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Re: [Discuss-gnuradio] GR, USRP, and GPIB measurements
From: |
madengr |
Subject: |
Re: [Discuss-gnuradio] GR, USRP, and GPIB measurements |
Date: |
Fri, 15 Aug 2014 21:41:28 -0700 (PDT) |
You don't need to take the FFT to get the power. See my attached example (in
GR 3.7). Just take the output from the USRP, complex_to_mag_squared,
integration with decimation to 1 Hz, 10*log10() + k, and probe at 1 Hz rate.
I'm using an N210 + WBX with gain=15 dB. That gives me a calibration factor
of k=-34.8 dB. I can vary power of my signal generator from -50 dBm to -10
dBm with less that 0.1 dB error in the calculated power.
https://dl.dropboxusercontent.com/u/49570443/power_calc.grc
https://dl.dropboxusercontent.com/u/49570443/power_calc.grc.png
Thanks,
Lou
KD4HSO
<http://gnuradio.4.n7.nabble.com/file/n49981/power_calc.png>
Gayathri Ramasubramanian wrote
> Hi
>
> Thank you for your note.
>
> I am trying to get the power of received signal using the blocks you had
> suggested previously.
> I have attached a flow graph snapshot ('uhd_fft_DK.grc.png").
>
> I am using the UHD:USRP Source to receive the signal which in turn sends
> the signal in the foll path
> "complex to Mag^2" block --> "integrate and decimate" block --> "10 log
> +k" block---> "signal probe" block.
>
> However there are errors mainly referring to the in-compatible I/O sizes
> of
> source (complex to Mag ^2 block) and sink (Integrate and Decimate block).
>
> The I/O size of "Complex_Mag^2" block is said to be 4096, while the I/p
> size of i"ntegrate and decimate" block is 4. ==> error as not compatible.
> Should I change the Vector length? I am not quite sure?
> The error propagates to other blocks if I change anything.
>
> Kindly help solve this.
>
> I have also attached another flowgraph (flowgraph screenshot.png) which
> works but it doesn't have the "integrate and Decimate" block or the
> Log10+K
> block but it works and receives the signal (developed by someone else
> previously in our lab). Now since the "Log10+K" block is missing, does it
> mean the output is given in mwatts instead of dBm?
> I cant seem to use this version on as the "probe_signal_vector" block does
> not seem to be supported in GRC 3.6.4.1 which is the version in my system.
>
> I tried using simple probe_signal block instead but again faced the I/o
> size incompatibility error? Is there a work around for this "probe signal
> vector" block?
>
> Also could you explain briefly how to approach and solve there I/o size
> errors.
>
> Look forward to your response
>
> Thanks
> Gayathri
--
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- [Discuss-gnuradio] GR, USRP, and GPIB measurements, madengr, 2014/08/03
- Message not available
- Re: [Discuss-gnuradio] GR, USRP, and GPIB measurements, Louis Brown, 2014/08/03
- Re: [Discuss-gnuradio] GR, USRP, and GPIB measurements, Gayathri Ramasubramanian, 2014/08/05
- Re: [Discuss-gnuradio] GR, USRP, and GPIB measurements, madengr, 2014/08/06
- Re: [Discuss-gnuradio] GR, USRP, and GPIB measurements, Gayathri Ramasubramanian, 2014/08/09
- Re: [Discuss-gnuradio] GR, USRP, and GPIB measurements, madengr, 2014/08/09
- Re: [Discuss-gnuradio] GR, USRP, and GPIB measurements, Gayathri Ramasubramanian, 2014/08/11
- Re: [Discuss-gnuradio] GR, USRP, and GPIB measurements, madengr, 2014/08/11
- Re: [Discuss-gnuradio] GR, USRP, and GPIB measurements, Gayathri Ramasubramanian, 2014/08/15
- Re: [Discuss-gnuradio] GR, USRP, and GPIB measurements,
madengr <=
- Re: [Discuss-gnuradio] GR, USRP, and GPIB measurements, Gayathri Ramasubramanian, 2014/08/22
- Re: [Discuss-gnuradio] GR, USRP, and GPIB measurements, madengr, 2014/08/23
- Re: [Discuss-gnuradio] GR, USRP, and GPIB measurements, Gayathri Ramasubramanian, 2014/08/25
- [Discuss-gnuradio] calibrating USRP N210 power (was: Re: GR, USRP, and GPIB measurements), Marcus Müller, 2014/08/25
- Re: [Discuss-gnuradio] GR, USRP, and GPIB measurements, madengr, 2014/08/25
- Re: [Discuss-gnuradio] GR, USRP, and GPIB measurements, mleech, 2014/08/25