Millimeter-Wave Low Side- and Back-Lobe SIW Filtenna Array Fed by Novel Filtering Power Divider Using Hybrid TE101/TE301 Mode SIW Cavities

In this article, a novel and simple design approach of millimeter-wave (mm-wave) low side- and back-lobe substrate integrated waveguide (SIW) filtenna array is investigated by using predefined filtering power divider (FPD). The FPD consists of two coupled SIW cavities operating at TE₁₀₁ and TE₃₀₁ modes, respectively. The TE₃₀₁ mode divides the energy from Cavity 1 into three parts equally and three outputs are loaded to Cavity 2 for power distribution, making the FPD design simplified. Based on this, the predefined power splitting ratio (1:1:1 and 1:3:1) of the FPDs can be obtained easily by controlling the output external quality factor ( $Q_{e}$ ). Accordingly, the side and back lobes of the filtenna array are suppressed by using the proposed FPD with predefined power splitting ratio of 1:3:1. To verify the proposed approach, a $3\times3$ filtenna array prototype centered at 27.2 GHz is designed, fabricated and measured. The measured results show an impedance bandwidth ( $\vert S_{11}\vert < -10$ dB) of 1.8 %. The filtenna array performs good gain-passband selectivity with an in-band peak gain of 11.1 dBi, and the side lobe is suppressed more than 20 dB while the front-to-back ratio is over 30 dB. Good agreement is achieved between simulated and measured results.