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<DIV dir=ltr align=left><SPAN class=145193507-28042022><FONT
face=Helvetica>Yes. I don't do digital.</FONT></SPAN></DIV><BR>
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<FONT size=2 face=Tahoma><B>From:</B> Synth-diy
[mailto:synth-diy-bounces@synth-diy.org] <B>On Behalf Of </B>ben gebhardt via
Synth-diy<BR><B>Sent:</B> Wednesday, April 27, 2022 8:01 PM<BR><B>To:</B>
synth-diy@synth-diy.org<BR><B>Subject:</B> Re: [sdiy] Weaver frequency
shifter<BR></FONT><BR></DIV>
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<DIV dir=ltr data-setdir="false">At David Dixon:</DIV>
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<DIV dir=ltr data-setdir="false">Was your weaver frequency shifter attempted in
the analog domain?</DIV>
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<DIV>On Wednesday, April 27, 2022, 10:39:48 PM EDT, Eric Brombaugh via Synth-diy
<synth-diy@synth-diy.org> wrote: </DIV>
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<DIV dir=ltr>On 4/27/22 17:41, Brian Willoughby wrote:<BR clear=none>> Do
these tuner stages at the beginning and end of the Weaver signal chain end up
shifting the frequency band of the content?<BR clear=none><BR clear=none>Yes.
The first tuner stage is used to create an analytic signal by doing <BR
clear=none>a quadrature shift of the center of the audio band, resulting in a
<BR clear=none>two-sided signal centered on DC. The quadrature LPF removes the
unwanted <BR clear=none>image that's created in the process.<BR clear=none><BR
clear=none>The tuner at the output shifts the analytic signal back up from DC
the <BR clear=none>difference between the input shift and output shift is the
total shift <BR clear=none>you end up hearing.<BR clear=none><BR clear=none>>
Would this help keep all signals within the sample rate? Are these questions
moot because of the potentials of under sampling?<BR clear=none><BR
clear=none>This depends on how you plan out the bandwidths and tuner
frequencies. <BR clear=none>In DSP systems the initial shift is often chosen to
be Fs/4 which <BR clear=none>simplifies a lot of the math (the quadrature LO
becomes a sequence of <BR clear=none>[1+j, -1+j, -1-j, 1-j] which is very easy
to do). That also allows the <BR clear=none>quadrature LPFs to be implemented
with half-band filters that can also <BR clear=none>simplify the math.
Regardless, you have to keep the bandwidths within <BR clear=none>that allowed
by Nyquist or suffer aliasing when the final real signal is <BR
clear=none>created.
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