how to get the noise figure of the antenna by measurement

hi, everybody,
i wanna test the noise figure of the antenna? how can i get it? does anybody have some papers about it? thx a lot.

to my best rgs,
xiyx

Re: how to get the noise figure of the antenna by measuremen

noise figure of the antenna????
Is it a small beam corrugated horn ?
In this case a calibrated radiometer and 2 temperature standard loads are required and the measurement is very difficult.
"Difficult" means that the uncertainty is larger tha the observed value.

Otherwise, in general and for all type of antenna, you may consider the antenna as a lossy line.
After Gain measurement , find efficency, then extract all "non lossy" coefficients (phase efficiency. , xpol efficiency., illumination efficiency etc.), then you'll have the loss efficiency. Now, after Impedance Measurement, find the Available Gain of the antenna, Gav=Gloss/(1-Γ²), then, if you prefere, format the result in dB.
The Available Gain of the antenna is numerically the same of Noise Figure only when the antenna is 290K hot.
But, since the available gain is usually very small, Noise Figure don't change a lot if physical temperature change.

Conclusion:
Noise Figure is measurable only if a switched hot/cold noise source exist.
The method suggested is a measurement. More exactly is a processing of a measurement. It'is not a simulation or a computing.

Ref.
Clarricoats - Olver, Corrugated horns for microwave antennas, Peter Peregrinus, pag. 8
Kraus, Radioastronomy, chap. Receivers
Agilent, AN57-1

Re: how to get the noise figure of the antenna by measuremen

Dear xiyx:

You give no details about your antenna at all. Mr. Marriotti is right in suggesting you first study the Radio Astronomy book by Kraus.
I think it is not correct to search for a "noise figure" of an antenna. Any antenna pointing to a warm object (like Earth) or in the space (Galaxy) will generate at its output a noise temperature corresponding to the temperature of that object or medium. The correspondence between the remote-object temperature and antenna noise temperature output is given by thermodynamics; the method of calculation is called radiometry (photometry in visible light).
Antenna noise temperature is evaluated by radiometers, sensitive receivers. A combination of the antenna and radiometer is e.g. a radio telescope, or a photometer if visible light is studied.
Antenna alone may contribute by its physical temperature and the loss in its conductive elements.
The known "minimum" noise temperature is the "Cosmic Background Radiation" of ~ 3.2 K, confirmed over frequency range of ~100 MHz through UV range.