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© Vishal Saxena
ECE 697 Delta-Sigma Converters Design
Lecture#4 Slides
Vishal Saxena(vishalsaxena@u.boisetstate.edu)
© Vishal Saxena
Spectral Estimation
© Vishal Saxena
Coherent Sampling
0 5 10 15 20 25 30 35 40 45 50-1
-0.5
0
0.5
1
samples (n)
x[n]
100 200 300 400 500 600 700 800 900 1000-350
-300
-250
-200
-150
-100
-50
0
FFT bins (k)
20*lo
g 10|X
(k)|,
dB
file:FFTdemo1.m
© Vishal Saxena
Non-Coherent Sampling : FFT leakage
100 200 300 400 500 600 700 800 900 1000-350
-300
-250
-200
-150
-100
-50
0
FFT bins (k)
20*lo
g 10|X
(k)|,
dB
129129.01129.001
file:FFTdemo2.m
© Vishal Saxena
FFT leakage contd.
file:FFTdemo2.m
100 200 300 400 500 600 700 800 900 1000
-120
-100
-80
-60
-40
-20
FFT bins (k)
20*lo
g 10|X
(k)|,
dB
129129.01129.001
© Vishal Saxena
Spectral Windows
5 10 15 20 25 300
0.2
0.4
0.6
0.8
1
Samples
Ampl
itude
Time domain
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9-150
-100
-50
0
50
Normalized Frequency ( rad/sample)
Mag
nitu
de (d
B)
Frequency domain
Rectangular#1BartlettHann
% Compare Rect, Bartlett and Hann windows
L = 32;
wvtool(rectwin(L), bartlett(L), ds_hann(L));
© Vishal Saxena
Spectral Windows contd.
5 10 15 20 25 300
0.2
0.4
0.6
0.8
1
Samples
Ampl
itude
Time domain
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9-140
-120
-100
-80
-60
-40
-20
0
20
40
Normalized Frequency ( rad/sample)M
agni
tude
(dB)
Frequency domain
Blackman-HarrisHann
% Compare Blackman-Harris and Hann windows
L = 32;
wvtool(blackmanharris(L), ds_hann(L));
© Vishal Saxena
FFT with Windowing
file:FFTdemo_windowing.m
100 200 300 400 500 600 700 800 900 1000-200
-150
-100
-50
0
50
100
FFT bins (k)
20*lo
g 10|X
(k)|,
dB
RectHannBlackman-Harris
© Vishal Saxena
References
[1] S. Pavan, N. Krishnapura, “EE658 VLSI Data Conversion Circuits Course,” 2008, [Online]: http://www.ee.iitm.ac.in/~nagendra/videolectures/doku.php?id=start
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