A ±45° Dual-Polarized Dual-Beam Series-Fed Metasurface Antenna Array With Stable Beam Angle

A novel method to realize positive phase response of antenna element is proposed conceptually and applied in +/- 45 degrees dual-polarized dual-beam series-fed metasurface antennas (MSAs). It takes the features of stable beam angle within the relative bandwidth of 10% and dual-polarized dual beams. Benefiting from the positive phase response zone of the antenna, the long-line effect is eliminated and the phase response between the elements is reshaped as expected. Therefore, a stable beam of series-fed array oriented at specific angle is guaranteed accordingly. To achieve the +/- 45 degrees dual-polarized dual-beam performance, a four-port MSA element with interwoven feeding network is designed and used for further array design. For demonstration, one prototype of MSA array is designed. Considering the band of 4.7-5.2 GHz (10%), the beam angle of the MSAs based on positive phase response control (PPRC) method is oriented to 30 degrees, and the variation versus frequency is less than 6 degrees, which is smaller than the variation of 19 degrees for traditional array. The simulation and measurement results show that stable beam angle is achieved for the dual-polarized series-fed MSA array, indicating a promising candidate for base-station application.