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Output power measurement

Julen Gutierrez
Prodigy 140 points
Other Parts Discussed in Thread: CC2520

Hello,

I have been measuring the output signal of CC2520 (chip+balun+pi) without the antenna connecting a coaxial cable and i have seen that depending of spectrum analyzer´s RBW i read different max output power.

 

 

The point is that when i reduce the RBW the maximum goes down the same amount of dBs as floor noise. Ok, i think that this is normal as we use DSSS. Anyway if i reduce the RBW i read very low output power for 5dBmCC2520 configuration: -20dBm. 

 

RBW=10KHz            P=-20dBm

RBW=100KHz            P=-2.97dBm

Am i configuring the spectrum analyzer correctly?

Why i see so low signal?

If we configure the output power to 5dBm, is 5dBm expected max power or this power is extended over the channel?

 

Thanks a lot!

  • 0
    TI__Expert 3205 points

    Hi Julen

     

    The datasheet power is the total power from CC2520. When CC2520 is transmitting a modulated signal this energy is spread over the channel bandwidth.

    There are two methods to get a more correct power measurement.

    You can configure CC2520 to transmit an un-modulated signal. Use SmartRF studio to configure the chip to un-modulated transmission. If CC2520 is controlled by your own MCU, you use SmartRF studio to identify the right configuration registers settings for un-modulated transmission.

    Alternatively, you can widen spectrum analyzer RBW to match channel bandwidth 5MHz and read peak power.

    Whit sufficient S/N ratio these two methods should provide similar results.

     

    Tor-Inge

     

  • 0 in reply to Tor-inge
    Prodigy 140 points

    Hi Tor-Inge,

    Perfect. I will try to measure the unmodulated signal. Anyway my Spectrum Analyzer ´s maximum RVW is 1Mhz so i can´t use the first method.

    Thanks!