94 GHz Butler Matrix-Integrated MTM SIW Beamforming Array in Glass IPD

In this letter, we propose a low-profile beamforming array operating in the W-band, which is based on the Butler matrix integrated with substrate-integrated waveguide metamaterial (MTM) antennas. The proposed MTM antenna achieves an enhanced bandwidth through the use of multiple resonance modes of the composite right/left-hand structure. The implementation of the proposed array is done using a low-cost glass-based integrated-passive-device (IPD) technology. The microstrip-type Butler matrix with crossover structures is designed, and its bandwidth of 12.8% at the W-band is verified with measurements. Experimental verifications of the radiation patterns are conducted to demonstrate the beamforming characteristics of the proposed IPD antenna array.