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Antenna of 2640(2650)EM and 2640(2650) SensorTag are different.

user4330687
Prodigy 145 points
Other Parts Discussed in Thread: CC2650, CC2640

I am making my IOT device based in Sensor Tag reference design.

I read many related document in ti.com and

I found that 2640(2650)EM and 2640(2650) SensorTag has different antenna.

2650 EM is

2650 Sensor Tag is

antenna matching capacitor(C15, ANT6) is different and (DNM and 0.5pF) and C32, C33 are different and C14 is added

both are CC2650 7x7 size. and each of thickness of PCB are about 1.0mm(2-layer) and 1.6mm(4-layer).

I'm not good at RF antenna... Please help me. I have to find right answer.

Thank you so much.

ps. one more question. Are CC2650 and CC2640 fully compatible in hardware design? SensorTag has CC2650 but I will use CC2640. Is it ok?

  • 0
    TI__Mastermind 18780 points

    The CC2650 and CC2640 are fully HW compatible, so replacing the CC2650 with the CC2640 is ok. The matching for the antenna depends on the size of the GND planes, encapsuling etc, thus the matching for the two boards are different. I suggest you have a look at AN058 

  • 0
    TI__Mastermind 18780 points
    The EM board has one DC block C14 before the antenna and one in the balun C31, while the sensortag has the DC blocks in the balun C32 and C33. The placement of the DC block does not affect the performance and is not important when using internal bias. Hoeverver, the placement of the DC block in the EM makes it easier to change config to external bial when not using the 7x7 size.
  • 0 in reply to CHS
    Prodigy 145 points
    Thank you so much, CHS.

    I did not read AN058 yet and I will try to read.
    If I make my device similar to sensor tag(4 layer, 1.6T) but two-layer and 10mm thickness, do I have to follow 2650 EM board(two-layer, 1mm thickness) antenna?
    (sensor tag has some 0603mm size parts, extreamly small size part, so re-try is really difficult for me!!!)

    Thanks again.
  • 0 in reply to user4330687
    TI__Mastermind 18780 points
    The antenna on the EM has no tuning components (only placeholders for them), but the antenna is tuned for a fairly large GND plane (EM with SmartRF06EB). The sensor tag has a much smaller GND plane and also has plastic encapsulation and is tuned for this. The antenna itself is not that affected by the stack-up but the matching components are dependent on the stack-up. So normally you will need to tune the board regardless if you do not copy shape, design, battery and capsuling. I would recommend you to start without tuning comp (but have the placeholders for them), so like the EM board then. The app note I referred to previously gives some indications on how to tune an antenna and you will need to do some measurements to see if the performance is as expected (do conducted measurements first, if these are good, then you can proceed to radiated measurements and range tests).