Wideband SIW Slot-Array Design Based on Reflection-Slope-Synthesis Method for 5G Services

Abstract

In the last decade, substrate integrated waveguide (SIW)-based solutions have been successfully introduced as a proper compromise between conventional strip and waveguide technologies, allowing the implementation of typical waveguide structures on planar circuits, as slot arrays. In this letter, a new technical approach to design wideband antennas by using radiant slots, which are usually considered narrow-band structures, is presented. Commonly, an equivalent circuit composed of admittances, whose conductance and susceptance are computed by well-known analytic methods, is widely used to design slot arrays. However, they are aimed at narrow-band services. The new synthesis method is based on the slope of the S-parameters and the impedance shown by the slots to optimize their position and distribution along the SIW to achieve the broadband-impedance performance, as well as a least-mean-square (LMS) system to mitigate the beam-squint effect and not to degrade the beam bandwidth. The novel antenna presents a relative impedance bandwidth above 20%, by using four slots, while keeping the beam bandwidth and a radiation efficiency higher than -0.7 dB.