Hi, everyone. I have a question about the quadrifilar helix antenna feeding design. Actually, it requires 4 different output with 0, 90, 180, 270 degree phase difference. Most of the literatures requires a 180 balun with 2-90 degree quadrature hybrid.
I am wondering whether there are any commercial chip or coupler for this type of applications, or any other good design topology which requires simpler feeding structure?
There are a numbeer of modes possible and useful for different siutuations. Look up reference material by Kilgus and see if you can run down a book by Corzine and Mosko on the subject. Both should be helpful. (....and no I do not have an e-book version)