A Compact Substrate Integrated Waveguide Notched-Septum Polarizer for 5G Mobile Devices

In this letter, a compact substrate-integrated waveguide (SIW) notched-septum polarizer is designed, manufactured, and tested. Metalized slots are used instead of vias in proximity to the notches to improve polarization purity. An impedance matching bandwidth of 7.9% at 29 GHz and transmission coefficient of better than -1.6 dB are demonstrated. The axial ratio is less than 3 dB over a bandwidth of 4.5% at 29 GHz (sufficient for 5G). An implementation of the polarizer in an array antenna was measured to validate its reliability in antenna applications. Given its performance and small form-factor (length of λ
_o
/7 at 29 GHz), the proposed polarizer may be a good option for SIW circularly polarized endfire antennas in 5G mobile devices.