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# How to add phase noise (in dBc) at a certain freq. offset - RF Cafe Forums

 The original RF Cafe Forums were shut down in late 2012 due to maintenance issues. Below are all of the old forum threads, including all the responses to the original posts. -- Amateur Radio -- Antennas-- CAE, CAD, & Software-- Circuits & Components-- Systems-- Test & Measurement

 Post subject: How to add phase noise (in dBc) at a certain freq. offset Posted: Wed Oct 28, 2009 6:18 am
 Lieutenant

Joined: Wed Oct 28, 2009 6:10 am
Posts: 1
Hi,
I have the following data

| Offset From Carrier | Phase Noise |
-------------------------------------------------------
| 1 kHz | -84 dBc/Hz |
| 10 kHz | -100 dBc/Hz |
| 100 kHz | -96 dBc/Hz |
| 1 MHz | -109 dBc/Hz |
| 10 MHz | -122 dBc/Hz |

I have a data of lengh L in time domain.
How do I use the above information on Phase noise and add to my signal ???

Thanks
Shilpika

 Post subject: Re: How to add phase noise (in dBc) at a certain freq. offset Posted: Thu Nov 05, 2009 4:05 am
 General

Joined: Fri Feb 17, 2006 12:07 pm
Posts: 304
Location: London UK
 Hi shilpikayou need to transform from the time domain to the frequency spectrum domain. I think I am right in saying that the data length L in the time domain is not relevant.What is relevant is the date rate and the modulation method. Thus a data rate of 8 megabits per second passed through a 64QAM modulator has a certain symbol rate and this relates to the spectrum width around the carrier frequency center. Armed with that knowledge and the level of the carrier, you can estimate the noise. Draw a spectrum distribution curve from the data you have of offset frequency and noise, and superimpose a Gaussian curve for the signal spectrum. That will show the relative noise and carrier levels. _________________At bottom, life is all about Sucking in and blowing out.

Posted  11/12/2012