I have begun to do the test on the system,
I have just get an spectrum analyzer and a amplifier.
Unfortunately I don't have a noise source, but I
have tried to measure de noise generated by a 50ohms
terminator placed in the input of the amplifier.
The noise figure of this device in unknow, I have
estimated the gain by measuring different synusoidal
frequencies and it is about 140 with a bandwith
of 1GHz. The preamplifer of the spectrum analyzer
has a NF of 11dB.
The problem is that I am obtaining
less espectral density than the expected in input
(about 805pV/sqrt Hz, while 50ohms have to have
about 900pV/sqrt Hz). I have check that the gain
compression begins at 1mVrms in the input, so I
am far away from compression region which could
explain such a low espectral density value. I also
check the amplifier with a vector network analyzer
and it has a reflection in the input of about -0.2
at 700MHz, could this be related with the obtained
reduced noise values? suggestions or ideas