[time-nuts] fast freq. synthesis schemes

EWKehren at aol.com EWKehren at aol.com
Thu Oct 15 12:10:23 UTC 2009


Luis
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:

Hi,

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
of such?

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.

Thanks.

Luis  Cupido.
ct1dmk.

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