A Low RCS Circularly Polarized Antenna Based on Scattering-Radiation Units

A broadband low-RCS circularly polarized (CP) antenna based on a bi-functional, single-layer polarization conversion metasurface (PCM) is proposed in this manuscript. The designed bi-functional PCM unit cell achieves a polarization conversion ratio (PCR) exceeding 90% across an ultra-wideband from 15.8 GHz to 31.2 GHz. According to the principle of phase cancellation, they are configured as a checkerboard array to reduce the monostatic RCS. A co-design strategy was employed for the design of the feeding structure. Analysis reveals that the slot has a significant impact on the subarray PCR, leading to multiple zeros that affect the RCS reduction. Notably, further analysis indicates that an appropriate feed structure can compensate for the zeros caused by the slot, achieving a balance between radiation performance and scattering performance. The array exhibits an RCS reduction exceeding 6 dB over a wide frequency band from 15.9 to 31.3 GHz and realizes a circularly polarized far-field pattern with an axial ratio (AR) below 0.5 from 16.3 to 17 GHz and a maximum gain of 10.38 dBi. Measured results of the antenna prototype match the simulations well. The proposed integrated design offers a viable solution for stealth platforms.