[time-nuts] LPRO 101 ADJUSTMENT

[Jim Lux]

Quoting Ulrich Bangert <df6jb at ulrich-bangert.de>, on Tue 05 Aug 2008  
09:46:35 PM PDT:

> Jim,
>
>> A 48-bit-accumulator DDS chip such as the Analog Devices AD9852 will
>> achieve such frequency resolution:  2^-48= 3.6*10^-15, call
>> it 10^-14. The issue with a DDS is handling the various spurs.
>
> To be even more precise: It achieves this resolution in terms of the
> CLOCK frequency and not in terms of the OUTPUT frequency which may be
> consirable less resolution.
>
> Best regards
> Ulrich Bangert

And the 9852 is the older generation of DDSes from AD. The newer 99xx  
series is generally better (spur reduction built in, faster clocks,  
longer registers, more bits in the built in DAC)  AND, there's all  
sorts of schemes combining a DDS and a PLL (granted, this rolls in a  
whole other set of problems)


>
>> -----Ursprungliche Nachricht-----
>> Von: time-nuts-bounces at febo.com
>> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Joseph M Gwinn
>> Gesendet: Dienstag, 5. August 2008 16:53
>> An: Discussion of precise time and frequency measurement
>> Betreff: Re: [time-nuts] LPRO 101 ADJUSTMENT
>>
>>
>> time-nuts-bounces at febo.com wrote on 08/02/2008 04:38:14 PM:
>>
>> >
>> [snip]
>> >
>> >     It would be nice to find a relatively simple and
>> inexpensive 10MHz
>> > synthesizer that has a resolution of closer to 1E-14 to
>> avoid messing
>> > with the EFC at all.
>>
>> A 48-bit-accumulator DDS chip such as the Analog Devices AD9852 will
>> achieve such frequency resolution:  2^-48= 3.6*10^-15, call
>> it 10^-14. The
>> issue with a DDS is handling the various spurs.
>>
>> Arbitrary function generators such as the Agilent 34220A-001
>> (the -001
>> option means that an external 10 MHz reference signal is
>> accepted) will
>> also do the job, in a nice albeit expensive ($2.4K new) package.
>>
>> Joe Gwinn
>>
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>
>
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