Millimeter-Wave Wide-Angle Scanning and Low-Cross-Polarization Magnetoelectric Monopole Antenna Array

Phased arrays with wide beam-scanning range and low cross polarization are significant for the millimeter-wave communication. To achieve this goal, this article presents a novel method of designing a millimeter-wave phased array based on unidirectional wide-beam monopole elements. The antenna is composed of a monopole radiator fed by a coplanar waveguide, a reflector and two grounded U-shaped patches with shorting pins. In order to realize wide beamwidth and high cross-polarization discrimination, a magnetic current is introduced by a current loop flowing along the path of the shorting pins and the reflector. Hence, a term “MagnetoElectric (ME) Monopole” is given to represent the novel antenna. Far-field radiation by the currents on the two grounded U-shaped patches cancel each other, so the cross polarization is reduced. Combining the magnetic current and the electric current on the monopole contribute to wide beamwidth. A metasurface consisting of periodic patches is designed to reduce mutual coupling for the phased array. The prototyped array has measured scanning angle of ±80° with small scan loss of 1.7 dB in 24-30 GHz. The simulated cross-polarization level is less than -19.4 dB during the scanning process.