Antenna apparatus and spacecraft to be deployed in a more compactly stored state are disclosed. In an example of the disclosed technology, a spacecraft includes: a main-reflection unit configured to reflect and emit a radio wave outside, a sub-reflection unit configured to face the main-reflection unit, a radiator arranged to face the sub-reflection unit and configured to radiate the radio wave in a direction of the sub-reflection unit, a main body configured to be able to accommodate at least one part of the sub-reflection unit therein, and a delivery device connected to the sub-reflection unit and configured to deliver the sub-reflection unit, at least one part of which is accommodated in the main body, to a position where the sub-reflection unit is able to reflect the radio wave radiated from the radiator to the main-reflection unit and cause the main-reflection unit to radiate the radio wave outside.

A secondary reflector is provided which has structural strength based on the hexagonal design and which show frequency selective features and low insertion loss. The antenna system includes a main reflector at which an incoming RF signal from a signal source reaches, a secondary reflector at which the incoming RF signal reaches by being reflected from the main reflector, a second antenna feed to which a transmitted RF signal through the secondary reflector is directed and a first antenna feed to which a reflected RF signal from the secondary reflector is directed. The surface of the secondary reflector has a dielectric support layer with hexagonal holes and a frequency selective surface located on the support layer and having circular rings.

A secondary reflector is provided which has structural strength based on the hexagonal design and which show frequency selective features and low insertion loss. The antenna system includes a main reflector at which an incoming RF signal from a signal source reaches, a secondary reflector at which the incoming RF signal reaches by being reflected from the main reflector, a second antenna feed to which a transmitted RF signal through the secondary reflector is directed and a first antenna feed to which a reflected RF signal from the secondary reflector is directed. The surface of the secondary reflector has a dielectric support layer with hexagonal holes and a frequency selective surface located on the support layer and having circular rings.

Microwave antenna systems include a parabolic reflector antenna having a feed bore and a feed assembly. The feed assembly includes a coaxial waveguide structure that extends through the feed bore, a sub-reflector, and a first dielectric block that is positioned between the coaxial waveguide structure and the sub-reflector. The coaxial waveguide structure includes a central waveguide and an outer waveguide that circumferentially surrounds the central waveguide. One of the central waveguide and the outer waveguide extends further from the feed bore towards the sub-reflector than the other of the central waveguide and the outer waveguide.

All existing state-of-the-art high resolution millimeter wave imaging systems experience a trade off between image acquisition time and transceiver array complexity. The proposed dual reflector antenna breaks this trade-off by drastically reducing the array formation time while maintaining the relative simplicity that comes with using a single transceiver element. It consists of a dual mode horn feed, a rotating ellipsoidal sub-reflector and a conic main reflector. The rotating sub-reflector creates a virtual phase center that rotates about an axis to produce a synthetic circular array with a diameter of 120λ. The main reflector redirects the beams from each of these virtual phase centers to overlap and illuminate the scene over a wide field of view. The proposed system can reduce the image acquisition time to the order of milliseconds/seconds which makes real-time SAR imaging a practical alternative to MIMO and phased arrays at millimeter-wave and sub-millimeter-wave frequencies.

All existing state-of-the-art high resolution millimeter wave imaging systems experience a trade off between image acquisition time and transceiver array complexity. The proposed dual reflector antenna breaks this trade-off by drastically reducing the array formation time while maintaining the relative simplicity that comes with using a single transceiver element. It consists of a dual mode horn feed, a rotating ellipsoidal sub-reflector and a conic main reflector. The rotating sub-reflector creates a virtual phase center that rotates about an axis to produce a synthetic circular array with a diameter of 120λ. The main reflector redirects the beams from each of these virtual phase centers to overlap and illuminate the scene over a wide field of view. The proposed system can reduce the image acquisition time to the order of milliseconds/seconds which makes real-time SAR imaging a practical alternative to MIMO and phased arrays at millimeter-wave and sub-millimeter-wave frequencies.

A system for reducing antenna spillover in a satellite communications system is disclosed. The system may include an apparatus comprising an antenna terminal, which in turn may include a sub-reflector and a main reflector. The main reflector may include at least one of an extension, a shroud, and a serrated edge. The extension may be a full rim extension or a partial extension. The shroud may be a full shroud or a partial shroud. The serrated edge may include a straight serration or a curved serration, the serrated edge also having various dimensions and profiles. In some examples, the sub-reflector and the main reflector of the antenna terminal may be provided and configured to reduce antenna spillover in accordance with antenna performance and interference restrictions set forth by one or more governing bodies.

A system for reducing antenna spillover in a satellite communications system is disclosed. The system may include an apparatus comprising an antenna terminal, which in turn may include a sub-reflector and a main reflector. The main reflector may include at least one of an extension, a shroud, and a serrated edge. The extension may be a full rim extension or a partial extension. The shroud may be a full shroud or a partial shroud. The serrated edge may include a straight serration or a curved serration, the serrated edge also having various dimensions and profiles. In some examples, the sub-reflector and the main reflector of the antenna terminal may be provided and configured to reduce antenna spillover in accordance with antenna performance and interference restrictions set forth by one or more governing bodies.

A twistarray reflector includes: a reflector having front reflecting surface comprising wires and a back reflecting surface, the front reflecting surface fabricated from the wires and composites where the wires are placed having an orientation at each point on the front surface to decompose an incident field into orthogonal components so that an electromagnetic reflected from the front surface when superposed with a phase-inverted electromagnetic field reflected from the back reflecting surface produces a net reflected electromagnetic field that is polarized in a specific vector direction with consistent phase.

A twistarray reflector includes: a reflector having front reflecting surface comprising wires and a back reflecting surface, the front reflecting surface fabricated from the wires and composites where the wires are placed having an orientation at each point on the front surface to decompose an incident field into orthogonal components so that an electromagnetic reflected from the front surface when superposed with a phase-inverted electromagnetic field reflected from the back reflecting surface produces a net reflected electromagnetic field that is polarized in a specific vector direction with consistent phase.