Wideband Millimeter Wave Antenna with Cavity Backed Slotted Patch and Magneto-Electric Dipole

This paper proposes a wideband cavity-backed slotted patch antenna, loaded with a magneto-electric (ME)-dipole and fed by a microstrip line, for millimeter wave (mm-Wave) applications. The coupled-feed cavity-backed slotted patch antenna is loaded with the ME-dipole. The slotted patch antenna serves as both a radiator and a ground for the ME-dipole. The combination of the ME-dipole antenna and the slotted patch antenna realizes a -10 dB impedance bandwidth covering over 22.86-44.35 GHz (63.9%). The pattern of the antenna element remains stable throughout this bandwidth. The proposed broadband antenna unit not only realizes single linearly polarized (LP) radiation but also can be designed for dual-LP radiation. The dual-polarized radiation can be achieved by changing the slot of the patch antenna to a crossed slot and altering the ME-dipole antenna to a dual-polarization form. A $2\times 2$ dual-polarized array has been designed, fabricated, and tested. A novel dual-polarized feeding network is proposed. To achieve higher isolation, broadband in-phase feed and differential feed are adopted, respectively. A low-loss single to the differential structure is proposed for differential feeding. The simulated isolation of the array is higher than 40 dB. Measured results show that the dual-polarized $2\times 2$ array has an overlapping bandwidth of 52.3% ( $\vert S_{11}\vert < -10\ \text{dB}$ and $\vert S_{21}\vert < -30\ \text{dB}$ ) with a peak gain of 14 dBi. The proposed antenna, featuring a wide overall bandwidth, low cost, and good radiation performance, is well suited for mm-Wave applications.