[time-nuts] Best way for generating 8994.03 MHz from 2899.00042272.....MHz?
Lux, Jim (337C)
james.p.lux at jpl.nasa.gov
Sat Aug 15 01:10:50 UTC 2009
These days, you might want to consider using the GaAs VCOs from Hittite,
rather than the DRO. DROs are SUCH a pain to build and tune, being a
mechanical resonator in a cavity. Everything you do seems to adversely
affect the DRO. The MMIC VCO is just a die (or a die in a package) and it's
pretty much immune to external effects, since the resonator is built into
the oscillator.
We built some prototypes at JPL using the VCO and a GaAs divider, and the
performance was better than DROs.
If you were building a very narrow band PLL, where tunability of the DRO
isn't needed over a wide range, the DRO might be a good solution, but still,
you have microphonics, etc. (we used to demonstrate the latter by hooking up
the output to a spectrum analyzer that has a FM demodulator, and talking to
the DRO)
On 8/14/09 5:53 PM, "Rick Karlquist" <richard at karlquist.com> wrote:
> David Bengtson wrote:
>> so there is one frequency that is X*(732/757), and he want to get X*3
>> from this? Seems like an integer-N PLL could do this pretty
>> straightforwardly, although I'd have to spend some time to figure out
>> the exact multiples. National Semiconductor has an app note on
>> frequency planning for synthsizers that would cover this.
>>
>> Dave
>
> Yes. The ideal architecture would be to use a dielectric resonator
> oscillator at 8994 MHz as the output source. Then divide its output by
> two. Take that ~4.5 GHz signal and divide it by 757 using the divide by N
> section of an Analog Devices ADF4106. Divide the 2998 MHz by 486
> using the divide by N section of a second ADF4106. 486 is 2/3 of
> 732.
>
> Feed the "muxout" of the second ADF4108 into the "ref in" of the first
> ADF4108 and use the phase detector in the first ADF4108 to tune the DRO.
> (This will become clear after you read the ADF4108 data sheet :-) The
> phase detector frequency will be about 5 MHz.
>
> Rick Karlquist N6RK
>
>
>
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