Design of a Low Mutual Coupling UPA for the Compact Sparse Array of U6G Band

In this paper, a U-shaped patch antenna (UPA) is proposed for the compact sparse array in the upper 6 GHz (U6G) band, aiming to achieve low mutual coupling with small spacing. Through the simulation and measurement, the proposed antenna meets $S_{11}\lt \mathbf{- 1 0} \text{dB}$ and $S_{12}\lt \mathbf{- 1 5} \text{dB}$ in the frequency band of 6.5-7 GHz. The results show that the UPA has the significant capability of low mutual coupling compared to the rectangular patch antenna (RPA), while the occupied area of the UPA is reduced by about $70 \%$ of that of the RPA, which brings the benefits of small spacing and miniaturization.