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It looks like this is a simple "TM10" type half-wave resonance, similar to a patch antenna. If you want currents on the outer edge, I'd suggest rotating the structure 90 degrees with respect to the magnetic field; likely you'll also need to adjust its electrical size.
My other main two...
The magnetic fields are directly linked to the currents on the surface of the conductor (\vec{J} ~ \hat{n}\times\vec{H}, etc.).
If you want the magnetic fields strongest on the outer circumference, this is where your currents need to be. It looks like you are going for a narrow-band resonant...
If the waveguide is "hollow", there is something inside of it that is not metal. You simply need to tell HFSS what this is.
HFSS (similarly to most FEM solvers) does not generally assume a vacuum by default.
Now you have no dielectric inside the waveguide. You need to explicitly add this - duplicate Box1 and assign material "vacuum"; I think that will solve your problem.
Ok, so it appears you are using a wave port. However, it appears that you do not have any metal or conducting boundary conditions in your setup. Assign a metal material to the waveguide (right now, "box2" is assigned as a vacuum), and let us know how this changes things for you.
Can you confirm that the "spikes" you observe are not just phase-wrapping points (e.g., between 180 and -180 degrees?)
The typical method is to terminate the coax with a port. It will not only match the impedance properly, but will also tell you how much power it is absorbing.
I would probably...
I recently (2021) completed a PhD in this field and am happy to offer some suggestions. Of course, there is much work going on, mostly on larger arrays / array theory these days - not so much individual element design. Are you looking for any particular place in Europe?
Volker has offered some...
Two questions:
1) Is phase wrapping being used? This could cause sudden 180-degree phase differences.
2) Are there any particular reasons your coax is left open instead of terminated (with, e.g., 50 ohms)?
The central trace can interact with the enclosure, even with a solid connection between your other PCB traces and the enclosure. In the worst case, this could cause your system to operate more like an antenna or filter. It's unlikely, but best to check in simulation if possible. Simulation with...
Nice job on the PCBs, they look great.
"The best" is of course subjective. What are your actual criteria? The return losses look decent over the measured frequency range, but only you know what you need...
Yes, the length of the line causes extra phase to be incurred.
How do we establish...
I think the typical way to do this is to have a switched bank of capacitors, with the switches being activated at various times. I'm not sure if a continuous time-dependent reactance is possible in ADS.
Are you observing Gain, or Realized Gain? Gain as defined by the IEEE does not include return loss. It sounds like you are expecting realized gain.
It sounds like you want to observe changes in return loss as you change your feeding position. I also recommend extracting input impedance from the...
All you need for NRW is the scattering parameters, reference impedance, and length of the metamaterial over which you are assuming homogenization, so yes -- why not? Via google, others have asked this.
You can also determine these properties more elaborately using eigenmode simulation results...
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