This document describes a multimode high-isolation antenna system and associated methods and systems. The described antenna system is implemented on a generally-circular printed circuit board and can be used for wideband and ultra-wideband applications. The multimode high-isolation antenna system includes two orthogonal antennas separated by a decoupling structure. This arrangement provides high isolation between the antennas and enables five unique resonant modes of operation for the multimode high-isolation antenna system.

According to one aspect, a radar-radiometric imaging method is disclosed that includes cyclical observation, with a time period T, of a selected space section due to antenna beam rotation with a period T.sub.a (T.sub.a≤T) around a rotation axis misaligned with the antenna's beam axis, along with the simultaneous change of the spatial orientation of this rotation axis using an antenna positioning device to ensure survey of the selected space domain for the time T without gaps.

According to one aspect, a radar-radiometric imaging method is disclosed that includes cyclical observation, with a time period T, of a selected space section due to antenna beam rotation with a period T.sub.a (T.sub.a≤T) around a rotation axis misaligned with the antenna's beam axis, along with the simultaneous change of the spatial orientation of this rotation axis using an antenna positioning device to ensure survey of the selected space domain for the time T without gaps.

An antenna system having a main reflector and at least two subreflectors is configured to provide at least two independently steerable beams. Each subreflector is configured to illuminate the main reflector, and each subreflector is configured to be illuminated by a respective dedicated feed element or dedicated feed array. At least one of the subreflectors is configured to steer a first beam, without affecting the shape or orientation of any other beam. One or more of the beams may also be independently shaped, by a contoured surface of one or more subreflectors and/or the main reflector.

A compensation circuit reduces the negative effects of antenna-to-antenna coupling between proximately located antennas. The compensation circuit is coupled between first and second antenna ports. A first transmit/receive path extends from radio frequency (RF) circuitry to the first antenna port. A second transmit/receive path extends from the RF circuitry to the second antenna port. Antennas are coupled to each of the antenna ports. The compensation circuit includes negatively coupled first and second inductors, which are coupled in series between the first antenna port and the second antenna port. At least one shunt acoustic resonator is coupled between a fixed voltage node and a common node between the first and second inductors. In operation, the compensation circuit presents a negative capacitance between the first antenna port and the second antenna port over the first frequency range to reduce the effects of the antenna-antenna coupling.

There is disclosed A directional multi-band antenna, the antenna comprising: —an optical unit comprising an optical sensor; —an RF unit comprising an RF sensor; —a substantially planar optical lens, the optical lens comprising surface relief elements for beam forming, the lens being arranged to focus optical signal beams, incident along a first optical axis, onto the optical sensor, the optical lens being substantially transparent to RF signals, —an RF beam forming device arranged to receive RF signals incident along the first optical axis and focus such RF signals onto the RF sensor.

There is disclosed A directional multi-band antenna, the antenna comprising: —an optical unit comprising an optical sensor; —an RF unit comprising an RF sensor; —a substantially planar optical lens, the optical lens comprising surface relief elements for beam forming, the lens being arranged to focus optical signal beams, incident along a first optical axis, onto the optical sensor, the optical lens being substantially transparent to RF signals, —an RF beam forming device arranged to receive RF signals incident along the first optical axis and focus such RF signals onto the RF sensor.

A magnetic resonance apparatus comprising: a magnetic system configured to provide a magnetic field throughout at least a portion of a cavity, the magnetic field based on magnetic-system-control-data; a transmitter antenna disposed at least partly within the cavity and configured to transmit radio-frequency-transmitted-signalling based on transmitter-control-data; and a receiver antenna disposed at least partly within the cavity and configured to receive radio-frequency-received-signalling representative of magnetic resonance interactions of at least one object, disposed within the portion of the cavity, with the magnetic field and the radio-frequency-transmitted-signalling; wherein, at least one of the transmitter antenna, the receiver antenna and the magnetic system comprises a plasma antenna, and the magnetic resonance imaging apparatus is configured to provide received-data representative of the radio-frequency-received-signalling, the received-data in combination with the magnetic-system-control-data and the transmitter-control-data suitable for providing magnetic resonance imaging and/or magnetic resonance spectroscopy of the at least one object.

A magnetic resonance apparatus comprising: a magnetic system configured to provide a magnetic field throughout at least a portion of a cavity, the magnetic field based on magnetic-system-control-data; a transmitter antenna disposed at least partly within the cavity and configured to transmit radio-frequency-transmitted-signalling based on transmitter-control-data; and a receiver antenna disposed at least partly within the cavity and configured to receive radio-frequency-received-signalling representative of magnetic resonance interactions of at least one object, disposed within the portion of the cavity, with the magnetic field and the radio-frequency-transmitted-signalling; wherein, at least one of the transmitter antenna, the receiver antenna and the magnetic system comprises a plasma antenna, and the magnetic resonance imaging apparatus is configured to provide received-data representative of the radio-frequency-received-signalling, the received-data in combination with the magnetic-system-control-data and the transmitter-control-data suitable for providing magnetic resonance imaging and/or magnetic resonance spectroscopy of the at least one object.

A modular node for an optical communication network includes one or more transceiver modules of a plurality of transceiver modules, and a node core including a plurality of electrical connectors to electrically join up to the plurality of transceiver modules to the node core. At least some of the transceiver modules has an optical transceiver configured to emit optical beams carrying data and without artificial confinement, and detect optical beams emitted and without artificial confinement. The up to the plurality of transceiver modules electrically joined to the node core are spatially separated to provide configurable coverage for optical communication based on their number and placement. And the node core further includes switching circuitry configured to connect the one or more transceiver modules to implement a redistribution point or a communication endpoint in the optical communication network.