You are thinking in terms of analog mixers, Digital QSD mixers are a whole other world. QSD mixers have to have a square wave clock, and function way better than a analog mixer if given a low phase noise "digital" clock. If they are given an analog sine wave for a clock, you would have to turn that back into a digital signal which can introduce jitter, so when possible it's best to keep the clock digital as much as possible. In a well designed QSD system a clock divider will improve the phase noise figures not make it worse.
Food for thought. At 04:03 PM 4/8/2006, you wrote: >An addendum to my info: > > From this paper, I gave You the internet-adress, You can clearly see >and take some consequences for receiver constructing. > >1.1. If one has an oscillator with phase-noise, You not only mix the >oscillator not only with the incoming frequency, but also with the >phase-noise of the oscilltor. It is something like a synchronous >mixing with a lot of frequencies and a lot of mixing products. The >less the bandwidth of the phase-noise the better for quality of mixing >result. > >1.2. At mixing You mix a strong signal (the oscillator-signal) with a >very little one, the incoming signal. Partly You have to filter the >product. > >1.3. You should avoid all solutions with phase noise inclusive >solutions with ic-dividers. > >1.4. The better the signal of the mixing process, the better the >result. Because of that, to gain ultimate quality, You should forget a >lot of solutions and change to a dds-circuit with a very high >working-frequency. All other solutions have a lack of quality, to >reach ultimate success. > >1.5. The alternative could be a quartz-osciallator, but one is not >able to change the frequency in a wider range. > >1.6. My "feeling is" even concepts with I,Q-solutions could be better, >if a fast dds-circuit is used. > >1.7. Having a rectangular signal meens a lot of filtering.... and a >lot of useless noise. > >One can see, that using a fast dds-circuit is at the moment even for >traditional receveiver concepts in let me say AM, SSB and other >modulation-types is "state of the art" and You miss-use time and >effort for other versions. > >I will look for answers coming. In the meantime, I will work with my DRT1. > >An incoming signal is always not a digital one even, if its >constructed digital by modulation as DRM. > >Wolfgang > >--- In [email protected], "Wolfgang Hartmann" ><[EMAIL PROTECTED]> wrote: > > > > Hallo to all, especially to Dan. > > > > Here is an email adress, wher You can find some informations in german > > language. > > > > http://www.elexs.de/clock3.htm > > > > You see the phase-noise and the noise carpet of several designs. > > > > They have a lot more on DRM, Elektor-receiver. > > > > Wolfgang > > > > > > > > > > > > >Yahoo! Groups Links > > > > Cecil Bayona KD5NWA www.qrpradio.com "Windows the worlds most successful software virus" Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/soft_radio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
