oberstet
Newbie level 6
Hi all,
I'm new here, also a RF newbie, and this is my first post, so pls bare with me
I'm looking for help with 2 specific questions rgd a Printed LPDA I am designing using openEMS.
The PLPDA goals are:
* 400 MHz - 2.8 GHz
* -10 to -20 dB S11 over the whole range
* 50 Ohm unbalanced connect
* Aisler HD 2L PCB
I'll post the current status and EM simulation results below, but to prefix the 2 mentioned questions I have are:
1)
The PLPDA (obviously) has a balanced output, and that output is already designed to ~50 Ohm, but I need to convert that to _unbalanced_ 50 Ohm.
I have learned that I need a "Balun", and that the easiest thing is to go for a "Lumped Balun" (thanks Volker on openEMS! https://github.com/thliebig/openEMS-Project/discussions/178#discussioncomment-8181172).
Essentially SMD 2 inductors and 2 capacitors.
That sounds great, but e.g. when using the https://www.changpuak.ch/electronics/LumpedBalunCalculator.php Volker hinted at, _what frequency_ do I need to enter?
It is 1:1 (50 Ohm in and out) since I designed the antenna for that, but I have to enter _one_ frequency, whereas in my design the antenna should work over a 1:7 frequency range from 400 MHz to 2.8 GHz.
2)
My current WIP results are posted below, I've posted some using different parameters, and while I've identified all relevant model parameters (<50 floats), before going the "last mile" of fine balancing and tuning those, there is one aspect left I am puzzled / wondering about:
What can be seen is that I can achieve broadband operation in a lower ~1GHz range (400-1300MHz), and in a higher range (1800-300MHz), BUT in the mid-range ~1300-1800MHz, there is a big hill (bad S11).
Why? I mean what could be the reason?
I should note: all sizing and geometry parameters of the model are completely set using formulas in a systematic and uniform way in all cases.
I am hence wondering _where_ that hill comes from, there must be some aspect of the geometry or whatever I am not yet aware of.
Any helps or hints or comments (pro or con) would be highly appreciated!
Thanks/Cheers,
/Tobias
----
Couple of results / current status
note that modeling / geometry parameters vary e.g. even number of dipoles etc
frequency/dipoles are using "equal tempering" but with a "triple-frequency per-octave", just different "number of half-tones per-octave" ... I have no idea whether this kind of "electrochromatic scaling" is something usually done, but for me it made sense
I'm new here, also a RF newbie, and this is my first post, so pls bare with me
I'm looking for help with 2 specific questions rgd a Printed LPDA I am designing using openEMS.
The PLPDA goals are:
* 400 MHz - 2.8 GHz
* -10 to -20 dB S11 over the whole range
* 50 Ohm unbalanced connect
* Aisler HD 2L PCB
I'll post the current status and EM simulation results below, but to prefix the 2 mentioned questions I have are:
1)
The PLPDA (obviously) has a balanced output, and that output is already designed to ~50 Ohm, but I need to convert that to _unbalanced_ 50 Ohm.
I have learned that I need a "Balun", and that the easiest thing is to go for a "Lumped Balun" (thanks Volker on openEMS! https://github.com/thliebig/openEMS-Project/discussions/178#discussioncomment-8181172).
Essentially SMD 2 inductors and 2 capacitors.
That sounds great, but e.g. when using the https://www.changpuak.ch/electronics/LumpedBalunCalculator.php Volker hinted at, _what frequency_ do I need to enter?
It is 1:1 (50 Ohm in and out) since I designed the antenna for that, but I have to enter _one_ frequency, whereas in my design the antenna should work over a 1:7 frequency range from 400 MHz to 2.8 GHz.
2)
My current WIP results are posted below, I've posted some using different parameters, and while I've identified all relevant model parameters (<50 floats), before going the "last mile" of fine balancing and tuning those, there is one aspect left I am puzzled / wondering about:
What can be seen is that I can achieve broadband operation in a lower ~1GHz range (400-1300MHz), and in a higher range (1800-300MHz), BUT in the mid-range ~1300-1800MHz, there is a big hill (bad S11).
Why? I mean what could be the reason?
I should note: all sizing and geometry parameters of the model are completely set using formulas in a systematic and uniform way in all cases.
I am hence wondering _where_ that hill comes from, there must be some aspect of the geometry or whatever I am not yet aware of.
Any helps or hints or comments (pro or con) would be highly appreciated!
Thanks/Cheers,
/Tobias
----
Couple of results / current status
note that modeling / geometry parameters vary e.g. even number of dipoles etc
frequency/dipoles are using "equal tempering" but with a "triple-frequency per-octave", just different "number of half-tones per-octave" ... I have no idea whether this kind of "electrochromatic scaling" is something usually done, but for me it made sense