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https://designers-guide.org/forum/YaBB.pl Design >> RF Design >> phase noise after frequency dividing https://designers-guide.org/forum/YaBB.pl?num=1282955615 Message started by nxing on Aug 27th, 2010, 5:33pm |
Title: phase noise after frequency dividing Post by nxing on Aug 27th, 2010, 5:33pm Hello everyone, I know that the phase noise of signal will be improve by 6 dB if the signal is divided by two. Can anybody explain why is that? Thanks |
Title: Re: phase noise after frequency dividing Post by pancho_hideboo on Aug 27th, 2010, 10:46pm nxing wrote on Aug 27th, 2010, 5:33pm:
Consider a definition of phase. T1 ; Period of input signal dt1 ; Jitter of input signal ph1 ; phase error of input signal, ph1=(dt1/T1)*2*pi T2 ; Period of divided signal, T2=N*T1, N ; Divide Ratio dt2 ; Jitter of divided signal, dt2=dt1 ph2 ; phase error of divided signal, ph2=(dt2/T2)*2*pi=ph1/N |
Title: Re: phase noise after frequency dividing Post by raja.cedt on Aug 28th, 2010, 11:36am hi, Phase noise means ratio of noise power in 1Hz BW to carrier power. So due to dividing there is no change in the signal, but coming to noise i guess it will be reduced by half because noise will occur mainly when ZERO crossing happening and division operation makes no of zero crossing half of the previous no. Thanks, Rajasekhar. |
Title: Re: phase noise after frequency dividing Post by pancho_hideboo on Aug 28th, 2010, 12:03pm raja.cedt wrote on Aug 28th, 2010, 11:36am:
See the followings. http://www.designers-guide.org/Forum/YaBB.pl?num=1241917016/6#6 http://www.designers-guide.org/Forum/YaBB.pl?num=1274422891 |
Title: Re: phase noise after frequency dividing Post by raja.cedt on Aug 28th, 2010, 12:16pm hi, i guess if i assume total noise dominated by PM then that Phase noise def is correct. or else could you please explain how it go down by 6db if you divide? Thanks, |
Title: Re: phase noise after frequency dividing Post by vp1953 on Aug 30th, 2010, 3:32pm Hi Raja, Assume that the total noise is dominated by phase noise and assuming that the effects of noise shows up at Zero crossing as you suggested : how does the noise power go down by 6db. When dividing by 2, the noise power is now halved and so should be down by 3dB? |
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