ELEC3242 Communications Engineering Laboratory Amplitude Modulation (AM)
|
|
- Christian Maxwell
- 5 years ago
- Views:
Transcription
1 ELEC3242 Communications Engineering Laboratory Amplitude Modulation (AM) 1. Objectives 1.1 Through this the laboratory experiment, you will investigate demodulation of an amplitude modulated (AM) signal using an envelope detector and subsequent filtering; investigate demodulation of an AM signal using a product detector and subsequent filtering; and investigate the spectrum of an AM signal. 1.2 On completion of this laboratory experiment, you will be able to: understand the concept of multiplying two sinusoidal waveforms; recognize that the result of such a multiplication is amplitude modulation; and determine the modulation index of an AM signal. 2. Theory 2.1 Concepts of Modulation A carrier is simply a single frequency of constant amplitude, phase and frequency. More properly, this is called an un-modulated or plain carrier. In itself, it does not carry any information. However, when referred to as an un-modulated carrier, the implication is that some information will be carried on it at some time. The carrier transports the information to be carried, hence the name. As it is an oscillation, it is sometimes also referred to as a wave. How is information to be carried? This information can be of many forms and can, by the time it reaches the carrier, be either analogue or digital in form. Even if the information is digital the process of transmission is analogue, because the real world is analogue. So, in general, there is no difference between the processes involved in carrying analogue or digital information. Information to be carried is often referred to as baseband. The reason for this name will become clearer later on. In order to be decoded at the receiving end of a communications channel, some characteristics of the carrier has to be varied to represent differences in the baseband signal. There are only three carrier characteristics that can be varied: its amplitude, its frequency and its phase. Some schemes vary more than one of these characteristics and also, as you will see, in some cases varying one will inadvertently vary the others. So it is important not to think of each in isolation. The term modulation arises from the implication that some part of the carrier characteristic is changing. When carrying information, the carrier is said to be modulated, and the sub system responsible for doing this is called a modulator. Page 1
2 The opposite process to modulation is demodulation, in which the baseband signal is recovered. The trick is to try and recover the baseband signal so that it is as near as possible to the original signal, even when it has been severely weakened and distorted during transmission. Another consideration is to use as little transmission bandwidth as possible, so that as many signals as possible can be sent down a cable or via a radio link. Transmission power is also important. Usually the minimum power that can be used to achieve a usable output is desirable. The concept of signal-to-noise ratio will also be introduced and how it is a measure of the quality of both the modulated and baseband signals. The assignments will introduce the modulation and demodulation concepts vital to an understanding of information transmission. 2.1 Equations of Amplitude Modulation The equation of a sinusoidal voltage waveform is given by : v = V maxsin(ωt + ) (1) where: v is the instantaneous voltage, Vmax is the maximum voltage amplitude, ω is the angular frequency in rad/s is the phase A steady voltage corresponding to the above equation conveys little information. To convey information the waveform must be made to vary so that the variations represent the information. This process is called modulation. From the above equation, the basic parameters of such a waveform are: its amplitude, Vmax its frequency, ω in rad/s (or f in Hz ) its phase, Any of these may be varied to convey information Amplitude Modulation (AM) Amplitude modulation uses variations in amplitude (Vmax) to convey information. The wave whose amplitude is being varied is called the carrier wave. The signal doing the variation is called the modulating signal. For simplicity, suppose both carrier wave and modulating signal are sinusoidal, i.e.: Page 2
3 vc = Vc sin ωc t (c denotes the carrier) and (2) vm = Vm sin ωmt (m denotes modulation) (3) We want the modulating signal to vary the carrier amplitude, Vc, so that: vc = (Vc + Vm sin ωmt). sinωc t (4) where (Vc + Vm sin ωmt) is the new and varying carrier amplitude. Expanding (4) gives: vc = Vc sin ωc t + Vm sin ωc t. sin ωmt (5) which may be rewritten as vc = Vc [sin ωc t + m sin ωc t. sin ωmt] (6) where m = Vm/ Vc and is called the Modulation Index. Now sin ωc t. sin ωmt = ½ [cos(ωc ωm) t cos(ωc + ωm) t] (7) so, we can express (6) as: vc = Vc sin ωc t + ½ (m Vc )[cos(ωc - ωm) t] ½(m Vc)[cos(ωc + ωm) t] (8) This expression for vc has three terms:- 1) The 1 st term is the original carrier waveform at frequency ωc, which contains no variations and thus carries no information. 2) The 2 nd term is a component at frequency (ωc ωm), whose amplitude is proportional to the modulation index. This is called the lower-side frequency. 3) The 3 rd term is a component at frequency (ωc + ωm), whose amplitude is proportional to the modulation index. This is called the upper-side fre4quency. It is the upper and lower side frequencies that carry the information. This is shown by the fact that only these 2 terms include the modulation index m. Because of this, the amplitudes of the side frequencies vary in proportion to that of the modulating signal; the amplitude of the carrier does not Sidebands If the modulating signal is a more complex waveform, for instance an audio voltage from a speech amplifier, there will be many side frequencies present in the total waveform. This gives Page 3
