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

[Henrique Miranda]

Hello Joseph,
          
(snip)    
          
> If the IF signal to be captured is centered at 10.7MHz with a full
> bandwidth of 2MHz (+/-1MHz) then only a 4MSample/second acquisition
> 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.

There is a small correction that ought to be made here. In your
calculations an undersampling restriction in being disregarded: the
signal spectrum must be fully contained in a Nyquist zone,
otherwise aliasing will occur!

In this case the minimum sample rate that can be used is
((10.7 + 1) / 2.5) = 4.68 Msps and the signal spectrum will be
placed in the fifth Nyquist region.

> If the IF signal to be captured is centered at 10.7MHz with a
> full bandwidth of 10MHz (+/-5MHz) then a 20MSample/second
> acquisition rate is required not 31.4MSample/second ((10.7 + 5) * 2).

31.4 Msps is really the minimum sample rate you can use in this
situation (1st Nyquist region) due to the same restriction.

Regards,  

Henrique Miranda