[time-nuts] DIY Frequency extension for HP Agilent

[David C. Partridge]

An option might be to use a comparator somewhere in the circuit to "square
up" the input signal.  The only question would be to find one that will work
happily at that sort of frequency without bursting into song, or sitting
there like a lemon (i.e. doing not a lot).   Certainly the ADCMP600 (or
MAX999) won't hack it.

The other alternative I can think of is to over-amplify the signal and then
use a (very) high speed Schottky diode limiter to clip it.

Dave
-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Grant Hodgson
Sent: 16 February 2009 12:54
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] DIY Frequency extension for HP Agilent

Samuel

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.

regards

Grant


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