4 rise to components 2 and 3 in the last equation being bands of frequencies, known as sidebands. Hence we have the upper sideband and the lower sideband, together with the carrier. 3. Theory on Frequency Translation 3.1 Translating from zero frequency Baseband signal can be thought of a signal having 0 Hz (i.e. dc) as the carrier frequency and the baseband signal is the upper sideband. However, through Fourier Transform and in the frequency domain, the signal will have positive and negative frequency sidebands, each having a half of the total power. The modulation process can be thought of as that of frequency translation. Through modulation, the upper and lower sidebands of the baseband signal are moved up in positive and negative frequency by an amount equal to the carrier frequency. 4. Theory on the Experimental Determination of the Modulation Index This is most easily done by measuring the maximum and minimum values which the instantaneous amplitude of the carrier reaches. Let us call these x and y. Taking (6) for a sinusoidal carrier modulated by a sinusoidal waveform (see the Modulation Maths Concept): vc = Vc [sin ωc t + m sin ωc t. sin ωmt] and re-arranging it, vc can be expressed as vc = Vc sin ωc t [1+ m sin ωmt] (9) so that the instantaneous amplitude of the carrier is Vc [1+ m sin ωmt] Since sin ωmt can only vary between +1 and 1, x = Vc (1+ mvc ) and y = (1 mvc ). (10) To obtain the value of modulation index m from x and y, Vc can be eliminated between these equations by division, i.e., y/x = (1 m)/(1 + m). (11) Solving for m gives: m = (x y)/ (x + y) (12) Page 4
5 5. Practical 1: Double-Sideband Amplitude Modulation with Full Carrier 5.1 Background In this practical work, you will investigate how two sinusoidal signals are multiplied together to produce a modulated signal. The two signals are generated on the workboard. The signal that is to be modulated onto the carrier is usually refer to as the baseband signal, as it often has frequencies close to dc and sometimes a dc component. In the simplest amplitude modulator, the carrier is multiplied by only positive magnitudes of baseband signal. The baseband signal is usually bipolar so, when a true, four-quadrant multiplier is used as a modulator, an offset has to be added to change the baseband signal to unipolar, so that the carrier is only multiplied by positive values. The result of this is usually referred to as amplitude modulation with full carrier, as the amplitude of the carrier signal is controlled, or modulated, by the baseband. The frequency of the carrier is determined by the transmission method. For example, it might be a particular radio frequency. The modulating signal may take many forms: a complex digital signal or simply audio speech for example. As you can see the modulating signal is being carried by the carrier. In the practical work, you will be using simple sine waves so that the principles are easier to understand. In this simplest form of amplitude modulation, the instantaneous amplitude of the modulated waveform is proportional to the instantaneous amplitude of the modulating signal. The diagram shows such a signal in the time domain. Figure 1 AM Modulated signal Notice that when the modulating signal is at its maximum amplitude, the modulated waveform amplitude is at maximum, and that when the modulation is minimum, the modulated waveform amplitude is zero. Because most modulating signals have no dc component, the carrier is at half the modulated waveform s peak amplitude when the modulating signal is zero. Mathematically, amplitude modulation is the result of multiplying the two signals together. However such a process would not produce exactly the signal seen above. Imagine two sine waves with peak amplitudes of 1, i.e. their instantaneous values vary between +1 and 1. Page 5
6 If they were multiplied together, the output would also vary between +1 and 1. However, during the time that the modulation was -1, the output would not be 0 but would be the carrier multiplied by 1; i.e. its phase would be reversed. Hence the need for a modulating signal that varies between 0 and +1. This would be produced by adding a constant of value +1 to the modulating signal in the mathematics. This is equivalent to adding a dc offset voltage to the modulating signal. The example shows the maximum amount of modulation that can be applied to the carrier. The amplitude of the modulated waveform varies from zero to twice its mean value. The amount of modulation is referred to as modulation index and it is expressed as a parameter between 0 to 1. It is sometimes expressed as a percentage. 5.2 Sidebands If the modulation process were simply an addition of the two signals, the output would consist only of the two frequency components put in. However, as the process is that of multiplication, the output consists of some new frequency components: the carrier frequency plus the modulating frequency and the carrier frequency minus the modulating frequency. These are called sidebands. Their existences can easily be proved mathematically by multiplying two sine wave equations together (see the Modulation Maths Concept). In the case of having a dc offset, the output will contain a component at the carrier frequency. The diagram shows such a signal in the frequency domain. Figure 2 Carrier and two sidebands In a real system, the modulating signal would comprise a band of frequencies rather than simply one frequency. The diagram below shows how the spectrum would look. Figure 3 Spectrum display of carrier and two sidebands This type of transmission is called amplitude modulation with full carrier. The reason for this is obvious, in that the carrier is transmitted as well as the two sidebands. Historically, it has been used extensively, as the equipment needed to produce it and to receive it is very simple. Page 6
7 In the practical work, you will use a balanced modulator to generate the modulated signal and use a dc offset on the baseband signal. Note that there is a low pass filter at the output of the modulator, before it reaches the instrumentation. This is so you can see more clearly the modulated signal on the spectrum analyser without having to be concerned about the second harmonic of the carrier frequency that is caused by small, but inevitable, distortion in the modulator. 5.3 Block Diagram Figure 4 Block diagram of practical Make Connections Diagram Figure 5 Connections made on the workboard for practical Perform Practical Use the Make Connections diagram to make the required connections on the hardware. 1. Open the voltmeter and use it to set the dc Source voltage to give a Carrier offset of approximately volts. 2. Set the modulating signal amplitude (I Mod) by adjusting the Signal Level Control to half scale. Page 7
