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CC1110 HW Design: Adaptation VS output power

Aitor Larruskain
Prodigy 100 points
Other Parts Discussed in Thread: CC2591, CC2430, CC2530, CC2590

We have done a HW design with the CC1110 SOC for the 868MHz band.  We did the design following the gerbers from TI web page.  Once we got the first prototypes using the Smart RF studio we put the SOC in RX mode and in TX mode and with the network analyzer we measured S11 parameter. We got a very poor adaptation between -1.5 dB and -2dB.  We measured same parameter in same conditions with the CC1110EM 2.1 and the levels of this parameter were almost the same. In both cases even if we had a very poor adaptation of TX , the output power delivered was correct. Then in our prototypes we tried to improve the RX and TX adaptation, we arrived to levels more suitable in a Rx or TX front-end,  between -10 dB and -14 dB. Then we measured the ouput power and in this case it was very poor  10 dB below the suitable level. Is this normal  for this kind of SOC? Is this OK because this products are no working in a lineal way? Do you have any application  note for how to measure and improve reception and transmisión in this products?

  • 0
    TI__Guru**** 317180 points

    The PA on the CC1110 is not linear and it's highly recommended to follow the reference design to get optimal results. If the PA doesn't see the correct load for the fundemental and some of the harmonics the output power will decrease and the energy in the harmonics increase.

  • 0 in reply to TER
    Prodigy 100 points

    Is it the same case for the CC2591 and CC2590 or are this amplifiers (PA and LNA) working in  the linear region? And for The CC2430 and CC2530, same case as CC1110?

  • 0 in reply to Aitor Larruskain
    TI__Mastermind 18780 points

    It is highly recommended to follow the reference design for all of our parts as they have been tuned for overall best perfomance (output power, current consumption, EVM, stability etc).

     

    Charlie

  • 0 in reply to Aitor Larruskain
    TI__Guru**** 317180 points

    The CC2590/91, CC2430 and CC2530 all operate more in the linear region.

    That said, it is still recommended to follow the reference design for these circuits and strongly recommended for CC2590/91. Looking at S11 will in some cases give a good starting point but in most cases tradeoffs between sensitivity and output power, suppression of harmonics and other large signal effects will give a different optimal load than indicated by S11.