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Unformatted text preview: 6/4/2010 1 ECE2025 Summer 2010 Lecture 7 Sampling & Aliasing 07 Jun 10 6/4/2010 3 ANNOUNCEMENTS HW 2 due 7-8 June 9-10 June: Turn in Lab 2 Do lab 3 (Bring Headphones) HW 3 due 14-15 June 16-17 June: Turn in Lab 3 Do Lab 4 6/4/2010 4 FIRST QUIZ Quiz #1, in lecture, Friday, June 11 10% of final grade You can use the full 1:20-2:30 time Review session June 10, 6-7 pm across from lab. Coverage: HW #1 and #2 Lectures #1 through #5 (but no Fourier series) Might have to read some MATLAB code (wont need to write any) Closed book, closed notes, except: One 8.5X11 crib sheet allowed, handwritten , OK to write on both sides 6/4/2010 5 Fourier Series: Final Thoughts = ) / 2 ( 1 ) ( T t k T j T k dt e t x a real is ) ( when * t x a a k k = t f k j N N k k e a t x 2 ) ( = = + + = ) 2 ( 1 ) ( T t k f j T k dt e t x a 6/4/2010 6 Fourier Series Properties If x(t)=x(-t) (even symmetry), only cosines are used. The coefficients are pure real. ( a k = a-k and a k = a *-k ) If x(t)=-x(-t) (odd symmetry), only sines are used. The coefficients are pure imaginary. ( a k = -a-k and a k = a *-k ) If x(t) is delayed: y(t)=x(t-d), the coefficients have the same magnitude, but have a phase of - dk 0 added. If the FS coefficients of x(t) are a k , then the FS coefficients of y(t) will be exp(-jk d)a k . A delay by period converts the coeffcients to (-1) k a k ....
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