Greetings everyone,
I am attempting to model and simulate a slot-ring patch antenna fed by ungrounded CPW in CST, although the S11 is fine, the e-field and h-field monitors shows strange results.
To be more specific, it seems like the field are not radiating through the patch, but through the slot instead. As a result, the farfield plot shows that the directivity is negative, which means it is not working properly as an antenna; however I have no clue at all about what is happening and there is few existing discussions about simulating ungrounded CPW fed antennas in CST. For anyone who has relative experience, attached below are the figures of the model and field behaviour.
As far as I am concerned, it could not be anything wrong with the dimensions and matching of the antenna since at current stage I am only realising this model from an existing research.
For now I am using open boundary conditions for all six directions, is it OK or I should change to add space?(I have tried to change but the S11 result is much worse if open add space is used)
Much appreciated for your kind help.
Surely you should use open-add space since as it is apparent from figure 1, your boundary is attached to your substrate. Open BC act as PML BC so it sees the substrate instead of air and want to match to the dielectric medium instead of air.
The e-field and h-field seem to be what I would expect. You have a standing wave pattern on your loop, which is one wavelength circumference.
It is behaving as an antenna, it has a radiation pattern similar to a dipole. It is a bit short in gain, perhaps a lot short in gain. Where does CST say that the missing 75 to 80% of the power has gone? The power budget is shown in the results tree on the left, a bit below the S-parameters.
It might be better to run with the operating frequency in the middle of the frequency range, rather than very close to one end.
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