Communication Theory I: Understanding Amplitude Modulation at Ankara University
Explore the concepts of amplitude modulation in Communication Theory I at Ankara University, specifically focusing on double-sideband modulation, carrier signals, spectra analysis, and signal extraction methods. Gain insights into AM signals and spectra, including Fourier transformations and the characteristics of AM spectrum components. Dive into the world of electrical and electronics engineering through practical applications and theoretical foundations.
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Presentation Transcript
EEE322 COMMUNICATION THEORY I ANKARA UNIVERSITY FACULTY OF ENGINEERING ELECTRICAL AND ELECTRONICS ENGINEERING DEPARTMENT
EEE322 COMMUNICATION THEORY - I LECTURE 5 CONTINUOUS WAVE MODULATION: AMPLITUDE MODULATION Ankara University, Electrical and Electronics Engineering Department, EEE322 Communication Theory I
AMPLITUDE MODULATION There are two types of double-sideband amplitude modulation: standard amplitude modulation (AM) suppressed-carrier double-sideband modulation (DSB). Ankara University, Electrical and Electronics Engineering Department, EEE322 Communication Theory I
AMPLITUDE MODULATION AM Signals and Spectra: If ??denotes the unmodulated carrier amplitude, modulation by x(t) produces the AM signal ??? = ??1 + ?? ? ?????? = ???????? + ???? ??????? where ? is a positive constant called the modulation index. Ankara University, Electrical and Electronics Engineering Department, EEE322 Communication Theory I
AMPLITUDE MODULATION AM Signals and Spectra: The signal s envelope is then ? ? = ??[1 + ?? ? ] Figure 4.2 1(Carlson, page 175) shows part of a typical message and the resulting AM signal with two values of . Ankara University, Electrical and Electronics Engineering Department, EEE322 Communication Theory I
AMPLITUDE MODULATION AM Signals and Spectra: The envelope clearly reproduces the shape of x(t) if ?? ? and ? 1 When these conditions are satisfied, the message ?(?) is easily extracted from ??(?) by use of a simple envelope detector. Ankara University, Electrical and Electronics Engineering Department, EEE322 Communication Theory I
AMPLITUDE MODULATION AM Signals and Spectra: Going to the frequency domain, Fourier transformation of the signal s envelope yields ??? =1 2??? ? ?? +? 2??? ? ??? > 0 Ankara University, Electrical and Electronics Engineering Department, EEE322 Communication Theory I
AMPLITUDE MODULATION AM Signals and Spectra: The AM spectrum consists of carrier-frequency impulses and symmetrical side bands centered at ??. The presence of upper sidebands and lower sidebands accounts for the name double-sideband amplitude modulation. Ankara University, Electrical and Electronics Engineering Department, EEE322 Communication Theory I
References Communication Systems, An Introduction to Signal and Noise in Electrical Communication, 5th edition, A.B. Carlson, P.B. Crilly, J.C. Rutledge, Mc Graw Hill. An Introduction to Analog and Digital Communications, 2nd edition, S. Haykin, M. Moher, Wiley. Ankara University, Electrical and Electronics Engineering Department, EEE322 Communication Theory I