8 3. In the IQ Modulator block, set all of the controls to half scale. 4. Open the oscilloscope and note the waveform on the upper trace (the modulated waveform). Compare it to that on the lower trace (the modulating waveform). 5. Connect the voltmeter probe (green) to the modulating signal (monitor point 3) and set the voltmeter functions to ac p-p. Use the Signal Level Control to set the amplitude of the modulating signal to 0.25 volts peak to peak. 6. Use the oscilloscope cursors to measure the values A1 and A2 shown below. 7. Use the formula to calculate modulation index m. Figure 6 Computing modulation index 8. Try other values of modulation signal amplitude and measure A1 and A2 and thus calculate m. Compare the values with the ratios of the modulation signal peak value to the dc offset. Launch an Excel spreadsheet to tabulate your results. Note that the voltmeter reads peak to peak values. 9. Open the spectrum analyser and observe the spectrum of the modulated signal (monitor point 4). Adjust the modulation amplitude using the Signal Level Control and observe the spectrum. Use the cursors to measure the relative levels of the two sidebands to the carrier at m=1, 0.5 and Move the spectrum analyser probe (orange) to the modulation source (monitor point 3). Measure modulating frequency using the cursor. 11. Return to the modulated output (monitor point 4) and measure the frequencies of the two sidebands. Calculate the frequency difference between the carrier and the upper sideband, and the carrier and the lower sideband. 12. Now measure the modulating frequency on the second channel. Compare the values. 13. Set the modulation index to 1 using the oscilloscope display. 14. Open the phasescope. Move the reference probe (yellow) to the carrier source (monitor point 1) and the input probe (blue) to the modulated signal (monitor point 4). Note that the display shows a signal with constant phase changing in amplitude between a radial point to zero. 15. Change the modulation amplitude and note that the phase does not change but the variation in amplitude does. What happens when the amplitude is zero? 16. Change the modulation source from the 62.5 khz Locked Sine Source to the Function Page 8
9 Generator. Set the Function Generator to Fast and the output to a sine wave. Adjust the Frequency control and observe the spacing of the sidebands from the carrier on the spectrum analyzer. 5.6 Questions for practical 1: (a) Use your own words and the figures shown in practical 1 to describe the AM process. (b) From the spectrum analyzer, you can see that there are two sidebands in the signal spectrum. Use equations to explain how the carrier frequency relates to the uppersideband frequency and the lower-sideband frequency. (c) Use screenshot or photograph to record the spectra and waveforms of the modulated signal with m=1, 0.5 and 0. (d) Compute m for maximum percentage of power in the sidebands. (e) Compute the percentage of power used to send the carrier signal in a DSB AM with full carrier signal using equation and the spectrum. Comment on the difference. (f) Is DSB AM with full carrier a power efficient modulation scheme? Suggest ways to improve the efficiency. (g) With your suggestions, how much power you can save in transmission? 6. Practical 2: Demodulation with an Envelope Detector 6.1 Background Demodulation Demodulation is the reverse process to modulation. It takes the carrier and two sidebands of the modulated signal and extracts the modulating signal from it. In this instance, this can be done very simply. If the modulated signal is passed through either a full or half wave rectifier, followed by a filter that passes only the modulation, then the output follows the amplitude of the carrier. The resulting signal is the modulating plus the dc offset, which can be removed. This type of demodulator is called an envelope detector. Figure 9 shows the output of the rectifier for an AM signal. Page 9
10 Figure 7 Output from a rectifier Note that the filter is usually simply a resistor-capacitor network and the time constant of the filter is important, as it determines the magnitude of the residual carrier, or twice-carrier frequency components. Mathematically, this demodulator can also be thought of as a multiplier that takes the signal and multiplies it by its own carrier (this is because the carrier is switching the diodes in the rectifier). The result of multiplying the two sidebands is the demodulated signal and multiplying the carrier produces the dc offset in the output. In other words, the envelope detector uses the carrier component to demodulate the signal. In this Practical Work, you will use the same set-up as in Practical 1 to generate an AM double sideband (DSB) signal and use an envelope detector to demodulate it. The envelope detector uses a full wave rectifier, so that both positive and negative peaks of the modulated signal contribute. You will also see how the addition of a filter removes much of the twice carrier component. 6.2 Block Diagram Figure 8 Block diagram of practical Make Connections Diagram Figure 9 Connections made on the workboard for practical Perform Practical Page 10
11 Use the Make Connections diagram to make the connections on the hardware that are required. This practical work uses the same AM generator circuit as Practical Use the voltmeter to set the dc carrier offset to 0.25 volts. 2. Use the oscilloscope and the Signal Level Control to set the modulation index to approximately In the IQ Modulator block, set all of the controls to half scale. 4. Observe the output of the Envelope Detector (monitor point 5). Note that it reproduces the modulating signal. 6.5 Questions (a) Use screenshots or photographs to record the demodulated waveforms from the Envelope Detector for m=0, 0.5 and 1. (b) Use screenshots or photographs to record the spectra from the Envelope Detector for m=0, 0.5 and 1. (c) Compare the spectra of the demodulated signals with the modulating signals and comment. 7. Practical 3: Demodulation with a Product Detector 7.1 Background An alternative type of demodulator is called a product detector. Here the demodulating process requires the modulated signal to be multiplied with a reference signal having the frequency and phase equal to those of the carrier. In the envelope detector, the modulated signal is simply multiplied by itself to achieve this. In the product detector, the source of the reference signal is obtained from an external oscillator. This results in better demodulation because the multiplying signal is not varying in amplitude and does not contain so much noise. The action of such a demodulator is achieved by using a balanced modulator fed from an oscillator. This oscillator is often referred to as a local oscillator as in a link it is, as viewed from the receiver point of view, local as opposed to remote at the transmitting end. The process of having a reference signal at the receiver at the same frequency and phase as the original carrier is used in many demodulator processes. 7.2 Synchronising Although it has been stated that the local oscillator needs to be on frequency and in phase, so far it has not been explained how this is achieved. It is, in fact not easy. Other assignments show how this can be achieved for other types of demodulators, but in this assignment, for simplicity, a sample of the original carrier is used to synchronise the local oscillator. In practice, AM double sideband with full carrier is usually demodulated with derivatives of the envelope detector. Page 11
