[time-nuts] OT - Portable Digital 'scope

[Jim Lux]

On 2/23/12 1:25 PM, Robert LaJeunesse wrote:
> FWIW Rigol pushes their 40MHz Analog Devices part to 100 MHz without any problem
> (seen in eevblog teardown). Yes it's sort of cheating, but if the part works
> fine because all of the suppliers parts now yeild that fast due to an improved
> process well, it saves a few dollars / quid / drachma...
>
> And the 40MSPS is over full temp range, likely this is not a problem for the DSO
> 203 which has NO temp rating.
>
> Yes the "72MHz analog" channel rating makes no sense for something sampling at
> 72MSPS, Nyquist says you get at most 36 MHz bandwith.

That doesn't mean you couldn't use a sampler running at, say, 50 MSPS to 
look at a 110 MHz signal (something we actually do in a radio).

There are lots of ADCs out there that have RF bandwidths of much more 
than the sample rate, intended for use in direct sampling receivers. 
What performance really depends on is how good the sample/hold or 
track/hold is and what the sample jitter is.  (and of course, whether 
there's a stage in front to keep unexpected signals from aliasing in)

There are several ADCs out there that have GHz bandwidths and max sample 
rates in the 100MSPS range.