[time-nuts] Down-conversion to IF and sampling

[Bob kb8tq]

Hi

What is the Time Nut goal here? Are we after the carrier frequency or after the
modulation on the signal?

Bob

> On Dec 23, 2017, at 10:46 AM, Stephan Sandenbergh <ssandenbergh at gmail.com> wrote:
> 
> Oops, I noted a sign error in the previous diagram. The attached seems
> better...
> 
> On Sat, Dec 23, 2017 at 4:46 PM Stephan Sandenbergh <ssandenbergh at gmail.com>
> wrote:
> 
>> Hi All,
>> 
>> Consider the following very common scenario: A perfect RF signal is
>> heterodyne down-converted to baseband using an offset oscillator. Let's
>> assume this oscillator has x(t) = xo + yot. This produces a time and
>> frequency offset baseband signal. Then, this baseband signal is coherently
>> ADC sampled using that same offset oscillator.
>> 
>> What would the effect of this coherent ADC sampling be?
>> 
>> See attached diagram. Here I assumed the ADC timebase is a time-dependent
>> function of the oscillator offset. However, it feels like I'm making a
>> logic error? I can't remember ever seeing anyone accounting for the ADC
>> time-base errors in coherent heterodyne down-converter stages. I have
>> limited experience though.
>> 
>> Regards,
>> 
>> Stephan.
>> 
>> 
>> 
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