Horn And Waveguide Feeder for 2.4Ghz

I always wonder haw to feed waveguide or horn from the back - all the designs are feeded from side as usual Cantennas.
Now I have picture - file is pretty old but interesting.



I cannot remember from where I take the PDF file to write a link. Here it is 8602-4.pdf ,I didn’t change the name of the file.
Most interesting is that the connector is on the back - also wide band feeder is used and antenna is DC grounded - which differ from original cantenna design.
I used a lot of cantenas and this will be tested at first possible moment.
Also may be used in slotted waveguides.