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Re: RF power combiner

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On Fri, 24 Oct 2025 13:17:37 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>Jeroen Belleman <jeroen@nospam.please> wrote:
>> On 10/23/25 22:48, Phil Hobbs wrote:
>>> On 2025-10-22 04:40, Jeroen Belleman wrote:
>>>> While musing over a text about transmission line transformers,
>>>> combiners, splitters and so on, I came up with a power combiner
>>>> that promises a bandwidth spanning from some kHz well into the
>>>> GHz domain, with good isolation between input ports, and that
>>>> does _not_ have a null where its transmission lines are half a
>>>> wavelength long.
>>>> 
>>>> I could find no other examples of this arrangement. The usual
>>>> combiners are wire- or coax- wound transformers, with 3 decade
>>>> bandwidths in the 100kHz-100MHz ballpark, or Wilkinson things
>>>> that only begin to work above half a GHz.
>>>> 
>>>> This design should be able to work from a few kHz up to well
>>>> into the GHz domain. Anyway, for what it's worth, here it is.
>>>> 
>>>> Jeroen Belleman
>>>> 
>>>> =========================
>>>> 
>>>> Version 4
>>> <snip>
>>> 
>>> That is one weird-ass combiner, for sure.?s like it has to be made 
>>> out of coax, on account of the switcheroo in the grounds.
>>> 
>>> I like it!
>>> 
>>> Cheers
>>> 
>>> Phil Hobbs
>>> 
>> 
>> The way I drew it was a bit clumsy. It's neater to arrange it
>> to have the center conductors cross over instead of the screens.
>> It should work quite well though, if constructed correctly. I got
>> 100kHz-9GHz (-3dB) out of a similar thing, with better than 40dB
>> of isolation between the inputs over almost the full bandwidth.
>> 
>> It appears I'm 38 years late though. A guy names Edwards, working for
>> Rockwell, came up with exactly the same thing in 1988! US patent 4774481.
>> 
>> Oh well.
>> 
>> Jeroen Belleman
>> 
>
>The low frequency behavior relies on the unphysical LTspice T-line model,
>unfortunately.  In spherical-cow land, the two ends are uncoupled, like a
>perfect transformer with a delay. 
>
>The combiner model works even better with 2 ps delay lines. ;)
>
>Cheers 
>
>Phil Hobbs 

I made a more realistic coax model, using three of the Tlines.

I have a diffusion problem, driving an ITO coating over a pretty hi-K
dielectric film. I was thinking about using an LTline to roughly model
that case, rather than doing calculus or anything nasty like that.


John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics

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RF power combiner Jeroen Belleman <jeroen@nospam.please> - 2025-10-22 10:40 +0200
  Re: RF power combiner Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2025-10-23 16:48 -0400
    Re: RF power combiner Jeroen Belleman <jeroen@nospam.please> - 2025-10-24 00:39 +0200
      Re: RF power combiner Joe Gwinn <joegwinn@comcast.net> - 2025-10-24 08:51 -0400
        Re: RF power combiner Jeroen Belleman <jeroen@nospam.please> - 2025-10-24 19:21 +0200
        Re: RF power combiner Bill Sloman <bill.sloman@ieee.org> - 2025-10-25 04:22 +1100
      Re: RF power combiner Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2025-10-24 13:17 +0000
        Re: RF power combiner Jeroen Belleman <jeroen@nospam.please> - 2025-10-24 19:15 +0200
          Re: RF power combiner Bill Sloman <bill.sloman@ieee.org> - 2025-10-25 14:49 +1100
        Re: RF power combiner Joe Gwinn <joegwinn@comcast.net> - 2025-10-24 15:33 -0400
        Re: RF power combiner john larkin <jl@glen--canyon.com> - 2025-10-24 12:48 -0700
    Re: RF power combiner Bill Sloman <bill.sloman@ieee.org> - 2025-10-24 18:17 +1100

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