The disclosed structures and methods are directed to antenna systems configured to transmit and receive a wireless signal in and from different directions. A switchable lens antenna has excitation ports radiating radio-frequency (RF) wave into a parallel-plate waveguide structure, and a frequency selective structure (FSS). The antenna presented herein is configured to operate in two modes depending on an initial steering angle of the RF wave propagating in the parallel-plate waveguide structure. When the initial steering angle is about or less than a threshold steering angle, FSS is OFF due to its stubs being electrically disconnected from the parallel-plate waveguide structure. When the initial steering angle is higher than the threshold, FSS is ON with stubs being electrically connected to the parallel-plate waveguide structure. When ON, FSS provides phase variance to the RF wave propagating in the parallel-plate waveguide structure and increases steering angle of the RF wave.

An antenna structure includes a substrate, a plurality of reflective plates, a grounding plate, a radiating member and a plurality of conductive vias. The substrate contains liquid crystal polymer and has opposite first and second surfaces. The reflective plates are arranged in an array on the first surface of the substrate. The grounding plate is arranged on the second surface of the substrate and overlaps with the reflective plates in a normal direction of the substrate. The radiating member is on the second surface of the substrate and does not overlap with the reflective plates in the normal direction of the substrate. The radiating member has an open slot which is defined by a first radiating branch and a second radiating branch that generate at least two different operating frequency bands. The conductive vias respectively penetrate the substrate and connect with the reflective plates and the grounding plate.

An antenna structure includes a substrate, a plurality of reflective plates, a grounding plate, a radiating member and a plurality of conductive vias. The substrate contains liquid crystal polymer and has opposite first and second surfaces. The reflective plates are arranged in an array on the first surface of the substrate. The grounding plate is arranged on the second surface of the substrate and overlaps with the reflective plates in a normal direction of the substrate. The radiating member is on the second surface of the substrate and does not overlap with the reflective plates in the normal direction of the substrate. The radiating member has an open slot which is defined by a first radiating branch and a second radiating branch that generate at least two different operating frequency bands. The conductive vias respectively penetrate the substrate and connect with the reflective plates and the grounding plate.

A multi-band antenna includes a reflector, and a plurality of first radiating elements on the reflector. The plurality of first radiating elements are configured to radiate a first antenna beam(s) in a first frequency band responsive to at least one feed signal. A passive radiation-filtering element is provided, which extends proximate the first antenna beam(s). The passive radiation-filtering element includes at least one of a low-pass LC circuit, a band-pass LC circuit, and a high-pass LC circuit therein, which is configured to provide a lower frequency-dependent impedance to radiation within the first frequency band relative to radiation at frequencies outside the first frequency band. The passive radiation-filtering element may be configured as a multi-segment fence having capacitive and inductive elements therein, which are electrically coupled in series.

A multi-band antenna includes a reflector, and a plurality of first radiating elements on the reflector. The plurality of first radiating elements are configured to radiate a first antenna beam(s) in a first frequency band responsive to at least one feed signal. A passive radiation-filtering element is provided, which extends proximate the first antenna beam(s). The passive radiation-filtering element includes at least one of a low-pass LC circuit, a band-pass LC circuit, and a high-pass LC circuit therein, which is configured to provide a lower frequency-dependent impedance to radiation within the first frequency band relative to radiation at frequencies outside the first frequency band. The passive radiation-filtering element may be configured as a multi-segment fence having capacitive and inductive elements therein, which are electrically coupled in series.

The antenna uses X Band frequencies for long-distance weather monitoring and W Band frequencies for imaging of terrain and obstacles, for use in a radar system in aircraft nose radome to operate effectively in a degraded visual environment. The antenna's feed structure includes concentrically positioned first and second horns. First and second rectangular waveguides are positioned on a cylindrical portion of the first horn, and at a first and second radial positions spaced 90 degrees apart. First and second coaxial cables respectively couple the first and second rectangular waveguides to a polarization converter, which launches linearly polarized waves received from each of the first and second coaxial cables to form a W-hand circularly polarized wave. The feed structure collects and disseminates W Band and X Band electromagnetic energy.

An antenna comprises an axial helical radiating element and a corrugated ground plane. The axial helical radiating element provides a radiation pattern substantially parallel to a primary axis of rotation of the helical radiating element. The corrugated ground plane, disposed proximate to a back region of the antenna, comprises corrugations to increase an electrical length of travel for radial standing waves between an axial helical input, at which the axial helical radiating element is coupled to the corrugated ground plane, to an outer edge of the corrugated ground plane.

A band changer includes a rotor having a rotation axis, and a plurality of transceivers disposed separately from the rotation axis and provided in the rotor along a circumferential direction of the rotor, and configured to transmit and receive waves respectively having different frequency bands.

A band changer includes a rotor having a rotation axis, and a plurality of transceivers disposed separately from the rotation axis and provided in the rotor along a circumferential direction of the rotor, and configured to transmit and receive waves respectively having different frequency bands.

The disclosure provides a multi-feed antenna including a first conductor layer, a second conductor layer, four supporting conductor structures and four feeding conductor lines. The second conductor layer has a first center position and is spaced apart from the first conductor layer at a first interval. The four supporting conductor structures respectively electrically connect the first conductor layer and the second conductor layer and form four electrically connected sections at the second conductor layer. The four electrically connected sections respectively extend from different side edges of the second conductor layer toward the first center position, so that the second conductor layer forms four mutually connected radiating conductor plates. The four feeding conductor lines are all located between the first conductor layer and the second conductor layer. The four feeding conductor lines and the four supporting conductor structures form an interleaved annular arrangement. Each of the feeding conductor lines has one end electrically connected to a coupling conductor plate. Each of the coupling conductor plates is spaced apart from a different one of the radiating conductor plates at a coupling interval. Each of the feeding conductor lines has another end electrically connected to a signal source respectively. The four feeding conductor lines excite the second conductor layer to generate at least four resonant modes. The at least four resonant modes cover at least one identical first communication band.