A Metal-Only Reflectarray Unit-Cell for Low-Cost K-band Applications

We present here a design of 3-bit metal-only reflectarray unit-cell operating at K-band. The corresponding unit-cell is based on a droplet-shaped slot interleaved with a circular arc slot. By interleaving slots, the unit-cell exhibits a phase shift range of 360° over the desired bandwidth (19.7 GHz-22.7 GHz). The quantized 3-bit phase curves show good linearity and wideband operation. The reflection loss of the proposed unit-cell is less than 0.7 dB across the bandwidth. To validate the concept, a 14-by-14 element reflectarray antenna is designed for beam at boresight and the feeding horn is tilted 15° from the center in H-plane to suppress the effect of feed blockage. The simulated gain of reflectarray antenna reaches 24.1 dBi at 21.5 GHz. The 1-dB and 3-dB gain bandwidth is around 8.1 % and 14.3 % at 21 GHz, respectively. The proposed design is eligible for low-cost high-gain wideband applications in harsh environment.