Amplitude modulation circuit implementation electrical. The method has considerable generality, but is particularly applicable to speed ratios not very different from unity. This invention relates to poleamplitude modulation p. Let us considered that the mmf distribution in the air gap of a three phase induction motor due to the stator winding carrying a three phase balanced currents can be written as shown below. Therefore, both fm and pm are often referred to as angle modulation. The special technique is pole amplitude modulation pam of the induction motor stator winding which can be accomplished with either. An interactive demo which enables you to both see and hear the result of multiplying a sine wave with a cosine amplitude envelope. The amplitude modulation am modulation depth figure is complementary to the modulation index.
Why modulation is used suitable for signal transmission distanceetc. Lenchine science and sustainability division, epa, gpo box 2607 adelaide sa 5001, australia abstract wind farms are gaining more and more popularity as a source of renewable energy. K nown in the industry as the pam motor, the tecowestinghouse pole amplitude modulation motor is the worlds most innovative ac induction motor. Modulationtypesamplitude,frequency,phase modulation. Both modulated carriers are summed to result in a signal with amplitude and phase modulation. Other is the pole amplitude modulation pam technique through which the windings are held in two sections per phase and reversing the current direction in one section of each phase with respect to the other. Before we study in detail about pam lets know the concepts of modulation. There are no amplitude scales shown, but you should be able to deduce the depth of modulation 1 by inspection. The original method of electronically encoding sound information on radio waves is called amplitude modulation, or am. The middle graph shows the modulated carrier, where is the message signal and is the modulation factor. The original waveform amplitude is quantized with a resulting loss of information. Power amplifiers are used to boost the carrier and modulating signals before modulation d. It is a modulation system in which the signal is sampled at regular intervals and each sample is made proportional to the amplitude of the signal at the instant of sampling.
Typically the modulation depth is the amplitude modulation index expressed as a percentage. The amplitude modulation definition is, an amplitude of the carrier signal is proportional to in accordance with the amplitude of the input modulating signal. Amplitude modulation ang man shun october 30, 2012 reference hwei p. At 100% modulation, the power efficiency of am is 33. In amplitude modulation, the amplitude signal strength of the carrier wave is varied in proportion to that of the message signal being transmitted. Rc audio generator, oscilloscope, and spectrum analyzer demonstrations with speech and radio. Modulation is inherently a nonlinear process, and always gives rise to frequency components that did not exist in either of the two original signals. Modulation is defined as a process by virtue of which, some characteristic of a high frequency sinusoidal wave is varied in accordance with the instantaneous amplitude of the baseband signal. This process of imposing an input signal on a carrier wave is known as modulation. Alternatively look into the early effect because this can also be used to create amplitude modulation. The pole amplitude modulation pam motor reduced wear and erosion on the driven equipment and less noise during operation at low speed.
Amplitude modulation an overview sciencedirect topics. 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. Pradeep kshetrapal, tutorials point india private limited. A pole changing induction motor with pole amplitude. Amplitude modulation definition, types, solved examples. The invention provides improved stator windings for pole amplitude modulation p. The components of each carrier are called inphase and quadrature. The pulse may take any real voltage value that is proportional to the value of the original waveform. Modulation techniques pwm and pulse code modulation.
Amplitude modulation part 1 in class you have studied the theory of amplitude modulation. In this modulation, the signal is sampled at regular intervals and each sample is made proportional to the amplitude of the modulating signal. Speed control three phase im using pole amplitude modulation the value of m 1 means reverse connecting pole groups 5. It was developed in the first few decades of the twentieth century. So, step up the analysis and take into account nonlinearities. Nov 19, 2015 the resulting signal from the process of amplitude modulation is called amplitude modulation signal of simply am wave. In small machines the effect, although present, is less important.
These might be operating with the transistor in the saturation region i. 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. The fact that rapidly modulating the amplitude of one wave results in a waveform identical to playing two notes of different frequencies is quite remarkable and for more information on such wave interference, please see our wave interference and beat frequency demo. Pulse amplitude modulation is a technique in which the amplitude of each pulse is controlled by the instantaneous amplitude of the modulation signal. Frequency division multiplexing, fdma amplitude modulation and demodulation. But when compared to frequency modulation, the amplitude modulation is weak, but still it. Also observe the rectifier output spectrum as the message dc offset is reduced see that dsbsc signals are not be properly demodulated using a rectifier detector. Tecowestinghouse pam motor an economical drive for multispeed applications through pole amplitude modulation. The first discovered a method for amplifying very weak signals and basically developed the amplitude modulation technique. Here well use the example of a square law fet as illustrated in figure 9. Amplitude modulation definition of amplitude modulation by. The other type of modulation in continuouswave modulation is the angle modulation. Amplitude modulation modulation is the process of varying a higher frequency carrier wave to transmit information.
