Design of high gain and low scattering circularly polarized antenna array with U-shaped slot metasurface

In this paper, a novel integrated metasurface antenna (MA) unit is proposed, capable of achieving in-band and out-of-band radar cross-section (RCS) reduction through angular rotation. At operating frequency of 9.15 GHz, the proposed metasurface antenna with U-slot (MAUS) unit exhibits a 180° reflection phase difference under x- and y-polarized incidence conditions, allowing 0° and its 90° rotating unit to achieve co-polarized scattering cancellation in-band. Consequently, this design realizes RCS reduction by the array itself. Concurrently, equivalent circuit theory is employed to elucidate this phenomenon. A ring-shaped frequency selective-absorber (FSA) unit is loaded above the MAUS unit to effectively suppress out-of-band signal interference. Furthermore, the reflected beam control and radiation characteristics of a 1-bit encoded MAUS array are simulated and compared. Therefore, the antenna array with a 4 × 4 subarray configuration is optimized and fabricated, in which the output phases of four subarrays are 0°, 270°, 0°, and 270°, respectively. The simulation and measurement results demonstrate that the proposed antenna system is able to cover 8.70 GHz–9.73 GHz with good right-handed circular polarization (RHCP) radiation performance and a maximum gain of 15.9 dBi. Moreover, it has been observed that antenna arrays exhibit disparate levels of RCS reduction performance within an incident angle of 45°. The proposed integrated antenna array is poised to be a suitable option for devices that require both efficient radiation management and enhanced stealth capabilities.