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

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 <mleech@ripnet.com>:

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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