[time-nuts] locking oscillators - an increase in power and/or stability ?

Bob Camp kb8tq at n1k.org
Wed Oct 8 15:26:09 EDT 2014


Hi

It’s called injection locking. The two oscillators (or what ever) lock up at exactly the same frequency and some arbitrary phase. Depending on the amplitude and phase at the sum point, the result can be anything from +6 db to zero power. Anything that oscillates can injection lock if given the right feedback at the right point. 

The gotcha is that they are at the same frequency, so they add as voltages rather than power. In phase, equal amplitude, you get 6 db more power. Exactly 180 degrees out of phase and exactly equal power and you get nothing (no power at all) at the sum point. Off by a fraction of a degree or a fraction of a db and you still get roughly 6 db in the zero degree case. Same error in the 180 degree case, the power starts to rise pretty quickly.

Bob

On Oct 8, 2014, at 3:11 PM, paul swed <paulswedb at gmail.com> wrote:

> David the locking makes sense but the other numbers do not make sense.
> Combined best case would be +3 DBm also you say the current on the diodes
> goes down. More power for less power in is not adding up.
> Though the right question is what are they using as power detectors?
> When the 2 are combined there could be a large lower frequency mix product.
> Broad band detectors just collect all of the stuff and add it up.
> Regards
> Paul
> WB8TSL
> 
> On Wed, Oct 8, 2014 at 1:10 PM, Dr. David Kirkby (Kirkby Microwave Ltd) <
> drkirkby at kirkbymicrowave.co.uk> wrote:
> 
>> There's a discussion on the "ukmicrowave" list about combining the
>> power from two 10 GHz Gunn oscillators with a magic T.  One might
>> expect to get nearly double the power if the two oscillators are
>> combined. What people are observing is getting more than double the
>> power. To quote from
>> 
>> http://www.bobatkins.com/radio/10GHz_gunn_power_combiner.html
>> 
>> "Individually, the two oscillators produced 64 and 70 mW,
>> respectively, but produced a combined power output of 235 mW. "
>> 
>> Another one
>> 
>> "The stability of the combined oscillators was found to be higher than
>> that of the individual oscillators. "
>> 
>> It is hardly surprising the two lock together in frequency.
>> 
>> I wonder if people see similar things with pendulums in clocks? I
>> can't think of any logical explanation for this, but it seems to be
>> more than an April fools joke.
>> 
>> What is interesting is someone who just tried it says the current in
>> the diodes goes down about a mA when combined, so the input power to
>> the devices go down very slightly. Typically these things run at a few
>> hundred mA, so 1 mA is likely to be less than 1 %.
>> 
>> 
>> 
>> Dr. David Kirkby Ph.D CEng MIET
>> Kirkby Microwave Ltd
>> Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3
>> 6DT, UK.
>> Registered in England and Wales, company number 08914892.
>> http://www.kirkbymicrowave.co.uk/
>> Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
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