CC2591 S-parameter

Hi Roshni,

We are working on a specifying the output impedance in more detail but for the time being please just use 30ohms for the output impedance.

Regards,

   Richard.

  The output impedance of the CC2591 best load (antenna) match is at 33+j7.

-Nissim@vitelix.com

Nissim, I'm really inteesting about this information ( the load for the antenna output). It seems crazy but TI give no information about this point.

Can you explain me how you determine this impedance ?

best regards

Hi Victorien,

As far I understand TI reply, cc2591 output impedance is very close to 25Ohms with not imaginary component to speak of. (when no load attached).

see The CC2530_CC2591EM reference design, Removing CC2591 from CC2591EM, measuring impedance presented on PIN ANT, result is close to 33+J7 ohm. 

see http://e2e.ti.com/support/low_power_rf/f/155/t/153328.aspx#555267 form. 

You can call my Skype: nissim.test 
or send e-mail, nissim@vitelix.com 

I need to conjugate impedance match to cc2591 input (105 +j35) a RF chip  differential output  of (34 - j72) . Since cc2591 has balun inside, do you think I can just microstip pcb wire RF_N output to cc159` RF_N input, and same with RF_P ? 

If not, 

My question:  if RF chip  differential output  is (34 - j72)  is the conjugate impedance match he balun  should be similar (34 – j72) or   (34 + j72) ? 

And I will need to find balun balance to balance, to hook the two impedances... ? with ratio of 105/34 or 35/72 ... something else.... 

Thank you for any information that can light me the path. 

-Nissim

Nissim, where do you get the number 33+j7 as Zopt from?

I do not know what is Zopt, 

The Z output is from http://e2e.ti.com/support/low_power_rf/f/155/p/16390/729641.aspx#729641 

Posted by Tor-inge  on Apr 10, 2012 4:59 AM TI employee.

" Removing CC2591 from CC2591EM, measuring impedance presented on PIN ANT result in close to 33+J7 ohm.
On CC2591EM the differential impedance between RF_N and RF_P is close to 105+j35 when CC2591 in TX and ANT connected to 33+J7 (CC2591 re-soldered onto the board.)
Tor-Inge
"

If have other information, espasaly for the inverted F pcb anttena please share. 

Thank you

Zopt is the impedance the CC2591 PA output should see to get maximum output power and this impedance is given in http://e2e.ti.com/support/low_power_rf/f/155/p/153328/653936.aspx#653936, posted by Tor-Inge Dec 19 6:14AM as 13+j0.

Hello Ter,

if you will read down that page you will see more reports from Tor-inge. Confirming my numbers.

But again. I do not understand why that has any relevant to my post about input impedance matching of cc2591 ? 

-Nissim