[time-nuts] fast freq. synthesis schemes

Lux, Jim (337C) james.p.lux at jpl.nasa.gov
Wed Oct 14 19:54:30 UTC 2009




On 10/14/09 12:25 PM, "Luis Cupido" <cupido at mail.ua.pt> wrote:

> 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?

Look at how the PTS synthesizers work.. A series of decade modules, lots of
adding, mixing, filtering.  Off the shelf they do sub microseconds.

A DDS feeding a multiplier (not a PLL mult, but a step recovery diode or
similar) also will have very fast switch time, and might even be phase
continuous.  Your challenge with this approach is going to be spurs.

> 
> 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.


That's partly because fast frequency hoppers and frequency agile radars are
export controlled, and that's one of the applications of a fast switching
synthesizer.




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