Name (Last, First)
Student ID number
EECS145M 2005 Midterm #2 Page 1 Derenzo
UNIVERSITY OF CALIFORNIA
College of Engineering
Electrical Engineering and Computer Sciences Department
EECS 145M: Microcomputer Interfacing Laboratory
Spring Midterm #2 (Closed book- equation sheet provided- calculators OK)
Full credit can only be given if you show your work.
Wednesday, April 13, 2005
Problem 1 (15 points)
You sample exactly 5 cycles of a 15 Hz symmetric square wave (after anti-alias filtering) and
compute the FFT. The magnitudes of your FFT coefficients are plotted in the figure below.
Explain the non-zero values at n = 5, 15, 20, 25, 35, 45, 55, 73, 83, 93, 103, 108, 113, and 123.
(You do not need to explain the amplitudes, just why they are non-zero.)
Frequency index
16
0
10
20
30
40
50
60
70
80
90
0 32 48 64 80 96 112 128
