Integration Design of Millimeter-Wave Bidirectional Endfire Filtenna Array Fed by SIW Filtering Power Divider

In this letter, a millimeter-wave (mmW) substrate integrated waveguide (SIW) filtering power divider (FPD) with differential outputs is proposed and used as a feeding network for bidirectional endfire filtenna array. By using theoretical design rule based on coupling coefficient and external quality factor (
Q_e
), the proposed FPD combines multiple functions such as filtering, power divider, and unbalanced-to-balanced (balun) conversion into one single circuit. Meanwhile, the FPD is insensitive to the load impedance so that it can be seamlessly connected to the back-to-back quasi-Yagi antenna array for bidirectional radiation. For demonstration, an mmW bidirectional endfire filtenna array centered at 27.5 GHz fed by three-order FPD is designed and fabricated. The measured results exhibit that the proposed filtenna array owns an impedance bandwidth (|
S
₁₁
| < −10 dB) of 3.4%, flat passband gain with a peak gain of 5.4 dBi, and good selectivity (the stopband gain roll-off is up to 25 dB/GHz. Good agreement is observed between the simulated and measured results.