Millimeter-Wave Huygens’ Transmit Arrays Based on Coupled Metallic Resonators

A novel Huygens' transmit array (TA) is proposed based on a coupled-resonator approach to demonstrate millimeter-wave (mm-Wave) beamforming for linear polarization. The proposed structure is simple and compatible with standard printed circuit board (PCB) processes and utilizes a single dielectric substrate only. It is shown that by engineering the geometrical dimensions of the resonator, its electric (even-mode) and magnetic (odd-mode) resonances are excited in a balanced manner to achieve zero backscattering in a large bandwidth. This operation principle of the proposed Huygens' cell is explained in detail using both an insightful equivalent circuit model, as well as full-wave eigenmode analysis. Next, the proposed Huygens' cell is placed on top of a high-gain 2-D slot-array antenna, in its near field, to engineer its aperture field distribution. Several TA prototypes designed around the 60 GHz frequency band are demonstrated and experimentally characterized in both their near and far fields, to achieve difference pattern generation, beam expansion, and beam steering as application examples, in addition to a uniform surface demonstrating its low-loss performance.