MDO4000B Datasheet, PDF (3/28 Pages) List of Unclassifed Manufacturers – Mixed Domain Oscilloscopes

Mixed Domain Oscilloscopes — MDO4000B Series
Figure 1 - Time and Frequency Domain view showing the turn-on of a PLL. Channel
1 (yellow) is probing a control signal that enables the VCO. Channel 2 (cyan) is probing
the VCO tune voltage. The SPI bus which is programming the PLL with the desired
frequency is probed with three digital channels and automatically decoded. Notice
Spectrum Time is placed after the VCO was enabled and coincident with the command
on the SPI bus telling the PLL the desired frequency of 2.400 GHz. Note that the RF is at
2.2202 GHz when the circuit turns on.
Figure 3 - Spectrum Time is moved another 120 μs to the right. At this point the spectrum
shows that the PLL has actually overshot the correct frequency and gone all the way to
2.4164 GHz.
Figure 2 - Spectrum Time is moved about 60 μs to the right. At this point, the spectrum
shows that the PLL is in the process of tuning to the correct frequency (2.400 GHz). It
has made it up to 2.3168 GHz.
Figure 4 - The PLL eventually settles on the correct 2.400 GHz frequency about 340 μs
after the VCO was enabled.
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