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CC1121: transmit current consumption affected by antenna tuning

Trevor Hunt
Intellectual 420 points
Part Number: CC1121

Hi there,

I hope you might be able to help with a question I have regarding the current drawn by the cc1121 chip during TX.. 

I recently compared the TX current drawn from a PCB with a badly tuned antenna to that of a good one and noticed that the TX current was greater on the PCB with the good antenna tuning 

I would have assumed that the PCB with the poorly tuned antenna would have drawn more than that of the tuned? 

  • 0
    TI__Mastermind 29560 points

    Hi Trevor,

    If the antenna is detuned then pending on the exact impedance this will affect the current consumption. 

    In this case, the detuned antenna will have a higher impedance (than "50 ohms") which can cause a reduction in output power and reduction in current consumption. The tuned antenna should be closer to "50 ohm" and the current consumption can increase.

    If you use a 50 ohm load at the SMA, then this should give you a reference of the current consumption expected for a perfect 50 ohm load. 

    Regards,

       Richard