Unit Cell Design for a Low-Profile Dual-Frequency Dual-Sense Circularly Polarized Folded Transmitarray

This paper presents a unit cell suitable for a dual-band, dual-sense circularly polarized (CP) transmitarray. To achieve dual-band operation, two types of patches are designed and interleaved to form a 2x2 array, serving as the unit cell for the transmitarray. Electromagnetic (EM) simulations under periodic boundary conditions are performed to optimize the unit cell's performance. The simulation results demonstrate that the 2x2 array can convert CP waves with opposite senses: the low-frequency patch transmits right-handed circularly polarized (RHCP) waves at 10.05 GHz, while the high-frequency patch transmits left-handed circularly polarized (LHCP) waves at 12.65 GHz. Moreover, the developed transmitarray element maintains stable CP performance with oblique incidence angles up to 42 degrees, making it well-suited for folded transmitarray designs.