Abstract: A method of employing multipath propagation in wireless radio communications uses an omnidirectional transmitting/receiving antenna at one end of a transmission link to send an interrogating signal across an environment subject to multipath disturbances to a phase-conjugating retrodirective antenna, and the retrodirective antenna returns a communication signal along the multiple pathways taken by the interrogating signal to the omnidirectional antenna despite the multipath disturbances. In a simplex communication mode, the retrodirective antenna sends a return signal mixed with a communication signal to the omnidirectional antenna. In a duplex communication mode, both an omnidirectional antenna and a phase-conjugating retrodirective antenna are operated in tandem at each end of the transmission link to provide effective two-way wireless radio transmissions.

Abstract: A high-directivity transponder system uses a dual system of a retrodirective array transmitting a data signal peak toward an interrogator source, and a self-null-steering array transmitting a null toward the interrogator source and a jamming signal elsewhere, resulting in high S/N reception at the interrogator source and avoidance of interception. Integrating modulators would allow each array to transmit different data while the spectra of the transmitted signals are identical, thus disabling interception. The system enables secure point-to-point communications and can be used for short-distance wireless data transmission systems such as wireless LAN and RFID servers.

Abstract: A self-steering retrodirective array capable of both full-duplex communication and maintaining a constant retrodirected power level uses an angle-detecting array with a phase detector to detect the angle of the incoming signal from a source and generate an error voltage signal, and a transmitting array having a phase shifter controlled by the error voltage signal to retrodirect a beam back in the direction of the source. A phase shifter in the receiving array also ensures coherent combination of the incoming signal. The angle-detection array and transmitter array are RF-decoupled for full-duplex communication. The efficiency of the system is increased by using an interrogator signal at a much lower frequency than the transmitted signal. In a preferred embodiment, a simple two-element angle detecting array detects the direction of the source.

Abstract: A high-directivity transponder system uses a dual system of a retrodirective array transmitting a data signal peak toward an interrogator source, and a self-null-steering array transmitting a null toward the interrogator source and a jamming signal elsewhere, resulting in high S/N reception at the interrogator source and avoidance of interception. Integrating modulators would allow each array to transmit different data while the spectra of the transmitted signals are identical, thus disabling interception. The system enables secure point-to-point communications and can be used for short-distance wireless data transmission systems such as wireless LAN and RFID servers. As another aspect, self-steering signal transmission is employed for randomly oriented satellites using circularly polarized, two-dimensional retrodirective arrays. Quadruple subharmonic mixing is used as an effective means of achieving phase conjugation when a high-frequency LO is not feasible or inapplicable.

Abstract: A high-directivity transponder system uses a dual system of a retrodirective array transmitting a data signal peak toward an interrogator source, and a self-null-steering array transmitting a null toward the interrogator source and a jamming signal elsewhere, resulting in high S/N reception at the interrogator source and avoidance of interception. Integrating modulators would allow each array to transmit different data while the spectra of the transmitted signals are identical, thus disabling interception. The system enables secure point-to-point communications and can be used for short-distance wireless data transmission systems such as wireless LAN and RFID servers. As another aspect, self-steering signal transmission is employed for randomly oriented satellites using circularly polarized, two-dimensional retrodirective arrays. Quadruple subharmonic mixing is used as an effective means of achieving phase conjugation when a high-frequency LO is not feasible or inapplicable.

Abstract: A high-directivity transponder system uses a dual system of a retrodirective array transmitting a data signal peak toward an interrogator source, and a self-null-steering array transmitting a null toward the interrogator source and a jamming signal elsewhere, resulting in high S/N reception at the interrogator source and avoidance of interception. Integrating modulators would allow each array to transmit different data while the spectra of the transmitted signals are identical, thus disabling interception. The system enables secure point-to-point communications and can be used for short-distance wireless data transmission systems such as wireless LAN and RFID servers. As another aspect, self-steering signal transmission is employed for randomly oriented satellites using circularly polarized, two-dimensional retrodirective arrays. Quadruple subharmonic mixing is used as an effective means of achieving phase conjugation when a high-frequency LO is not feasible or inapplicable.