Dual Polarized Open-Ended Waveguide Antenna With Periodic Structure Loading for Gain Enhancement

A novel gain enhancement method for a dual-polarized open-ended square waveguide antenna is proposed in this article. Slots are etched on the sidewalls near the input of the open-ended square waveguide, which couple part of the energy to the periodic structures loaded on the sidewalls and excite the TM0 modes. The surface wave is excited on the periodic structures. The periodic structures are equivalent to a dielectric rod with a graded dielectric constant. Part of the energy coupled to the periodic structures is radiated during the transmission, which combines with the energy radiated by the open waveguide, forming a plane wave to produce a high-gain endfire beam in the far-field. The antenna is printed using stereo lithography appearance (SLA) 3-D printing technology, and then a layer of copper is plated on the outer surface to make the antenna equivalent to an all-metal structure. Compared with the dielectric-loaded open-ended waveguide antennas, 3-D-printed all-metal periodic structures reduce dielectric loss and processing costs. The antenna structure is a square waveguide, so an orthogonal-mode transducer (OMT) and circular polarizer can be used to achieve dual linear polarization (LP) and dual circular polarization (CP). The simulated results show that the proposed antenna achieves a gain enhancement of about up to 8 dB (compared with an unloaded open waveguide antenna). The measured results show that a peak gain of 17.8 dBi is realized for LP states. The antenna is very suitable for millimeter-wave (mm-wave) high-gain application scenarios, such as point-to-point communication applications.