A single‐layer circularly polarized planar lens antenna at millimetre‐wave

Abstract

Abstract This paper proposes a novel single‐layer planar lens antenna with the capability of keeping circular polarization (CP) of the incoming CP wave and enhanced gain for millimetre‐wave applications. Because of the symmetric design of the lens unit cell, a 90‐degree phase difference between two modes of the incoming CP wave can be maintained with high amplitude. Furthermore, the phase variations created by the designed unit cells change the phase of the incoming wave and result in antenna gain enhancement. Two different feeding antennas, a CP patch antenna and a 2 × 2 CP antenna array, are used as the feeding section to evaluate the performance of the proposed lens. Maximum gains of 19.2 dBiC and 23.4 dBiC with −10 dB impedance bandwidths of 3.5% and 2.9% at Ka‐band are reported for the proposed lens fed by these two CP antennas, respectively, while keeping the axial ratio value below 3 dB. The substrate material of the proposed lens design is RO4003 C with the total dimensions of 9.79λ0 × 9.79λ0 × 0.047λ0 (where λ0 is the free space wavelength at 28 GHz). The measurements conducted on the fabricated prototypes agree very well with the simulation and analysis results.