Re: [Discuss-gnuradio] Measure the power using USRP

[w xd]

Thanks.

           What is the deviation between the result calculate by the formula and the result measured by the calibration source for the USRP N210?  For example,when I ues the formula:10*log10(var(x))+30 to calculate the power of the receiver data is -20dbm.What is the true range for the true result?

           Thanks.

2015-12-08 10:53 GMT+08:00 Marcus D. Leech <address@hidden>:

On 12/07/2015 09:34 PM, w xd wrote:

Hi,
    I want to measure the power.I'm now transmit the OFDM signal.

    I use the usrp to receive data,and I save it to a file.I read all the data.Then:
I use the formula to calculate the power:
    10*log10(sum(abs(data).^2)/0.001)   dbm
    Is it the right way to calculate the power under the ofdm?
    Thanks.

Best Regards,
z sw

Instantaneous signal power is proportional to:

(I**2)+(Q**2)

You can average that to whatever interval you want, and then scale (perhaps converting into dB, as above).  But to determine *absolute*
  power at the antenna terminals you'll need a known calibration source or two, and use that to come up with calibration constants for
  your particular setup of frequency/gain/bandwidth/sample-rate.




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