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

[Bruce Griffiths]

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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