[Help] BPF for Differential LNA

[cmosbjt]

In a transceiver design, in differential LNA is used, the off-chip SAW BPF should have single-ended input and differential ouput, am I correct? Or is it necessary to insert a balun between the BPF and LNA?

Can anyone tell me something more detail about that?

Thanks.

 

[vfone]

You can use a balun, but to keep all the advantages of differential design is better to use a differential connection.
In both situations you need to design matching networks to obtain the correct filter performance and power transfer.
**broken link removed**

 

[cmosbjt]

You can use a balun, but to keep all the advantages of differential design is better to use a differential connection.
In both situations you need to design matching networks to obtain the correct filter performance and power transfer.
h**p://www.eetasia.com/ARTICLES/2000DEC/2000DEC04_AMD_AN7.PDF

Hi, thanks. You mean I should use a balun and there is no differential output SAW BPF in the world?

 

[vfone]

No. I said that you could use the SAW filter in both configurations, single-ended or differential connection (check the above application from Siemens)
If you have differential output from mixer (or LNA) is better to use differential connection. but the matching network is a little hard to be implemented.

 

[cmosbjt]

You mean the following structure?

Antenna -> SAW(Single end input, Diff output) -> LNA (Diff input)

 

[vfone]

Yes.

 

[DonJ]

You can also specify the input and output of your SAW filter and have it produced by a SAW manufacturer.

A.T.B