Realisation of X-band circularly-polarised waveguide-fed microstrip array

A novel design of a circularly-polarised microstrip patch array fed by a waveguide is developed. A special central microstrip patch-to-slotted waveguide topology helps a simple truncated patch array realising the circular polarisation. The simulated and measured return losses, gains, axial ratios, and radiation patterns are presented for this new 4×4 array at X-band with good results.