Beam‐steering capability for OAM‐based reflectarray at 5G‐mmWave frequencies

Abstract

The ability of the reflectarray antenna (RA) to perform orbital angular momentum (OAM) beam‐steering with low divergence angles at the fifth generation (5G) millimetre‐wave (mmWave) bands is demonstrated. To provide steered OAM beams, it is necessary to regulate the scatterer's geometries smoothly throughout the focal area to follow the required twisted distribution. The traditional numerical method to compensate for the phase is modified to enable the 3D scanning property of OAM beams, so it is possible to avoid the feeder blockage and produce high‐gain steered OAM beams. Likewise, reducing the inherent beam divergence of OAM beams can be obtained by examining the most satisfactory phase distribution of the scatterers by fitting the focal length. The simulated radiation pattern is validated by the measured radiation pattern of the fabricated RA in the frequency range between 28.5 and 31.5 GHz.

Two Approaches for Designing Circularly Polarized OAM Reflectarrays

“…To validate the effectiveness of the three approaches, three CP-OAM RAs of mode l = −1 are designed utilizing the polarization-insensitive element structure [22], with the smooth horn as the array's feed. Since the original RA element in [22] was designed for operation at 30 GHz, we rescale its dimensions to shift the center frequency to 15 GHz, and a dynamic phase range of approximately 336 • is attained (which is larger than 325 • as in [22]), as shown in Fig. 4, where w 0 in the inset is the side length of the square patch and P 0 is the element spacing.…”

“…Mode purity is commonly used to evaluate the quality of the generated OAM beam [21][22][23]. Low mode purity means that the orthogonality between different OAM modes is poor, and as a result deteriorates the receiving signal-to-noise ratio (SNR) [24,25].…”

“…FIGURE 4. Phase curve of the square-latticed RA element from[22] and the interpolated phases required for three approaches. (P0 = 9.2 mm and t0 = 0.51 mm).…”

Reflective Metasurface With Steered OAM Beams for THz Communications

“…The generation of helical waves has been addressed in the literature by various structures of different features. The majority of the state-of-the-art designs are restricted to producing a single OAM state [21], [22], or are not feasible to be fabricated in the immediate term [23]. Nevertheless, many successful designs introduced multi-OAM states at the expense of increasing the system's complexity, price, and beam divergence through concentric uniform circular arrays (UCAs) [24].…”