Re: [Discuss-gnuradio] USB2 <-> fast ADC & DAC

[Chris Albertson]

There are two areas were software defined radio is usful
The requirements for ADC are different

1) Wide bandwidth, strong signals like broadcast HDTV
2) Narrow bandwidth, very weal signals. One example of 
   this is HAM weak signal CW.  The bandwidth is only about
   500Hz but the signal/noise ratio is very low requiring
   a 24 bit ADC and nearly 100db dynamic range if any signal
   is to be captured at all

So it's pretty clear you can't build a totally generic
ADC. You need to choose your application area



--- Andy Green <address@hidden> wrote:
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> On Tuesday 27 May 2003 20:01, Joseph DiVerdi wrote:
> 
> Hi Joseph -
> 
> > Based on the signal processing I expect to do to the data I could
> > probably live with 10-bit resolution but must admit some reluctance
> ...
> > rate is required not 23.4MSample/second ((10.7 + 1) * 2). The front
> > end amplifier and track/hold devices must operate at the highest
> > frequency but the ADC need not sample that high.
> ...
> > BTW, some applications will require that the data be sampled by the
> > ADCs at a specific time, that is, will require an external sampling
> 
> It seems that 2 differential ADC channels of 10...12 bit resolution 
> are needed, capable of 21.4Msps, with differential input buffering.
> 
> An external differential clock input is needed (can this be done with
> 
> a simple unipolar opamp as a saturating comparator with capacitively 
> coupled inputs followed by a Schmitt trigger?).
> 
> I assume that a matching DAC with differential output buffering is 
> also called for.
<SNIP>

=====
Chris Albertson
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