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Re: [Discuss-gnuradio] The noise power of the USRP

From: Marcus D. Leech
Subject: Re: [Discuss-gnuradio] The noise power of the USRP
Date: Sun, 20 Dec 2015 23:34:56 -0500
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On 12/20/2015 10:42 PM, w xd wrote:
Thanks so much.

            If in a general indoor environment(no people),we just use a usrp as a receiver and in a quiet frequency band,have someone have the
general data?Can you give a non-official data?around -80dbm?or -70dbm?

            Or how to measure it?What is the true way to measure it?

For an example.  In a perfectly-sealed microwave anechoic chamber, with no other equipment inside it, and no unwanted in-band
  leakage from whatever device you do have in said chamber with you, at an ambient temperature of 25C, your antenna can expect
  to receive just the thermal noise from the walls, which would, at 25C, be equivalent to a PSD of -174dBm/Hz, or a 3dB noise figure,
  or an equivalent noise temperature of 297K.  Take your pick, they're all equivalent.



Noise figure depends on frequency and gain setting:


Performance data includes noise figure.

Not sure what you mean by "true noise power".  But noise figure tells you how much extra noise is added by the device itself.

A 3dB noise figure is equivalent to a PSD of -174dBm/Hz.
A 5dB noise figure is equivalent to a PSD of -172dBm/Hz.

And so on.

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