Offset-Fed and Offset-Beam OAM Reflectarray Antenna with Wide Angular Stability

For first time, a square aperture orbital angular momentum (OAM) reflectaray antenna (RA) with wide angular stability is analyzed and designed. The angular stability thanks to sub-wavelength elements, low substrate thickness and design procedure of the proposed element. The element consists of two square rings and the inner width of the inner ring increases by expansion of element size. This causes phase variations of the phase-length curve to be less than 10° compared to normal state till 40° angle. Additionally, the suggested element shows reduced manufacture error and element loss. A linear polarization offset -fed offset-beam OAM RA has been designed with mode (l) +1 for first time. Results indicate the maximum gain of 21.5dBi at 10 GHz with 11.6% efficiency and side lobe level (SLL) below than -17.3dB.