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Service Providers >> Satellite Internet - Middle East >> C/N and (C+N)/N https://www.satsig.net/cgi-bin/yabb/YaBB.pl?num=1259133992 Message started by satnew on Nov 25th, 2009 at 7:26am |
Title: C/N and (C+N)/N Post by satnew on Nov 25th, 2009 at 7:26am
Hi,
Please help. May i know the difference between (Co + No)/No and C/N? how do you convert from one another and relationship? Please correct me if im wrong..am i looking at C/N on a spectrum analyzer when i have my marker noise on from the noise floor to the top of the carrier? thnx |
Title: Re: C/N Post by Eric Johnston on Nov 25th, 2009 at 8:00am
Make sure the spectrum analyser resolution bandwidth is significantly less then the carrier bandwidth.
Use this page EbNo calculator to calculate the C/N starting with (C+N)/N. Just set FEC=1 and Bits/Symbol=1. When your marker is on top of the carrier you are measuring C+N. When your marker is on the noise floor you are measuring N The difference between the two is (C+N)/N. If you set "Marker Noise function ON" you are measuring (Co+No) or No. The analyser works out the power per Hz knowing what is the noise bandwidth of the internal resolution bandwidth filter (ie. - 10 * log(-3dB bandwidth in Hz) - 0.5 dB). It also corrects for noise not being like a sinewave (+2.5 dB). Normally an analyser detector measures peak voltage and displays RMS value, assuming a sinewave input. Noise has a different peak to mean ratio from sinewave so display value is wrong unless you do "MKR NOISE ON". A scrambled digital carrier is "noise like". If you see a 3 dB high hump in the noise floor the carrier level and the noise level are the same and add together to make twice, so C/N=0 dB and (C+N)/N = 3 dB. If you see a 20 dB (or higher) high hump in the noise floor then C/N is about the same as (C+N)/N. For intermediate values use the calculator. Read more: HP application Note 150 (3.4 Mbytes pdf. print out 67 pages, pages 31 - 33 refer) Best regards, Eric. |
Title: Re: C/N Post by satnew on Nov 25th, 2009 at 9:16am
hi eric,
many thanks. will check |
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