Dependency of Ka-band reflectarray unit cell reflection properties on the spacing between antenna elements

In this paper, effects of inter-element spacing on the performance of reflectarray unit cells are studied to provide guidelines for an optimum reflectarray design. A reflectarray unit cell is designed at 32 GHz which is the frequency of interest for reflectarray´s space applications. By changing the distance between the reflectarray elements from 0.35 to 0.85 λ₀ in E plane and 0.45 to 0.95 λ₀ in H plane, the resonant frequency is varied from 30.5 to 32.5 GHz (representing more than 6% change), the reflection phase is shifted by 140°, bandwidth is decreased by 4% and the maximum reflection loss is increased by 1.3 dB. To prove the concept, two 5×5 sub-arrays with different inter-element spacing are fabricated, measured and compared with simulations with good agreement.