Using branch line couplers in LNA design

[mwmmboy]

lna branch line coupler

Hi,
designing microwave LNA is difficult to have very high input matching and very low NF. I red that using a balanced structure with two branch line couplers is possible to have good performance.
Can anyone suggest me the best solution: branch line, splitter......or any other solution.
Can you suggest me a book or a paper where is explained why the NF of the amplifier is not increased using souplers?

Tx a lot.

 

[eladg]

Re: LNA and branch line

Hi,
designing microwave LNA is difficult to have very high input matching and very low NF. I red that using a balanced structure with two branch line couplers is possible to have good performance.
Can anyone suggest me the best solution: branch line, splitter......or any other solution.
Can you suggest me a book or a paper where is explained why the NF of the amplifier is not increased using souplers?

Tx a lot.

1 use 4 port div (branch,lange) not wilkinson
2 the noise is increasing by the loss of the spliter (about 0.3 , 0.4 dB)

 

[kent616]

Re: LNA and branch line

use lange coupler to desgin balanced amplfier is the best......size of ur design will be small too.....

 

[mreza1355]

Re: LNA and branch line

use wilkinson power divider first so your signal will divided to two section and then place your amplifiers in each branch with their matching circuits and finaly a wilkinson power combiner.

in this way you'll get good matching when your transistor matching isn't very good, when you use it in a simple amplifiere form.

 

[eladg]

Re: LNA and branch line

use wilkinson power divider first so your signal will divided to two section and then place your amplifiers in each branch with their matching circuits and finaly a wilkinson power combiner.

in this way you'll get good matching when your transistor matching isn't very good, when you use it in a simple amplifiere form.

dont forget the lamda/4.

but use branceline coupler. !!!
it is the best way !!!