12 As you will see later, the product detector is used for suppressed carrier single sideband transmission. However, it is important that you understand that a product detector can be used to detect full carrier AM. Figure 10 Output from the multiplier You will also see how the addition of a filter can remove much of the twice carrier component. A filter in this position is often referred to as a post detection filter. 7.3 Block Diagram 7.4 Make Connections Diagram Figure 13 Block diagram of practical 3 Page 12
13 Figure 11 Connections made on the workboard for practical Perform Practical 3 Use the Make Connections diagram to make the connections on the hardware that are required. Again, you use the same generator configuration to generate the AM waveform. 1. Use the voltmeter to make sure that the dc carrier offset is set to 0.25 volts. 2. Use the Signal Level Control to set the modulation index to approximately In the IQ Modulator block, set all of the controls to half scale. 4. Use the oscilloscope to observe the output of the product detector (monitor point 5) and the spectrum analyser to note the twice carrier frequency component. Observe the output after the post detection filter (monitor point 6). 7.6 Questions for practical 3: (a) Describe the operations of an envelope detector and a product detector. (b) Use screenshot or photograph to record the waveform and spectrum at the input of the lowpass filter. (c) Use screenshot or photograph to record the waveform and spectrum at the output of the lowpass filter. (d) What is the function of filter in demodulation? (e) What is the advantage of product detector compared to envelop detector? Page 13
ELEC3242 Communications Engineering Laboratory Frequency Shift Keying (FSK)
ELEC3242 Communications Engineering Laboratory 1 ---- Frequency Shift Keying (FSK) 1) Frequency Shift Keying Objectives To appreciate the principle of frequency shift keying and its relationship to analogue
More informationUNIVERSITY OF NORTH CAROLINA AT CHARLOTTE Department of Electrical and Computer Engineering
UNIVERSITY OF NORTH CAROLINA AT CHARLOTTE Department of Electrical and Computer Engineering EXPERIMENT 8 AMPLITUDE MODULATION AND DEMODULATION OBJECTIVES The focus of this lab is to familiarize the student
More informationAmplitude Modulation. Ahmad Bilal
Amplitude Modulation Ahmad Bilal 5-2 ANALOG AND DIGITAL Analog-to-analog conversion is the representation of analog information by an analog signal. Topics discussed in this section: Amplitude Modulation
More informationDepartment of Electronic and Information Engineering. Communication Laboratory. Phase Shift Keying (PSK) & Quadrature Phase Shift Keying (QPSK)
Department of Electronic and Information Engineering Communication Laboratory Phase Shift Keying (PSK) & Quadrature Phase Shift Keying (QPSK) Objectives To familiar with the concept of describing phase
More informationEE-4022 Experiment 2 Amplitude Modulation (AM)
EE-4022 MILWAUKEE SCHOOL OF ENGINEERING 2015 Page 2-1 Student objectives: EE-4022 Experiment 2 Amplitude Modulation (AM) In this experiment the student will use laboratory modules to implement operations
More informationPart I - Amplitude Modulation
EE/CME 392 Laboratory 1-1 Part I - Amplitude Modulation Safety: In this lab, voltages are less than 15 volts and this is not normally dangerous to humans. However, you should assemble or modify a circuit
More informationLaboratory Assignment 5 Amplitude Modulation
Laboratory Assignment 5 Amplitude Modulation PURPOSE In this assignment, you will explore the use of digital computers for the analysis, design, synthesis, and simulation of an amplitude modulation (AM)
More informationAmplitude Modulation Chapter 2. Modulation process
Question 1 Modulation process Modulation is the process of translation the baseband message signal to bandpass (modulated carrier) signal at frequencies that are very high compared to the baseband frequencies.
More informationIntroduction to Amplitude Modulation
1 Introduction to Amplitude Modulation Introduction to project management. Problem definition. Design principles and practices. Implementation techniques including circuit design, software design, solid
More informationProblems from the 3 rd edition
(2.1-1) Find the energies of the signals: a) sin t, 0 t π b) sin t, 0 t π c) 2 sin t, 0 t π d) sin (t-2π), 2π t 4π Problems from the 3 rd edition Comment on the effect on energy of sign change, time shifting
More informationSpeech, music, images, and video are examples of analog signals. Each of these signals is characterized by its bandwidth, dynamic range, and the
Speech, music, images, and video are examples of analog signals. Each of these signals is characterized by its bandwidth, dynamic range, and the nature of the signal. For instance, in the case of audio
More informationcosω t Y AD 532 Analog Multiplier Board EE18.xx Fig. 1 Amplitude modulation of a sine wave message signal
University of Saskatchewan EE 9 Electrical Engineering Laboratory III Amplitude and Frequency Modulation Objectives: To observe the time domain waveforms and spectra of amplitude modulated (AM) waveforms
More informationModulation is the process of impressing a low-frequency information signal (baseband signal) onto a higher frequency carrier signal
Modulation is the process of impressing a low-frequency information signal (baseband signal) onto a higher frequency carrier signal Modulation is a process of mixing a signal with a sinusoid to produce
More informationCharan Langton, Editor
Charan Langton, Editor SIGNAL PROCESSING & SIMULATION NEWSLETTER Baseband, Passband Signals and Amplitude Modulation The most salient feature of information signals is that they are generally low frequency.
