[time-nuts] DIY Frequency extension for HP Agilent

[John Miles]

>
> The NLB-300 and NBB-300 series MMICs from RFMD work very at up to 13GHz
> or so, certainly far better than a Mini-circuits ERA- whose gain will
> start to roll off at higher frequencies.  Designing a broadband gain
> stage to work up to 12GHz+ may not be as easy as it seems.  However it
> is made somewhat easier by the use of broadband chokes from the likes of
> Mini-Circuits, wideband inductors from Coilcraft and broadband
> capacitors from ATC - to name but three - there may be others as well.
>
> The 4-stage amplifier used by HP not only increases the signal level, it
> increases the slew rate (V/uSec) at lower frequencies.  It's not just
> about signal level, it's about getting fast edges.  The Hittite HMC363
> /8 is a great IC, using static flip-flops, and will work all the way
> down to DC - IF the edges are fast enough.  Ironically it may be the
> case that the lower frequency limit presents more of a challenge than
> the higher frequency limit.

True.  The Hittite parts can be used all the way down to DC, if the edges
are fast enough. :)

The last time I wanted to build a prescaler capable of DC operation, I ended
up using a tunnel diode to speed up the edges of low-frequency input
signals.  I used some crude LC filtering to bypass the TD for faster
signals, routing them directly to the prescaler chip.  The circuit worked
well enough, but it was pretty twitchy.

-- john, KE5FX