I. Introduction
Slotted traveling-wave rectangular waveguide arrays have attracted the attention of planar broadside antenna designers because of their superior low-loss performance, high-gain, and high-power handling capability in comparison with that of planar microstrip arrays. However, the cost of manufacturing a waveguide design is prohibitive and they are heavy and bulky. Alternatively, substrate integrated waveguide (SIW) technology is a low-cost fabrication solution for microwave and millimeter-wave systems [1], whereas waveguide components can be implemented using the standard PCB process on dielectric substrates.