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Unformatted text preview: Lecture 11 Outline Announcements Midterm Details and Extra OHs this week Examples of Noise in Communications Introduction to Modulation DoubleSideband Modulation Midterm Coverage and Review Midterm Details Midterm is Thursday, 2/17, 56:30pm (room TBD) Summary of MT material this lecture MT Review: Monday 2/14, 4:305:30pm, 5051P Covers parts of Chapters 14 and 89 (details shortly) Open book and notes, bring calculator Practice MTs posted 10 bonus points for taking an exam Solutions to all exams when you turn in practice exam Extra OHs Mine: 2/10 34pm, 2/15 121pm, and by appt. Aakanksha: this W 4.305.30 and Th 12.301, next M after review, next TW 56, and by appt. All in 109 Review of Last Lecture Power Spectral Density Filtering and Modulation of WSS Processes Multiple Random Processes Uncorrelated and Orthogonal Random Processes Gaussian Random Processes Samples jointly Gaussian RVs (x(t),x(t+ ) indep if R x ( )=0) Filtering a Gaussian RP results in a Gaussian RP Integrating a Gaussian RP results in a Gaussian RV H(f) 2 S n (f) S n (f) H(f) S n (f) .25[S n (ff c )+ S n (ff c )] X cos(2 f c t+ ) ) , ( ~ , ) ( ) ( 2 y T g y N y dt t x t g y = Examples of noise in Communication Systems The signaltonoise power ratio (SNR) is obtained by integrating the PSD of the signal and integrating the PSD of the noise. In digital communications, the bit value is obtained by integrating the signal, and the probability of error by integrating Gaussian noise. Introduction to Carrier Modulation Basic concept is to vary carrier signal relative to information signal or bits The carrier frequency is allocated by a regulatory body like the FCC spectrum is pretty crowded at this point. Analog modulation varies amplitude (AM), frequency (FM), or phase (PM) of carrier Digital modulation varies amplitude (MAM), phase (PSK), pulse (PAM), or amplitude/phase (QAM) Wireless Spectrum Double Sideband (Suppressed Carrier) Amplitude Modulation Modulated signal is s(t)=m(t)cos(2 f c t) Called doublesideband suppressed carrier (DSBSC) AM Generation of DSBSC AM modulation Direct multiplication (impractical) Nonlinear modulators: Basic premise is to add m(t) and the carrier, then perform a nonlinear operation Generates desired signal s(t) plus extra terms that are filtered out....
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This note was uploaded on 01/20/2012 for the course EE 301 taught by Professor Ahmetçakar during the Spring '11 term at Gazi Üniversitesi.
 Spring '11
 ahmetçakar

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