>Date: Sun, 29 Jun 2008 14:49:13 +0200 >To: Magnus Danielson <[EMAIL PROTECTED]> >From: Predrag Dukic <[EMAIL PROTECTED]> >Subject: Re: [time-nuts] Home built cesium clocks??? > > > >Magnus, Bruce, > >One of the requirements for applying for a reference laboratory in >Croatia is also to show "scientific excellence" in the area of work >(of the lab). > >So I'd have to make a some original contribution to the subject and >of course to publish it. > >It is true that at the moment I need only 250+ optical shift. That >with 9+ GHz achieved through "optical frequency shift >multiplication" (apart from "optical frequency multiplication" which >is more difficult) > >is one of the ideas that I didn't find reference to in existing >published articles. Something to be explored in the future (see >above), but very interesting, because I could avoid phase noise from >SRD multiplication. > >Another idea to be tried is to use PREDICTABLE jitter from FPGA DDS >as phase modulation normally used to find the center of the central >Ramsey fringe. > >DDS achieve desired frequency by slipping reference frequency cycles >from time to time and that way shifting the phase of the output >signal. It is a jitter, but it is not random. Well thought > >phase shift/modulation plan can exploit this as phase modulation. > >Predrag > > > > > > > > >At 14:17 29.6.2008, you wrote: >>From: Predrag Dukic <[EMAIL PROTECTED]> >>Subject: Re: [time-nuts] Home built cesium clocks??? >>Date: Sun, 29 Jun 2008 12:10:46 +0200 >>Message-ID: <[EMAIL PROTECTED]> >> >> > >> > >> > Bruce, >> > >> > I did my homework and collected everything from the internet I could >> > get. I have this one too. >> > >> > If I go optical way, I still need 9+GHz electrical source, so I will >> > first recreate electronics. Using off the shelf DDS chips, or using FPGA. >> >>A YIG oscillator or similar should be considered. The FPGA would be great >>for the state handling, but be sure to externally reclock the signal >>before use to remove the FPGA jitter. >> >> > Also I need 9 GHz AOM, so that I can split the same optical beam and >> > have two wavelengths 9ghz apart. That is a problem because I have >> > only 350 MHz AOM. >> >>In the article he referenced, the AOM only needs to handle 250,1 MHz. >>Only if you intend to achieve 100% pumping and detection ratios you need >>a full set of frequencies. Notice the important note on relation between >>laser linewidth and S/N relationship. Luckilly those are limitations >>outside of the cavity. >> >>The interesting aspect with an optically pumped cesium is that one of the >>common failuremodes, the contamination of the masspectrometer is removed. >>The detection is off-axis from the beam. Wonder if an open oven could not >>be installed there. That would allow for a ping-pong mode of operation, >>which the optical pumping itself fits very nicely too. It would cancel >>some of the systematic shifts due to assymetries in the microwave >>assembly which to the best of my knowledge is hard to compensate normally. >>Maybe state of art designs have found a way to handle it properly. >> >> > Multiple pass is difficult, it would take cca 27 passes to get 9 >> > GHz. On the other side, I wouldn't need the last stages of SRD >> > multiplication to get 9 GHz microwave. >> > >> > No doubt, I will have a lot of fun with the project. >> >>Surely. It could be hairpulling too. >> >>Cheers, >>Magnus
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