How to plot phase noise curve of LO

Discussion in 'Wireless & RF Design' started by sohagiut, Nov 4, 2010.

  1. sohagiut

    Thread Starter New Member

    May 5, 2008
    from a LNB data sheet i got the phase noise of the LO as below:
    -65 dBc/Hz @1 kHz
    -90 dBc/Hz @10 kHz
    -110 dBc/Hz @100 kHz
    as these values are relative to the LO power, How can i get the actual values and can plot the phase noise. I don't find any info related to the LO power. Can some one help with link or any info regarding the typical values of LO power so that i can calculate the actual phase noise and plot it.

    thanks in advance
  2. golferkid

    New Member

    Oct 22, 2010
    The relative numbers are all you need to know, since the LO noise spectrum is impressed on the incoming signal and appears as noise on the LNB output signal at the same dBc levels and same offset frequencies as in the LO spectrum. So, it's not related to the actual LO power. A plot of the output phase noise would be just the numbers as given for the LO (assuming the input had no phase noise of it's own, or was much lower than the LO phase noise).