[time-nuts] wtd: WWVB info
jimlux at earthlink.net
Fri Aug 7 19:02:56 EDT 2015
On 8/7/15 1:40 AM, Hal Murray wrote:
> kb8tq at n1k.org said:
>> Well, at least *some* of the chips out there do not make it to 96 KHz when
>> sampling at 192 KHz. Itâ€™s been a few years since I dug into them. Back then
>> a chip that had an internal filter that went to 96K was very much the
>> exception rather than the rule. If the only point of 192K is getting to a
>> 96K bandwidth, a lot of the chip guys missed out on it â€¦.
> Where did 192 KHz come from? Why is anybody interested in anything that far
> over 2*44 KHz?
There's lots of high resolution parts at that rate..
And if it's that fast, odds are the built in sample/track/hold is good
enough that you could directly sample the 60kHz without much trouble.
With a slower ADC and a good analog BPF and a good sample/hold, you
could sample at a few kHz, but that shifts the design burden to the BPF
and the sample/hold.
> It's common to have an audio ADC run much faster than Nyquist, but that's a
> hack to make it easier to build the cut off filter. You build a simple
> analog filter and a sharp digital filter and decimator so the output is 2x
> the target frequency. You get what you want without a fancy analog filter.
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