Hi, I'm measuring the power of a signal received by a B200mini USRP (mean(abs(TXsig)^2)). But I'm getting a large number, like 3e5, which is clearly just a digital power and not a physical power. How to determine the actual received signal power?

Convert to log-scale, then calibrate with a known signal power using a calibrated signal generator or noise power source. Make sure you protect the front end though - USRPs are usually subject to damage above -15 dBm. On Fri, Jul 15, 2016 at 5:14 PM Mohanad via USRP-users < usrp-users@lists.ettus.com> wrote: > Hi, I'm measuring the power of a signal received by a B200mini USRP > (mean(abs(TXsig)^2)). But I'm getting a large number, like 3e5, which is > clearly just a digital power and not a physical power. How to determine the > actual received signal power? > > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > -- Very Respectfully, Dan CaJacob

Could you please explain more?What do mean by "calibrate with a known signal power"? > On Jul 15, 2016, at 8:44 PM, Dan CaJacob <dan.cajacob@gmail.com> wrote: > > Convert to log-scale, then calibrate with a known signal power using a calibrated signal generator or noise power source. Make sure you protect the front end though - USRPs are usually subject to damage above -15 dBm. > >> On Fri, Jul 15, 2016 at 5:14 PM Mohanad via USRP-users <usrp-users@lists.ettus.com> wrote: >> Hi, I'm measuring the power of a signal received by a B200mini USRP (mean(abs(TXsig)^2)). But I'm getting a large number, like 3e5, which is clearly just a digital power and not a physical power. How to determine the actual received signal power? >> >> >> _______________________________________________ >> USRP-users mailing list >> USRP-users@lists.ettus.com >> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > > -- > Very Respectfully, > > Dan CaJacob

 Hi, I'm measuring the power of a signal received by a B200mini
 USRP (mean(abs(TXsig)^2)). But I'm getting a large number, like
 3e5, which is clearly just a digital power and not a physical
 power. How to determine the actual received signal power?


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Hi Mohanad, as you correctly noticed, the values you get from a USRP are just digital numbers – since the USRPs aren't calibrated devices, these numbers will be /proportional/ to the analog signal you provide to the USRP, but this analog power / digital power relationship is different for each USRP, at each frequency, at each gain, at different bandwidth and different sampling rates. Hence, the only possibility to map digital power to analog power is to use exactly the same configuration (frequency, gain, bandwidth, sampling rate, master clock rate) and measure a signal with known power. As soon as you've done that (assuming you are in the linear range), you know the ratio between analog power and digital power. Do a few more than just one measurement, though – with 3 or 4 different known powers, you can verify you're in the linear range of operation, get a noise floor estimate and the proportionality factor mentioned above at once. Best regards, Marcus On 16.07.2016 05:20, Mohanad via USRP-users wrote: > Could you please explain more?What do mean by "calibrate with a known > signal power"? > > On Jul 15, 2016, at 8:44 PM, Dan CaJacob <dan.cajacob@gmail.com > <mailto:dan.cajacob@gmail.com>> wrote: > >> Convert to log-scale, then calibrate with a known signal power using >> a calibrated signal generator or noise power source. Make sure you >> protect the front end though - USRPs are usually subject to damage >> above -15 dBm. >> >> On Fri, Jul 15, 2016 at 5:14 PM Mohanad via USRP-users >> <usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>> wrote: >> >> Hi, I'm measuring the power of a signal received by a B200mini >> USRP (mean(abs(TXsig)^2)). But I'm getting a large number, like >> 3e5, which is clearly just a digital power and not a physical >> power. How to determine the actual received signal power? >> >> >> _______________________________________________ >> USRP-users mailing list >> USRP-users@lists.ettus.com <mailto:USRP-users@lists.ettus.com> >> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >> >> -- >> Very Respectfully, >> >> Dan CaJacob > > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com