# Noise Figure Q - RF Cafe Forums

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James
Post subject: Noise figure Q.
Unread postPosted: Thu May 13, 2004 6:55 pm

If a filter has 1dB IL at ambient, the noise figure is 1dB. If at hot temperature, the filter has 1.5dB IL, will the NF be higher than 1.5dB?

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Guest
Post subject: Noise Figure will remain 1.5
Unread postPosted: Fri May 14, 2004 6:57 am

At higher temperature the overall noise power floor will be higher (KTB). However, noise figure is the ratio between the signal to noise ratio at the output to the signal to noise ratio at the input therefore the noise floor is cancelled out and what is left is the additive noise from the filter, or what you know as noise figure. In this case the additive noise is 1.5dB, which is the noise figure.

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Itay
Post subject: Correction to the formula
Unread postPosted: Fri May 14, 2004 10:48 am

Correction to the ratio you provided, the noise figure is the ratio between the S/N in the input to the one in the output.

Thanks,

Itay Reiss

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Tony Kurlovich
Post subject: Consider
Unread postPosted: Tue May 18, 2004 11:38 am

When NF is tested over temprature, is the ENR source in the chamber? Most people have it out side the chamber and NF is calculated based on an ambient reference temp.

Posted  11/12/2012

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