Application Examples
Identifying the Source of
Noise
Noise in mixed d
igital/analog circuits can be easily observed with an oscilloscope.
However, identifying the sources of the observed noise can be difficult.
The FFT wavefo
rm displays the frequency content of the noise. You may then
be able to associate those frequencies with known system frequencies, such as
system clocks, oscillators, read/write strobes, display signals, or switching power
supplies.
The highest frequency on the example system is 40 MHz. To analyze the example
signal, you would set the oscilloscope and FFT parameters as listed in the next
table.
Control Setting
1 Coupling AC
Acquisition Mode
Sample
Horizontal Resolution
Normal (10k points)
Horizontal Scale
4.00 μs
Bandwidth 150 MHz
FFT Source Ch1
FFT Vert Scale
dBV
FFT Window Hanning
40 TDS3000C Series Oscilloscope User Manual
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