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

[Leon Pavlovic]

The HP K22 had a specified noise figure as <7.5dB (I'm guessing its NF is
not around 1dB) and the measured noise floor -175dBc/Hz at 10kHz and up at
400MHz from the datasheet.

Since I've had a need for a low-gain (2-4dB) isolation amp at the
100-500MHz range, I've experimented with a cascode design with Infineon's
BFR106. Measured PN: -151dBc at 100Hz, -161dBc at 1k, -171dBc at 10k and -178dBc at
100k and up (@400MHz). P1db should be around +15dBm and the NF was not
measured yet.

Cheers,
Leon


>
> ---------- Forwarded message ----------
> From: John Miles <john at miles.io>
> To: "'Discussion of precise time and frequency measurement'" <
> time-nuts at lists.febo.com>
> Cc:
> Bcc:
> Date: Thu, 9 Jan 2020 22:23:23 -0800
> Subject: Re: [time-nuts] low phase noise, noise floor and noise figure
> amplifier at 400MHz
> > 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.
>
> You could take a look at the approach behind the option-K22 amplifiers that
> were sold by HP for use with the 3048A.  I've got one of those but I needed
> a couple more of them at one point, so I built some (literally) quick and
> dirty copies with BFG591 transistors with good results.
>
> I've mentioned them before on here, I think.  There are a few photos and
> plots at http://www.ke5fx.com/k22.htm .  Basically a CE amplifier with an
> LED-referenced bias stage originally suggested by Bruce Griffiths.
>
> A single stage won't deliver the gain you're after, but these amplifiers
> are
> relatively well-behaved and can be cascaded at will.  That was the original
> intent with the K22, which consisted of two independent amps in one box.
> If
> you want to use the K22 amps to keep oscillators from injection locking,
> you
> pretty much have to cascade them due to lack of reverse isolation.  The
> homebrew hack job is similar to the HP original in most respects including
> that one.
>
> I'd be inclined to use a dual-emitter part (BUF590G) instead of the
> BUF590Q,
> if I were building more of these.
>
> -- john, KE5FX
>
>
>
>
>