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CC1310: RF Impedance Matching

VICTOR VALENCIA
Expert 1070 points
Part Number: CC1310
Other Parts Discussed in Thread: CC1190,

Hi,

We are working with a CC1310 + CC1190 design at 915 MHz. Due to physical constraints on our design, we are unable to follow a reference design layout

as far as trace lengths, pad sizes, etc. We are also evaluating a few possible antennas. This means that some tuning optimization will be needed.

We must maximize both Rx sensitivity and Tx power performance in our design. Several impedance-matching component values in the Evaluation Model

(CC1190 datasheet SWRR064) and the USA CC1310-CC1190 Reference Design (SWRA517) differ, and both documents note the importance of the

impedance matching and following the reference design layout for achieving optimized performance. The CC1190 datasheet shows a couple of Smith Chart

impedance measurements as seen from the connectors on the SWRR064 Evaluation Model, but that isn't particularly helpful for starting a new design.

The CC1310-CC1190 USA design (SWRA517) does not quantify any impedances. This makes it difficult to know how to tune the system to optimize for a

different layout, different antenna, etc. Is there any specification or guidance for what the optimum impedances should be as seen from the CC1190 RF pins

(PA_OUT, PA_IN, LNA_OUT, LNA_IN)?

The early versions of our product used the 1310 but we are now transitioning to the 1312. Does the 1312 have different impedance numbers than the 1310?

Victor

  • 0
    TI__Guru**** 317180 points

    - CC1310 and CC1312 require the same load and source impedances meaning that you can swap between CC1310 and CC1312 on the same PCB. 

    - The matching requirements for CC1190 are fairly complex

    - CC1190 have to see the wanted impedance on the fundamental frequency (around 6 ohm if I remember correctly) 

    - The attenuation on the harmonics have to be sufficient to pass ETSI/ FCC

    - CC1190 has to be stable for most possible loads in the smith chart. 

    Meaning that it's not possible to express the requirement in a couple of impedance numbers.

    What I would recommend when you have to deviate from the reference design is to simulate the ref design in ADS or similar and then simulate  your layout and adjust adjust your component values until S11, S21 and S22 for the ref design and your design are close to equal.