Longitudinally Slotted SIW Leaky-Wave Antenna for Low Cross-Polarization Millimeter-Wave Applications

A longitudinally slotted TE20-mode-driven substrate integrated waveguide (SIW) leaky-wave antenna (LWA) with low side-lobe and low cross-polarization is proposed and presented for millimeter-wave applications. In this work, a pair of long slots is etched symmetrically on the top broadside of an SIW working in the TE20 mode. With the odd-symmetry of TE20 mode field distribution, the even-symmetrically etched long slots paired along the centerline of the SIW have aperture fields of the same direction, thereby resulting in a constructive superposition of radiation. Thanks to these long slots with a meandering shape that is designed according to a specific aperture amplitude illumination (e.g., -35 dB Taylor line-source distribution) and their even-symmetry with respect to the centerline of the SIW, both low side-lobe and low cross-polarization are simultaneously achieved. Two meandering schemes with respect to the centerline of the SIW are adopted and, thus, two types of the designed LWAs are developed. For experimental prototypes of the proposed LWAs, a 3 dB directional coupler and a 90° phase shifter are combined together to excite the desired TE20 mode of the SIW. The proposed two types of LWAs are modeled, simulated, and fabricated. Both the simulated and measured results are in a good agreement.