[time-nuts] Comparing 10 MHz Oscillators at 10 GHz

Christophe Huygens Christophe.Huygens at cs.kuleuven.ac.be
Wed Jan 5 08:32:17 UTC 2011

Some related measurements on 10GHz at 
Of course, the objective was not really to measure 10MHz, but rather to 
mimic XO PN at 10GHz
using a DDS for the system as a whole (whatever that means).

- the 20logN is followed very well outside the PLL loop, even though 
transistor multiplier
stages are used, they don t seems to add significant noise compared to 
- > 10KHz is ref (8662A) limited.

Just some ideas,

On 05/01/11 09:17, Ulrich Bangert wrote:
> Bruce,
> I had the same idea as you and my friend Frank and I performed the following
> experiment to check whether it is possible or not:
> Two brick oscillators (I believe to remember in the 8 GHz region) were
> locked to the same source (HP8660) in the 100 MHz region which in turn was
> locked to my local 10 MHz reference (Z3805). The two signals were mixed down
> to DC with a M14A mixer. By means of a phase shifter in one of the cables we
> were able to change the phase between the signals and so to determine the
> mixer's sensivity as a phase detector. The mixer's output was sampled with a
> HP3457 at a one second sample rate. The voltage measurements were then
> re-computed into phase fluctuations and this data was fed into my PLOTTER
> utility to compute what must be considered the AD noise floor of this
> system. I have not documented the results but I remember that the noise
> floor indicated a clear improvement against a direct phase comparison at 10
> MHz for a given TIC resolution.
> What you suggest will produce you a mixer output signal which (when looked
> at with a scope) will easily enable you to trim your LPRO within seconds. If
> you can lock the bricks directly to 10 MHz this is even better.
> I have been thinking to use this scheme as a general tool for oscillator
> stability measurements. Since we must consider that two odcillators may not
> always be THAT close to each other in terms of frequency it would be better
> not to mix to zero but to a beat freaquency of say some 1-100 kHz (depends
> of course on the brick's pull range). This would involve a offset generator
> for one of the signals. I have drawn a circuit but not actually built that
> uses a ADF4002 and a DDS block to lock a 100 MHz signal to a 10 MHz signal
> where the DDS will provide the possibility to offset the 100 MHz signal in
> small amounts. I plan to lock two low noise WENZEL 100 MHz OCXOs to the 10
> MHz sources with one of them with a small offset. Then these two 100 MHz
> signals are compared after being multiplied by the brick oscillators (I have
> two bricks that translate 100 MHz to 10 GHz).
> Perhaps the group can comment on the feasibility of the plan.
> Best regards
> Ulrich Bangert
>> -----Ursprungliche Nachricht-----
>> Von: time-nuts-bounces at febo.com
>> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Brucekareen at aol.com
>> Gesendet: Mittwoch, 5. Januar 2011 00:09
>> An: time-nuts at febo.com
>> Betreff: [time-nuts] Comparing 10 MHz Oscillators at 10 GHz
>> Luciano Paramithiotti's January 1 post about his 10-to-100
>> MHz multiplier
>> project reminded me of past musings about using two 10GHz,
>> phase-locked
>> oscillators to compare the 10MHz outputs of my T-bolt and
>> LPRO so I  could
>> quickly adjust the latter by observing the mixed 10 GHz
>> signals with  a
>> microammeter.  I am talking about the California Microwave,
>> Frequency  West, etc.,
>> modules that were used as local oscillators in commercial
>> microwave  systems.
>> I was about to ask Luciano for more information on his coil forms,
>> amplifiers, and RF chokes when it occurred to me that
>> loop-noise in the PLOs  might
>> force a very narrow bandwidth and correspondingly long
>> observation  time.
>> Have members of the list been successful with this technique?
>> While most common PLO modules require an input signal in the 100
>> MHz-range, I have heard of versions that lock directly to a
>> 10 MHz input.   Is anyone
>> familiar with these and how difficult it would be to modify
>> conventional
>> oscillators to securely lock to 10 MHz?
>> Bruce, KG6OJI
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