Design of reflective array with broadband OAM non-diffractive bessel beam base on meta surface

In this paper, a broadband Bessel vortex wave array antenna based on a 1-bit reflective metasurface is designed. By adopting an H-shaped fractal metasurface unit, multiple resonances can be excited to extend the bandwidth. Furthermore, by placing the metasurface unit at ±45° along the X-axis to achieve 1-bit encoding, the phase difference of 180°±5° and a reflection amplitude higher than 0.9 are obtained within the frequency range of 8–18.7 GHz. The reflective metasurface consists of 28 × 28 fractal H-shaped elements. Experiment results demonstrate that the proposed metasurface can effectively generate l=+1 OAM Bessel vortex beams in 11–18 GHz, with a maximum gain of 20.7 dBi, a peak mode purity of 84%, and non-diffraction distance of up to 108 λ0.