A Dual-Layer T-Shaped Element for Broadband Circularly Polarized Reflectarray With Linearly Polarized Feed

A novel dual-layer T-shaped element is presented for designing a circularly polarized (CP) reflectarray that converts the linearly polarized incident field of the feed into an outgoing circularly polarized field. Compared to the microstrip rectangle patch, the T-shaped one can show an almost linear behavior and a much larger phase variation range that exceeds 500° with a low slope. Then, a prime-focus 81-element reflectarray with this type of element has been designed and implemented. The measured results show that the obtained 1-dB gain bandwidth and 3-dB axial-ratio bandwidth of the reflectarray with the T-shaped elements can reach as large as 20% and 28%, respectively.