question: the design of a x-band low noise amp

[littlemmx]

i'd designed a x-band lna,the noise of my calculation was 0.4db.
in testing,i found it was 2db after it was manufactured . but the vswr and gain are as much as my calculation.
i wonder what had happened? the noise was so bad?

 

[eladg]

well it is very hard to get this n.f. even when u take good transistor like ne321000 (i got 0.6dB nf) at 25 deg.
u should look for:
1)bais is it ok
2)the input matching
3) the connector is giving u 0.1 db
4) there are alot of thing that can be worng, i need more info,like did u put it in box, and your design

anyway it is hard to muasre those small nf

good luck

 

[littlemmx]

Thanks for u reply.
the 0.4db noise i said,was calculated by the soft.
i want to get about 0.7db,i used ne334s01.
the noise match is accomplished by a microstrip,which Zo=38ohm and physical length equals 9mm,and i find that the shunt inductor (high impedance microstrip) is not as important as the low frequency lna,is it?
thanks a lot.

 

[eladg]

Thanks for u reply.
the 0.4db noise i said,was calculated by the soft.
i want to get about 0.7db,i used ne334s01.
the noise match is accomplished by a microstrip,which Zo=38ohm and physical length equals 9mm,and i find that the shunt inductor (high impedance microstrip) is not as important as the low frequency lna,is it?
thanks a lot.

it may be osilate out of band.
u should stability the ciruits