An antenna is used in a radar, sensor, communication, discovery, electronic warfare and/or networking system. The antenna system includes a disc-shaped conductive substrate, a ring-shaped conductive substrate being positioned generally parallel with respect to the disc-shaped conductive substrate, the ring-shaped conductive substrate having an outer diameter generally coincides with an outer diameter of the disc-shaped conductive substrate. Antenna elements, such as, Balanced Antipodal Vivaldi Antenna (BAVA) elements, are disposed between the disc-shaped conductive substrate and the ring-shaped conductive substrate.

A system and methods for RF (Radio Frequency) penetration imaging of one or more objects in a medium, the system including a generation and reception subsystem configured to generate and receive a plurality of RF signals, an RF antenna array including a plurality of antennas, the antennas being configured to transmit the RF signals towards the medium and receive a plurality of RF signals reflected from the medium, a data acquisition subsystem configured to receive and store the reflected RF signals, and a processor configured to estimate the distance between the surface of the target medium and the antenna array, the delay between the transmitted signals and the plurality of signals reflected from the object using a dedicated frequency sub-band of the received signals, the location of the antennas at each transmitting time, and determine whether there is an object within the medium.

A system and methods for RF (Radio Frequency) penetration imaging of one or more objects in a medium, the system including a generation and reception subsystem configured to generate and receive a plurality of RF signals, an RF antenna array including a plurality of antennas, the antennas being configured to transmit the RF signals towards the medium and receive a plurality of RF signals reflected from the medium, a data acquisition subsystem configured to receive and store the reflected RF signals, and a processor configured to estimate the distance between the surface of the target medium and the antenna array, the delay between the transmitted signals and the plurality of signals reflected from the object using a dedicated frequency sub-band of the received signals, the location of the antennas at each transmitting time, and determine whether there is an object within the medium.

A wireless handheld or portable device includes an antenna system operable in a first frequency region and a higher, second frequency region. The antenna system comprises an antenna structure, a matching and tuning system, and an external input/output (I/O) port. The antenna structure comprises at least one radiating element including a connection point, a ground plane layer including at least one connection point, and at least one internal I/O port. At least one radiating element of the antenna structure protrudes beyond the ground plane layer. The antenna structure features at any of its internal I/O ports when disconnected from the matching and tuning system an input return loss curve having a minimum at a frequency outside the first frequency region of the antenna system. The matching and tuning system modifies the impedance of the antenna structure and provides impedance matching to the antenna system in the first and second regions.

A wireless handheld or portable device includes an antenna system operable in a first frequency region and a higher, second frequency region. The antenna system comprises an antenna structure, a matching and tuning system, and an external input/output (I/O) port. The antenna structure comprises at least one radiating element including a connection point, a ground plane layer including at least one connection point, and at least one internal I/O port. At least one radiating element of the antenna structure protrudes beyond the ground plane layer. The antenna structure features at any of its internal I/O ports when disconnected from the matching and tuning system an input return loss curve having a minimum at a frequency outside the first frequency region of the antenna system. The matching and tuning system modifies the impedance of the antenna structure and provides impedance matching to the antenna system in the first and second regions.

Antenna systems are described which provide means of mitigating the undesirable transmission line effect(s) by using fractal metamaterials in close proximity to an antenna, with both the antenna and fractal metamaterials being positioned a conductive surface, which may be inside or adjacent to a cavity. The fractal metamaterial can include an array of close spaced (e.g., less than 1/10 wavelength separation) resonant structures of a fractal shape, resonant at or near the intended frequency of use of the antenna. The fractal metamaterial can reverse the phase of the reflected wave so that the metal cavity no longer produces an out of phase current induced by the antenna. Without the cavity being out of phase to the antenna, the transmission line effect is mitigated substantially and the antenna performance can accordingly be enhanced. Further embodiments omit a cavity and locate a fractal metamaterial and antenna(s) adjacent to an underlying conductive surface.

The present invention relates to a base station antenna comprising: a reflective plate; at least one first band radiation element positioned on the upper surface of the reflective plate, including a first power feed unit, and having a first wavelength (.sub.H); and at least one second band radiation element positioned on the upper surface of the reflective plate, including a second power feed unit, and having a second wavelength (.sub.L), wherein the first power feed unit is connected to a power feed line on the lower surface of the reflective plate, and the power feed line is shorted with the reflective plate at a short point spaced apart at a preset interval from the first band radiation element.

A method for upgrading a dual-band antenna assembly to a tri-band antenna assembly is provided. The dual-band antenna assembly includes a main reflector, and first and second antenna feeds arranged in a coaxial relationship and directed toward the main reflector. The first and second antenna feeds are for first and second frequency bands, respectively. The method includes positioning a third antenna feed through a medial opening in a center of the main reflector, with the third antenna feed directed towards the first and second antenna feeds. The third antenna feed is for a third frequency band. A subreflector is positioned between the main reflector and the first and second antenna feeds. The subreflector includes a frequency selective surface (FSS) material that is reflective for the third frequency band and transmissive for both the first and second frequency bands.

A method for upgrading a dual-band antenna assembly to a tri-band antenna assembly is provided. The dual-band antenna assembly includes a main reflector, and first and second antenna feeds arranged in a coaxial relationship and directed toward the main reflector. The first and second antenna feeds are for first and second frequency bands, respectively. The method includes positioning a third antenna feed through a medial opening in a center of the main reflector, with the third antenna feed directed towards the first and second antenna feeds. The third antenna feed is for a third frequency band. A subreflector is positioned between the main reflector and the first and second antenna feeds. The subreflector includes a frequency selective surface (FSS) material that is reflective for the third frequency band and transmissive for both the first and second frequency bands.

A communication system is described where multiple communication networks are simultaneously accessible from a plurality of fixed and/or mobile communication devices. A Master and Slave hierarchy is implemented among the communication devices to improve communication properties on one or multiple networks. A network system controller is implemented to select the network with optimal communication characteristics for subsets of communication devices as well as assigning Master status to a communication device within these subsets.