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

[Marcus D. Leech]

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.