[time-nuts] External clock for Analog to Digital Converter in GPS Rx front-end

[Dr Bruce Griffiths]

John Miles wrote:
> Well, sure, but it also causes all kinds of secondary distortion effects
> (such as potential clipping at the rails of whatever you're feeding the
> signal into).  I don't think AM'ing the signal when you want PM is a good
> idea, when it's so easy to apply PM by itself.
>
> -- john, KE5FX
>
>   
>> John
>>
>> Since the sinewave has a finite slope at the zero crossing AM noise
>> produces PM noise on the output of a comparator.
>>
>> Bruce
>>
>>     
>
>
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>   
John

Try looking at the circuit of a typical GPS front end.
There is a built in comparator of some sort, digital dividers are used 
in the PLL.


Also if you thought about it you would realise that the amount of noise 
required to cause problems with the ADC is unlikely to cause clipping 
problems.

There's no need to use a complicated circuit when with proper design a 
simpler one will suffice.

Bruce