[time-nuts] low phase noise, noise floor and noise figure amplifier at 400MHz

[Magnus Danielson]

I think one should recall that for very deep phase-noise numbers for
far-out noise, we cannot remove the suspicion of cross-correlation
cancellation problems have overstated the phase-noise levels. I've seen
both instrument makers and oscillator makes handwaving to protect the
values which so far is understood to be non-physical.

Cheers,
Magnus

On 2020-01-10 03:25, Bruce Griffiths wrote:
> That's not possible at room temperature since thermal noise will limit the residual PN to -180DbC/Hz with a noiseless amplifier and a +3dBm input.
>
> Bruce
>
>> On 10 January 2020 at 14:38 Lifespeed <lifespeed at claybuccellato.com> wrote:
>>
>>
>> Hi Time Nuts,
>>
>>  
>>
>> I have a need for a low phase noise, noise floor and noise figure amplifier
>> at 400MHz.  I have tried some off-the-shelf 50 ohm amplifiers, the best of
>> which degrades phase noise by a couple dB.  I'm working with a signal with
>> -172dBc/Hz PN, so not much tolerance for degradation here.  The input signal
>> level is only 3dBm, so noise figure still matters as well.  I'm looking for
>> 15dB gain, 16dBm P1.  The residual phase noise would have to be better than
>> -180dBc/Hz, and I would probably operate the amplifier slightly compressed.
>>
>>  
>>
>> Any suggestions on topologies, transistors, white papers, etc?  I'm
>> considering the NXP BFU590Q silicon bipolar transistor, which I have used in
>> a transformer feedback configuration at 100MHz with less than -180dBc/Hz PN.
>> But this topology doesn't appear practical for 400MHz due to the difficulty
>> maintaining a high collector impedance at that frequency with a transformer.
>> Nor do I need to control the gain, which is one of the features of the
>> transformer-feedback topology.  I was thinking about common emitter with
>> inductive emitter degeneration.  Not sure cascode is right for this UHF
>> application.
>>
>>  
>>
>> Lifespeed
>>
>>  
>>
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