Abstract
An Orbital angular momentum (OAM) antenna with both mode reconfigurability and polarization agility is proposed in this paper. The proposed antenna is designed based on a four-element uniform circular array with a phase-shifting reconfigurable feed network. To reduce its dimensions and complexity, the feed work is constructed with two stages of single-pole double-throw switches and a stage of 90° phase-shifting power dividers, partially of which can be shared among the chosen operating states. Moreover, the use of a small amount of p-i-n diodes as binary switches allows low insertion loss and low component cost. By varying the ON/OFF status of the diodes strategically, the resultant array can be reconfigured to horizontal polarization (HP) or vertical polarization (VP), along with OAM mode $l = -1$ or +1 achieved for each polarization. The antenna performance is evaluated in terms of reflection coefficients, near-field distributions and far field radiation patterns. According to the measured results, the antenna exhibits an overlapped frequency band ranging from 2.29 to 2.59 GHz among the different operating states. Meanwhile, stable radiation patterns as well as high cross-polarization discrimination can be obtained. Benefiting from the above features, the antenna could help to improve the signal quality and increase the channel capacity in wireless communications.
Highlights
Owing to the merits of orthogonality among integer topological modes and rotational degree of freedom, orbital angular momentum (OAM) technology is considered a promising approach to achieving large transmission capacity and high spectral efficiency for wireless communications [1]–[3]
For realizing electrical control of the available states, low-loss p-i-n diodes are introduced in the feed network as radio frequency (RF) switches, and their status can be altered with a bias circuit for mode and polarization switching
The antenna can produce four operating states corresponding to OAM mode l = +1 or −1 along with horizontal polarization (HP) or vertical polarization (VP)
Summary
Owing to the merits of orthogonality among integer topological modes and rotational degree of freedom, orbital angular momentum (OAM) technology is considered a promising approach to achieving large transmission capacity and high spectral efficiency for wireless communications [1]–[3]. The antenna array [21] enables OAM-mode and polarization manipulation by switching the excitation ports, while its feed structure is relative bulky and complex. The design of antennas with reconfigurabilities in both OAM-mode and polarization still poses challenges in terms of realization complexity, fabrication cost, power loss, and tuning speed.
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