To remain on topic (RHCP): last weeks G0MJW, M0EYT and I were busy designing, modelling and building prototypes of alternative 2.4 - 10 GHz dual band feeds.
There are several variations of the same theme, but I wanted to have a design without needing lathes or CNC-machines. The result is a (well known) 'cropped' patch, sized and matched with a waveguide in the center.
It took some time to model the correct position of the feedpoint as the waveguide seems to introduce some 'issues', making it not trivial to find the proper position to have (what I call) the 'S11-balloon' circling around Z=1 in the Smith Chart.
Attached a picture of sweeping my interpretation of a prototype, which we name ' 29-16° '. Return Loss (RL) could be improved even more with some tweaking of the patch height at the feedpoint position.