[time-nuts] Build my own dist. amp ??
Bruce Griffiths
bruce.griffiths at xtra.co.nz
Fri Dec 19 04:35:32 UTC 2008
BriMDavis at aol.com wrote:
> Bruce Griffiths wrote:
>
>> That is a very effective way of elevating the phase noise floor.
>> Its usually far better to amplify the input and then split the output
>> maintaining a gain to the splitter outputs of at least 0dB.
>>
>>
> As I already explained the last time you mentioned this,
> I am well aware of noise floor limitations when operating
> an LO or clock at reduced signal levels.
>
Have you actually estimated the resultant phase noise floor with 0dBm
output??
An optimistic estimate can be done using the noise figure at the
frequency of interest.
>
> It is nice to keep the drive levels as high as possible;
> however, as long as the overall system noise floor is not
> impacted, it really doesn't matter if the reference level
> drops somewhere along the way.
>
When is a noise penalty of around 30dB (for the better sources) not
significant?
>
>
>>> Some data sheets contain this information at spot frequencies;
>>> this one does not.
>>>
>>>
>> Very few datasheets from Maxim specify much about the noise
>> characteristics of such devices.
>>
>>
> Perhaps we are suffering from a language barrier here.
>
> When I look at all 21 devices in their "VCOs/VCO Buffers"
> parts category, the only ones _without_ noise specs are the
> very parts about which I am asking, the MAX274x family.
>
>
Very little useful phase noise data is given (for a distribution
amplifier application), particularly for low offset frequencies.
For example MAX9989 only gives a spot phase noise at 100MHz output for a
1500MHz input.
I was also referring to the lack of low frequency noise data for devices
like the MAX477.
Maxim aren't alone in this.
> Brian
>
>
>
Bruce
More information about the time-nuts
mailing list