Abstract
Abstract Millimeter-wave (mmWave) and orbital angular momentum (OAM) multiplexing are two key technologies for modern wireless communications, where significant efforts have been devoted to combining these two technologies for extremely high channel capacities. Recently, programmable metasurfaces have been extensively studied for stimulating dynamic multi-mode OAM beams, owing to their ability of subtle dynamic modulation over electromagnetic waves in a digital manner. However, programmable metasurfaces for mmWave OAM stimulation are rarely mentioned, due to the requirement of extremely high processing precision for mmWave applications. In this paper, a programmable metasurface is presented to stimulate dynamic multi-mode mmWave vortex beams. The proposed metasurface is composed of electronically reconfigurable units, which is obtained through configuration integration of a PIN diode within each radiation patch for modulating the unit resonant property. Both low reflection losses and stabilized inverse phase states are obtained for the binary unit coding states within the operation band. Through modulating the real-time coding distribution on the metasurface by programmable bias circuit, the generation of mmWave OAM beams with mode numbers l = 0, l = +1, l = +2, and l = +3 are numerically designed and experimentally verified. Our study paves a new perspective for the cross amalgamation of both mmWave and multi-mode OAM technologies.
Highlights
With the rapid development of smart terminals and internet of things, large-bandwidth, and high-speed transmissions are highly demanded in modern wireless communications [1]
Vortex beams associated with orbital angular momentum (OAM) technology have become a key promoter for the next-generation wireless communications, owing to its multimode orthogonal characteristic and potential improvement in channel capacity and spectrum efficiency [9]
A reflective programmable metasurface constructed from reconfigurable units with 1 bit phase modulation has been presented for stimulating multimode millimeter wave (mmWave) vortex beams dynamically
Summary
With the rapid development of smart terminals and internet of things, large-bandwidth, and high-speed transmissions are highly demanded in modern wireless communications [1]. MmWave technologies associated with massive MIMO and cellular communications are introduced to expand the transmission scale and enhance service quality [5, 6] In all these applications, smart antenna arrays with the ability of dynamic directional beamforming or beam scanning are indispensable, bringing enormous expenses based on the conventional phased array systems [7, 8]. Bai et al.: Dynamic millimeter-wave OAM beam generation the same spectral channel, which brings a tremendous increase in spectrum efficiency and channel capacity [12, 13] Owing to this unique orthogonal property, multiplex OAM has been widely studied and implemented in microwave domain [14, 15]. The proposed mmWave OAM metasurface may become an eligible candidate for the hybrid communications of both mmWave and multi-mode OAM technologies in the future
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