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### UNFORMATTED ATTACHMENT PREVIEW

IT300 Virtual Lab 3 V5 ASK, FSK and PSK Digital Modulation Student Name: ___________________ GMU ID: ____________Date: _____________ Objectives. VLAB3 covers part 1: On-Off Keying (OOK), part 2: Amplitude Shift Keying (ASK), part 3: Frequency Shift Keying (FSK), and part 4: Phase Shift Keying (PSK) digital signaling techniques. As you read through this procedure, you will find multiple choice questions appearing in blue text. You are required to answer these questions in a separate VLAB assignment which will appear in the VLAB folder. The question format is similar to that of a homework assignment (i.e., select the correct answers and submit). In addition, you will be asked to copy and submit plots that you create using MatLab. These will also be identified by blue text within the procedures. A document “plot submission” template will be available for you to paste requested copies for submission into the VLAB assignment. Students are highly encouraged to change the values of variables during each part of the lab in order to observe changes in the signal plots. Note: In this lab (VLAB3) no MatLab code modification is necessary. Part 1. OOK (On Off Keying) Digital Modulation Logical Data Set data = [1 0 0 1 0 0 1 0] Simple Line Code Voltages a1 volts representing logical “1” a2 volts representing logical “0” Carrier: c(t) = Ac cos(2πfct), c=Ac*cos(2*pi*fc*t) Step 1.1 Use the following MATLAB code and create plots using the following code. %OOK clear clc clf Ac=3 %amplitude of the carrier fc=5 %frequency of the carrier data=[1 0 0 1 0 0 1 0] a1=1 %simple line code amplitude 1 a2=0 %simple line coded amplitude 2 blc2=1:8 %replace data with line coded voltage n = length(data) %number of data bits t = 0:.01:n %time x-axis x = 1:1:(n+1)*100 %”for j” matrix statement, populate matrix dat2 for m=1:n %replace logical data with voltage line coding if data(m)>0 Index=data(m)/Ac %ASK index blc2(m)=a1 else blc2(m)=a2 1 end end for i = 1:n %expand line coded volatges by x10 for j = i:.1:i+1 dat2(x(i*100:(i+1)*100)) = blc2(i) %populate line code matrix by expanding x10 end end dat2 = dat2(100:end) cosine=cos(2*pi*fc*t) c = Ac*cos(2*pi*fc*t) %carrier wave st = (Ac*dat2).*cosine %OOK modulated signal subplot(4,1,1) plot(t,dat2)%plot line coded data title(‘Simple Line Coded Data’) grid on axis([0 n -1 +3]) subplot(4,1,2) plot(t,c) %plot carrier wave title(‘Carrier Wave’) grid on axis([0 n -8 +8]) subplot(4,1,3) plot(t,st) %plot OOK modulated signal title(‘OOK Modulated Signal’) grid on axis([0 n -7 +7]) %combined modulated carrier and line coded data plot subplot(4, 1, 4) yyaxis left plot(t, st) ylim([-8 8]) yyaxis right plot(t, dat2) ylim([-1 2]) title(‘Combined Line Coded Data and OOK Modulated Carrier’) xlabel(‘time’) ylabel(‘amplitude’) Question 1. The OOK modulated signal does not accurately represents the logical data. a. True b. False Plot 1 – OOK Signal Plot Submission: Submit (i.e., copy/paste) the MATLAB plots from step 1.1 above into the “IT300 Virtual Lab Plot Submission” . Part 2. ASK Digital Modulation Logical Data Set: data = [1 0 0 1 0 0 1 0] Simple Line Code Voltages: a1 volts representing logical “1” 2 a2 volts representing logical “0” Carrier: c(t) = Ac cos(2πfct), c=Ac*cos(2*pi*fc*t) Index: Index=data(m)/Ac Step 2.1 Use the following MATLAB code and create plots. %ASK clear clc clf Ac=3 %amplitude of the carrier fc=5 %frequency of the carrier data=[1 0 0 1 0 0 1 0] a1=4.5 %simple line code amplitude 1 a2=0.5 %simple line coded amplitude 2 blc2=1:8 %replace data with line coded voltage n = length(data) %number of data bits t = 0:.01:n %time x-axis x = 1:1:(n+1)*100 %”for j” matrix statement, populate matrix dat2 for m=1:n %replace logical data with voltage line coding if data(m)>0 Index=data(m)/Ac %ASK index blc2(m)=a1 else blc2(m)=a2 end end for i = 1:n %expand line coded volatges by x10 for j = i:.1:i+1 dat2(x(i*100:(i+1)*100)) = blc2(i) %populate line code matrix by expanding x10 end end dat2 = dat2(100:end) cosine=cos(2*pi*fc*t) c = Ac*cos(2*pi*fc*t) %carrier wave st = (Ac + dat2).