Ti 253x matching question

[liletian]

Hi guys
Can anyone explain the attched TI 253x matching network. The network matches balance output to a unbalnance antenna.
Thanks

 

[Mazz]

It goes like this:

C251, C251 are DC block
L251 is used to compensate some internal cap, to have a real differential impedance
C252, L252, C262, L261 is the real balun; it gives a 90 deg phase shift on each branch (with opposite sign) plus a certain impedance transformation.
C253, C254, C255 probably a match to 50 Ohm plus some filtering

Hope it can help.

Mazz

 

[liletian]

What should be the value of the c252 and l252?
It looks to me the value of cap and inductor are not unique
It seems as long as omega=sort(1/Lc)
It seems it will work
Do I miss something here ?
Thanks

It goes like this:

C251, C251 are DC block
L251 is used to compensate some internal cap, to have a real differential impedance
C252, L252, C262, L261 is the real balun; it gives a 90 deg phase shift on each branch (with opposite sign) plus a certain impedance transformation.
C253, C254, C255 probably a match to 50 Ohm plus some filtering

Hope it can help.

Mazz

 

[Mazz]

You are right, the cap and inductor are not unique. If you consider the ratio between single ended to balanced resistance, they become unique.

See here: https://www.edaboard.com/threads/143361/
and here: http://www.atmel.com/dyn/resources/prod_documents/doc8113.pdf

Mazz

 

[tony_lth]

Hi, Mazz,

Your file doc8113.pdf has password, can you remove the password?

BR,
Tony Liu

 

[Mazz]

Hi Tony

I'm not an Atmel engineer, no I can't.

Mazz