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The gradual transition from a radiative to a reactive regime is studied for leaky modes supported by planar waveguiding structures such as those used in Fabry-Perot cavity leaky-wave antennas (FPC-LWAs). These are typically studied above the so-called leaky cutoff, i.e., the frequency for which the leaky phase constant β equals the leaky attenuation constant α. However, an FPC-LWA can efficiently radiate even below the leaky cutoff, the condition for minimizing the beamwdith at broadside occurring for β < α. Nevertheless, well below the leaky cutoff, reactive phenomena may dominate radiative phenomena. These aspects are investigated here, providing a criterion to determine whether the relevant leaky waves are responsible for radiation rather than reactive phenomena. It is seen that the minimum-beamwidth condition occurs in a region where reactive effects can prevail over radiative effects. It is concluded …
Publication date: 
4 Aug 2020

Walter Fuscaldo, Paolo Burghignoli, Alessandro Galli

Biblio References: 
Pages: 13-16
2020 IEEE/MTT-S International Microwave Symposium (IMS)