A Millimeter-Wave Multilayer Lens Antenna for Circularly Polarized Applications

This paper presents a multilayer lens structure constructed from a unit cell that is capable of simultaneously increasing the gain of feeding antenna and maintaining the circular polarizationn (CP) of the incoming wave as it can keep the 90 degree phase difference between two modes of the incoming CP wave and does not weaken the amplitude of the modes. A lens prototype was designed at millimeter-wave (mm-wave) frequency of 28 GHz. Three different feeding antennas, a linearly polarized patch antenna, a circularly polarized patch antenna and 2×2 CP array antenna, were used to test the lens. Maximum gains of 19.36 dB, 18.58 dB, and 20.3 dB with bandwidths of 1024, 746, and 540 MHz, were obtained for the three antennas, respectively. The substrate material of the lens is RO4003C with permittivity of 3.38 and the total dimension of the antenna 9.79λ
0
× 9.79λ
0
× 0.19λ
0
.