|
 |
broadband noise measurements - RF Cafe Forums
|
| cubeleg
|
|
Post subject: broadband noise measurements
Posted: Thu Oct 04, 2007 1:18 pm
|
|
| |
| Captain |
 |
Joined: Tue Dec 05, 2006
1:55 pm
Posts: 5 |
|
Hi!
I want to ask a question, please I'm
newbye in microwave and RF thecniques, so please,
feel free to close the thread if it is just a stupid
question.
I am trying to measure noise of
resistive elements in the GHz range. We are looking
for new devices based on ferromagnetic materials,
then the ferromagnetic resonance is an important
noise source.
In first place I am not sure
about the equipment needed in order to perform such
a task. I can imagine that a broadband (about 0.1-20GHz)
low noise amplifier and a spectrum analyzer are
needed, also a low loss line is recommended in order
to reduce the noise introduced by the line. It is
needed anything else?
Secondly, is there any
book which would help me in this task, I have read
pozar's book: microwave and RF design of wireless
systems, and search in forums information related
with it.
Regards
Rubén
|
|
| |
|
 |
|
cubeleg |
|
Post subject: more questions
Posted: Tue Nov 13, 2007 6:36 am
|
|
| |
| Captain |
|
|
Joined: Tue Dec 05, 2006
1:55 pm
Posts: 5 |
Hi all! 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
? Cubeleg
|
|
Posted 11/12/2012
|
|
|
|
