Periodic leaky-wave antennas fed by a modified half-mode substrate integrated waveguide

This study presents two configurations of periodic leaky-wave antennas fed by a modified half-mode substrate integrated waveguide (HMSIW) where a metallised trough is employed as the waveguide´s side wall. The first antenna configuration is constructed from periodically etching a row of transverse slots on the ground plane of the feeding HMSIW, whereas in the second configuration, the row of slots is cut into the HMSIW top wall. Influence of the slot length and period on the propagation constant of the fundamental space harmonic is quantitatively characterised through analytical equations, simulations and measurements of fabricated prototypes. This provides essential information towards the synthesis of more sophisticated HMSIW-fed leaky-wave antennas. The performance of the two prototypes demonstrates forward-to-backward radiation within the mono-mode regime of the feeding HMSIW. The agreement between the theoretical, numerical and experimental results validates both the overall analysis procedure and the concept of periodically slotted thru HMSIW as leaky-wave antennas.