[sdiy] BBD question

[Nicholas Gregorich]

Magnus Danielson wrote:
> Nicholas Gregorich wrote:
>> Ian Smith wrote:
>>> I've got the old Panasonic BBD manual and it shows one with a 20 kHz 
>>> 12dB lowpass filter at both the input and output... I'm guessing 
>>> that's to reduce clock noise. So I'm thinking have a filter at the 
>>> beginning of the chain and between each BBD and one at the end.
>>>
>>
>> The one at the input is probably considered an anti-aliasing filter, 
>> and at the output a reconstruction filter (reduces clock noise). In 
>> that case a filter between BBD stages is probably a good idea to 
>> prevent aliasing in the second BBD.
> 
> How can you get aliasing in the second BBD when they run off the same 
> clock? The second BBD will keep shifting the voltages just as if they 
> where the same BBD.
> 

I guess this is the part I'm having a hard time with here, why is there 
not aliasing between every single stage in a BBD?

Nick.