Re: [Discuss-gnuradio] USRP GNU radio receiver

[CEL]

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

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