Application Examples
Identifying the Source
of Noise
Noise in mixed digital/an a log circu its can be easily ob served w ith an
oscilloscope. Howeve
r, identifying the sources of the observed no ise
can be difficult.
The FFT waveform di
splays the frequency content of the noise. You
may then be able to associate thos e 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 sig
nal, you would s et 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 μ
s
Bandwidth 150 MHz
FFT Source Ch1
FFT Vert Scale
dBV
FFT Window Hanning
46 TDS3000C Series Oscilloscope User Manual
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