Hi For that matter, drive a microwave VCO with a couple high speed dac's. Calibrate the tuning curve as best you can and run an "open loop" synth.
Appropriately summing a couple of 16 bit parts could give you KHz level "steps". You can also dress it up a bit by running a pair of VCO's with one in "calibrate" while the other is "in use". A lot of this depends on just what the end application requires.... Bob -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Magnus Danielson Sent: Wednesday, October 14, 2009 4:48 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] fast freq. synthesis schemes Bob Camp wrote: > Hi > > At least on paper you can run a DDS at VHF/UHF and put it into a (very) > wideband PLL driving a 12-18 GHz VCO. > > As mentioned previously - spurs will be an issue. You also will need to get > a hold of some DDS chips with GHz-ish clock rates. One could use a suitably high frequency VCO or even YIG, locked to a DDS and then use a suitable fixed oscillator for up-conversion. The PLL locking would also use a DAC for VCO "bias" being updated at the same time as the DDS. A look-up-table could be used for top DDS frequency to bias conversion and a calibration round could be used to trim the table up to minimize the bias-error. That way the VCO can be quick-jumped and the PLL will immediatly steer the frequency back into lock. The PLL loop thus only needs to handle error in bias-table, the remaining difference in frequency and phase-relationship. Quite a different task than the overall lock-range. An ADC for the non-biased value of the loop-filtered detector would enable calibrations to be made automatic. Cheers, Magnus _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
