eldo_user

Setting Up An Analysis
Transient Noise Analysis
Figure 6-21. Phase Noise Plots Comparison
Summary
The upper frequency of the phase noise spectrum is Fout/2 (where Fout is the frequency of the
PLL output). The lower frequency is defined by the length of the transient noise analysis.
Therefore, increasing frequency resolution has a direct impact on simulation time.
In this example, this functionality is illustrated with an integer rank PLL but it can be used
exactly in the same way with a fractional PLL. The same methodology can be applied to get the
phase noise spectrum for other kind of circuits, for instance free running oscillators, frequency
dividers, clock trees.
Related Commands
• .NOISETRAN in the Eldo Reference Manual
• .SSTNOISE in the Eldo RF User’s Manual
• .SST PLL in the Eldo RF User’s Manual.
Related Topics
Transient Noise Analysis
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Eldo® User's Manual, 15.3