[time-nuts] Commercial software defined radio for clock metrology

jimlux jimlux at earthlink.net
Sat May 28 09:16:46 EDT 2016


On 5/27/16 6:58 PM, Hal Murray wrote:
>
> bruce.griffiths at xtra.co.nz said:
>> All the filtering and down mixing is done in the digital domain.
>> Anitialiasing filters in front of the ADCs are also be required.
>
> What sort of bandwidth is expected?
>
> The usual trick with audio ADCs is to have a low cost analog filter that
> does't have a sharp corner but lets everything you want through, sample at a
> high rate - say 16x, run that through a digital filter with a sharp cutoff,
> then decimate down to the desired sample rate.
>

The USRP uses fast ADCs intended for the wireless market. Sample rates 
are >50MSPS.  You can get daughter cards which have an analog PLL and 
mixer to tune over a wider band - as you can imagine, 2.5 and 5.8 GHz 
are popular.




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