More informationOBJECTIVES EQUIPMENT LIST
1 Reception of Amplitude Modulated Signals AM Demodulation OBJECTIVES The purpose of this experiment is to show how the amplitude-modulated signals are demodulated to obtain the original signal. Also,
More informationSignals and Systems Lecture 9 Communication Systems Frequency-Division Multiplexing and Frequency Modulation (FM)
Signals and Systems Lecture 9 Communication Systems Frequency-Division Multiplexing and Frequency Modulation (FM) April 11, 2008 Today s Topics 1. Frequency-division multiplexing 2. Frequency modulation
More informationCHAPTER 2! AMPLITUDE MODULATION (AM)
CHAPTER 2 AMPLITUDE MODULATION (AM) Topics 2-1 : AM Concepts 2-2 : Modulation Index and Percentage of Modulation 2-3 : Sidebands and the Frequency Domain 2-4 : Single-Sideband Modulation 2-5 : AM Power
More informationPRODUCT DEMODULATION - SYNCHRONOUS & ASYNCHRONOUS
PRODUCT DEMODULATION - SYNCHRONOUS & ASYNCHRONOUS INTRODUCTION...98 frequency translation...98 the process...98 interpretation...99 the demodulator...100 synchronous operation: ω 0 = ω 1...100 carrier
More informationYEDITEPE UNIVERSITY ENGINEERING FACULTY COMMUNICATION SYSTEMS LABORATORY EE 354 COMMUNICATION SYSTEMS
YEDITEPE UNIVERSITY ENGINEERING FACULTY COMMUNICATION SYSTEMS LABORATORY EE 354 COMMUNICATION SYSTEMS EXPERIMENT 3: SAMPLING & TIME DIVISION MULTIPLEX (TDM) Objective: Experimental verification of the
More informationAMPLITUDE MODULATION
AMPLITUDE MODULATION PREPARATION...2 theory...3 depth of modulation...4 measurement of m... 5 spectrum... 5 other message shapes.... 5 other generation methods...6 EXPERIMENT...7 aligning the model...7
More informationAnalogue & Digital Telecommunications
Analogue & Digital Telecommunications 53-004 Tuned Circuits & Filters Amplifiers & Oscillators Description Modulation & Coding This modern training system provides a learning platform that involves the
More informationExperiment 7: Frequency Modulation and Phase Locked Loops
Experiment 7: Frequency Modulation and Phase Locked Loops Frequency Modulation Background Normally, we consider a voltage wave form with a fixed frequency of the form v(t) = V sin( ct + ), (1) where c
More informationCMPT 368: Lecture 4 Amplitude Modulation (AM) Synthesis
CMPT 368: Lecture 4 Amplitude Modulation (AM) Synthesis Tamara Smyth, tamaras@cs.sfu.ca School of Computing Science, Simon Fraser University January 8, 008 Beat Notes What happens when we add two frequencies
More informationEE 400L Communications. Laboratory Exercise #7 Digital Modulation
EE 400L Communications Laboratory Exercise #7 Digital Modulation Department of Electrical and Computer Engineering University of Nevada, at Las Vegas PREPARATION 1- ASK Amplitude shift keying - ASK - in
More informationFourier Transform And Its Application In Modulation Techniques
ourier Transform And Its Application In Modulation Techniques Mrs. Supriya Nilesh Thakur Mrs. Megha Kishor Kothawade Assistant Professor, Basic Engineering Science Department, Guru Gobind Singh College
More informationExperiment 6: Amplitude Modulation, Modulators, and Demodulators Fall 2009
Experiment 6: Amplitude Modulation, Modulators, and Demodulators Fall 009 Double Sideband Amplitude Modulation (AM) V S (1+m) v S (t) V S V S (1-m) Figure 1 Sinusoidal signal with a dc component In double
More informationChapter 14 FSK Demodulator
Chapter 14 FSK Demodulator 14-1 : Curriculum Objectives 1. To understand the operation theory of FSK demodulator. 2. To implement the FSK detector circuit by using PLL. 3. To understand the operation theory
More information1B Paper 6: Communications Handout 2: Analogue Modulation
1B Paper 6: Communications Handout : Analogue Modulation Ramji Venkataramanan Signal Processing and Communications Lab Department of Engineering ramji.v@eng.cam.ac.uk Lent Term 16 1 / 3 Modulation Modulation
More informationChapter 3. Amplitude Modulation Fundamentals
Chapter 3 Amplitude Modulation Fundamentals Topics Covered 3-1: AM Concepts 3-2: Modulation Index and Percentage of Modulation 3-3: Sidebands and the Frequency Domain 3-4: AM Power 3-5: Single-Sideband
More informationAM, PM and FM mo m dula l ti t o i n
AM, PM and FM modulation What is amplitude modulation In order that a radio signal can carry audio or other information for broadcasting or for two way radio communication, it must be modulated or changed
More informationCommunication Systems Lab
LAB MANUAL Communication Systems Lab (EE-226-F) Prepared by: Varun Sharma (Lab In-charge) Dayal C. Sati (Faculty In-charge) B R C M CET BAHAL DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING Page
More informationInternal Examination I Answer Key DEPARTMENT OF CSE & IT. Semester: III Max.Marks: 100
NH 67, Karur Trichy Highways, Puliyur C.F, 639 114 Karur District Internal Examination I Answer Key DEPARTMENT OF CSE & IT Branch & Section: II CSE & IT Date & Time: 06.08.15 & 3 Hours Semester: III Max.Marks:
More informationCME 312-Lab Communication Systems Laboratory
Objective: By the end of this experiment, the student should be able to: 1. Demonstrate the Modulation and Demodulation of the AM. 2. Observe the relation between modulation index and AM signal envelope.
More informationEE 368 Electronics Lab. Experiment 10 Operational Amplifier Applications (2)
EE 368 Electronics Lab Experiment 10 Operational Amplifier Applications (2) 1 Experiment 10 Operational Amplifier Applications (2) Objectives To gain experience with Operational Amplifier (Op-Amp). To
More informationCME312- LAB Manual DSB-SC Modulation and Demodulation Experiment 6. Experiment 6. Experiment. DSB-SC Modulation and Demodulation
Experiment 6 Experiment DSB-SC Modulation and Demodulation Objectives : By the end of this experiment, the student should be able to: 1. Demonstrate the modulation and demodulation process of DSB-SC. 2.
