Cavity feed technique for slot-coupled microstrip patch array antenna

Slot-coupled microstrip patch arrays fed by rectangular overmoded cavities are described and their radiation characteristics analysed using simplified cavity models both for the illuminating and patch resonant cavities. In particular, 4×4 single cavity-fed and 8×8 stepped cavity-fed patch arrays were built and studied. With regard to the radiation patterns and directivity the measurements indicated a satisfactory agreement with the theory. The measured relative gain bandwidth ranges from 1.2% to 3.1% depending on the antenna configuration. Compared with a similar size microstripline network-fed patch array the 8×8 stepped cavity-fed patch array antenna has better efficiency and much lower side lobes