Harmonic Distortion in Communication SignalsObjectives:

Equipment Required: Multisim version 8.0, Computer or laptop

Theory: Total Harmonic Distortion (THD):(i)Harmonics are integer multiples of the fundamental or input frequency.(ii)Harmonics of 60 Hz are 60Hz (fundamental), 120 Hz, 180 Hz, 300 Hz, 420 Hz…(iii)Total Harmonic Distortion (THD) is the ratio of square root of the sum of the squares of individual rms harmonic voltages to the rms value of the fundamental and is given byWhereTHD = percent total harmonic distortionv1 = rms voltage of first harmonic or fundamentalv2 = rms voltage of 2nd harmonicvn = rms voltage of nth harmonic Distortion:

Procedure:1.Use Multisim to build the circuit as shown in the diagram:2. You are applying a square wave to the spectrum analyzer (XSA1) which is located 13th on the instrument panel on the right hand side of your Multisim page.3. XDA1 is a distortion analyzer which is located 12th from top to bottom on the instrument panel.4. Use the spectrum analyzer controls to observe the harmonic frequency contents in the square wave. Make a table and write down the power in dBm and harmonic frequency for the first four harmonics.5. Turn on the distortion analyzer (XDA1) and note down the % THD and SINAD in dB.6. Print out the screen shots of the spectrum analyzer screen and distortion analyzer screens.7. Submit your report in the format as mentioned in lab 2.Complete the lab report document for this iLab.Your report document should include the required calculations and your analyses, along with a copy of the circuit that you used. Copy and paste all the screen captures from Tutor Tim into the Word document for your lab. The screen captures must include the circuit as well as the waveforms.The report cover sheet must be completed along with the lab report. The key parts of this sheet include:

• Summary: A one- or two-sentence explanation of the purpose of the lab
• Key Results: Measurements from the experiment and/or a statement of the final output, such as whether the circuit/software worked properly
• Key Conclusions (technical): Conclusions based on the Key Results–usually directly related to the purpose of the lab
• Key Conclusions (critical thinking): Your speculation on why this lab is important to your future career or field of study. Think about what use you can make of what you learned in this lab.