[time-nuts] fast freq. synthesis schemes
EWKehren at aol.com
EWKehren at aol.com
Thu Oct 15 12:10:23 UTC 2009
There is not really enough information to make a good recommendation. Is
this a one off or is the plan to make multiple units, what are the phase
noise requirements, what are the cost limitations? If cost is a major issue
there are in my opinion only two options.
In both cases a VCO has to be used presetting with a fast D/A. In the
first case you pre scale by 16 and feed an AD 9910 DDS as a programmable
divider using a 100 MHz output in to a Hittite HNC 439 phase comparator with
all the shortcomings of a DDS multiplied by the total divider ratio.
The second option is a Hittite HMC 700 fractional PLL and use 50 or 60 MHZ
compare frequency. You have to pre scale by 2 . Having used the all the
above components I can tell you the DDS works reliable at 1200 MHz in and the
700 works great at 9 GHz.
I have not gone for switching speed but in my case emphasis is on phase
noise and resolution. As a matter of fact a friend of mine and I are doing a
low cost signal generator from 100KHz to 26 GHz in one Hz resolution using
the Hittite 700 part. Phase noise goal at 8 GHz is -100 dbc, 10 KHz offset.
We use surplus yigs.
Bert Kehren WB5MZJ
In a message dated 10/14/2009 3:25:33 P.M. Eastern Daylight Time,
cupido at mail.ua.pt writes:
I'm looking for the schemes used on the
frequency synthesizers that change frequency
in few microseconds time (or less)
at microwaves lets say circa 12-18Ghz)
Obviously with some resolution (let's say 100Khz step
or in that order)(otherwise it would
be a trivial exercise in the BW of the PLL loop filter)
Does anyone know of some paper or tech notes from
some instrument or modules that show block diagrams
I have many info on mw synthesizers but all fall into
microwave radio style of things with much higher
resolution (khz and less) and much longer
switching times (millisencods or more).
Info on fast stuff I can't really find.
I'm thinking of experimenting on something along those
lines so... all comments are welcome.
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