Broadband polarization rotator for arbitrary angles with enhanced substrate integrated waveguide cavities

A broadband polarization rotator for rotating linear polarization to every intended angle is introduced. The proposed rotator is constituted of frequency selective surface and enhanced substrate integrated waveguide (SIW) cavities. Considering the current distribution of circular or square SIW cavity dominant modes, two slots are inserted on the front and back surfaces of the enhanced SIW cavities where the arrows of distributed current are orthogonal to them. Accordingly, the angle between the input and output slots determines the amount of polarization rotation. Moreover, a method of cascading enhanced circular and square SIW cavities for the proposed structure is analyzed to produce a sharper roll-off response in stop-bands. Design and simulation of the proposed method are presented for 45^°, 60^° and 90^° polarization rotators in Ka frequency band with 35 GHz central frequency. To verify the proposed method, a prototype of 90^° polarization rotator is fabricated and measured. The measurement demonstrates 18.8% bandwidth which proves broadband performance of the proposed structure.