Microwave Noise - RF Cafe Forums

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Avalan

Post subject: Microwave Noise

Posted: Wed Mar 18, 2009 11:21 am

Lieutenant

Joined: Wed Mar 18, 2009 11:07 am
Posts: 2

Hi

I am a junior RF planner and just need some guidance in a thought that a have. In a split configuration microwave setup you have your ODU up on the mast and your IDU down in a protected housing right. Now if I want to calculate the thermal noise I use
Nt = kTB
(k = Boltzmann, T = temperature in kelvin and B spectrum bandwidth)

My problem, as the receiver sits in the IDU should I use the IF bandwidth in the feeder as my spectrum bandwidth or should I use the channel bandwidth that is received by my antenna? Maybe I should use a combination of both?
I figure you can't just use the IF bandwidth as some thermal noise would have already been added to the system by the amplification of the antenna and ODU.

Does anybody have some thoughts on this?

Thanks

nubbage

Post subject: Re: Microwave Noise

Posted: Thu Mar 19, 2009 6:14 am

General

Joined: Fri Feb 17, 2006 12:07 pm
Posts: 304
Location: London UK

Hi avalon
A better approach is to convert all significant elements into equivalent noise temperature, then add them up.
There are some excellent sources on the net to guide you through the process. See for example http://www.satsig.net/noise.htm
Also agilent have an Application Note on the subject number 57-1 which can probably be downloaded from [url]hp.woodshot.com[/url]

_________________
At bottom, life is all about
Sucking in and blowing out.

Avalan

Post subject: Re: Microwave Noise

Posted: Sun Mar 29, 2009 2:37 pm

Lieutenant

Joined: Wed Mar 18, 2009 11:07 am
Posts: 2

hi nubbage

thanks for the info, it answers alot of my questions...

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