An antenna feed for a stackable antenna system includes a polarization converter that continuously surrounds an omnidirectional antenna. Electromagnetic radiation emitted by the omnidirectional antenna and having an initial polarization passes through the first polarization converter, which converts the initial polarization into a non-vertical linear polarization. A feedline located outside of the first polarization converter forms a helix that wraps around the first polarization converter such that it runs perpendicularly to the non-vertical linear polarization. When the width of the feedline is sufficiently small, electrons in metal of the feedline will not be excited by the radiation, and the radiation will transmit through the feedline with minimal impact on the omnidirectional antenna's gain profile. The feedline may be used to feed a second antenna located vertically above the omnidirectional antenna. When the first polarization converter outputs horizontally polarized radiation, the feedline may form a straight vertical line.

Aspects of the subject disclosure may include, for example, detecting, by a monitoring system associated with a communication system, signals received at an array of orthogonally-polarized radiating elements of an antenna, causing, via a motorized drive assembly, the array of orthogonally-polarized radiating elements to sequentially rotate to a plurality of positions, obtaining, by a control system from the monitoring system and for each of the plurality of positions, data relating to signals from the array of orthogonally-polarized radiating elements, based on the data, determining, by the control system, an optimal position of the plurality of positions for the array of orthogonally-polarized radiating elements at which an impact of passive intermodulation (PIM) on the communications system is minimized, and controlling, by the control system, the motorized drive assembly to cause the array of orthogonally-polarized radiating elements to occupy the optimal position. Other embodiments are disclosed.

A two-port antenna system is proposed that uses a polarization-independent spatial power divider to align the beams from two orthogonally oriented dual-polarized feeds. This antenna system is compatible with fully polarimetric radar and provides high port isolation. It simultaneously provides a common aperture for transmit and receive to minimize radar parallax. The spatial power divider is designed using a combination of all-dielectric metamaterial techniques and the concept of miniaturized-element frequency selective surfaces, and is fabricated on a silicon wafer using standard microfabrication technology.

A dual-mode polarizer for selectively switching between linear polarization and circular polarization includes a first meander-line polarizer, and a second meander-line polarizer spaced apart from the first meander-line polarizer to define a first gap therebetween. A first angular orientation between the first and second meander-line polarizers produces variably-oriented linear polarization of a signal passing through the first and second meander-line polarizers, and a second angular orientation between the first and second meander-line polarizers produces variably-oriented circular polarization of a signal passing through the first and second meander-line polarizers.

A wireless system may include a central processor and an access point. The central processor may generate an optical signal on an optical fiber. The optical signal may include an optical local oscillator (LO) signal and one or more carriers. The central processor may modulate different combinations of transverse optical modes, orbital angular momentum, polarization, and/or carrier frequency of the optical signal to concurrently convey respective wireless data streams. The orthogonality of the transverse optical modes, orbital angular momentum, polarization, and carrier frequency may allow many wireless data streams to be modulated onto the optical signal and concurrently transmitted and propagated on the optical fiber independent of each other for transmission to one or more external devices.

A wireless system may include a central processor and an access point. The central processor may generate an optical signal on an optical fiber. The optical signal may include an optical local oscillator (LO) signal and one or more carriers. The central processor may modulate different combinations of transverse optical modes, orbital angular momentum, polarization, and/or carrier frequency of the optical signal to concurrently convey respective wireless data streams. The orthogonality of the transverse optical modes, orbital angular momentum, polarization, and carrier frequency may allow many wireless data streams to be modulated onto the optical signal and concurrently transmitted and propagated on the optical fiber independent of each other for transmission to one or more external devices.

In an aspect, a polarization converter comprises a plurality of alternating high Dk layers and low Dk layers that alternate along an x-direction; wherein neighboring broad surfaces of the respective high Dk layers and low Dk layers are bonded together. In another aspect, a polarization converter can comprise a plurality of alternating high Dk layers and low Dk layers that alternate along a radial direction; wherein neighboring broad surfaces of the respective high Dk layers and low Dk layers are bonded together. The polarization converter is capable of converting an incoming electromagnetic wave to an outgoing electromagnetic wave having a different polarization.

An antenna having high isolation and a low cross-polarization level, a base station, and a terminal are provided. The antenna includes a radiation layer, a feed layer, and an aperture coupling layer disposed between the radiation layer and the feed layer. The aperture coupling layer includes a metal sheet. A first feeding slot, a second feeding slot, and a middle slot are configured in the metal sheet. The middle slot is located between the first feeding slot and the second feeding slot, and is located in a weak electric field region of the metal sheet. The middle slot is configured between the first feeding slot and the second feeding slot of the metal sheet.

This elementary antenna includes a cavity delimited by front and rear faces and side walls, the front face being provided with first and second slots arranged in a cross, so that, when the cavity operates in a TE210 mode, a wave polarized perpendicularly to the first slot is emitted and when the cavity operates in a TE120 mode, a wave polarized perpendicularly to the second slot is emitted. This elementary antenna is characterized in that the rear face is brought to a reference electric potential, and in that the elementary antenna includes an excitation device, such as a metallized via, capable of exciting the front face through the cavity, the excitation device exciting the front face at a plurality of excitation points, distributed over the front face and presenting a common predefined impedance

Aspects of the subject disclosure may include, for example, a polarization shifter including a lower substrate having disposed thereon first and second transmission lines for coupling to a feed network, an upper substrate having disposed thereon third and fourth transmission lines for respective communicative coupling to orthogonally-polarized elements of a radiating element, and a dielectric layer residing between the lower substrate and the upper substrate, the upper substrate being configured to mechanically couple to the radiating element, the dielectric layer coupling the first transmission line with the third transmission line and coupling the second transmission line with the fourth transmission line, the upper substrate being rotatable relative to the lower substrate to effect polarization adjusting for the radiating element to facilitate avoidance of interference or passive intermodulation (PIM). Other embodiments are disclosed.