The radiation performance of orbital angular momentum vortex waves (OAMVWs) generated by reflective metasurface is comprehensively investigated. According to the different incident sources, the issue is classified into two cases, namely the plane wave incidence and the focused incidence. In both cases, the radiation performance deteriorates with the increasing of topological charge l. Moreover, the largest l that can be generated is limited by the scale of the metasurface. In addition, detailed analysis reveals that phase quantization affects the lobes levels of OAMVWs but has no influence on the divergence angle of the main lobe. Nevertheless, for the case of plane wave incidence, 1-bit phase quantization method is not able to generate OAMVWs in normal direction and will cause grating lobe when the beam scans. Meanwhile, the grating lobe carries OAM with opposite l against the main lobe. Finally, a focused-feed metasurface based on 1-bit phase quantization is simulated and measured. The simulation and measurement results show that OAMVW with topological charge l=1 is successfully generated and detected, validating the effectiveness of phase quantization method in OAMVWs generation. It is worth to point out that phase quantization is highly promising in electronic-controlled reconfigurable OAMVWs generation.

In this letter, a shared aperture 1-bit metasurface for orbital angular momentum (OAM) multiplexing is studied. A phased array antenna fed by the phase shift network is embedded on the reflective aperture of the 1-bit metasurface. The proposed device can work on reflectarray mode from 7.1GHz to 7.5GHz and phased array mode from 7GHz to 7.5GHz. Correspondingly, OAM vortex beam with topological charge l = -1 and l = 1 can be generated. The transmission coefficient between the two working modes is below -30dB and the envelop correlation coefficient (ECC) is quite close to 0, which reveals the excellent isolation and diversity performance. A prototype of the proposed device is fabricated and tested. The measured S parameters and radiation patterns agree well with the simulation results.

Phase modulated metasurface (PMM) can control the transmission state of electromagnetic (EM) wave through phase modulation scheme on the interface. Orbital angular momentum (OAM) vortex wave is denoted by the helical phase distribution of the wave front. The interaction between OAM vortex wave and PMM is investigated in this paper. The mathematical model is firstly established according to the array theory. Whereafter, two typical PMMs of chessboard metasurface (CBM) and phase gradient metasurface (PGM) are exploited as examples to uncover the scattering characteristics under illumination of OAM vortex wave. For CBM, the phase cancellation scheme is found to be broken when the OAM order l equals to ±2 under both normal incidence and oblique incidence. It reveals that the OAM vortex wave is a promising approach for metasurface stealth target detection. For PGM, the scattered wave still keeps the OAM feature but is deflected to the non-specular direction, which reveals that the generalized Snell’s law is also suitable to OAM vortex wave. The discoveries of this paper may find applications in radar detection fields using OAM vortex wave.

In this paper, a patch array antenna with wideband circular polarization and high gain is proposed by utilizing a hybrid metasurface (MS). A corner-cut slotted patch antenna was chosen as the source due to the possible generation of CP mode. The hybrid MS (HMS), consisting of a receiver MS (RMS) arranged in a 2 × 2 array of squared patches and a linear-to-circular polarization conversion (LCPC) MS surrounding it was then utilized as the superstrate driven by the source. The LCPC MS cell is a squared-corner-cut patch with a 45° oblique slot etched, which has the capability for wideband LCPC. The LCPC unit cell possesses wideband PC capabilities, as demonstrated by the surface current analysis and S-parameter simulations conducted using a Floquet–port setup. The LP EM wave radiated by the source antenna was initially received by the RMS, then converted to a CP wave as it passed through the LCPC MS, and ultimately propagated into space. To further enhance the LCPC properties, an improved HMS (IHMS) was then proposed with four cells cut at the corners, based on the original HMS design. To verify this design, both CMA and E-field were utilized to analyze the three MSs, indicating that the IHMS possessed a wideband LCPC capability compared to the other two MSs. The proposed antenna was then arranged in a 2 × 2 array with sequential rotation to further enhance its properties. As demonstrated by the measurements, the array antenna achieved an S11 bandwidth of 60.5%, a 3 dB AR bandwidth of 2.85 GHz, and a peak gain of 15.1 dBic, all while maintaining a low profile of only 0.09λ₀.