Spectral Analysis of Broadband Fabry–Perot Antennas With Multiple Coupled Cavities

The anomalous dispersion observed in wideband Fabry–Perot Antennas formed by multiple coupled cavities is explained in terms of modal coupling between several leaky waves. In this way, the negative group velocity associated to the homogenized mode can be explained. Moreover, the enhancement in the radiation pattern bandwidth can also be described from the contribution of these coupled leaky waves to the total interference pattern. Theoretical dispersion results are reported for 1-D and 2-D Fabry–Perot Antennas with
$N =$
2 and
$N =$
3 coupled cavities operating in broadside and off-broadside scanned patterns. The theory is also corroborated with experimental results.