88
Keysight InfiniiVision 3000 X-Series Oscilloscopes User's Guide
4
Math Waveforms
FFT Units
0 dBV is the amplitude of a 1 Vrms sinusoid. When the FFT source is channel 1 or
channel 2 (or channel 3 or 4 on 4-channel models), FFT units will be displayed in
dBV when channel units is set to Volts and channel impedance is set to 1 M
Ω
.
FFT units will be displayed in dBm when channel units is set to Volts and channel
impedance is set to 50
Ω
.
FFT units will be displayed as dB for all other FFT sources or when a source
channel's units has been set to Amps.
FFT DC Value
The FFT computation produces a DC value that is incorrect. It does not take the
offset at center screen into account. The DC value is not corrected in order to
accurately represent frequency components near DC.
FFT Aliasing
When using FFTs, it is important to be aware of frequency aliasing. This requires
that the operator have some knowledge as to what the frequency domain should
contain, and also consider the sampling rate, frequency span, and oscilloscope
vertical bandwidth when making FFT measurements. The FFT resolution (the
quotient of the sampling rate and the number of FFT points) is displayed directly
above the softkeys when the FFT Menu is displayed.
Aliasing happens when there are frequency components in the signal higher than
half the sample rate. Because the FFT spectrum is limited by this frequency, any
higher components are displayed at a lower (aliased) frequency.
NOTE
Nyquist Frequency and Aliasing in the Frequency Domain
The Nyquist frequency is the highest frequency that any real-time digitizing oscilloscope can
acquire without aliasing. This frequency is half of the sample rate. Frequencies above the
Nyquist frequency will be under sampled, which causes aliasing. The Nyquist frequency is also
called the folding frequency because aliased frequency components fold back from that
frequency when viewing the frequency domain.
Содержание InfiniiVision 3000 X Series
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Страница 48: ...48 Keysight InfiniiVision 3000 X Series Oscilloscopes User s Guide 1 Getting Started...
Страница 62: ...62 Keysight InfiniiVision 3000 X Series Oscilloscopes User s Guide 2 Horizontal Controls...
Страница 72: ...72 Keysight InfiniiVision 3000 X Series Oscilloscopes User s Guide 3 Vertical Controls...
Страница 122: ...122 Keysight InfiniiVision 3000 X Series Oscilloscopes User s Guide 6 Digital Channels...
Страница 128: ...128 Keysight InfiniiVision 3000 X Series Oscilloscopes User s Guide 7 Serial Decode...
Страница 134: ...134 Keysight InfiniiVision 3000 X Series Oscilloscopes User s Guide 8 Display Settings...
Страница 182: ...182 Keysight InfiniiVision 3000 X Series Oscilloscopes User s Guide 11 Trigger Mode Coupling...
Страница 200: ...200 Keysight InfiniiVision 3000 X Series Oscilloscopes User s Guide 12 Acquisition Control...
Страница 210: ...210 Keysight InfiniiVision 3000 X Series Oscilloscopes User s Guide 13 Cursors...
Страница 252: ...252 Keysight InfiniiVision 3000 X Series Oscilloscopes User s Guide 15 Mask Testing...
Страница 256: ...256 Keysight InfiniiVision 3000 X Series Oscilloscopes User s Guide 16 Digital Voltmeter...
Страница 290: ...290 Keysight InfiniiVision 3000 X Series Oscilloscopes User s Guide 19 Print Screens...
Страница 324: ...324 Keysight InfiniiVision 3000 X Series Oscilloscopes User s Guide 21 Web Interface...
Страница 344: ...344 Keysight InfiniiVision 3000 X Series Oscilloscopes User s Guide 22 Reference...
Страница 370: ...370 Keysight InfiniiVision 3000 X Series Oscilloscopes User s Guide 24 FlexRay Triggering and Serial Decode...
Страница 424: ...424 Keysight InfiniiVision 3000 X Series Oscilloscopes User s Guide 28 UART RS232 Triggering and Serial Decode...