More informationDepartment of Electronic and Information Engineering. Communication Laboratory
Department of Electronic and Information Engineering Communication Laboratory Frequency Shift Keying (FSK) & Differential Phase Shift Keying (DPSK) & Differential Quadrature Phase Shift Keying (DQPSK)
More informationWeek 8 AM Modulation and the AM Receiver
Week 8 AM Modulation and the AM Receiver The concept of modulation and radio transmission is introduced. An AM receiver is studied and the constructed on the prototyping board. The operation of the AM
More informationSignal Characteristics
Data Transmission The successful transmission of data depends upon two factors:» The quality of the transmission signal» The characteristics of the transmission medium Some type of transmission medium
More informationB.Tech II Year II Semester (R13) Supplementary Examinations May/June 2017 ANALOG COMMUNICATION SYSTEMS (Electronics and Communication Engineering)
Code: 13A04404 R13 B.Tech II Year II Semester (R13) Supplementary Examinations May/June 2017 ANALOG COMMUNICATION SYSTEMS (Electronics and Communication Engineering) Time: 3 hours Max. Marks: 70 PART A
More informationUNIT-I AMPLITUDE MODULATION (2 Marks Questions and Answers)
UNIT-I AMPLITUDE MODULATION (2 Marks Questions and Answers) 1. Define modulation? Modulation is a process by which some characteristics of high frequency carrier Signal is varied in accordance with the
More informationEE 460L University of Nevada, Las Vegas ECE Department
EE 460L PREPARATION 1- ASK Amplitude shift keying - ASK - in the context of digital communications is a modulation process which imparts to a sinusoid two or more discrete amplitude levels. These are related
More information(b) What are the differences between FM and PM? (c) What are the differences between NBFM and WBFM? [9+4+3]
Code No: RR220401 Set No. 1 1. (a) The antenna current of an AM Broadcast transmitter is 10A, if modulated to a depth of 50% by an audio sine wave. It increases to 12A as a result of simultaneous modulation
More informationData Conversion Circuits & Modulation Techniques. Subhasish Chandra Assistant Professor Department of Physics Institute of Forensic Science, Nagpur
Data Conversion Circuits & Modulation Techniques Subhasish Chandra Assistant Professor Department of Physics Institute of Forensic Science, Nagpur Data Conversion Circuits 2 Digital systems are being used
More informationMaster Degree in Electronic Engineering
Master Degree in Electronic Engineering Analog and telecommunication electronic course (ATLCE-01NWM) Miniproject: Baseband signal transmission techniques Name: LI. XINRUI E-mail: s219989@studenti.polito.it
More informationCommunication Engineering Prof. Surendra Prasad Department of Electrical Engineering Indian Institute of Technology, Delhi
Communication Engineering Prof. Surendra Prasad Department of Electrical Engineering Indian Institute of Technology, Delhi Lecture - 10 Single Sideband Modulation We will discuss, now we will continue
More informationOutline. Communications Engineering 1
Outline Introduction Signal, random variable, random process and spectra Analog modulation Analog to digital conversion Digital transmission through baseband channels Signal space representation Optimal
More informationFDM- FREQUENCY DIVISION MULTIPLEXING
FDM- FREQUENCY DIVISION MULTIPLEXING Multiplexing to refer to the combination of information streams from multiple sources for transmission over a shared medium Demultiplexing to refer to the separation
More informationLecture 6. Angle Modulation and Demodulation
Lecture 6 and Demodulation Agenda Introduction to and Demodulation Frequency and Phase Modulation Angle Demodulation FM Applications Introduction The other two parameters (frequency and phase) of the carrier
More informationExperiment 02: Amplitude Modulation
ECE316, Experiment 02, 2017 Communications Lab, University of Toronto Experiment 02: Amplitude Modulation Bruno Korst - bkf@comm.utoronto.ca Abstract In this second laboratory experiment, you will see
More informationLaboratory Exercise 6 THE OSCILLOSCOPE
Introduction Laboratory Exercise 6 THE OSCILLOSCOPE The aim of this exercise is to introduce you to the oscilloscope (often just called a scope), the most versatile and ubiquitous laboratory measuring
More informationELG3175: Introduction to Communication Systems. Laboratory II: Amplitude Modulation
Introduction: ELG3175: Introduction to Communication Systems Laboratory II: Amplitude Modulation In this lab, we shall investigate some fundamental aspects of the conventional AM and DSB-SC modulation
More informationModulations Analog Modulations Amplitude modulation (AM) Linear modulation Frequency modulation (FM) Phase modulation (PM) cos Angle modulation FM PM Digital Modulations ASK FSK PSK MSK MFSK QAM PAM Etc.
More informationPulse-Width Modulation (PWM)
Pulse-Width Modulation (PWM) Modules: Integrate & Dump, Digital Utilities, Wideband True RMS Meter, Tuneable LPF, Audio Oscillator, Multiplier, Utilities, Noise Generator, Speech, Headphones. 0 Pre-Laboratory
More informationDepartment of Electronics & Telecommunication Engg. LAB MANUAL. B.Tech V Semester [ ] (Branch: ETE)
Department of Electronics & Telecommunication Engg. LAB MANUAL SUBJECT:-DIGITAL COMMUNICATION SYSTEM [BTEC-501] B.Tech V Semester [2013-14] (Branch: ETE) KCT COLLEGE OF ENGG & TECH., FATEHGARH PUNJAB TECHNICAL
More informationAmplitude Modulated Systems
Amplitude Modulated Systems Communication is process of establishing connection between two points for information exchange. Channel refers to medium through which message travels e.g. wires, links, or
More informationEXPERIMENT 4 - Part I: DSB Amplitude Modulation
OBJECTIVE To generate DSB amplitude modulated signal. EXPERIMENT 4 - Part I: DSB Amplitude Modulation PRELIMINARY DISCUSSION In an amplitude modulation (AM) communications system, the message signal is
More informationKeywords Internet, LabVIEW, Smart Classroom-cum-Laboratory, Teaching and Learning process of communication.
