Circularly Polarized High-Gain K-Band Liquid Crystal Phased Array Antenna

A <inline-formula> <tex-math notation="LaTeX">$16\times 16$ </tex-math></inline-formula> liquid crystal (LC) phased array based on LC delay line phase shifters operating at 25.52 GHz is presented. We first propose and demonstrate a numerical model for calculating the relationship between the phase shift of an independent LC phase shifter and the external bias voltage. Then, we design a <inline-formula> <tex-math notation="LaTeX">$16\times 16$ </tex-math></inline-formula> circularly polarized microstrip patch antenna array, combined with 256 spiral inverted microstrip delay line LC phase shifters. The whole array is fed by a rectangular waveguide power divider to maintain low radio frequency feeding loss. Via the measurements, we find that the LC phase shifter reveals a maximum differential phase shift of 370° under 0–8-V bias voltage. The beam of LC phased array can be steered continuously, covering ±30° in the elevation plane and 0°–360° in the azimuth plane. The measured gain at the broadside direction is 25.85 dBic, and the minimum axial ratio (AR) is 1.1 dB.