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1.9G LNA s problem with gain

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jupitorcuu

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1.9G LNA 's problem

I have used ATF 54143 to design a LNA for 1.9 GHz.
When I test it use Agilent's Noise Meter, there is a peak in NF.

In band 1.9 - 2GHz
The Gain is within + /- 1 dB, and is correct hign 15dB
except one point, NF is very low 1.2 dB
but at that point is nearly 10dB

Does any body meet the same problem in LNA test.
Seems not self oscillating
 

eladg

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Re: 1.9G LNA 's problem

jupitorcuu said:
I have used ATF 54143 to design a LNA for 1.9 GHz.
When I test it use @gilent's Noise Meter, there is a peak in NF.

In band 1.9 - 2GHz
The Gain is within + /- 1 dB, and is correct hign 15dB
except one point, NF is very low 1.2 dB
but at that point is nearly 10dB

Does any body meet the same problem in LNA test.
Seems not self oscillating
i had the same problem with lna.

u may get osilation. (out of band), take spectrum ana full span and look for it.

if u dont have osi send me the design and i will look for the prablem, but in 90% u have osilation

good lack
 

chb8795412

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There are 2 reasons
1.Input Impendance does not match.
2.power supply does not connect capacitance.
 

godz

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Re: 1.9G LNA 's problem

eladg said:
jupitorcuu said:
I have used ATF 54143 to design a LNA for 1.9 GHz.
When I test it use @gilent's Noise Meter, there is a peak in NF.

In band 1.9 - 2GHz
The Gain is within + /- 1 dB, and is correct hign 15dB
except one point, NF is very low 1.2 dB
but at that point is nearly 10dB

Does any body meet the same problem in LNA test.
Seems not self oscillating
i had the same problem with lna.

u may get osilation. (out of band), take spectrum ana full span and look for it.

if u dont have osi send me the design and i will look for the prablem, but in 90% u have osilation

good lack
Hi eladg,
I don't believe it is oscillation, if it is oscillation the gain as well should have a similar peak at the same point, which i understand from the message, didn't happen. Try to measure another DUT at the same frequency using the same cables and setup. may be there is a problem in the cables or so.
 

Aprecede

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Re: 1.9G LNA 's problem

I have used ATF 54143 to design a LNA for 1.9 GHz.
When I test it use Agilent's Noise Meter, there is a peak in NF.

In band 1.9 - 2GHz
The Gain is within + /- 1 dB, and is correct hign 15dB
except one point, NF is very low 1.2 dB
but at that point is nearly 10dB

Does any body meet the same problem in LNA test.
Seems not self oscillating
Have you solved this problem?
 

jiripolivka

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If the NF is low over the band, with only one spot high as you indicate, make sure your test setup cannot pick an external interference ( a nearby base station around 2 GHz). I have often seen even a well made test setup as vulnerable to interference over FM band (88-108 MHz).
I would advise to use a spectrum analyzer tuned to your LNA pass band; try a short wire antenna to check the presence of cellular signals. Maybe your cell phone makes the problem...
 

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