*cosine %ASK modulated signal subplot(4,1,1) plot(t,dat2)%plot line coded data title(‘Simple Line Coded Data’) grid on axis([0 n -8 +8]) subplot(4,1,2) plot(t,c) %plot carrier wave title(‘Carrier Wave’) grid on axis([0 n -8 +8]) subplot(4,1,3) plot(t,st) %plot ASK modulated signal title(‘ASK Modulated Signal’) grid on 3 axis([0 n -8 +8]) %combined modulated carrier and line coded data plot subplot(4, 1, 4) yyaxis left plot(t, st) ylim([-8 8]) yyaxis right plot(t, dat2) ylim([-8 8]) title(‘Combined Line Coded Data and ASK Modulated Carrier’) xlabel(‘time’) ylabel(‘amplitude’) Question 2. Select the correct statement regarding the modulated ASK waveform. a. There is no difference between the OOK and ASK waves b. It is seen that logical “1s” and “0s” are represented by different carrier wave amplitudes c. Unlike OOK where logical data is represented by a voltage or the absence of a voltage, ASK represents logical data using different voltage levels operating at the same frequency d. both b and c are correct statements Plot 2 – ASK Signal Plot Submission: Submit (i.e., copy/paste) the MATLAB plots from step 2.1 above into the “IT300 Virtual Lab Plot Submission” . Part 3. FSK Digital Modulation Logical Data Set: data = [1 0 0 1 0 0 1 0] Simple Line Code Frequencies: f1 Hz representing logical “1” f2 Hz representing logical “0” Carrier: c(t) = Ac cos(2πfct), c=Ac*cos(2*pi*fc*t) Index: Index=Df*(1/fc) Step 3.1 Use the following MATLAB code and create plots. %FSK clear clc Ac=5 %amplitude of the carrier fc=7 %frequency of the carrier data=[1 0 0 1 0 0 1 0] f1=7 %simple line code frequency 1 f2=2 %simple line coded fequency 2 Df=f1-f2 %differential frequency (variation between f1 and f2) Index=Df*(1/fc) %FSK modulation index blc2=1:8 %replace data with line coded frequency changes n = length(data) %number of data bits t = 0:.01:n %time x-axis x = 1:1:(n+1)*100 %”for j” matrix statement, populate matrix dat2 4 for i = 1:n for j = i:.1:i+1 bw(x(i*100:(i+1)*100)) = data(i); end end bw = bw(100:end); for m=1:n %replace logical data with frequency line coding if data(m)>0 blc2(m)=f1 else blc2(m)=f2 end end for i = 1:n %expand line coded frequencies by x10 for j = i:.1:i+1 dat2(x(i*100:(i+1)*100)) = blc2(i) %populate line code matrix by expanding x10 end end dat2 = dat2(100:end) cosine=cos(2*pi*dat2.*t) c = Ac*cos(2*pi*fc*t) %carrier wave st = Ac*cosine %FSK modulated signal subplot(4,1,1) plot(t,bw)%plot line coded data title(‘Simple Logical Data’) grid on axis([0 n -1 +2]) subplot(4,1,2) plot(t,c) %plot carrier wave title(‘Carrier Wave’) grid on axis([0 n -8 +8]) subplot(4,1,3) plot(t,st) %plot FSK modulated signal title(‘FSK Modulated Signal’) grid on axis([0 n -7 +7]) %combined modulated carrier and line coded data plot subplot(4, 1, 4) yyaxis left plot(t, st) ylim([-8 8]) yyaxis right plot(t, bw) ylim([-2 2]) title(‘Combined Logical Data and FSK Modulated Carrier’) xlabel(‘time’) ylabel(‘amplitude’) Question 3. Select the correct statement regarding the modulated FSK waveform. a. The modulated signal does not accurately represent the message because the amplitude of the modulated signal does not change with changes in the logical data. b. The modulated signal indicates changes in frequency, but no changes in amplitude. Therefore, the modulated signal is distorted and does not accurately represent the logical data. 5 c. It can be seen that logical “1s” and “0s” are accurately represented by changes in carrier frequency; therefore, the modulated signal accurately represents the logical data. d. There are no accurate statements above. Plot 3 – FSK Signal Plot Submission: Submit (i.e., copy/paste) the MATLAB plots from step 3.1 above into the “IT300 Virtual Lab Plot Submission” . Step 3.2 Using the MATLAB code provided below, create plots. Note the following change: (1) Change f1 = 2 Hz (2) Change Ac = 2 volts %FSK clear clc Ac=2 %amplitude of the carrier fc=7 %frequency of the carrier data=[1 0 0 1 0 0 1 0] f1=2 %simple line code frequency 1 f2=2 %simple line coded fequency 2 Df=f1-f2 %differential frequency (variation between f1 and f2) Index=Df*(1/fc) %FSK modulation index blc2=1:8 %replace data with line coded frequency changes n = length(data) %number of data bits t = 0:.01:n %time x-axis x = 1:1:(n+1)*100 %”for j” matrix statement, populate matrix dat2 for i = 1:n for j = i:.1:i+1 bw(x(i*100:(i+1)*100)) = data(i); end end bw = bw(100:end); for m=1:n %replace logical data with frequency line coding if data(m)>0 blc2(m)=f1 else blc2(m)=f2 end end for i = 1:n %expand line coded frequencies by x10 for j = i:.1:i+1 dat2(x(i*100:(i+1)*100)) = blc2(i) %populate line code matrix by expanding x10 end end dat2 = dat2(100:end) cosine=cos(2*pi*dat2.*t) c = Ac*cos(2*pi*fc*t) %carrier wave st =

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