[Microwave] Doubling from 12 to 24 GHz

[Dr. Gerald N. Johnson]

Most frequency doublers or triplers work at milliwatt levels, often 
using a couple diodes fed 180 degree out of phase RF, a full wave 
rectifier that has a fairly strong 2x and other even harmonic outputs 
with very little fundamental. Triplers often use two anti parallel 
diodes as shunt clippers to convert the sinewave drive to something 
approaching a square wave that has a spectrum of fundamental and odd 
harmonics. The clipper can be a transistor or MMIC. There has been some 
work that shows the distance between the output of the clipper and the 
harmonic filter can enhance the desired harmonic, I think mentioned on 
the W1GHZ web page from quite some time ago.

A push-pull amplifier with the active device outputs connected in 
parallel instead of 180 degree out of phase would be a strong doubler, 
and with the normal connection would minimize the 2nd harmonic but if 
the output network presented a mismatch impedance to the active devices 
at the fundamental and impedance matched the third harmonic would be a 
very effective frequency tripler.

I'm not aware of any passive multipliers that would take in several 
watts, nor any diodes that would absorb that much power and have a 
fraction of an RF cycle switching time. A junction that could handle 
several watts would have so much capacitance because of its large cross 
section that it would not work at 12 GHz at all, probably not 1 GHz.

73, Jerry, K0CQ

On 8/3/2017 6:30 PM, Dave Brown wrote:
> I'm looking, ideally,  for some surplus piece of hardware that can be used
> (with a retune?) to do this.  I have up to several  watts at 12 GHz
> available from an amp ex some surplus analog TV link gear and want to use
> that doubled to make a 24 GHz  TX. I can generate a good stable 12 GHz drive
> signal for the amp so that's no issue but wondered if there's some surplus
> piece of gear around to use for the doubler stage. There's nothing like this
> available down here in ZL. The 12 GHz amp output is SMA, but I expect
> anything surplus that could be used for a doubler would likely  be waveguide
> input-  again, no issue,  as I have 12 GHz and 24 GHz  coax to w/g
> transitions available.
>   I can also come up with several watts at 8 GHz and triple, if surplus  gear
> to triple with is more readily available.
>   All suggestions welcome.
>   73
>   Dave, ZL3FJ
>
>
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