Systems and methods are provided for power beaming that increase power density at the target location by exploiting scattering from terrain. The disclosed systems and methods further provide a variable focus feature allowing the beam power to be concentrated at specified standoff distances from the transmitter and increase the radio frequency (RF) power handling of the receiver using an overvoltage protection circuit in the DC load.

A highly-secure wireless communication system has a transmitter for transmitting the same information at predetermined polarized wave angles having different rotation-polarized waves for rotating the polarized waves of a carrier wave, and a receiver for restoring the reception information at the aforementioned predetermined polarization wave angles and for comparing the restoration results of the predetermined polarization wave angles with one another.

A highly-secure wireless communication system has a transmitter for transmitting the same information at predetermined polarized wave angles having different rotation-polarized waves for rotating the polarized waves of a carrier wave, and a receiver for restoring the reception information at the aforementioned predetermined polarization wave angles and for comparing the restoration results of the predetermined polarization wave angles with one another.

A Software Defined Radio Earth Atmosphere Imaging system comprising at least one imager, which comprises: a radio wave emitter configured to emit a sky wave, a ground wave and a first time signal; a radio wave detector, the radio wave detector including a two dimensional array of radio wave receivers, the radio wave detector for receiving a carrier wave and the ground wave and transmitting a second time signal; a vector network analyzer including a Global Navigation Satellite System and at least one synchronization clock, the vector network analyzer in electrical communication with the radio emitter via a first wire and with the radio wave detector via a second wire, the wires for transmitting the time signals; a software defined radio in electronic communication with the vector network analyzer; and a computing device, the computing device in electronic communication with the vector network analyzer.

A backscatter transmission scheme is provided in which a carrier signal is transmitted by a carrier communication device discontinuously as carrier signal bursts. The carrier signal, while it is on, is divided into carrier time segments. Each carrier time segment has a specified time. The different carrier time segments represent different times that backscatter devices can make backscatter transmissions. In addition, in some embodiments, a set of frequencies are available for backscatter transmission. The set of frequencies includes the carrier frequency and a set of frequencies with respective frequency shifts relative to the carrier frequency. The combination of a specific carrier time segment, a specific frequency shift, together constitutes a specific backscatter transmission opportunity.

A backscatter transmission scheme is provided in which a carrier signal is transmitted by a carrier communication device discontinuously as carrier signal bursts. The carrier signal, while it is on, is divided into carrier time segments. Each carrier time segment has a specified time. The different carrier time segments represent different times that backscatter devices can make backscatter transmissions. In addition, in some embodiments, a set of frequencies are available for backscatter transmission. The set of frequencies includes the carrier frequency and a set of frequencies with respective frequency shifts relative to the carrier frequency. The combination of a specific carrier time segment, a specific frequency shift, together constitutes a specific backscatter transmission opportunity.

A backscatter tag device includes, in part, a receiver configured to receive a packet conforming to a communication protocol defining a multitude of codewords, a codeword translator configured to translate at least a first subset of the multitude of codewords disposed in the packet to a second multitude of codewords defined by the protocol in response to a data the backscatter tag is invoked to transmit, and a transmitter configured to transmit the packet supplied by the codeword translator at a frequency different than the first frequency at which the packer is received. The communication protocol may optionally be the 802.11 g/n, ZigBee or the Bluetooth communication protocol.

A wireless communication system includes a first wireless communication node for transmitting a data signal that is sent to a second wireless communication node by skywave propagation over at least two different data transmission paths. The first data transmission path includes at least one reflection point where the data signal is reflected by the atmosphere and the second data transmission path includes more reflection points than the first data transmission path. The data signal that travelled along the first data transmission path is decoded before the data signal that travelled along the second data transmission path.

A wireless communication system includes a first wireless communication node for transmitting a data signal that is sent to a second wireless communication node by skywave propagation over at least two different data transmission paths. The first data transmission path includes at least one reflection point where the data signal is reflected by the atmosphere and the second data transmission path includes more reflection points than the first data transmission path. The data signal that travelled along the first data transmission path is decoded before the data signal that travelled along the second data transmission path.

A wireless communication method includes: a first device reports first information to a second device, the first information being applied to backscatter communication.