Modulation and Demodulation, Lecture notes of Analog Communication

Download Modulation and Demodulation and more Lecture notes Analog Communication in PDF only on Docsity! Electronic Communication EEE 359 © Md.Manjurul Gani Presented by-Sancoy Barua Lecturer, Department of EEE CHITTAGONG UNIVERSITY OF ENGINEERING & TECHNOLOGY (CUET) 1 Prepared By- Md. Manjurul Gani Assistant Professor, EEE, CUET Amplitude Modulation (AM) Amplitude Modulation (AM) Lor OF —_ fs fTs Signal wave Vc + Vmsin(ωmt) Modulation index, Vm = mVc© Md.Manjurul Gani 5 Let, vm = Vm sin(ωmt) vc = Vc sin(ωct)……(1) In amplitude modulated signal the amplitude of the carrier is varied according to the message signal. So amplitude of the AM wave is: Message signal Carrier signal DSB-FC 𝑉𝐴𝑀(𝑡)= (Vc+ Vm sinωmt) sinωct = (Vc + mVc sinωmt) sinωct = Vc sinωct + mVc sinωmt.sinωct© Md.Manjurul Gani 6 = (Vc sinωct + mVc sinωmt.sinωct) © Md.Manjurul Gani 7 𝑉𝐴𝑀(𝑡) Suppose that on an AM signal, the V...¢.—p) Value read from the graticule on the oscilloscope screen is 5.9 divisions and Viyingpip) is 1.2 divisions. a. What is the modulation index? Vinx ~ Vinin 5.9 —- 1.2 47 FE 0082 "Vimar + Vain ~S9F12 TA b. Calculate V,, V.. and m if the vertical scale is 2 V per division. (Aint: Sketch the signal.) Vinx + Vinin 5.9 41.2 Tl 2¥V SOD ABO TL Vo = 355 XIV =ST71V Vinax — Finis 59-12 47 — 2 2. 2 2V = 2.35 @ — div Ve = 2.35 X2V=S4.7V V, 47 = — = 0.662 Vv. Tl ~ i n= 10 Message vm = Vm sin(ωmt) Vc Carrier vc = Vc sin(ωct) AM signal vAM Block Diagram of DSB-FC Vc © Md.Manjurul Gani 11 DSB-FC Demodulation (Envelope/Diode/rectifier detection) oe AM Modulated ——* Wave