulse modulation. In your lab write up compare this with what is expected for a modulation depth of m 1. Langemann, in auditory physiology and perception, 1992. Take a screenshot of output of the tlpf and output of the audio oscillator under the scope mode. The main difference in generating balanced amplitude modulation to standard amplitude modulation is the missing offset of the 1 offset in the modulating signal. Essentially an amplitude modulated wave consists of a radio frequency carrier a sine wave at one frequency, typically in the radio frequency portion of the spectrum. In this experiment, you will examine the characteristics of amplitude modulation am. This lab introduces students to communications theory with amplitude modulation and demodulation. Amplitude modulation an interactive demo which enables you to both see and hear the result of multiplying a sine wave with a cosine amplitude envelope.
In this process, the amplitude of the carrier signal is varied so that it is proportional to the instantaneous amplitude of the modulating. Amplitude modulation is a process by which the wave signal is transmitted by modulating the amplitude of the signal. Sinusoidal modulation slowly increase the modulation signal voltage am over the range 0 v to 4 v i. These videos explain you what is modulation, different kinds of modulations like amplitude modulationam and frequency modulationfm,qpsk,qam,phase modulat.
The range of modulation frequencies found was between 109 and 358 hz, and most sounds were both modulated in frequency and amplitude see greenewalt 1968. Modulation is a process by which some characteristics of the carrier signal like its amplitude, frequency or phase are varied in proportion to message signal. The idea is simple, though the notion that it can be used to modulate signals for transmission was hardly obvious before its discovery. By combining the i and qchannel outputs in phase d. Ee3 prelab 1 amplitude modulation and demodulation. Amplitude modulated signal can be represented by the following equation. The carrier signals phase is modulated to follow the amplitude of the message signal. The percentage modulation can be calculated using the formula.
Amplitude modulation an overview sciencedirect topics. Here we will address the question, whether the birds. Am waveform the waveform of am consist of two signals, modulating that is baseband or low frequency signal and carrier that is high frequency signal. Experiment 10 amplitude modulation and demodulation introduction in this experiment we generate and display. Amplitude modulation a1 53 experiment aligning the model the low frequency term at to generate a voltage defined by eqn.
We also see how to use a balanced mixer to modulate a signal. In the case where the coefficients fn are real we can combine these two plots into one plot. Prof mist mist, hyderabad ece department page 7 experiment 1 4. Lab assignment 2 amplitude modulation 1 introduction this lab assignment is concerned with practical issues associated with the implementation of modulators and demodulators for doublesideband suppressed carrier dsbsc and doublesideband large carrier dsblc modulation. Amplitude modulation modulation is the process of varying a higher frequency carrier wave to transmit information. No information is lost, but the energy is redistributed in the frequency domain. Understanding the principle of amplitude modulation am and.
In amplitude modulation, it is the voltage level of the signal to be transmitted. The basic theory and equations behind amplitude modulation are relatively straightforward and can be handled using straightforward trigonometric calculations and manipulation. Am and fm examples are constructed by combining two wavetables. Group3 umang gupta 2010ee50564 indrabhushan 2010ee50548 vivekmangal 2010ee50566 jitendra kumar meena 2009ee50483 12912 experiment 2. It is often called as am and is commonly used in transmitting a piece of information through a radio carrier wave.
The pulse may take any real voltage value that is proportional to the value of the original waveform. Amplitude modulation part 1 in class you have studied the theory of amplitude modulation. The receivers used to listen to amdsbc are perhaps the simplest receivers of any radio modulation technique. For a perfect modulation, the value of modulation index should be 1, which implies the percentage of modulation should be 100%. Matlab code for amplitude modulation am file exchange. If the audio signal message signal is and the carrier signal is, the amplitudemodulated signal can be expressed. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. To study amplitude demodulation by linear diode detector 3. Yet, am continues to be used today in many communication applications. Modulation is a process by which characteristics of a highfrequency carrier signal are altered to convey information contained in a lowerfrequency message. This experiment examines the characteristics of the amplitude modulation am process. Amplitude modulation definition, types, solved examples. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. Figure 2 shows a radio signal with amplitude modulation.
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