A wave has two important components amplitude and frequency. In am radio broadcasts, is the audio signal being transmitted usually bandlimited to less than 10 khz, and is the channel center frequency that one dials up on a radio receiver. In amplitude modulation, the message signal mt is impressed on the amplitude of the carrier signal ct a c cos2 f c t there are several different ways of amplitude modulating the carrier signal by mt each results in different spectral characteristics for the transmitted signal we will describe these methods, which are. We also see how to use a balanced mixer to modulate a signal. Modulation allows us to transmit multiple signals in the same medium i. Amplitude modulation am 9 t15 use speech or music from trunks as the message, and show that this also generates a trapezoid, and that setting the message amplitude so that the depth of modulation reaches unity on peaks a triangle is especially easy to do, using the gain control g of the adder. Basic concept of modulation the information source typically a low frequency signal referred to as the baseband signal carrier a higher frequency sinusoid example. This is further divided into frequency and phase modulation. 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. It is often called as am and is commonly used in transmitting a piece of information through a radio carrier wave. This type of modulation technique is used in electronic communication.
Amplitude modulation is a powerful tool that allows you to create and play new sounds that you cannot obtain using conventional oscillators alone. Pulse amplitude modulation pam, quadrature amplitude modulation qam 12. It requires that the amplitude of the dc a part of a t is equal to the amplitude of the ac part a. No information is lost, but the energy is redistributed in the frequency domain. This is a lowfrequency signal as we have seen earlier. Am shifts the spectrum of the signal by the carrier frequency. The concepts of amplitude modulation, modulation and demodulation, along with their differences is explained below. Amplitude modulation a continuouswave goes on continuously without any intervals and it is the baseband message signal, which contains the information. The basic theory and equations behind amplitude modulation are relatively straightforward and can be handled using straightforward trigonometric calculations and manipulation. Speeds are changed electronically, not mechanically, which means additional apparatus between the.
In amplitude modulation or am, the carrier signal has its amplitude. 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. The message signal is, for example, a function of the sound to be reproduced by a. The pole amplitude modulation technique is explained in this article with the help of an example.
Pulse position modulation ppm is an analog modulation scheme in which, the amplitude and the width of the pulses are kept constant, while the position of each pulse, with reference to the position of a reference pulse varies according to the instantaneous sampled value of the message signal. Amplitude modulation is first type of modulation used for transmitting messages for long distances by the mankind. In the process of amplitude modulation, the frequency and phase of the carrier remain constant whereas the maximum amplitude varies according to the instantaneous value of the information signal. Sinusoidal amplitude modulation am mathematics of the dft. Demonstration with professor sandy hill from the university of massachusetts at amherst. The first is to gain a firsthand experience in programming the usrp to act as a transmitter and a receiver.
Jan 01, 2012 single sideband amplitude modulation one method to produce signal sideband ssb amplitude modulation is to produce dsbam, and pass the dsbam signal through a band pass filter, usually called a single sideband filter, which passes one of the sidebands as illustrated in the diagram below. Phase modulation pm is a different form of frequency modulation and the carrier is similar in appearance to a frequencymodulated carrier. How to measure modulation index for simple signals like sinut its easy to measure modulation index for complicated signals like speech you have to use more complicated techniques one such technique is to use oscilloscope in xy mode on x axis apply the message on y axis apply the am signal follow the procedure in the lab handout. Amplitude modulation or am as it is often called, is a form of modulation used for radio transmissions for broadcasting and two way radio communication applications. The minimumdistance receiver for a firstorder allpole folded spectrum.
Varying these parameters in proportion to the baseband signal results in amplitude modulation am, frequency16 modulation fm, and phase modulation pm, respectively. Pulse amplitude modulation is the basic form of pulse modulation. In amplitude modulation amplitude of the carrier wave is changed. Multiple choice questions and answers on amplitude modulation. The am radio ranges in between 535 to 1705 khz which is great. Inductionmotor speedchanging by poleamplitude modulation iet. 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 first transmission however, was performed by fessenden in 1906 from brant rock, massachusetts. Amplitude modulation definition is modulation of the amplitude of a radio carrier wave in accordance with the strength of the audio or other signal. Amplitude modulation was developed in the beginning of the 20th century. Although it is basically a singlewinding, twospeed squirrel cage motor, the pam motor features one outstanding characteristic.
