[Top][All Lists]

 From: Simona Sibio Subject: Re: [Discuss-gnuradio] USRP GNU radio receiver Date: Wed, 17 Jul 2019 14:18:46 +0100

Hi Marcus,

I tried to change the offset in the transmitter but the output in the receiver is the same, also if I send a sine signal with 10 Hz and 0,1 amplitude: the output became unstable in frequency and in time is always zero (see attached, 130K).
The flow graph is attached.
Do you have any suggestions?

Simona

Il giorno mar 16 lug 2019 alle ore 18:59 Müller, Marcus (CEL) <address@hidden> ha scritto:
That phase is not any more or less random than that of your local
oscillator, so there might be some misunderstanding here.
On Tue, 2019-07-16 at 18:52 +0100, Simona Sibio wrote:
> Thank you very much!
> But, with the offset tuning I cannot edit the phase.
> Maybe, I have to change method.
> Best Regards,
>
> Simona
>
> Il giorno mar 16 lug 2019 alle ore 18:25 Müller, Marcus (CEL) <address@hidden> ha scritto:
> > Well, there's leakage / DC blocking filters in most mixers, so yes.
> >
> > But the solution is simple (and hardware-supported transparently on
> > USRPs): Just tune at an offset, and mix down to 0 Hz (==constant!) in
> > digital. Your USRP can do that for you, google for "USRP offset
> > tuning".
> >
> > Best regards,
> > Marcus
> >
> > On Tue, 2019-07-16 at 18:15 +0100, Simona Sibio wrote:
> > > Thank you very much!!
> > > Then, I cannot measure a constant because, in the RX chain, maybe, some filter deletes the information, doesn't it?
> > > Thank you for your time and tour tips!
> > >
> > > Best Regards,
> > >
> > > Simona
> > >
> > > Il giorno mar 16 lug 2019 alle ore 18:01 Müller, Marcus (CEL) <address@hidden> ha scritto:
> > > > Look up what a quadrature modulator does. It's just a multiplication
> > > > with e^{j2\pi f_{carrier}t}, in the end.
> > > >
> > > > Your constant signal s(t) = c const. would hence be transmitted as
> > > >
> > > > c·e^{j2\pi f_{carrier}t}
> > > >
> > > > whereas a complex sinusoid of frequency f and amplitude a,
> > > > s(t) = a·e^{j2\pi f t) would be transmitted as
> > > >
> > > > a·e^{j2\pi f t)·e^{j2\pi f_{carrier}t} = a·e^{j2\pi (f+f_{carrier})t}
> > > >
> > > > so, identical to the constant signal, just at a different frequency.
> > > >
> > > >
> > > > Best regards,
> > > > Marcus
> > > >
> > > > On Tue, 2019-07-16 at 17:53 +0100, Simona Sibio wrote:
> > > > > Hi Marcus,
> > > > >
> > > > > Thank you for tip!
> > > > > I know that calibration is not so easy but I hope that.
> > > > > Could you help me to understand what happened with a constant complex baseband signal?
> > > > > I am beginner in this field.
> > > > > Thank you for your time.
> > > > >
> > > > > Best Regards,
> > > > >
> > > > > Simona
> > > > >
> > > > > Il giorno mar 16 lug 2019 alle ore 17:39 Müller, Marcus (CEL) <address@hidden> ha scritto:
> > > > > > Watch out! What do you get at the *output* of your SDR device when you
> > > > > > transmit a constant complex baseband signal, mixed to a carrier
> > > > > > frequency? How does that differ from transmitting a complex baseband
> > > > > > sinusoid mixed to a carrier frequency?
> > > > > >
> > > > > > On Tue, 2019-07-16 at 18:32 +0200, sumit kumar wrote:
> > > > > > > Ok, so for a constant source, in the time domain you will see a flat signal only! Try connecting a spectrum analyzer and you shud see a peak at DC becz Fourier transform of constant signal is impulse.
> > > > > > > And yes, as Marcus said, increase the sampling rate!
> > > > > > >
> > > > > > >
> > > > > > > On Tue, 16 Jul 2019 at 18:06, Simona Sibio <address@hidden> wrote:
> > > > > > > > Thank you for the assistance.
> > > > > > > >
> > > > > > > > I put the module "constant source" in my flow grap.
> > > > > > > > With this module, I can choose witch amplitude I want to send.
> > > > > > > > I attached the flow graph.
> > > > > > > > And, I would want to read these values in the receiver.
> > > > > > > >
> > > > > > > > Simona
> > > > > > > >
> > > > > > > > Il giorno mar 16 lug 2019 alle ore 16:58 sumit kumar <address@hidden> ha scritto:
> > > > > > > > > Hi Simona, what is the "constant signal" here ?
> > > > > > > > >
> > > > > > > > > On Tue, 16 Jul 2019 at 17:54, Simona Sibio <address@hidden> wrote:
> > > > > > > > > > Hi all,
> > > > > > > > > >
> > > > > > > > > > I want to use GNU radio to measure the amplitude and the phase of a signal.
> > > > > > > > > > I send a constant signal with the transmitter USRP but in the receiver there is a flat signal with amplitude 0 and offset 0.
> > > > > > > > > > I tried to send a sine signal and the receveir works fine.
> > > > > > > > > > How can I do to send only a constant and measure the amplitude?
> > > > > > > > > >
> > > > > > > > > > Thank you for your time.
> > > > > > > > > >
> > > > > > > > > > Simona
> > > > > > > > > >
> > > > > > > > > > _______________________________________________
> > > > > > > > > > Discuss-gnuradio mailing list
> > > > > > > > > > address@hidden
> > > > > > > > > > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > --
> > > > > > > > > Sumit Kumar
> > > > > > > > >
> > > > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > _______________________________________________
> > > > > > > Discuss-gnuradio mailing list
> > > > > > > address@hidden
> > > > > > > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

Screenshot from 2019-07-17 14-15-47.png
Description: PNG image

Screenshot from 2019-07-17 14-18-02.png
Description: PNG image