Cross-Slotted Waveguide Array With Dual Circularly Polarized Radiation at W-Band

This article discusses the design of a cross-slotted waveguide array structure to be adopted for W-band communication between 84 and 86 GHz. Each array waveguide element contains 16 cross-slots along the broad wall to enable circularly polarized radiation behavior with a gain reaching up to 14 dBi and a cross-polarization isolation of more than 20 dB in the elevation plane. The design of the cross-slots is implemented with bent arms in order to accommodate them at an offset position from the waveguide narrow wall. Such position ensures the radiation of a circularly polarized wave. A waveguide-based feeding network with serpentine-shaped transitions is implemented to feed the eight-element cross-slotted array topology. The design of the feeding network ensures an equal power split and in-phase distribution between the eight elements with a phase deviation that does not exceed 20 degrees. The overall cross-slotted waveguide array is prototyped as a proof of concept. The measured results show a maximum gain of 24.5 dBi for both polarization schemes. The measured half power beamwidth (HPBW) is 8 degrees in the elevation plane and 12 degrees in the azimuthal plane. The measured cross-polarization between the two circularly polarized schemes at both ports reaches a level of more than 26 dB. The comparison between the simulation and measurement results proves the validity of the proposed approach in achieving a high-gain dual circularly polarized structure for millimeter-wave communication.