I found the problem; one of the pins of the fst3253 was not soldered
well. The pin which is connected to one of the signals from the DDS.
Now iam able to reduce the image. The signal fed to the soundcard is
now 90 degree out of phase iso of the 180 defrees i measured before.
Tnx for the support.
I did learn something.
73 Johan PA3GSB
--- In [email protected], "johanmaas2001"
<[EMAIL PROTECTED]> wrote:
>
> Hi Alberto,
>
> Oke, Than it seems that i have a hardware problem because i see
The
> upper half is just repeated in the lower half, but reversed, as if
> it were reflected by a mirror.
>
> The hardware is based on the sdr1000. Iam using an AD9854
quadrature
> chip.
>
> I measured a phase difference of 90 (also after the comparators).
>
> The signal fed to the soundcard (delta44) shows me a sinus with a
> phase difference of 180. Is it also required to have 90 phase
> difference for the signal fed to the soundcard?
>
> 73 Johan PA3GSB
>
>
> --- In [email protected], Alberto I2PHD <i2phd@> wrote:
> >
> > johanmaas2001 wrote:
> > > Hi again,
> > >
> > > I found the problem; the connector is defect; after replacing
> the
> > > connector the system is doing the demodulation for only the I
or
> Q
> > > signal.
> >
> > I am not sure to understand you fully. What you mean when you
say
> that the demodulation is done for only the I or Q
> > signal ? What should happen is the following. If you connect
only
> I or only Q, you should see the spectrum mirrored
> > about its center. The upper half is just repeated in the lower
> half, but reversed, as if it were reflected by a mirror.
> > If both I and Q are correctly connected and they have the right
> balance in amplitude and phase, then the lower and upper
> > half are independent, and each shows correctly its range of
> frequencies.
> > >
> > > Only using the RF source to see the one or two peaks... iam
> seeing 2
> > > peaks.
> >
> > If connecting an external signal generator you see two peaks
> symmetric with respect to the band center, then something
> > is wrong with your hardware. Either one of the two I/Q is
missing,
> or their amplitude/phase balance is completely wrong.
> > >
> > > I did measure the amplitude of the dds signal this seems oke.
> > >
> > Do you use a quadrature DDS that produces I/Q LO ?
> >
> > > Also the phase seems oke, at least on the scoop. what is the
> best
> > > approach of measuring the phase error?
> > >
> > What you mean saying that the phase looked good on the scope ?
> What measure did you do ?
> >
> > 73 Alberto I2PHD
> >
>
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