C oncepts TIPL 4700 Presented amp Prepared by Neeraj Gill 1 Sampling A n Analog Signal 2 Fin is frequency of analog input signal Fs is sampling frequency of ADC NyquistShannon sampling theorem ID: 701707
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Slide1
Bandwidth vs Frequency (Subsampling Concepts)TIPL 4700
Presented & Prepared by Neeraj Gill
1Slide2
Sampling An Analog Signal
2
Fin is frequency of analog input signalFs is sampling frequency of ADCNyquist-Shannon sampling theorem: Fin < Fs/2Slide3
3What is Aliasing(Undersampling)?
Aliasing - two different sinusoids give the same digital samples
If F
s
is the Sampling Frequency (clock rate)
a high frequency F
red
= 10/9 * F
s
and a low frequency at F
blue = 1/9 * Fs = Fred – FsBoth look like 1/9 * Fs to the ADCSlide4
Oversampling & Undersampling in Frequency Domain
4Slide5
Nyquist Zones5
When talking about High Speed Data Converters, often the term ‘NYQUIST ZONE’ is used
One Nyquist zone has a bandwidth of half the data converters sampling frequency
1
st
Nyquist zone: DC – 1/2 Fs
2
nd
Nyquist zone: 1/2 Fs – 1 Fs
3
rd
Nyquist zone: 1 Fs – 3/2 Fs4th Nyquist zone: 3/2 Fs – 2 FsAnd so on…Slide6
6Practical Aliasing Example - UndersamplingSlide7
7Practical Aliasing Example - UndersamplingSlide8
8Can all ADCs Undersample? (depends on input bandwidth)
Analog Input Bandwidth is the analog input frequency at which the power of the fundamental is reduced by 3dB with respect to the low-frequency value
ADC12DJ3200
(12bit, 6.4Gsps), with a 8 GHz Analog Input Bandwidth(-3dB), can sample input frequencies up to 8GHz.
There are ADCs that cannot under-sample, which are sometimes called Nyquist Converters, and are usually high precision and a little slowerSlide9
Thank you for your time9Slide10
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