A beacon network includes a plurality of beacons arranged at predetermined positions to periodically or intermittently emit a signal wave including identification information, and a radio wave absorber to adjust an emission angle of the signal wave emitted from at least one of the plurality of beacons.

Systems, methods, and circuitries are disclosed for providing a retrodirective array. One example retrodirective array includes a plurality of dual-polarized antenna elements configured to receive a pilot signal having a first polarization and phase conjugation circuitry. The phase conjugation circuitry includes, for each of the plurality of antenna elements, a mixer configured to mix the pilot signal with an LO signal to generate a phase conjugated signal and excitation circuitry configured to generate an excitation signal for the antenna element to transmit the phase conjugated signal with a second polarization that is different from the first polarization.

An identification device that provides identification information is described. This identification device includes a set of radar reflectors that reflect radar signals having a fundamental wavelength. The set of radar reflectors may be arranged in a pattern corresponding to the identification information. For example, the set of radar reflectors may be passive and retrodirective, where a given radar reflector reflects a radar signal back along its prior direction of propagation. Moreover, the pattern may include regions that reflect the radar signals and second regions that do not reflect or scatter the radar signals. During operation, the identification device may receive the radar signals, and then may selectively reflecting the radar signals using the set of radar reflectors to provide the identification information.

A Van Atta antenna array comprising a number of antenna elements electrically connected to operate as a Van Atta antenna array and fabricated on and within a substrate. Each antenna element has a number of patch elements fabricated on the top surface of the substrate, with the patch elements being interconnected by substrate integrated waveguides. The antenna array provides a two-dimensional retro-reflective surface, which makes it especially suitable for InSAR monitoring of infrastructures.

An apparatus is provided for transmission of RF signals between a transmitter and a receiver. The apparatus includes a transmitter comprising a first retroreflector having a first array of sub-wavelength retroreflective elements at one end of an open cavity for transmitting RF seed signals. The apparatus also includes a receiver comprising a second retroreflector having a second array of sub-wavelength retroreflective elements at an opposite end of the open cavity for receiving the transmitted seed signal, the transmitted RF seed signals being in form of a beam directed toward the receiver.

A metasurface includes a dielectric material, a ground plane on a back side of the dielectric material; and at least one conductive element on a top surface of the dielectric material, wherein the at least one conductive element includes at least one of a ground-backed dipole or a slot array.

An antenna apparatus is provided that has a strip of antenna elements extending in a first dimension, and a signal processing interface for connection to signal processing circuitry. A plurality of beamforming networks are also provided, wherein each beamforming network is arranged, when coupled to the strip of antenna elements, to cause an associated beam pattern of the beamforming network to be generated by the strip of antenna elements. Switching circuitry is used to enable any one of the plurality of beamforming networks to be inserted between the strip of antenna elements and the signal processing interface. Each beamforming network couples a first node of the beamforming network with multiple second nodes of the beamforming network in accordance with a coupling pattern of that beamforming network. As a result, when the switching circuitry causes a given beamforming network to be inserted between the strip of antenna elements and the signal processing interface, the signal processing interface is coupled to the first node, each antenna element is coupled to an associated one of the second nodes, and the coupling pattern of the given beamforming network causes the associated beam pattern to be generated by the strip of antenna elements.

Present invention is a wireless device comprising a Van Atta array, said Van Atta array comprising a plurality of antenna pairs, each of said antenna pairs comprising two antenna elements electrically coupled by a signal path of pre-determined length. The wireless device further comprises a measurement unit, said measurement unit is adapted to perform electrical measurements between two measurement points. One of said two measurement points is located at a first pre-determined location on the signal path of one of the antenna pairs, and the other of said two measurement points is located on a second pre-determined location on the signal path of one of the other antenna pairs. The present invention is also a method for retro-reflection of an incident wave using a plurality of antenna pairs.

The invention relates to a method for protecting an object, in particular a land vehicle or watercraft, in particular a ship, from of a radar-guided missile by deploying and using an active offboard reflector, which is arranged at a decoy and comprises at least one receiving antenna and at least one transmitting antenna, wherein a radar signal transmitted by the radar-guided missile is picked up and is returned to the missile as an amplified signal in the previously ascertained opposite direction of reception; the invention proposes carrying out the method by deploying a plurality of flying drones, each having at least one active offboard reflector, and positioning the drones relative to one another in space in such a way that the active offboard reflectors thereof act as individual scattering centers and the signals therefrom that are returned to the missile collectively produce a radar scatter pattern that simulates the object to be protected.

The proposed retro-directive quasi-optical system includes at least a lens set and a pixel array. The lens set is positioned on one side of the pixel array and the lens set instantly establishes retro-directive space channels between the pixels in the pixel array and the object(s) distributed in the accessible space defined by the lens set through infinite or finite conjugation. In the pixel array, a number of pixels are arranged as an array and each pixel is composed of at least one pair of transmitter antenna and receiver antenna. To guarantee that the electromagnetic waves transmitted from a pixel into the accessible space may be reflected back to the receiver of the same pixel, the size of each pixel is not larger than the point-spread spot size defined by the lens set, wherein the point-spread spot size can be contributed either from lens diffraction or aberration.