Volume 4, Issue 10, October 2014 ISSN: 2277 128X International Journal of Advanced Research in Computer Science and Software Engineering Research Paper Available online at: www.ijarcsse.com Smart Classroom-cum-Laboratory
More informationDISCRETE DIFFERENTIAL AMPLIFIER
DISCRETE DIFFERENTIAL AMPLIFIER This differential amplifier was specially designed for use in my VK-1 audio oscillator and VK-2 distortion meter where the requirements of ultra-low distortion and ultra-low
More informationCode No: R Set No. 1
Code No: R05220405 Set No. 1 II B.Tech II Semester Regular Examinations, Apr/May 2007 ANALOG COMMUNICATIONS ( Common to Electronics & Communication Engineering and Electronics & Telematics) Time: 3 hours
More informationElements of Communication System Channel Fig: 1: Block Diagram of Communication System Terminology in Communication System
Content:- Fundamentals of Communication Engineering : Elements of a Communication System, Need of modulation, electromagnetic spectrum and typical applications, Unit V (Communication terminologies in communication
More informationMusic 171: Amplitude Modulation
Music 7: Amplitude Modulation Tamara Smyth, trsmyth@ucsd.edu Department of Music, University of California, San Diego (UCSD) February 7, 9 Adding Sinusoids Recall that adding sinusoids of the same frequency
More informationEasy SDR Experimentation with GNU Radio
Easy SDR Experimentation with GNU Radio Introduction to DSP (and some GNU Radio) About Me EE, Independent Consultant Hardware, Software, Security Cellular, FPGA, GNSS,... DAGR Denver Area GNU Radio meet-up
More informationModule 5. DC to AC Converters. Version 2 EE IIT, Kharagpur 1
Module 5 DC to AC Converters Version 2 EE IIT, Kharagpur 1 Lesson 37 Sine PWM and its Realization Version 2 EE IIT, Kharagpur 2 After completion of this lesson, the reader shall be able to: 1. Explain
More informationThe quality of the transmission signal The characteristics of the transmission medium. Some type of transmission medium is required for transmission:
Data Transmission The successful transmission of data depends upon two factors: The quality of the transmission signal The characteristics of the transmission medium Some type of transmission medium is
More informationUNIT-2 Angle Modulation System
UNIT-2 Angle Modulation System Introduction There are three parameters of a carrier that may carry information: Amplitude Frequency Phase Frequency Modulation Power in an FM signal does not vary with modulation
More informationExercise 2: FM Detection With a PLL
Phase-Locked Loop Analog Communications Exercise 2: FM Detection With a PLL EXERCISE OBJECTIVE When you have completed this exercise, you will be able to explain how the phase detector s input frequencies
More informationChapter 3: Analog Modulation Cengage Learning Engineering. All Rights Reserved.
Contemporary Communication Systems using MATLAB Chapter 3: Analog Modulation 2013 Cengage Learning Engineering. All Rights Reserved. 3.1 Preview In this chapter we study analog modulation & demodulation,
More informationLecture-3 Amplitude Modulation: Single Side Band (SSB) Modulation
Lecture-3 Amplitude Modulation: Single Side Band (SSB) Modulation 3.0 Introduction. 3.1 Baseband Signal SSB Modulation. 3.1.1 Frequency Domain Description. 3.1. Time Domain Description. 3. Single Tone
More informationECE 4670 Spring 2014 Lab 1 Linear System Characteristics
ECE 4670 Spring 2014 Lab 1 Linear System Characteristics 1 Linear System Characteristics The first part of this experiment will serve as an introduction to the use of the spectrum analyzer in making absolute
More informationDSBSC GENERATION. PREPARATION definition of a DSBSC viewing envelopes multi-tone message... 37
DSBSC GENERATION PREPARATION... 34 definition of a DSBSC... 34 block diagram...36 viewing envelopes... 36 multi-tone message... 37 linear modulation...38 spectrum analysis... 38 EXPERIMENT... 38 the MULTIPLIER...
More informationCHAPTER 2 DIGITAL MODULATION
2.1 INTRODUCTION CHAPTER 2 DIGITAL MODULATION Referring to Equation (2.1), if the information signal is digital and the amplitude (lv of the carrier is varied proportional to the information signal, a
More informationtwo computers. 2- Providing a channel between them for transmitting and receiving the signals through it.
1. Introduction: Communication is the process of transmitting the messages that carrying information, where the two computers can be communicated with each other if the two conditions are available: 1-
More informationDigital Communication
Digital Communication Laboratories bako@ieee.org DigiCom Labs There are 5 labs related to the digital communication. Study of the parameters of metal cables including: characteristic impendance, attenuation
More informationEECS 216 Winter 2008 Lab 2: FM Detector Part II: In-Lab & Post-Lab Assignment
EECS 216 Winter 2008 Lab 2: Part II: In-Lab & Post-Lab Assignment c Kim Winick 2008 1 Background DIGITAL vs. ANALOG communication. Over the past fifty years, there has been a transition from analog to
More informationOn-off keying, which consists of keying a sinusoidal carrier on and off with a unipolar binary signal
Bandpass signalling Thus far only baseband signalling has been considered: an information source is usually a baseband signal. Some communication channels have a bandpass characteristic, and will not propagate
More informationSINUSOIDS February 4, ELEC-281 Network Theory II Wentworth Institute of Technology. Bradford Powers Ryan Ferguson Richard Lupa Benjamin Wolf
SINUSOIDS February 4, 28 ELEC-281 Network Theory II Wentworth Institute of Technology Bradford Powers Ryan Ferguson Richard Lupa Benjamin Wolf Abstract: Sinusoidal waveforms are studied in three circuits:
More informationT.J.Moir AUT University Auckland. The Ph ase Lock ed Loop.
T.J.Moir AUT University Auckland The Ph ase Lock ed Loop. 1.Introduction The Phase-Locked Loop (PLL) is one of the most commonly used integrated circuits (ICs) in use in modern communications systems.
More informationEET 223 RF COMMUNICATIONS LABORATORY EXPERIMENTS
EET 223 RF COMMUNICATIONS LABORATORY EXPERIMENTS Experimental Goals A good technician needs to make accurate measurements, keep good records and know the proper usage and limitations of the instruments
More informationUNIT I FUNDAMENTALS OF ANALOG COMMUNICATION Introduction In the Microbroadcasting services, a reliable radio communication system is of vital importance. The swiftly moving operations of modern communities
More informationDefinitions. Spectrum Analyzer
SIGNAL ANALYZERS Spectrum Analyzer Definitions A spectrum analyzer measures the magnitude of an input signal versus frequency within the full frequency range of the instrument. The primary use is to measure
More informationOptical Modulation and Frequency of Operation
Optical Modulation and Frequency of Operation Developers AB Overby Objectives Preparation Background The objectives of this experiment are to describe and illustrate the differences between frequency of
More informationExperiment No. 3 Pre-Lab Phase Locked Loops and Frequency Modulation
Experiment No. 3 Pre-Lab Phase Locked Loops and Frequency Modulation The Pre-Labs are informational and although they follow the procedures in the experiment, they are to be completed outside of the laboratory.