Am is a relatively simple way to add audio information to a carrier wave so that sounds can be transmitted. Although one of the earliest used forms of modulation it is still used today, mainly for long, medium and short wave broadcasting and for some aeronautical point to point. Learn the concise history of amplitude modulation or am broadcasting technique. 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. Analog communication pulse modulation tutorialspoint. Amplitude modulation am is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. It was the earliest modulation technique used to transmit voice by radio. Amplitude modulation is a simple method to transmit a signal for example sound, from one end to other. Pole amplitude modulation pdf inductionmotor speedchanging by poleamplitude modulation. Bpsk, qpsk, msk frequency shift keying, fsk quadrature amplitude modulation, qam. This is also called an input signal or baseband signal speech for example. In large machine of high pole numbers, the effect of adjacent harmonics of m.
Amplitude modulation is mostly used in the form of electronic communication. The second is to investigate classical analog amplitude modulation and the envelope detector. In amplitude modulation, it is the voltage level of the signal to be transmitted. Amplitude modulation definition and its applications. Inductionmotor speedchanging by poleamplitude modulation. There are no amplitude scales shown, but you should be able to deduce the depth. Angle modulation is the process in which the frequency or the phase of the carrier varies according to the message signal. Modulation is done at high power of carrier and modulating signal b. Its basic feature is that the winding layout is irregular. Collector modulation method is high level amplitude modulation c. For a perfect modulation, the value of modulation index should be 1, which implies the percentage of modulation should be 100%. Amplitude modulation am is widely used for transmitting information or signals. Quadrature amplitude modulation is widely used for carrying many digital signals, everything from wifi to mobile phone communications and very much more.
The resulting signal from the process of amplitudemodulation is called amplitude modulation signal of simply am wave. This lab gives you the opportunity to actually work on amplitude modulation and reinforce the theory taught in class. So this form of amplitude modulation offers a way to create complex nonharmonic timbres that change pitch normally as you play up and down the keyboard. The information is considered as the modulating signal and it is superimposed on the carrier wave by applying both of them to the. If the amplitude modulated signal shown here is passed through a frequency analyzer, the following spectrum is the result. Amplitude modulation is a process by which the wave signal is transmitted by modulating the amplitude of the signal. What is amplitude modulation, am electronics notes. The modulated signal can be written as the sum of the unmodulated carrier wave. Known in the industry as the pam motor, the pole amplitude modulation motor is an innovative ac induction motor. An original method of changing the speed of squirrelcage induction motors has recently been developed which enables efficient and economic operation to be. When modulation index is more than 1 over modulation then detection is possible only with, synchronous modulation, such signal can not be detected with envelope detector.
Amplitude modulation in wind turbine noise valeri v. Research article feedback amplitude modulation synthesis. The aim of this topic is to explore the reasons for using modulation. Two signals are involved in the modulation process. Pdf in electric drive applications that are based on highspeed induction machines. Set g so that the sinewave peaks just fall to zero. Poleamplitude modulation polechanging electric motors and. In this experiment, you will examine the characteristics of amplitude modulation am. Amplitude modulation can be produced in various ways. Pole amplitude modulation is a flexible method of pole changing which can be used in applications where speed ratios other than 2. Appendix a mathematics of amplitude modulation dsbsc double sideband suppressed carrier modulation is produced by the product of the message.
To involve data information or speech information, another wave has to be imposed known as input signal above the carrier wave. An original method of changing the speed of squirrelcage induction motors has. The motors designed for speed changing based on the poled amplitude modulation scheme are known as pam motors. Notice that the sine wave will move up and down as the dc is varied, its mean value equalling the dc value. This technique applies the logic of amplitude modulation to the spacedistribution of the windings of an electrical machine. Hsu analog and digital communication summary equation message general mt monotone am cos. This gives us something to modulate and carry the information pattern from. Frenzeljr, in handbook of serial communications interfaces, 2016. In this modulation, the amplitude of the carrier signal varies in accordance with the message signal, and other factors like. The history of amplitude modulation brighthub engineering. 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. An original method of changing the speed of squirrelcage induction motors has recently been developed which enables efficient and economic operation to be obtained at either of two chosen speeds, using a single winding of standard type. Amplitude modulation am is a welldescribed technique of sound processing.