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

[Magnus Danielson]

Patrick,

I try to share what I have learned as generously as others before me
have done. Somewhere along the line I transitioned from noob to actually
know something and now, well, I can't claim complete lack of knowledge
anymore. But, I enjoy the many questions, as it forces me to think,
think and think. There is always things to learn in obscure corners and
plain questions. It turns out that if you are stringent enough there is
many white spots that you may not expect. So there is still things to
learn and angles to cover. So thank you for asking questions, it is the
constant challenge that makes us think, share and learn stuff.

Most importantly, we need to enjoy the fun of challenge and learning!

Cheers,
Magnus

On 2020-01-18 17:29, Patrick Murphy wrote:
> Magnus,
>
> Well you kindly explain what you mean by your comment "I've seen
> both instrument makers and oscillator makes handwaving to protect the values
> which so far is understood to be non-physical." , especially the
> non-physical part.
>
> While I can keep up with a lot of the discussions here, I will likely die
> an old man before I consider myself anything more than a noob. Thanks for
> your patience.
>
> -Pat (KG5YPQ)
>
>
> On Sat, Jan 18, 2020, 8:57 AM Magnus Danielson <magnus at rubidium.se> wrote:
>
>> 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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