SLM Printed Roll-Off Enhanced Wideband Millimeter-Wave ALTSA Array Based on Waveguide Mode Converter and Metallic Split Ring Resonator

In this communication, a selective laser melting (SLM) printed 1 × 8 roll-off enhanced wideband antipodal linearly tapered slot antenna (ALTSA) array is proposed using waveguide mode converter and metallic split ring resonator for millimeter-wave (mm-Wave) applications. The antenna array is composed of a TE₈₀ mode waveguide converter and eight ALTSA elements. The TE80 mode converter operates as a compact feeding network, which eliminates the complicated multi-level T-junction to realize a 1-to-8 power divider. Besides, a modified operational principle is proposed to analyze the multimode feeding ALTSA array, which enhances the impedance matching and front-to-back ratio (FTBR) while simultaneously reducing the cross-polarization level (XPL). Moreover, metallic split ring resonators (MSRRs) are integrated to realize a roll-off enhanced response. The proposed methodology is validated through an SLM fabricated prototype, which shows a bandwidth of 22.26-29.04 GHz and a peak gain of 17.8 dBi, with boresight XPL lower than -25 dB. The average in-band efficiency is about 94%. The FTBRs at E- and H- planes are over 28 dB and 18 dB, respectively. The maximum out-of-band suppression is 38 dB, exhibiting a good response. Due to the flexible array scalability with compact footprint and enhanced performance, the proposed roll-off enhanced ALTSA array can be a promising candidate for various mm-Wave application scenarios.