More informationLAB Assignment No. 6: TO STUDY GENERATION OF DOUBLE SIDE BAND AMPLITUDE MODULATE (AM) WAVEFORMS, USING DSB/SSB TRANSMITTER
LAB Assignment No. 6: TO STUDY GENERATION OF DOUBLE SIDE BAND AMPLITUDE MODULATE (AM) WAVEFORMS, USING DSB/SSB TRANSMITTER APPARATUS: Oscilloscope DSB/SSB Traine Power supply Connecting leads THEORY: A
More informationResidual Phase Noise Measurement Extracts DUT Noise from External Noise Sources By David Brandon and John Cavey
Residual Phase Noise easurement xtracts DUT Noise from xternal Noise Sources By David Brandon [david.brandon@analog.com and John Cavey [john.cavey@analog.com Residual phase noise measurement cancels the
More informationLAB 1: Familiarity with Laboratory Equipment (_/10)
LAB 1: Familiarity with Laboratory Equipment (_/10) PURPOSE o gain familiarity with basic laboratory equipment oscilloscope, oscillator, multimeter and electronic components. EQUIPMEN (i) Oscilloscope
More informationmultiplier input Env. Det. LPF Y (Vertical) VCO X (Horizontal)
Spectrum Analyzer Objective: The aim of this project is to realize a spectrum analyzer using analog circuits and a CRT oscilloscope. This interface circuit will enable to use oscilloscopes as spectrum
More information4.1 REPRESENTATION OF FM AND PM SIGNALS An angle-modulated signal generally can be written as
1 In frequency-modulation (FM) systems, the frequency of the carrier f c is changed by the message signal; in phase modulation (PM) systems, the phase of the carrier is changed according to the variations
More informationEE-4022 Experiment 3 Frequency Modulation (FM)
EE-4022 MILWAUKEE SCHOOL OF ENGINEERING 2015 Page 3-1 Student Objectives: EE-4022 Experiment 3 Frequency Modulation (FM) In this experiment the student will use laboratory modules including a Voltage-Controlled
More informationReal and Complex Modulation
Real and Complex Modulation TIPL 4708 Presented by Matt Guibord Prepared by Matt Guibord 1 What is modulation? Modulation is the act of changing a carrier signal s properties (amplitude, phase, frequency)
More informationNarrowband Data Transmission ASK/FSK
Objectives Communication Systems II - Laboratory Experiment 9 Narrowband Data Transmission ASK/FSK To generate amplitude-shift keyed (ASK) and frequency-shift keyed (FSK) signals, study their properties,
More informationAC CURRENTS, VOLTAGES, FILTERS, and RESONANCE
July 22, 2008 AC Currents, Voltages, Filters, Resonance 1 Name Date Partners AC CURRENTS, VOLTAGES, FILTERS, and RESONANCE V(volts) t(s) OBJECTIVES To understand the meanings of amplitude, frequency, phase,
More informationTHE SINUSOIDAL WAVEFORM
Chapter 11 THE SINUSOIDAL WAVEFORM The sinusoidal waveform or sine wave is the fundamental type of alternating current (ac) and alternating voltage. It is also referred to as a sinusoidal wave or, simply,
More informationAC Theory and Electronics
AC Theory and Electronics An Alternating Current (AC) or Voltage is one whose amplitude is not constant, but varies with time about some mean position (value). Some examples of AC variation are shown below:
More informationCS311: Data Communication. Transmission of Analog Signal - I
CS311: Data Communication Transmission of Analog Signal - I by Dr. Manas Khatua Assistant Professor Dept. of CSE IIT Jodhpur E-mail: manaskhatua@iitj.ac.in Web: http://home.iitj.ac.in/~manaskhatua http://manaskhatua.github.io/
More informationAmplitude Modulation II
Lecture 6: Amplitude Modulation II EE 3770: Communication Systems Lecture 6 Amplitude Modulation II AM Limitations DSB-SC Modulation SSB Modulation VSB Modulation Multiplexing Mojtaba Vaezi 6-1 Contents
More informationExercise 2: Demodulation (Quadrature Detector)
Analog Communications Angle Modulation and Demodulation Exercise 2: Demodulation (Quadrature Detector) EXERCISE OBJECTIVE When you have completed this exercise, you will be able to explain demodulation
More informationECE5713 : Advanced Digital Communications
ECE5713 : Advanced Digital Communications Bandpass Modulation MPSK MASK, OOK MFSK 04-May-15 Advanced Digital Communications, Spring-2015, Week-8 1 In-phase and Quadrature (I&Q) Representation Any bandpass
More informationTwelve voice signals, each band-limited to 3 khz, are frequency -multiplexed using 1 khz guard bands between channels and between the main carrier
Twelve voice signals, each band-limited to 3 khz, are frequency -multiplexed using 1 khz guard bands between channels and between the main carrier and the first channel. The modulation of the main carrier
More informationCommunication Channels
Communication Channels wires (PCB trace or conductor on IC) optical fiber (attenuation 4dB/km) broadcast TV (50 kw transmit) voice telephone line (under -9 dbm or 110 µw) walkie-talkie: 500 mw, 467 MHz
More informationTable of Contents...2. About the Tutorial...6. Audience...6. Prerequisites...6. Copyright & Disclaimer EMI INTRODUCTION Voltmeter...
1 Table of Contents Table of Contents...2 About the Tutorial...6 Audience...6 Prerequisites...6 Copyright & Disclaimer...6 1. EMI INTRODUCTION... 7 Voltmeter...7 Ammeter...8 Ohmmeter...8 Multimeter...9
More information