A Novel Wideband Differentially-Fed Higher-Order Mode Millimeter-Wave Patch Antenna

This paper presents a novel differentially-fed wideband patch antenna working at millimeter-wave band. The antenna is fabricated using conventional low-cost printed-circuit-board and plated-through-hole technologies and the patch size of the element has been enlarged by exploiting higher-order mode operation for good fabrication tolerance. The antenna element is a 0.86 guided wavelength ( λ
_g
at 60 GHz) long patch shorted at one end. A slot of 0.09 λ
_g
in width is introduced on the shorted patch and the distance between the slot center to the other end of the patch is 0.5 λ
_g
. The shorted patch resonates at TM
₃₀
mode and the 0.46 λ
_g
patch, created by presence of the slot, operates at TM
₁₀
mode. The combination of these two modes broadens the impedance bandwidth of the element to 18%. Asymmetric radiation patterns in the E-plane and large cross-polarization levels in the H-plane generated by a single patch are eradicated by feeding two mirrored elements differentially. The designed differentially-fed prototype has more than 18% measured impedance bandwidth, stable gain at 9-10 dBi and symmetric and stable radiation patterns across the operating band from 56 to 67 GHz.